How to Watch Doctor Who

Eleventh Doctor Meets The Tenth Doctor | The Day of the Doctor ...

It’s common for people to argue about the order in which one should watch the Star Wars Trilogy. Should you go with release order? Episode Order? The Machete order? Or my suggestion, the right order? But not many argue about what order to watch Doctor Who—the British show about a time traveling time lord that regenerates when he dies (so he can be played by a different actor and the show can go on). And there’s a lot of orders to choose from. It’s been on for more than 50 years.

Now, the obvious answer to the watching order question is “watch them in order.” Just start with 1963’s “An Earthly Child” and go on from there. This, however, will prove difficult because (a) there are many missing episodes from those early years and (b) some of those early episodes are difficult to watch. TV was just…different back then. Now, you could look up a list of the best Classic Who episodes, like this one, and watch just those; but if you are completely unfamiliar with Doctor Who, even the best of the old episodes can be pretty hard to stomach. Doctor Who has always been campy, even for its own time. Unless you are already a fan, watching any Classic Who might leave a bad taste in your mouth.

Now, the series was restarted—not rebooted but restarted—in 2005. The classic, which ended in 1989, featured 7 doctors. There was an 8th in an American made-for-TV movie in the 90s. And then, in 2005, the show started up again, with Christopher Eccleston starring as the 9th Doctor. Now this might make one think that those unfamiliar with Doctor Who could just start there. And, I grant you, that’s not a bad way to go. Since I watched the episodes as they can out, that’s what I did. But 2005 was 15 years ago now. Even those episodes are pretty campy by modern standards—and, a few things have happened in the series since then that, I think, entail that a different watching order is better.

What’s the best order?

For those who just want to do it, let me tell it to you straight out, so I don’t spoil anything. Then, if you want to know why this is the best order, I’ll follow up with an explanation for why this is best.

First, watch “Blink” (3×10)

Second “The Eleventh Hour” (5×01) through “The Name of the Doctor” (7×13).

Then watch the 50th Anniversary special, “The Day of the Doctor.”

After that, go back to the first episode of the New Who, which is “Rose” (1×01).

Watch up through end of Season 4 (“Journey’s End” 4×13). (Watch Blink again!)

What the five specials that followed it (“The Next Doctor” through “The End of Time Part II”)

Then watch the 50th Anniversary special again.

Continue on with the next episode, which is a special entitled “The Time of the Doctor”

Then start Season 8 (“Deep Breath, 8×01) and catch up to what is current.

It is at this point that, if you are interested, you can go back and watch “the best of” Classic Who.

Now, why this order?

“Blink” is arguably the best who episode of all time, and serves as the perfect introduction to who the Doctor is. You are introduced to him through the eyes of Sally Sparrow, as this mysterious man with special powers and a knowledge of the universe. He’s in the background; he’s not even the main character. It’s brilliant. Those new to who will be hooked.

“The Eleventh Hour” is the first episode of the 11th Doctor; and since it is when the show moved to introduce itself to an American audience, it requires no knowledge of previous episodes, enemies, or characters. It explains why The Doctor looks different (than he did in “Blink”), and sets up a full four seasons of big stakes adventures with lovable characters. You’ll laugh, you’ll cry, you’ll scream. And the 10th Doctor will remain this mysterious background character. And if you are worried about the new viewer being confused about Who the Master is when he shows up—don’t worry. The 11th doctor never meets the Master. And the viewer won’t be confused by River Song’s appearance, because the Doctor has to explain her to his companions.

After this, watching that 50th anniversary special will be a very special experience. After four seasons, the new viewer may have forgot about that mysterious 10th Doctor that they only got to see for a few minutes in Blink—but then it will all come rushing back once they see him on screen. They will be excited to get to know him, and wonder a bit about the inside jokes that they miss. But they will also meet The War Doctor, and be enthralled by John Hurt’s portrayal.

Careful viewers of the special will realize that, at the very end, when The War Doctor regenerates, we see that he is just about to regenerate into Eccleston’s “9th” Doctor (although I would argue that the War Doctor is The Doctor and Eccleston’s is really the 10th). At any rate, at this point, by going back to the first episode of Season 1, you follow the War Doctor’s story (rather than the 11th), and the episodes will take on a very special meaning as you, the viewer, know things about the time war that not even The Doctor on the screen knows. Indeed, since they were introduced to Rose in the 50th universe special, meeting her again in the first episode will have a special kind of significance. Of course, the new viewer will wonder if that mysterious 10th doctor they were first introduced to is going to show up; but they will be especially pleased as he appears in the beginning of season 2.

The next step is to watch the 10th Doctor’s story all the way to the end, and includes probably the best season of Doctor Who ever (Season 3). It will also include the “introduction/demise” of River Song in “Silence in the Library,” which will take on a whole new light given that the viewer already knows her from her story with the 11th. Then, once the 10th Doctor is done, watching the 50th anniversary again will take on a new significance. The “new viewer” will now know both doctors well, get all of the inside jokes, and revel in the comradery. It will remind them again of the 11th Doctor –the Doctor that they first got to know and love—and they will be thrilled, now knowing his entire back story, to pick his story back up and see where it leads.

But, of course, the thrill will be short lived, as the 11th Doctor dies and regenerates in the very next episode. Having just seen the 10th Doctor do the same, the viewer will likely feel like they can take no more emotional toil—which is a sign of a story well told. And indeed, if the viewer wants to stop there, they could.

But I would recommend all the episodes of the next two Doctors; although people have legitimate complaints about some (the moon is an egg?), others are among my very favorites (e.g. “World Enough and Time,” and “Heaven Sent.”) And let’s not forget “The Husbands of River Song,” River’s first/last episode. And if the viewer is still into it—that’s when to look up some of the best of the classic episodes. Or, even, dare I say it—start from the beginning in 1963,  watch all the way through to 1989, and end with 90’s TV movie (it’s pretty good).

That’s my suggestion anyway. You asked for, you got it! But in whatever order you watch it, Doctor Who is some of the best TV science fiction ever made.

Why Do You Have to Wear A Mask in Class?

David Kyle Johnson

King’s College (PA)[1]

[Feel free to use this for your own class. You can download a word copy of this paper on academia.edu and/or researchgate.net.]

Why do you have to wear a mask in class? The short answer is because wearing a mask makes it less likely that you will unknowingly pass COVID on to others. The school is requiring everyone to do it because that makes a campus outbreak much less likely. But since the issue of mask wearing is so hotly debated in public discourse, before the semester starts, it will be worth our time to gain a basic understanding of (a) how masks work, (b) how we know they work, (c) how we know they are not dangerous—and (d) why the pseudoscientific arguments and misinformation that you have heard is wrong.

How Masks Work (To Help Prevent the Spread of COVID)

There is no longer any debate in the scientific community about whether masks can help prevent the spread of COVID-19. There was some debate back in March and April 2020, but once the evidence was clearly laid out, and the function of masks was made clear, the issue was settled and the experts agreed: yes, widespread mask use can significantly curtail the spread of COVID. Still, misinformation is prevalent and has confused the issue.

For example, it’s commonly believed that, if masks are going to help mitigate the spread, they will do so by filtering the air that a person inhales, thus protecting the person who wears the mask. This is why many think mask wearing should be a choice. “If I want to risk getting COVID, that’s my right.” This is also why many initially thought that mask use would be ineffective. While there is some evidence that cloth masks may be able to offer some protection to their wearer by filtering inhaled air, that protection is limited.[2] Indeed, boxes of surgical masks come with a warning that they are not a reliable means of protecting the wearer from infection.

In reality, however, this is irrelevant because the primary way masks help mitigate the spread is by protecting others from the person wearing them, if that person happens to be infected. This is called mitigating source spread. And they do so filtering the air a person exhales—when they sneeze, cough, speak, or breathe.[3] This helps because a virus doesn’t travel by itself; it travels in droplets of moisture propelled from an infected person’s mouth.

The largest droplets, which carry the majority of the viral load, settle on people and objects in the nearby vicinity of the person expelling them.[4] (This probably expands beyond 6 feet.)[5] If they end up in someone’s nose, mouth, or eye, that person could get infected. The smallest, called aerosols, carry the least viral load, [6] but are so light they can float in the air for hours and travel much further.[7] If they are inhaled into a person’s lungs, that person could get infected. Those in the middle carry a midsize viral load, but can actually evaporate and aerosolize, after they leave an infected person’s mouth.[8] Consequently, they might be the worst, because they can deliver pretty large viral loads over significant distances for hours.[9]

Now, there is still scientific debate about whether droplets or aerosols are the primary mode of infection for COVID.[10] But since masks can capture any of these kinds of droplets, that doesn’t matter. When they do, they lower the number of infected droplets in the air and environment, and thus reduce the risk of exposure for other people. [11] Once the experts started thinking in terms of a mask’s ability to protect others from their wearer, and realized how common it was for people to have COVID at not know it,[12] experts realized the usefulness of widespread mask use and began recommending it. 

Why are masks effective in capturing such droplets? The biggest droplets, which carry the majority of the viruses expelled from your mouth, are too big to even attempt to get through the mask; they are just intercepted by its surface. The smaller ones are stopped by something called impaction as they try to make it through the mask. The tiny pathways in the mask are too convoluted (twisty/turny); the particles can’t make their way through and end up adhering to the mask material. The smallest droplets are diffused by the mask because of something called Brownian motion–the erratic way they move.[13]Indeed, because they don’t travel in straight lines, they are pretty easy to catch.

Now it’s important to note that, while all masks filter exhalations, certain kinds of masks do that better than others.[14] The early woven cloth masks were effective, but not as effective as later non-woven ones—what we today call “medical” or “surgical masks.” (According to Anna Davies, while both types are effective, surgical masks are about three times more effective.[15]) But different kinds of cloth, layered or combined, can offer better filtration, by making the pathway particles would have to travel to get through the mask more convoluted. Onur Aydin found that layering cotton fabrics can make homemade masks almost as effective as surgical masks,[16] and Abhiteja Konda found that layering different kinds of fabrics (like cotton with flannel) could also increase their efficacy.[17]  Such masks filtered 80% of particles smaller than 300 nanometers (0.3 microns) and 90% of those larger.[18] Filters can also improve mask efficacy.[19] But if a mask has an unfiltered exhaust valve, they are almost completely useless; they might even project the droplets of an infected person farther. (So don’t use them!)

Now, if an infected droplet is already in the air that a masked person is about to inhale, the mask will be less likely to catch that particle. This is why they protect their wearer less efficiently. But masks are very efficient at filtering the air a person exhales. This is partly due to air flow; unlike when you are breathing in, when you are breathing out, you are forcing most of the air directly through the mask. But, more importantly, the longer a droplet is in the air, the more opportunity it has to evaporate and become smaller (and even aerosolize)—and (generally)[20] the smaller it is, the less likely a droplet is to be caught by a mask. So infected droplets in the air that an unmasked person has exhaled are going to be smaller and thus have a better chance at making it through your mask. But most of the infected droplets exiting your mouth won’t; they will be larger since they have not yet had a chance to evaporate.[21] So your mask is much more likely to catch them.

So, all in all, masks unquestionably work to help prevent the spread of COVID because they filter droplets (those on the right of the picture), including most of them that would become aerosols (those in the middle), and can even capture those that start out small (on the far left)—although, admittedly, a bit less efficiently.

So, if you are in a classroom with a non-masked infected person, you are pretty likely to be infected even if you are wearing a cloth mask and are more than six feet away. Just by breathing, they are spewing loads of infected droplets and aerosols into the air and surrounding environment. However, if that infected person is wearing a good cloth or surgical mask, you are much less likely to be infected—even if you are not wearing a mask and only 6 feet away. This is why it is said “My mask protects you; your mask protects me.”[22] Your choice to not wear a mask does not put you at risk; it puts others at risk. And it is for this reason that the “it’s my right to not wear a mask” argument has no legs to stand on. While you might have a right to endanger yourself, you unquestionably do not have a right to endanger others.

How We Know Masks Help Prevent the Spread Of COVID

Given what we know masks do, the fact that mandating them helps curb the spread of COVID is just common sense. But the evidence also bears this out.

For example, transmission rates slowed in hospitals,[23] German cities,[24] North Texas,[25] and in US states[26] after mandates went into effect. (In Germany, they reduced growth rates by 40%.) What’s more, U.S. States with mandates have seen much less spread than those without.[27] The same is true in countries around the world where mask use is popular.[28] Now some will argue that such correlational studies can’t prove anything because “correlation doesn’t entail causation.” But this is a misuse of that logical rule. A single correlation does not guarantee causation, but enough of them can imply it strongly enough to produce knowledge. For example, deaths rates dropped 27% after seat belt mandates were enacted in New York State,[29] and similar numbers were seen in all states that enacted such laws. Something similar happened for deaths in motorcycle accidents after helmet mandates were enacted. When the physical connection is obvious, and the correlation is repeated, it most definitely entails causation.

Modeling has also confirmed the effectiveness of mask mandates.[30] According to Richard Stutt and Steffen Eikenberry, if masks are just 50% effective, they could help bring down infection rates to non-epidemic levels and reduce the death rate by as much as 45%.[31] Large reviews of observational and comparative studies have also concluded that mask mandates are highly effective,[32] as have collections of collaborating experts.[33] And, of course, there were those infected hair stylists in Missouri who didn’t pass it on to 140 of their clients because they were wearing a mask.[34] The IHME found that mask mandates could save 33,000 by October 1st,[35] and (according to Brooks) if everyone wore a mask, we could get the pandemic under control in four to eight weeks.[36] [37]

If one is being stubborn, however, one might demand that this is not good enough. We need randomized control trials (RCTs) for mask safety and efficacy—the supposed “golden standard” in science. Well, we actually do have some. Nancy Leung, for example, performed a randomized controlled trial in which she masked some people (but not others) with respiratory illness and tested for infected droplets and aerosols; she found that “Surgical face masks reduced detection of coronavirus RNA in both respiratory droplets and aerosols.”[38] But anti-mask activists are likely to insist that such studies are not good enough. We need a RCT that measures how many people got sick with infected people wearing, or not wearing, a mask.

What such arguments fail to recognize, however, is not only the limits that ethical considerations put on such studies. They also fail to recognize that, while RCTs are great (indeed necessary) for testing drugs and treatments,[39] RCTs are not necessary or even appropriate for other scientific fields or questions. Indeed, RCTs are often easily misused and can lead to confusion.[40] To understand why, consider an example.

Suppose you wanted to know about the safety and efficacy of Kevlar vests regarding their ability to protect people from bullets. So someone explains the science—the physics of how Kevlar resists bullets—and show you how it works in a lab. Maybe they shoot bullets at plastic dummies, some wearing and some not wearing Kevlar vests, and see how they fare. They also show you correlational studies of how, say, death and injuries drop in army platoons after Kevlar vests are issued. That would be good enough, right? Of course. At that point, you would now know that they work.

And if anyone went further and performed a RCT on Kevlar vests, it would be pretty much useless. Why? Because the only way to do a completely controlled and bias free fully analogous RCT on Kevlar vests would be to put 1000 people in a room, give half of them Kevlar vests at random, and then start blindly shooting at them. Obviously, that kind of study cannot ethically be done. So, at best, an RCT could only compare, say, different groups of soldiers, already out in the field, who are either wearing or not wearing vests.

But since the real world is filled with all kinds of randomness and chaos, if such a study failed to find a difference in death and injury rates between the two groups, it wouldn’t be because vests offer no protection. It would be because real-world randomness threw off the results—because, say, the non-vested soldiers fought in less dangerous battles, or because the vested soldiers didn’t wear them right. To be clear, enough very carefully monitored studies might be able to show what certain kinds of vests are needed in certain circumstances; “Soldiers in X conditions need Y type vests.” But given what we already know about how Kevlar works, and what we have proved Kevlar can do in a lab, it would be absurd to think that a single RCT (or even a bunch of RCTs) could ever prove that they offer no protective effect to their wearer.

That’s how it is with masks. We understand the science of how they work. We know they block droplets and aerosols; we know that is how COVID is spread; we know mask mandates make more people wear masks, and we know COVID is spread pre- and asymptomatically. We even have trials where their use reduces the number of infected particles in the air. Combine that with the above examples from around the world of rates dropping with mask use and mandates, and that’s all you need. We know they work. No ethically dubious RCTs, where we see who gets sick after we throw healthy people into rooms with COVID patients who may or may not be wearing masks, are necessary.

And any other kind of limited RCT that we did in the field on masks would be pretty useless. Even if it found no significant results, that wouldn’t tell us masks don’t work. Random variables (like proper mask use) skewing the results would always be the more likely explanation. If they are carefully designed enough, such studies might be able to point towards one kind of mask being more effective than the other, or more needed in this or that situation. But proving masks don’t work at all is going to be next to impossible. Such studies can’t be controlled well enough to overturn something that is already well established. (And people who cite such studies, but leave out the part where the author acknowledges this, are trying to mislead you.) And since the evidence we have (which I reviewed above) has already well established that masks can block droplets and aerosols, and thus reduce the number of infected particles in the air, we know people wearing them will help reduce the spread of COVID-19.

So we know mask use helps mitigate the spread of COVID. And that, dear student, is why you have to wear a mask in class. But you probably still have a few questions, like…

Are Masks Dangerous?

You are bound to find stories and examples on the internet about how masks are dangerous. Some people claim they restrict your oxygen, for example, or can cause carbon dioxide poisoning. You may have even heard a story about a guy who passed out while driving his car and wearing a mask, or saw a video of a carbon dioxide detector going off the scale while under some kid’s mask. But in reality, such concerns are nonsense.

First of all, anecdotes are not evidence. People fall asleep or pass out while driving all the time; with mask use so prevalent, it’s not surprising it would eventually happen while someone was wearing a mask. This is most certainly a time where correlation does not equal causation. Such stories are only evidence that people don’t understand what masks are for. Unless you are driving with people outside your household, you don’t need to wear a mask while driving. 

Second, carbon dioxide detectors are designed to detect slight increases in indoor/household air, not the amount of carbon dioxide in the air coming directly out of your mouth. If you breathed directly on one without a mask, it would start going off too. Such “experiments” prove nothing. What’s more, I can find you a lot more videos of people wearing two or three masks while the oxygen level in their blood is shown to be completely normal. Masks do not restrict oxygen or hold in carbon dioxide.

And third, the claim is self-contradictory. The same people who say masks are dangerous are those that say they don’t work. But which is it? Either masks are so porous that they can’t block droplets and aerosols, or they are so non-porous that they trap carbon dioxide and restrict oxygen. You can’t have it both ways. Carbon dioxide and oxygen are gases; droplets and aerosols are liquid. Masks can’t restrict gas flow and choke you to death, while at the same time not restrict infectious liquids. (They can, however, be designed to block liquids but not gases—which they are.)

What’s more, masks have been worn by medical and other professionals for over 100 years. If we were going to see some negative side effects, we would have seen them by now. The notion that they are dangerous is absurd.

Debunking the Pseudoscience

Stuff you have seen online might also raise some questions, like…

How can masks work if they can’t block everything?

The answer here is simple: Masks don’t have to block everything to lower risk. By merely blocking some infected particles, masks reduce the risk of infection to others, by lowering the number of infected particles in the air. As I discussed above, if they were just 50% effective, they could keep COVID below epidemic levels—and tests show they are 80% to 90% effective.

Or think of it this way. Bullet proof vests can’t block everything either. Armor piercing bullets can still get through, and your head, legs, and arms are still exposed. That doesn’t mean they “don’t work”—that Kevlar vests offer no protection. This argument commits what’s called the “all or nothing” fallacy.

            Didn’t the CDC and the WHO change their tune on masks?

Yes, but that doesn’t mean masks don’t work. It means that the CDC and WHO updated their recommendations based on the evidence, as any good scientific organization should. In fact, they didn’t do so quickly enough. The old recommendations were based on thinking in terms of a mask’s ability to protect its wearer; that is why they did recommend mask use for higher risk patients—they do offer a little protection in this regard. But once they shifted to thinking in terms of source spread (the mask’s ability to protect others from the wearer), and realized how long those with COVID can be asymptomatically infectious, they updated their recommendation.

            What about those studies that say masks don’t work?

Online you will find people citing studies they say prove “masks don’t work.” In reality, they are usually studies about whether cloth or surgical masks offer enough protection to healthcare workers in high-risk environments. As we have already discussed, they usually don’t. (Healthcare workers should usually be wearing N95 respirators.) But whether or not masks protect their wearer is completely irrelevant to whether they can protect others from their wearer. As we discussed above, the air that someone exhales is filled with large droplets; the air that someone inhales is not.

Worse still, even if the studies are about source spread, anti-maskers will selectively quote them to make it seem like the studies entail something that they don’t—by, say, leaving out the part where the authors admit that the study was limited and inconclusive (which they all must be, given what we discussed above about RCTs). This is called quote mining.

To use a real world example: a study that says “Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention” sounds like convincing evidence that parachutes don’t work…until you read the next sentence: “However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps.”[41]

Likewise, “Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza” sounds convincing … until you read “Most studies were underpowered because of limited sample size, and some studies also reported suboptimal adherence in the face mask group.”[42]

And then sometimes the very study anti-maskers quote to show masks don’t work actually proves that they do. Take Faisal bin-Reza’s study for example.[43] I’ve seen anti-maskers point out that he says 

“None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”

That sounds convincing! But if you bother to actually look at that sentence in its full context, you will realize that the authors were actually comparing masks and respirators and saying that they were equally effective (not grouping them together and saying they were both ineffective). What’s more, that quote comes from the part of the study about influenza, and the authors specifically state that their findings about influenza cannot be extrapolated to things like SARS  because “SARS is an unusual acute viral respiratory infection with a very different epidemiology to almost all other respiratory viral infections. It is fundamentally different from human influenza.” (This is significant because the virus that causes COVID (SARS-CoV-2) is much more like the virus that causes SARS (SARS-CoV-1) than it is like the viruses that cause the flu.) Furthermore, the authors of the study specifically state their study did find that “mask and⁄or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome [SARS].” Funny how they left that part out, right?

Now, of course, the anti-masker might go on to quote more studies—but once a person establishes that they have a habit of misrepresenting the evidence, you can no longer trust that they are telling you the whole truth about what studies say and show. But if you bothered to look closer anyway, you would see that the studies are either irrelevant, being quote mined, or actually contradict their conclusion.

            Isn’t Humidity to Blame?

If you really dig deep, you might find people who try to blame the humidity for COVID transmission, and thus argue that masks are useless. But while low humidity might be the explanation for why certain long-standing respiratory disease rates spike in the winter, that has nothing to do with whether or not masks can filter particles and thus reduce infection rates for COVID. Regardless of the humidity, they can reduce the number of particles in the air. What’s more, according to Rachel Baker

“in a pandemic like the one we’re in now, what decides how quickly the new virus spreads is how many people are susceptible, or not immune, to it. Climate would play a bigger role only as more people become immune.”  

And given how COVID spread like wildfire in Texas and Florida in July, she seems to be right.

Conclusion

So, while we all know that wearing a mask is a pain, we also know it works—and it’s a relatively small inconvenience compared to its benefits. Please know, your professor hates trying to teach in it more than you hate sitting and listening in it. So please do your part, and wear your mask—over both your mouth and your nose. I can’t emphasize this enough: it does very little good if it’s not over your nose. Remember–we’re all in this together! My mask protects you, and your mask protects me.  So, I thank you in advance for protecting me!


[1] This paper was inspired by my course “Scientific, Pseudoscientific, and Medical Reasoning” which was moved online in the spring of 2020 due to the COVID pandemic.

[2] See Rick Kushman, “Your Mask Cuts Own Risk by 65 Percent,” UC Davis, July 6, 2020, https://www.ucdavis.edu/coronavirus/news/your-mask-cuts-own-risk-65-percent/. Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298  See WH Seto,et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6. and Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25, https://pubmed.ncbi.nlm.nih.gov/16014825/. Lijie Zhang, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseases 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765.  See Christian J. Kähler and Rainer Hain, “Fundamental Protective Mechanisms of Face Masks Against Droplet Infections,” Journal of Aerosol Science 148 (2020) https://doi.org/10.1016/j.jaerosci.2020.105617. C. Raina MacIntyre, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare Workers,” BMJ Open 5 no. 4, (2015) https://doi.org/10.1136/bmjopen-2014-006577.  This study suggested that 95% of viruses in aerosols could be blocked by homemade masks, and 97% could be blocked by surgical masks: Qing-Xia Ma, et al, “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805. This is a study out of Hong Kong which suggested that people wearing a mask was very effective at reducing transmission of alpha coronaviruses”; Nancy H. L. Leung, et al., “Respiratory Virus Shedding in Exhaled Breath and Efficacy of Face Masks,” Nature Medicine 26 (2020): 676-80, https://doi.org/10.1038/s41591-020-0843-2.

[3] See also WH Seto, et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6; see also Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25; Harvey Fineberg, Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020), (The National Academies Press, 2020), chapter 1 and 2, https://www.nap.edu/read/25769/chapter/1#2.

[4] Here I am thinking of droplets approx. 120 mircons and up.

[5] The idea that they travel only around 6 feet is based on outdated evidence; they likely travel farther. See See Zeshan Qureshi, et al., “What is the Evidence to Support the 2-metre Social Distancing Rule to Reduce COVID-19 Transmission?” CEBM, June 22, 2020, https://www.cebm.net/COVID-19/what-is-the-evidence-to-support-the-2-metre-social-distancing-rule-to-reduce-COVID-19-transmission/.

[6]              Only about 1 in every 700 of the smallest droplets (smaller than 10 microns), expelled from an infected persons mouth, contain even a single virus. Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

[7] Here I am thinking of droplets smaller than 10 microns.

[8] Depending on the humidity, droplets between 10 and 120 microns can evaporate and aerosolize at different rates.

[9] Neeltje van Doremalen, N., Bushmaker T., Morris D.H., Holbrook M.G., Gamble A., Williamson B.N., Tamin A., Harcourt J.L., Thornburg N.J., Gerber S.I., Lloyd-Smith J.O. “Aerosol and surface stability of SARS-CoV-2 as Compared with SARS-CoV.: N. Engl. J. Med 382 (2020):1564–1567. https://www.nejm.org/doi/10.1056/NEJMc2004973

[10] See Mahesh Jayaweera (et. al.), “Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy” Environ Res. 188 (Sep 2020): 109819. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7293495/

[11] Talib Dbouk and Dimitris Drikakis, “On Respiratory Droplets and Face Masks,” Physics of Fluids 32, no. 063303, published electronically June 16, 2020, https://doi.org/10.1063/5.0015044. Bhanu Bhakta Neupane, Sangita Mainali, Amita Sharma, and Basant Giri, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks,” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

[12] Wycliffe E Wei, Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee, ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020,” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

[13] Depending on your definition, aerosols range from around 100 microns to 0.1 micron. “Various sources will put the cutoff at 2 µm, 5 µm, 10 µm, 20 µm, or even 100 µm.” Justin Morgenstern, “Aerosols, Droplets, and Airborne Spread: Everything You Could Possibly Want to Know,” First10EM, April 6, 2020, https://first10em.com/aerosols-droplets-and-airborne-spread/. For simplicity, I’ll define aerosol as a droplet that is 10 µm in size. Brownian motion dominates in particles less than 0.3 µm in size. 

[14] Cloth masks of only one material seem to have very little effectiveness: Samy Rengasamy, Benjamin Eimer, and Ronald E. Shaffer, “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles,” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044. This is why those who are just wearing bandanas or pulling their t-shirt over their mouth, are not doing anyone much good.

[15]  Both types “significantly reduced the number of microorganisms expelled by volunteers,” “the surgical mask was 3 times more effective.”) Anna Davies, et al., “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (August 2013): 413-8, https://doi.org/10.1017/dmp.2013.43;  Milton (2013) found that surgical masks decreased emission of large particles by 25 fold, and aerosols by 3 fold in flu patients. See Donald K Milton, et al., Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks,” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205.

[16] Aydin et al. (2020), suggests that layering greatly increases the filtering efficiency of cloth masks while also maintaining some breathability, Onur Aydin, et al., “Performance of Fabrics for Home-Made Masks Against the Spread of Respiratory Infections through Droplets: A Quantitative Mechanistic Study,” medRxiv,preprint, submitted July 8, 2020  https://doi.org/10.1101/2020.04.19.20071779.

[17]             Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

[18] “Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.” Konda, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks.”

[19] Dr. Marty, a professor of infectious diseases at Florida International University told Good Morning America “But if you add that filter, then you’re also adding a really good protection for yourself.” See Becky Worley, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe, “Face Masks With Filter add Another Layer of Protection, Experts Say,” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

[20] Unless it is smaller than 0.3 microns.

[21] Some clarification here is useful. Technically, depending on how you classify “aerosols” (definitions range from 5 microns to 100 microns), most of  the particles you breathe out could be classified as aerosols–and depending on their size, the mask will filter them with different efficiencies. Even cloth masks are very good at filtering down to 10 microns, pretty good down to 5 microns, but not great below 5. See B.B. Neupane, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.” PeerJ. 2019; 7: e7142. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599448/

In one way, this is concerning because according to Adrien Burch (2020), the average size for aerosols leaving your mouth is 3 microns.  The good news is, despite the fact that they make up the largest number, they only represent 0.00024% of the liquid leaving your mouth during a cough. Consequently, very few of them are infected (at worst 1 out of every 700). A full 99.99976% of the viruses sprayed during a cough are carried in droplets — not aerosols.’) So the majority of transmission happens from droplets. What’s more, the deadliest aerosols are those that started out as droplets, but then evaporated down; they have higher concentrations of the virus. Masks catch those. So the inability of masks to filter out 3 micron (or 0.3 micron) particles does not greatly hinder their ability to keep infected particles out of the air, and thus does not prevent them from efficiently preventing the spread of COVID.
                Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” The Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

[22] From the abstract of: Richard O. J. H. Stutt, Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin, “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic,” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

[23]             Anthony D Sung, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial,” Clin Infect Dis 63, no. 8 (October 2016): 999-1006, https://doi.org/10.1093/cid/ciw451. Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/10.1001/jama.2020.12897. In this study, cases of COVID-19 declined after mask mandates were put into effect in hospitals (that required all health care workers and patients to mask up). The study concluded that such mandates reduce the transmission of SARS-CoV-2.

[24] Timo Mitze, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde, “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach,” IZA (June 2020) http://ftp.iza.org/dp13319.pdf. This study shows the impact of mask mandates in Germany. In Jena, for example, the first German city to enact such a mandate, COVID-19 cases fell by almost 25% in 20 days. The study concluded that similar mandates could reducethe daily growth rate by 40% in the long term, although it did acknowledge that, outside Germany, different norms and climatic conditions in other countries might result in different protective outcomes.

[25]             “HSC COVID-19 Report #5 – July 20, 2020,” University of North Texas Health Science Center at Fort Worth, https://www.scribd.com/presentation/469858261/COVID-19-Report-July-20-Updated?fbclid=IwAR1ta8C-x5yYfpqQ5eghmiPFr42ndbA6rYCmTv3WbcGU9tDt3a_RU1BOIL0.

[26] In those 15 US States, they likely prevented up to 450,000 cases in under two months. Wei Lyu and George L. Wehby, “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” Health Affair 39, no. 8 (2020): 1-7, https://doi.org/ 10.1377/hlthaff.2020.00818.

This was a retrospective analysis which examined the effects that different governmental orders to wear face masks had on COVID-19 growth rates, from April 9-May 15, 2020. It estimated that they prevented between 230,000 and 450,000 cases by May 22 (a reduction of 14-27%).

[27] Kasra Zarei and John Duchneskie, “Coronavirus Cases Rise in States with Relaxed Face Mask Policies,” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/COVID-19-coronavirus-face-masks-infection-rates-20200624.html.

[28]             American Thoracic Society, “Countries with Early Adoption of Face Masks Showed Modest COVID-19 Infection Rates,” Medical Xpress, June 24, 2020, https://medicalxpress.com/news/2020-06-countries-early-masks-modest-COVID-.html.

[29]             Joseph Berger, “Death Drops 27% With State’s Seat-belt Law, The New York Times, May 1, 1985, https://www.nytimes.com/1985/05/01/nyregion/death-drops-27-with-state-s-seat-belt-law.html.

[30]             Samantha M. Tracht, Sara Y. Del Valle, and James M. Hyman, “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1),” Plos One 5, no. 2 (February 2010): 1-12, doi.org/10.1371/journal.pone.0009018.

[31] Stutt, et al., “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.” To keep the infection rate (R0) below 1.0, the authors argue for widespread use of face masks. “[F]acemask adoption by entire populations would have a significant impact on reducing COVID-19 spread.” “[I]n summary, our modelling analyses provide support for the immediate, universal adoption of facemasks by the public.”
                See also, Eikenberry, et. al. “To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic.” Infectious Disease Modelling doi: 10.1016/j.idm.2020.04.001 https://www.medrxiv.org/content/10.1101/2020.04.06.20055624v1

[32] Derek K Chu, et al., “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-analysis,” The Lancet 395, no. 10242 (2020): 1973-87, https://doi.org/10.1016/S0140-6736(20)31142-9. This was a review of 172 observational studies and 44 relevant comparative studies. The authors concluded “Face mask use could result in a large reduction in risk of infection.”

[33] Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley, “Reducing Transmission of SARS-CoV-2,” Science 368, no. 6498 (June 2020): 1422-24, https://doi.org/10.1126/science.abc6197. In this paper, aerosol chemists and an infectious disease specialist argue that, because “airborne spread from undiagnosed infections will continuously undermine the effectiveness of even the most vigorous testing, tracing and social distancing programs,” the widespread use of masks are necessary to help prevent the spread of COVID. Both analytical information about the virus and information about countries where masks are commonplace was used.

Catherine M. Clase, et al., “Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Annals of Internal Medicine, published electronically May 22, 2020, https://doi.org/10.7326/M20-2567. This study, done by an international research team of medical doctors and other medical specialists not only concluded that cloth masks worn by the public will reduce COVID-19 transmission rates but that the benefits of widespread mask use outweigh any risks that may be brought about by wearing masks (such as improper use).

[34]             M. Joshua Hendrix, Charles Walde, Kendra Findley, and Robin Trotman, “Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy – Springfield, Missouri, May 2020,” Weekly 69, no. 28 (July 1, 2020): 930-32, http://dx.doi.org/10.15585/mmwr.mm6928e2.

[35] “New IHME COVID-19 Model Projects Nearly 180,000 US Deaths,” IHME,June 24, 2020, http://www.healthdata.org/news-release/new-ihme-COVID-19-model-projects-nearly-180000-us-deaths.

[36] For the quote, see McCabe, “Face Masks Really Do Matter.” For the evidence behind it, see John T. Brooks, Jay C. Butler, Robert R. Redfield, “Universal Masking to Prevent SARS-CoV-2 Transmission – The Time is Now,” Jama, published online July 14, 2020, https://doi.org/10.1001/jama.2020.13107.

[37] For more such evidence, see “Face Masks – A Summary of Relevant Research Papers for COVID-19,” Sound Reason & More,June 11, 2020, https://soundreasonandmore.wordpress.com/2020/06/11/face-masks-a-summary-of-relevant-research-papers-for-COVID-19/.

[38] Leung et al. 2020. Respiratory virus shedding in exhaled breath and efficacy of

face masks. Under review. https://www.researchsquare.com/article/rs-16836/v1

[39]             Markus MacGill, “What is a Randomized Controlled Trial?” Medical News Today, December 4, 2018, https://www.medicalnewstoday.com/articles/280574.

[40]             Rebecca A. Clay, “More than One Way to Measure,” American Psychological Association 41, no. 8 (September 2010): 52, https://www.apa.org/monitor/2010/09/trials; Roger Mulder, et al., “The Limitations of Using Randomised Controlled Trials as a Basis for Developing Treatment Guidelines,” Evidence-Based Mental Health 21, no. 1 (2018): 4-6, http://dx.doi.org/10.1136/eb-2017-102701.

[41] Robert W. Yeh, et al., “Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial,” BMJ 363: k5094 (2018): 1-6, https://doi.org/10.1136/bmj.k5094.

[42] Jingyi Xiao, et al., “Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures,” EID26, no. 5 (2020): 967-75, https://dx.doi.org/10.3201/eid2605.190994.

[43] Faisal bin-Reza, Vicente Lopez Chavarrias, Angus Nicoll, and Mary E. Chamberland, “The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence,” Influenza and Other Respiratory Viruses 6, no. 4 (December 2011): 257, https://do8i.org/ 0.1111/j.1750-2659.2011.00307.x.

How We Know Masks Work

Sadly, the issue of whether or not people simply wearing a mask can help prevent the spread of COVID is a hotly debated topic. It’s no longer debated in the scientific community, but it is online and in the public. Indeed, with adults throwing produce and tantrums in the middle of supermarkets, the issues surrounding “wear-a-mask mandates” could not be a hotter topic.

How Masks Work (To Help Prevent The Spread of COVID)

The explanation for how and why they work is simple, but misinformation has confused the issue. It’s commonly believed that masks simply protect their wearer from becoming infected by filtering the air that a person inhales. While there is some evidence that cloth masks maybe offer some protection to their wearer in this regard,[1] the primary way they help mitigate the spread is by filtering the air a person exhales—by sneezing, coughing, speaking, or breathing.[2]

Why are masks effective in filtering viruses from the exhaled air? Because a virus doesn’t travel by itself; it travels in droplets of moisture propelled from the mouth that can be captured. The largest droplets are intercepted by the surface of the mask; smaller ones are stopped by impaction as they try to make it through the mask; and the smallest, including aerosols, are diffused by the mask because of something called Brownian motion–the erratic way they move.[3] This lowers the number of infected droplets in the air, and thus reduces the risk of exposure for other people.[4]

Now, it’s important to note that, while all masks filter exhalations, certain kinds of masks are better than others.[5] The early woven cloth masks were effective, but not as effective as later non-woven ones—what we today call “medical” or “surgical masks.” (According to Davies, while both types are effective, surgical masks are about three times more effective.[6]) But different kinds of cloth, layered or combined, can offer better filtration, by making the pathway particles would have to travel to get through the mask more convoluted. Aydin found that layering cotton fabrics can make homemade masks almost as effective as surgical masks,[7] and Konda found that layering different kinds of fabrics (like cotton with flannel) could also increase their efficacy.[8]  Such masks filtered 80% of particles smaller than 300 nanometers (0.3 microns) and 90% of those larger.[9] Filters can also improve mask efficacy.[10]

Now if an infected droplet is already in the air that a masked person is about to inhale, the mask will be less likely to catch that particle. That might make one question how cloth masks can filter the air that someone exhales. But that question is easily answered. Part of it is due to air flow; when you are breathing in, you are not pushing the air directly through the mask. But also–the longer a droplet is in the air, the more opportunity it has to evaporate and become smaller (and even aerosolize)—and (unless it’s smaller than 0.3 microns) the smaller it is, the less likely a particle is to be caught by a mask. So infected droplets in the air that an unmasked person has exhaled has a better chance at making it through your mask. But most of the infected droplets exiting your mouth won’t, since they have not yet had a chance to evaporate.[11] [12]

In other words, masks unquestionably work to help prevent the spread of COVID because they filter droplets (those on the right of the below picture), including most of them that would become aerosols (those in the middle), and they can even capture those that start out small (on the far left)—just a bit less efficiently. (And only about 1 in every 700 of the latter such droplets, expelled from an infected persons mouth, contain even a single virus.) [13]

So, if you are in a room with a non-masked infected person, you are pretty likely to be infected even if you are wearing a cloth mask. However, if that infected person is wearing a cloth mask, you are much less likely to be infected—even if you are not wearing a mask. This is why it is said “My mask protects you; your mask protects me.”[14] Your choice to not wear a mask does not put you at risk; it puts others at risk.

Now, since the fact that the majority of the work that masks do in curbing the spread of COVID is done by the masks that infected persons are wearing, one might wonder: why don’t we just have infected people wear them? Indeed, this was part of the reasoning behind the traditional, years long, CDC and WHO recommendations that said mask wearing is not necessary for seemingly healthy individuals. With many diseases, it is not. But then experts realized just how long a person could be infected with COVID without knowing it and even that many infected never have any symptoms.[15] Consequently, public mask mandates are the only way to ensure that infected persons—including those who are pre- or asymptomatic—are wearing a mask. Such mandates would thus reduce the number of infected people without masks, thus reduce the number of infected particles in the air, and thus reduce the probability of transmission. Once we realized this, mask wearing was recommended. Granted, the CDC and WHO lagged behind the experts in this regard, but scientists change their mind based on evidence all the time. That’s not unusual. It’s just usually not that public.

How We Know Masks Help Prevent the Spread Of COVID

So given what we know masks do, the fact that mandating them helps curb the spread of COVID is just common sense. But the evidence also bears this out.

For example, transmission rates slowed in hospitals,[16] German cities,[17] North Texas,[18] and in US states[19] after mandates went into effect. (In Germany, they reduced growth rates by 40%.) What’s more, U.S. States with mandates have seen much less spread than those without, [20] as have countries where mask use is popular.[21] Now some will argue that such correlational studies can’t prove anything because “correlation doesn’t entail causation.” But this is a misuse of that logical rule. A single correlation does not guarantee causation, but enough of them can imply it strongly enough to produce knowledge. For example, deaths rates dropped 27% after seat belt mandates were enacted in New York State,[22] and similar numbers were seen in all states after enacting such laws. Something similar happened for deaths in motorcycle accidents after helmet mandates were enacted. When the connection is obvious, and the correlation is repeated, it most definitely entails causation.

Modeling has also confirmed the effectiveness of mask mandates.[23] According to Stutt and Eikenberry, if masks are just 50% effective, they could help bring down infection rates to non-epidemic levels and reduce the death rate by as much as 45%.[24] Large reviews of observational and comparative studies have also concluded that mask mandates are highly effective,[25] as have collections of collaborating experts.[26] And, of course, there were those infected hairstylists in Missouri who didn’t pass it on to 140 of their clients because they were wearing a mask.[27] The IHME found that mask mandates could save 33,000 by October 1st,[28] and (according to Brooks) if everyone wore a mask, we could get the pandemic under control in four to eight weeks.[29] [30]

Now, if one is being stubborn, one might demand that this is not good enough. We need randomized control trials (RCTs) for mask safety and efficacy—the supposed “golden standard” in science. Well, we actually do have some. The previously mentioned study by Leung, for example, which masked some people (but not others) with respiratory illness and tested for infected droplets an aerosols found that “Surgical face masks reduced detection of coronavirus RNA in both respiratory droplets and aerosols.”[31] A lot of the other studies I mentioned above are along this line. But anti-mask activists are likely to insist that this is not good enough. We need a RTC that measures how many other people got sick with the infected wearing, or not wearing, a mask. What such arguments fail to recognize is that, while they are great (indeed necessary) for testing drugs and treatments,[32] RCTs are not necessary or even appropriate for other scientific fields or questions. Indeed, they are easily misused and can lead to confusion.[33]

To understand why, consider an example. Supposed you wanted to know about the safety and efficacy of Kevlar vests regarding their ability to protect people from bullets. So I explain the science—the physics of how Kevlar resists bullets—and show you how it works in a lab. Maybe I shoot bullets at plastic dummies, some wearing and some not wearing, Kevlar vests. I also show you correlational studies of how, say, death and injuries drop in army platoons after Kevlar vests are issued. That would be good enough right? Of course.

In fact, if anyone went further and performed a RCT on Kevlar vests, they would be pretty much useless. Why? Because a true RCT would involve lining a whole bunch of people up on a wall, giving some Kevlar vests and some not at random, and then shooting them. Obviously, that kind of study cannot ethically be done. At best—because you can’t take vests away for experimental purposes—an RCT could only compare, say, different groups of soldiers, already out in the field, who happen to be wearing vests or not (for all kinds of various reasons and in different situations). If you found a significantly lower rate of injury among those wearing Kevlar, the study would be pretty useless because it would just tell you what you already know. But if it found no significant difference in the two groups, it would still be useless. Not only is it well known that a RCT not finding a difference is not proof that it is not there, but you would immediately think that there was a random variable that skewed the results. The soldiers with the vests probably happened to find themselves in a much more dangerous situation than those without, and so it biased the study. A “failed” RCT on vests would tell you very little about the efficacy of vests.

That’s how it is with masks. We understand the science of how they work. We know they block droplets and aerosols; we know that is how COVID is spread; we know mask mandates make more people wear masks, and we know COVID is spread pre- and asymptomatically. We even have trials where their use reduces the number of infected particles in the air. Combine that with the above examples from around the world of rates dropping with mask use and mandates, and that’s all you need. We know they work. No ethically dubious RCTs, where we throw healthy people into rooms with COVID patients who may or may not be wearing masks, are necessary. And any other kind of limited RCT that we did in the field would be pretty useless. Even if it found no significant results, that wouldn’t tell us mask don’t work. Not finding something is not evidence that it is not there; random variables skewing the results would be the more likely explanation. If they are carefully designed enough, they might be able to point towards one kind of mask being more effective than the other; but proving they don’t work at all is going to be next to impossible. Field studies just can’t be controlled well enough to overturn something that is already well established. And since the evidence we already have has established that they work, we know that they do.

And that, dear reader, is how we know public masks use helps mitigate the spread of COVID-19.


[1] See Rick Kushman, “Your Mask Cuts Own Risk by 65 Percent,” UC Davis, July 6, 2020, https://www.ucdavis.edu/coronavirus/news/your-mask-cuts-own-risk-65-percent/. Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298  See WH Seto,et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6. and Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25, https://pubmed.ncbi.nlm.nih.gov/16014825/. Lijie Zhang, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseases 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765.  See Christian J. Kähler and Rainer Hain, “Fundamental Protective Mechanisms of Face Masks Against Droplet Infections,” Journal of Aerosol Science 148 (2020) https://doi.org/10.1016/j.jaerosci.2020.105617. C. Raina MacIntyre, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare 1Workers,” BMJ Open 5 no. 4, (2015) https://doi.org/10.1136/bmjopen-2014-006577.  This study suggested that 95% of viruses in aerosols could be blocked by homemade masks, and 97% could be blocked by surgical masks: Qing-Xia Ma, et al, “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805. This is a study out of Hong Kong which suggested that people wearing a mask was very effective at reducing transmission of alpha coronaviruses”; Nancy H. L. Leung, et al., “Respiratory Virus Shedding in Exhaled Breath and Efficacy of Face Masks,” Nature Medicine 26 (2020): 676-80, https://doi.org/10.1038/s41591-020-0843-2.

[2] See also WH Seto, et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6; see also Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25; Harvey Fineberg, Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020), (The National Academies Press, 2020), chapter 1 and 2, https://www.nap.edu/read/25769/chapter/1#2.

[3] Depending on your definition, aerosols range from around 100 microns to 0.1 micron. “Various sources will put the cutoff at 2 µm, 5 µm, 10 µm, 20 µm, or even 100 µm.” Justin Morgenstern, “Aerosols, Droplets, and Airborne Spread: Everything You Could Possibly Want to Know,” First10EM, April 6, 2020, https://first10em.com/aerosols-droplets-and-airborne-spread/. For simplicity, I’ll define aerosol as a droplet that is 10 µm in size. Brownian motion dominates in particles less than 0.3 µm in size. 

[4] Talib Dbouk and Dimitris Drikakis, “On Respiratory Droplets and Face Masks,” Physics of Fluids 32, no. 063303, published electronically June 16, 2020, https://doi.org/10.1063/5.0015044. Bhanu Bhakta Neupane, Sangita Mainali, Amita Sharma, and Basant Giri, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks,” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

[5] Cloth masks of only one material seem to have very little effectiveness: Samy Rengasamy, Benjamin Eimer, and Ronald E. Shaffer, “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles,” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044. This is why those who are just wearing bandanas or pulling their t-shirt over their mouth, are not doing anyone much good.

[6]  Both types “significantly reduced the number of microorganisms expelled by volunteers,” “the surgical mask was 3 times more effective.”) Anna Davies, et al., “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (August 2013): 413-8, https://doi.org/10.1017/dmp.2013.43;  Milton (2013) found that surgical masks decreased emission of large particles by 25 fold, and aerosols by 3 fold in flu patients. See Donald K Milton, et al., Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks,” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205.

[7] Aydin et al. (2020), suggests that layering greatly increases the filtering efficiency of cloth masks while also maintaining some breathability, Onur Aydin, et al., “Performance of Fabrics for Home-Made Masks Against the Spread of Respiratory Infections through Droplets: A Quantitative Mechanistic Study,” medRxiv,preprint, submitted July 8, 2020  https://doi.org/10.1101/2020.04.19.20071779.

[8] Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

[9] “Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.” Konda, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks.”

[10] Dr. Marty, a professor of infectious diseases at Florida International University told Good Morning America “But if you add that filter, then you’re also adding a really good protection for yourself.” See Becky Worley, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe, “Face Masks With Filter add Another Layer of Protection, Experts Say,” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

[11] This is actually what N95 masks are named for; they protect their wearer by being 95% effective at filtering the air that a person breathes in. And because they often have unfiltered exhaust vents, they usually don’t filter the air a person breathes out. Combine that with the fact that they don’t even perform their intended function well unless they are perfectly fit, and you can realize why they should likely only be worn by health care workers in high risk environments.

[12] Some clarification here is useful. Technically, depending on how you classify “aerosols” (definitions range from 5 microns to 100 microns), most of  the particles you breath out could be classified as aerosols–and depending on their size, the mask will filter them with different efficiencies. Even cloth masks are very good at filtering down to 10 microns, pretty good down to 5 microns, but not great below 5. Neupane, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.”

In one way, this is concerning because according to Burch (2020), the average size for aerosols leaving your mouth is 3 microns.  The good news is, despite the fact that they make up the largest number, they only represent 0.00024% of the liquid leaving your mouth during a cough. Consequently, very few of them are infected (at worst 1 out of every 700). A full 99.99976% of the viruses sprayed during a cough are carried in droplets — not aerosols.’) So the majority of transmission happens from droplets.  What’s more, the deadliest aerosols are those that started out as droplets, but then evaporated down; they have higher concentrations of the virus. Masks catch those. So the inability of masks to filter out 0.3 micron particles does not greatly hinder their ability to keep infected particles out of the air, and thus does not prevent them from efficiently preventing the spread of COVID.
                Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” The Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

 [13] Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

[14] From the abstract of: Richard O. J. H. Stutt, Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin, “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic,” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

[15] Wycliffe E Wei, Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee, ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020,” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

 [16]Anthony D Sung, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial,” Clin Infect Dis 63, no. 8 (October 2016): 999-1006, https://doi.org/10.1093/cid/ciw451. Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/ 10.1001/jama.2020.12897. In this study, cases of COVID-19 declined after mask mandates were put into effect in hospitals (that required all health care workers and patients to mask up). The study concluded that such mandates reduce the transmission of SARS-CoV-2.

[17] Timo Mitze, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde, “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach,” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

This study shows the impact of mask mandates in Germany. In Jena, for example, the first German city to enact such a mandate, COVID-19 cases fell by almost 25% in 20 days. The study concluded that similar mandates could ruse the daily growth rate by 40% in the long term, although it did acknowledge that, outside Germany, different norms and climatic conditions in other countries might result in different protective outcomes.

[18] “HSC COVID-19 Report #5 – July 20, 2020,” University of North Texas Health Science Center at Fort Worth, https://www.scribd.com/presentation/469858261/COVID-19-Report-July-20-Updated?fbclid=IwAR1ta8C-x5yYfpqQ5eghmiPFr42ndbA6rYCmTv3WbcGU9tDt3a_RU1BOIL0.

[19] In those 15 US States, they likely prevented up to 450,000 cases in under two months. Wei Lyu and George L. Wehby, “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” Health Affair 39, no. 8 (2020): 1-7, https://doi.org/ 10.1377/hlthaff.2020.00818.

This was a retrospective analysis which examined the effects that different governmental orders to wear face masks had on COVID-19 growth rates, from April 9-May 15, 2020. It estimated that they prevented between 230,000 and 450,000 cases by May 22 (a reduction of 14-27%).

[20] Kasra Zarei and John Duchneskie, “Coronavirus Cases Rise in States with Relaxed Face Mask Policies,” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/COVID-19-coronavirus-face-masks-infection-rates-20200624.html.

[21] American Thoracic Society, “Countries with Early Adoption of Face Masks Showed Modest COVID-19 Infection Rates,” Medical Xpress, June 24, 2020, https://medicalxpress.com/news/2020-06-countries-early-masks-modest-COVID-.html.

[22] Joseph Berger, “Death Drops 27% With State’s Seat-belt Law, The New York Times, May 1, 1985, https://www.nytimes.com/1985/05/01/nyregion/death-drops-27-with-state-s-seat-belt-law.html.

[23] Samantha M. Tracht, Sara Y. Del Valle, and James M. Hyman, “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1),” Plos One 5, no. 2 (February 2010): 1-12, doi.org/10.1371/journal.pone.0009018.

[24] Stutt, et al., “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.”

To keep the infection rate (R0) below 1.0, the authors argue for widespread use of face masks. “[F]acemask adoption by entire populations would have a significant impact on reducing COVID-19 spread.” “[I]n summary, our modelling analyses provide support for the immediate, universal adoption of facemasks by the public.”

[25] Derek K Chu, et al., “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-analysis,” The Lancet 395, no. 10242 (2020): 1973-87, https://doi.org/10.1016/S0140-6736(20)31142-9.

This was a review of 172 observational studies and 44 relevant comparative studies. The authors concluded “Face mask use could result in a large reduction in risk of infection.”

[26] Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley, “Reducing Transmission of SARS-CoV-2,” Science 368, no. 6498 (June 2020): 1422-24, https://doi.org/10.1126/science.abc6197. In this paper, aerosol chemists and an infectious disease specialist argue that, because “airborne spread from undiagnosed infections will continuously undermine the effectiveness of even the most vigorous testing, tracing and social distancing programs,” the widespread use of masks are necessary to help prevent the spread of COVID. Both analytical information about the virus and information about countries where masks are commonplace was used.

Catherine M. Clase, et al., “Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Annals of Internal Medicine, published electronically May 22, 2020, https://doi.org/10.7326/M20-2567. This study, done by an international research team of medical doctors and other medical specialists not only concluded that cloth masks worn by the public will reduce COVID-19 transmission rates but that the benefits of widespread mask use outweigh any risks that may be brought about by wearing masks (such as improper use).

 [27] M. Joshua Hendrix, Charles Walde, Kendra Findley, and Robin Trotman, “Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy – Springfield, Missouri, May 2020,” Weekly 69, no. 28 (July 1, 2020): 930-32, http://dx.doi.org/10.15585/mmwr.mm6928e2.

[28] “New IHME COVID-19 Model Projects Nearly 180,000 US Deaths,” IHME,June 24, 2020, http://www.healthdata.org/news-release/new-ihme-COVID-19-model-projects-nearly-180000-us-deaths.

[29] For the quote, see McCabe, “Face Masks Really Do Matter.” For the evidence behind it, see John T. Brooks, Jay C. Butler, Robert R. Redfield, “Universal Masking to Prevent SARS-CoV-2 Transmission – The Time is Now,” Jama, published online July 14, 2020, https://doi.org/10.1001/jama.2020.13107.

[30] For more such evidence, see “Face Masks – A Summary of Relevant Research Papers for COVID-19,” Sound Reason & More,June 11, 2020, https://soundreasonandmore.wordpress.com/2020/06/11/face-masks-a-summary-of-relevant-research-papers-for-COVID-19/.

[31] Leung et al. 2020. Respiratory virus shedding in exhaled breath and efficacy of

face masks. Under review. DOI: 10.21203/rs.3.rs-16836/v1.

[32] Markus MacGill, “What is a Randomized Controlled Trial?” Medical News Today, December 4, 2018, https://www.medicalnewstoday.com/articles/280574.

 [33] Rebecca A. Clay, “More than One Way to Measure,” American Psychological Association 41, no. 8 (September 2010): 52, https://www.apa.org/monitor/2010/09/trials; Roger Mulder, et al., “The Limitations of Using Randomised Controlled Trials as a Basis for Developing Treatment Guidelines,” Evidence-Based Mental Health 21, no. 1 (2018): 4-6, http://dx.doi.org/10.1136/eb-2017-102701.

A (Complete) Debunking of Denis Rancourt’s Argument That “Masks Don’t Work.”

In April 2020, Physicist Denis Rancourt posted a short article to ResearchGate.net that was later taken down by the website’s administration because of its poor quality. In June, River City Reader posted it under the title “Masks Don’t Work: A Review of Science Relevant to COVID-19 Social Policy.” In it, River City Reader pledges “to publish all letters, guest commentaries, or studies refuting [Rancourt’s] general premise that this mask-wearing culture and shaming could be more harmful than helpful.” This is just such an article.

In his article, Rancourt concludes “there is no known benefit arising from wearing a mask in a viral respiratory illness epidemic.”[1] The article is now widely cited by the “anti-mask” movement as proof that masks don’t work and thus laws requiring citizens to wear masks are ineffectual. But, to put it mildly, Rancourt’s argument is fraught with pseudoscience and logical mistakes, and it fails entirely to even provide evidence for (much less proof of) his thesis.

The heavy presence of pseudoscientific mistakes as well as the low academic quality of the work should not surprise those familiar with Rancourt or the issue at hand. Scientifically, the argument is already settled. And as a climate change denier, Rancourt has proven himself to be incapable of recognizing and avoiding mistakes common to pseudoscientists. As a physicist (who specialized in metals but no longer works in academia), not an epidemiologist (or climate scientist), Rancourt is completely outside of his area of expertise.

But to establish that his argument is faulty, I will have to go farther. So, although I do so recognizing the danger of giving legitimacy to his argument by engaging with it, I will now summarize and point out the many ways that Rancourt’s argument goes wrong. Although I am not an epidemiologist either, I am a logician who teaches entire courses on argumentation and medical pseudoscience. So, unlike with Rancourt, my writing of this article falls squarely within my area of expertise. Indeed, I already did these things in a debate I had with him on this very subject. But since he talked over me most of the time, and wouldn’t let me finish any argument I made, I felt it warranted to lay out everything clearly here.

Rancourt’s article is convoluted, and intentionally obtuse. But in the confusion, you can find four reasons that he thinks masks don’t work—indeed that they “cannot possibly work.”

  1. Not even wearing surgical or N95 masks reduces the risk of contracting a verified illness, so how could cloth masks do so?
  2. The seasonal nature of outbreaks of flu-like illnesses is due to varying humidity levels; thus masks can’t help prevent their spread.
  3. The particles that transmit the virus are too small to be blocked by even N95 masks, much less cloth masks.
  4. A single exposure will cause you to get infected, and masks can’t guarantee no exposure.

All four utterly fail. For those who don’t have time to read this 10,000 word article, you can find a quick refutation of it at the end of the article referenced in this endnote.[2] But for those who would like to see a complete debunking of his entire argument, point by point, that is what follows. But first, I need to make clear how masks do work to help prevent the spread of COVID, and how we know that they do. This will be important for understanding the fallacies of Rancourt’s argument to the contrary. Then we will tackle each of his arguments in turn.

How Masks Help Prevent the Spread of COVID

The explanation is simple, but misinformation has confused the issue. It’s commonly believed that masks simply protect their wearer from becoming infected by filtering the air that a person inhales. While there is some evidence that cloth masks maybe offer some protection to their wearer in this regard,[3] the primary way they help mitigate the spread is by filtering the air a person exhales—by sneezing, coughing, speaking, or breathing.[4]

Why are masks effective in filtering viruses from the exhaled air? Because a virus doesn’t travel by itself; it travels in droplets of moisture propelled from the mouth that can be captured. The largest droplets are intercepted by the surface of the mask; smaller ones are stopped by impaction as they try to make it through the mask; and the smallest, including aerosols, are diffused by the mask because of something called Brownian motion–the erratic way they move.[5] This lowers the number of infected droplets in the air, and thus reduces the risk of exposure for other people.[6]

Now, it’s important to note that, while all masks filter exhalations, certain kinds of masks are better than others.[7] The early woven cloth masks were effective, but not as effective as later non-woven ones—what we today call “medical” or “surgical masks.” (According to Davies, while both types are effective, surgical masks are about three times more effective.[8]) But different kinds of cloth, layered or combined, can offer better filtration, by making the pathway particles would have to travel to get through the mask more convoluted. Aydin found that layering cotton fabrics can make homemade masks almost as effective as surgical masks,[9] and Konda found that layering different kinds of fabrics (like cotton with flannel) could also increase their efficacy.[10]  Such masks filtered 80% of particles smaller than 300 nanometers (0.3 microns) and 90% of those larger.[11] Filters can also improve mask efficacy.[12]

Now if an infected droplet is already in the air that a masked person is about to inhale, the mask will be less likely to catch that particle. That might make one question how cloth masks can filter the air that someone exhales. But that question is easily answered. Part of it is due to air flow; when you are breathing in, you are not pushing the air directly through the mask. But also–the longer a droplet is in the air, the more opportunity it has to evaporate and become smaller (and even aerosolize)—and (unless it’s smaller than 0.3 microns) the smaller it is, the less likely a particle is to be caught by a mask. So infected droplets in the air that an unmasked person has exhaled has a better chance at making it through your mask. But most of the infected droplets exiting your mouth won’t, since they have not yet had a chance to evaporate.[13] [14]

In other words, masks unquestionably work to help prevent the spread of COVID because they filter droplets (those on the right of the below picture), including most of them that would become aerosols (those in the middle), and they can even capture those that start out small (on the far left)—just a bit less efficiently.

So, if you are in a room with a non-masked infected person, you are pretty likely to be infected even if you are wearing a cloth mask. However, if that infected person is wearing a cloth mask, you are much less likely to be infected—even if you are not wearing a mask. This is why it is said “My mask protects you; your mask protects me.”[15] Your choice to not wear a mask does not put you at risk; it puts others at risk.

Now, since the fact that the majority of the work that masks do in curbing the spread of COVID is done by the masks that infected persons are wearing, one might wonder: why don’t we just have infected people wear them? Indeed, this was part of the reasoning behind the traditional, years long, CDC and WHO recommendations that said mask wearing is not necessary for seemingly healthy individuals. With many diseases, it is not. But then experts realized just how long a person could be infected with COVID without knowing it and even that many infected never have any symptoms.[16] Consequently, public mask mandates are the only way to ensure that infected persons—including those who are pre- or asymptomatic—are wearing a mask. Such mandates would thus reduce the number of infected people without masks, thus reduce the number of infected particles in the air, and thus reduce the probability of transmission. Once we realized this, mask wearing was recommended. Granted, the CDC and WHO lagged behind the experts in this regard, but scientists change their mind based on evidence all the time. That’s not unusual. It’s just usually not that public.

How We Know Masks Help Prevent the Spread Of COVID

So given what we know masks do, the fact that mandating them helps curb the spread of COVID is just common sense. But the evidence also bears this out.

For example, transmission rates slowed in hospitals,[17] German cities,[18] North Texas,[19] and in US states[20] after mandates went into effect. (In Germany, they reduced growth rates by 40%.) What’s more, U.S. States with mandates have seen much less spread than those without, [21] as have countries where mask use is popular.[22] Now some will argue that such correlational studies can’t prove anything because “correlation doesn’t entail causation.” But this is a misuse of that logical rule. A single correlation does not guarantee causation, but enough of them can imply it strongly enough to produce knowledge. For example, deaths rates dropped 27% after seat belt mandates were enacted in New York State,[23] and similar numbers were seen in all states after enacting such laws. Something similar happened for deaths in motorcycle accidents after helmet mandates were enacted. When the connection is obvious, and the correlation is repeated, it most definitely entails causation.

Modeling has also confirmed the effectiveness of mask mandates.[24] According to Stutt[25] and Eikenberry, if masks are just 50% effective, they could help bring down infection rates to non-epidemic levels and reduce the death rate by as much as 45%. Large reviews of observational and comparative studies have also concluded that mask mandates are highly effective,[26] as have collections of collaborating experts.[27] And, of course, there were those infected hairstylists in Missouri who didn’t pass it on to 140 of their clients because they were wearing a mask.[28] The IHME found that mask mandates could save 33,000 by October 1st,[29] and (according to Brooks) if everyone wore a mask, we could get the pandemic under control in four to eight weeks.[30] [31]

Now, if one is being stubborn, one might demand that this is not good enough. We need randomized control trials (RCTs) for mask safety and efficacy—what Rancourt calls the “golden standard” in science. We actually do have some. The previously mentioned study by Leung, for example, which masked some people (but not others) with respiratory illness and tested for infected droplets an aerosols found that “Surgical face masks reduced detection of coronavirus RNA in both respiratory droplets and aerosols.”[32] A lot of the other studies I mentioned find something similar. But Rancourt is likely to insist that this is not good enough. We need a RTC that measures how many other people got sick with the infected wearing, or not wearing, a mask. What Rancourt fails to recognize is that, while they are great (even necessary) for testing drugs and treatments,[33] RCTs are not necessary or even appropriate for other scientific fields or questions.[34]

To understand why, consider an example. Supposed you wanted to know about the safety and efficacy of Kevlar vests regarding their ability to protect people from bullets. So I explain the science—the physics of how Kevlar resists bullets—and show you how it works in a lab. Maybe I shoot bullets at plastic dummies, some wearing and some not wearing, Kevlar vests. I also show you correlational studies of how, say, death and injuries drop in army platoons after Kevlar vests were issued. That would be good enough right? Of course.

In fact, any RCT that anyone performed on Kevlar vests would be pretty much useless at that point. Why? Because a true RCT would involve lining a whole bunch of people up on a wall, giving some Kevlar vests and some not at random, and then shooting them. Obviously, that kind of study cannot ethically be done. At best—because you don’t take vests away for experimental purposes—an RCT could only compare, say, different groups of soldiers, already out in the field, who happen to be wearing vests or not (for all kinds of various reasons). If you found a significantly lower rate of injury among those wearing Kevlar, the study would be pretty useless because it would just tell you what you already know. But if it found no significant difference in the two groups, it would still be useless. Not only is not finding a difference not proof that it is not there, but you would immediately think that there was a random variable that skewed the results. The soldiers with the vests probably happened to find themselves in a much more dangerous situation than those without, and so it biased the study. It would tell you very little about the efficacy of vests.

That’s how it is with masks. We understand the science of how they work. We know they block droplets and aerosols; we know that is how COVID is spread; we know mask mandates make more people wear masks, and we know COVID is spread pre- and asymptomatically. We even have trials where their use reduces the number of infected particles in the air. Combine that with the above examples from around the world of rates dropping with mask use and mandates, and that’s all you need. We know they work. No ethically dubious RCTs, where we throw healthy people into rooms with COVID patients who may or may not be wearing masks, are necessary. And any other kind of limited RCT that we did in the field would be pretty useless. Even if it found no significant results, that wouldn’t tell us mask don’t work. Not finding something is not evidence that it is not there; random variables skewing the results would be more likely. If they are carefully designed enough, they might be able to point towards one kind of mask being more effective than the other; but proving they don’t work at all is going to be next to impossible. Field studies just can’t be controlled well enough to overturn something that is already well established.

With that understanding fully in place, let us turn to what is wrong with Rancourt’s first argument.

Failed Argument 1: N95 and Surgical Masks Don’t Work.

Rancourt states the major premise of his first argument plainly: “extensive scientific literature establishes that wearing surgical masks and respirators (e.g., “N95) does not reduce the risk of contracting a verified illness.[35] But there are essentially four problems with this argument.

Problem 1: Confirmation Bias

Rancourt gives the impression that he is doing a systematic review of the literature, but in reality, he is merely selecting and citing studies that (he thinks) support his conclusion while ignoring those that do not. The CDC, for example, lists 19 studies that Rancourt ignores, all of which not only contradict his conclusion but are more recent than any study he lists. He also ignores all the evidence I mentioned above, not to mention these four that directly find that N95 masks do reduce the risk of contracting a verified illness.[36] In logic, we call this confirmation bias–only seeking out evidence that confirms what one wants to believe.[37] And confirmation bias is most effective in leading one astray. Rancourt engaging in it clearly demonstrates he has failed to establish that the scientific consensus comports with his conclusion that by “making mask-wearing recommendations and policies for the general public, or by expressly condoning the practice, governments have…ignored the scientific evidence.”[38]

Problem 2: The Point Is Irrelevant; He’s Equivocating 

As I made clear in the last section, the scientists who have advocated for universal public mask-wearing during the COVID-19 pandemic have not claimed that by wearing a mask, an uninfected person protects himself or herself from becoming infected. Instead, scientists claim it helps prevent those who are infected from spreading their infection to others, by spraying infected droplets and aerosols into the environment—what is known as source contamination. The fact that they don’t protect wearers all that well is why it has not generally been recommended that healthy people need to wear masks in public during, say, flu season. Those who are sick should wear them, to keep from spreading whatever they have around, but for healthy people, it is overkill.

However, with most diseases it becomes clear, pretty early on, when a person is sick. Once we realized that with COVID, people could be infected and infectious for days without knowing (some even never developing symptoms), everything changed. It made sense to ask everyone to wear a mask, to make sure that everyone who didn’t know they were sick was wearing one.

If keeping the wearer from getting sick is how masks help prevent the spread of COVID, then the thesis of the entire first section of Rancourt’s article—that “wearing surgical masks and respirators (e.g., “N95”) does not reduce the risk of contracting a verified illness”—is completely irrelevant to the issue of whether mask mandates help reduce the spread of COVID. Even if it were true that masks do not protect those who wear them, it would still be true that public laws requiring masks help by mitigating the spread of COVID by helping prevent those who are infected (especially without knowing they are) from transmitting it to others. Thus, the evidence Rancourt provides here is completely irrelevant to the issue.

To help illustrate Rancourt’s mistake, let us return to our analogy. Suppose, to challenge your idea that Kevlar vests are safe and effective, a man named Dennis cited a study that showed that Kevlar vests can’t keep you warm in a blizzard. While that study might be accurate, it is irrelevant to the issue. The issue is whether they can stop bullets, not keep you warm. In the same way, studies about the effectiveness of mask to prevent infection in the wearer are irrelevant to the issue of whether they are able reduce source contamination. In other words, if public health officials say that you wearing a mask helps protect others, citing a study saying that you wearing a mask doesn’t protect you, is irrelevant. In logic, we call this a non-sequitur.

This error actually haunts Rancourt’s entire article because almost all the evidence he presents is about masks not protecting the wearer; he says very little that’s relevant to whether they protect others from the wearer. Indeed, the entire article is essentially one giant equivocation. He says masks “don’t work,” but what does he mean by “work?” If he means cloth masks don’t protect the wearer very much–yeah, we already suspected that (although, as I mentioned above, some new evidence points in a different direction). But if he means they don’t protect others, he needs to provide evidence. What “work” in the title means is the latter, but then all he really provides evidence for is the former. This is like titling an article “My Kids Don’t Work” to try to motivate your biological children to get a job, and then writing an article about how your young pet goats are unemployed.

            Problem 3: The Studies Rancourt Cites about N95s Don’t Actually Support His Claim

Rancourt claims that the medical literature shows that “wearing surgical masks and respirators (e.g., “N95”) does not reduce the risk of contracting a verified illness.”[39] Most of the studies he cites, however, are not only contradicted by many others, [40] but merely show that the effectiveness of N95 and surgical masks is roughly the same. Obviously, the fact that they work equally well doesn’t mean that they don’t work at all (or that cloth masks don’t work at all).   

Now, in a way, Rancourt anticipates this objection when he states “if there were any benefit to wearing a mask, because of the blocking power against droplets and aerosol particles, then there should be more benefit from wearing a respirator (N95) compared to a surgical mask.”[41] If that were true, then the studies he cites would be relevant to whether masks offer protection. But it is not. Even if N95 masks offer no more protection than surgical masks, it would not follow that cloth masks don’t offer protection. Why?

With most protective gear, as you increase the quality or quantity of the gear, there is a gradual increase in its effectiveness. But once you reach a certain point, increases in effectiveness slow and eventually become insignificant, such that there is no longer a benefit to having even higher quality. (It’s a bit like, but not exactly like, diminishing returns.[42]) So if the quality of masks levels off at a certain point, in such a way that N95 masks don’t offer that much more protection than surgical masks, that would not be completely surprising–and it certainly wouldn’t show that cloth masks provide no protection.

To illustrate this logical error, let us return to the Kevlar vest example. A vest with Kevlar that is, say, 1mm thick will clearly be less effective than one with Kevlar 2mm thick; and 2mm will be less effective than 3mm, etc. But at some point, continuing to increase the thickness will be unhelpful. For example, 7mm of Kevlar will likely stop all the same bullets as 14mm. A study that showed that 7mm and 14mm thick vests offer the same protection might not be surprising—but it certainly wouldn’t entail that there is no protective benefit to wearing a bulletproof vest. In the same way, a study that shows N95 and surgical masks offer around the same amount of protection doesn’t indicate that there is no protective benefit to wearing a cloth mask.

To make matters worse, he basically just misrepresents the findings of all studies he cites. Consider Smith’s study.[43] While this study does compare the effectiveness of N95 and surgical masks, it admits that it doesn’t prove that they do offer equal protection—just that the available evidence so far is inadequate for proving that N95 masks offer more protection in a clinical setting.

“Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.”

However, even though it was not enough to prove they were superior, they did find that “In general, compared with surgical masks, N95 respirators showed less filter penetration, less face-seal leakage and less total inward leakage under the laboratory experimental conditions described.” This study is far from the proof that N95’s don’t work better than surgical masks that Rancourt claims it is.

Or consider Offedu’s study.[44] Again, this study is about whether N95 and surgical masks protect their wearer, but it found that N95 masks do protect better than surgical masks against clinical respiratory illness, just not against viral infections and influenza-like illness; N95s and surgical masks seem to protect equally well in that regard. Rancourt takes the quote about this, “Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant,” out of context to make it seem like it is about the effectiveness of masks. What’s more, the study specifically found that masks and respirators do protect against SARS (which, again, is the closest thing to Covid-19). Indeed, it specifically stated that “This systematic review and meta-analysis supports the use of respiratory protection.”

Consider Radonovich’s study.[45] While it too is about the effectiveness of N95 and medical masks, it’s about the flu—not SARS, so its findings really can’t be transferred over to COVID. Also, the author admits, the non-difference could just be due to the N95’s not being properly sealed or used. Something similar is true of Youlin’s study, which is also only about the flu—not SARS—and merely suggests that N95 masks should be reserved for health care workers in the most high risk situations—not that cloth masks can’t filter out droplets.[46]

Problem 4: The Other Studies He Cites Actually Prove Him Wrong.

The other studies Rancourt cites actually contradict his thesis. Now, he says they support it–but to make it seem so, he takes quotes from them out of context and/or ignores findings in the paper that discredit his thesis. Take for example his quote from bin-Reza, the only one Rancourt mentions from that paper:

“None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.”[47]

Given that it appears in the section of his paper where he is arguing that masks don’t work, his quoting of this line from the study implies that the authors intended this statement to mean there is no benefit to wearing masks. In reality, however, the slash in the “mask/respirator” phrase is meant to indicate a comparison between the two types of facial coverings. The study is not lumping them together and declaring them both ineffective; the study actually concludes that masks and respirators are equally effective. Several of the sentences before and after the one he quotes demonstrate this. For example,

“Eight of nine retrospective observational studies found that mask and ⁄ or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS).”[48]

What’s more, the part of that study Rancourt cities is about influenza, not COVID—and the authors themselves specifically state that their findings about influenza cannot be extrapolated to SARS-CoV-1. “SARS is an unusual acute viral respiratory infection with a very different epidemiology to almost all other respiratory viral infections. It is fundamentally different from human influenza.” But SARS-CoV-1 is now know to be very similar to SARS-CoV-2 (the cause of COVID-19); and about SARS-CoV-1 this study “found that mask and ⁄or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome.”

Or take Cowling’s article.[49] The part of that study Rancourt mentions is about whether masks (in this case, cloth masks) protect their wearer from infection, not whether they filter exhaled air and thus protect others. So it is irrelevant to his thesis. What’s more, the authors admit that the body of evidence they are examining is not sufficient to draw a conclusion, but they also suggest that the evidence that does exist at least suggests that cloth masks do provide some protection for their wearer—probably not enough for a healthcare setting but maybe enough for household use. They recommend further study on this topic. The part of the study that Rancourt doesn’t mention is the part that examines whether cloth provides protection to others by filtering air, and they conclude that they do. “There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission.”[50] Again, in logic, we call this “confirmation bias.

Lastly, consider Jacobs’ article: This study showed that N95 masks cause headaches in some, and that (surgical) facemasks don’t protect their wearer. This only tells us what we already know: Wearing a tight banded mask on your face for 12 hours is bound to cause headache, and surgical masks don’t provide adequate protection in high risk environments. Since both findings are irrelevant to whether cloth masks filter outgoing particles, this study is irrelevant to his thesis. About Rancourt’s use of his study, in correspondence with me, Jacobs said

“Dr. Rancourt’s opinion piece mischaracterizes the research findings I reported in my 2009 peer-reviewed article…. It was not designed to examine mask effectiveness of preventing the mask-wearer from spreading a respiratory infection. My study has no bearing on addressing that recommendation. My study was statistically powered to detect a difference between the two groups. There was no such difference in number of colds detected, which is not the same as determining there is no difference. It was not sufficiently powered to conclude that the absence of a difference meant there is no difference. This is termed ‘non-inferiority’, and requires a much larger sample size and/or longer study duration.”

So, of the studies Rancourt cites, none of them provides any evidence to support his claim that masks do not work in reducing the spread of viruses, and several of them provide evidence that they do. This is important, not only because it shows his thesis to be unsupported, but because it establishes a pattern of academic recklessness that makes Rancourt untrustworthy.

Indeed, he did this again in my debate with him when he cited the Xiao. “Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza.” He left out the part where the study admits that the trials in looked at were flawed, and that conclusions can’t be drawn from them—which makes sense since they also entailed that handwashing is useless. And he also didn’t cite the part that says:

“There are still few uncertainties in the practice of face mask use, such as who should wear the mask and how long it should be used for. In theory, transmission should be reduced the most if both infected members and other contacts wear masks, but compliance in uninfected close contacts could be a problem. Proper use of face masks is essential because improper use might increase the risk for transmission. Thus, education on the proper use and disposal of used face masks, including hand hygiene, is also needed.”

The authors of the study were not convinced by it that masks don’t work, and Rancourt’s specialization in metals doesn’t qualify him to draw a different conclusion.

Consider our Kevlar vest analogy once again. Suppose, this time, to challenge the idea of Kevlar vest safety and effectiveness, our friend Dennis quotes a RCT which, he says, proves they don’t work. He even quotes from the conclusion: “Kevlar vest use did not reduce death or major traumatic injury in subjects after being shot in any randomized evaluation of this intervention.”[51] What would you think? Like we discussed before, you would probably think it was flawed. “Did a random variable throw it off?” You’d want to take a closer look.

But suppose when you did, you found that—right after the sentence that Dennis quoted—was the sentence: “However, the trial was only able to enroll participants willing to be shot by rubber bullets at a distance of 50 yards; the authors causation against extrapolating from this study anything regarding real world use of Kevlar Vests.” Clearly, that explains it. This study proves nothing.

But now a new question arises. Why did Dennis leave that part out? Does he work for some lobby that has it out for Kevlar vests? Whatever the reason, you would rightly no longer trust him to provide reliable information about the results of studies. This would especially be true if he did this same kind of thing, seven or eight times over. He already gave you irrelevant studies; now he’s just blatantly misrepresenting them. I don’t care how many more studies he cites, at this point I’m not going to believe that they show or entail what he says they do.

In our debate, when I called him on this, and finally got to essentially admit that he had done it, he said that he was just “interpreting” the studies. But as a physicist who specialized in metals, he is not qualified to interpret the findings of medical studies—certainly not more qualified than the people who wrote the paper whose findings contradict his. What’s more, a study to determine X can only demonstrate X, not some other thing Y. It might suggest to you some other conclusion Y, but it cannot determine whether Y is true. For that, you would need to do a separate study on Y. Scientific studies are not short stories. You can’t “interpret” them to mean whatever you want them to mean.

Failed Argument 2: Humidity Causes Seasonal Variation, So Masks Can’t Help 

Everyone knows that colds and the flu “go around” more in the winter. This is one reason flu shots are given in the fall. But explanations for this seasonal variation vary widely. Your mother perhaps told you that “being cold makes you get a cold.” This is why you were instructed not to go outside with wet hair. Since, of course, we now know that tiny organisms like viruses cause disease, we know that “being cold” does not. Other proposed explanations vary from “people are indoors more in the winter,” to “soft tissue irritation,” to “lack of sunlight (which causes a vitamin D deficiency).”  But in 2010, Shaman suggested something else: variations in humidity. Air is humid in the summer, dry in the winter, and (so the theory goes) viruses spread more easily from person to person in dry conditions.[52]

Now, I don’t know whether Shaman’s hypothesis has gained a consensus in the scientific community; I have not reviewed all the relevant research. What I do know is that, contrary to Rancourt’s suggestion, even if Shaman is right, it does not follow that masks don’t help prevent the spread of viral contagions—that a second wave of COVID could not be a “consequence of human sin regarding mask wearing and hand shaking [but instead] an inescapable consequence of an air-dryness-driven many-fold increase in disease contagiousness, in a population that has not yet attained immunity.” What’s more, Rancourt’s argument suggesting it does is fundamentally flawed. There are essentially two main problems to point out.

Problem 1: Oversimplified Cause

The first mistake is not easy to explain. Rancourt claims that, if Shaman’s humidity hypothesis is correct, then COVID’s basic reproduction number (R0) (which reflects how many people, on average, each sick person infects) is “highly or predominantly dependent on ambient absolute humidity.”[53] Consequently, “all the epidemiological mathematical modeling of the benefits of mediating policies (such as social distancing [or masks]), which assumes humidity-independent R0 values, has a large likelihood of being of little value” because “the seasonal infectious viral respiratory diseases that plague temperate latitudes every year go from being intrinsically mildly contagious to virulently contagious, due simply to the bio-physical mode of transmission controlled by atmospheric humidity, irrespective of any other consideration.”[54]

While that sounds convincing, it shouldn’t convince you. Why? That last phrase is key: “irrespective of any other consideration.” Not quite. Even if humidity has been the most causally efficacious factor when it comes to how fast viral infections in the past have spread, it does not follow that there are no other causal factors (even if those causal factors have been constant in the past). Consequently, it does not follow that guarding against other factors can’t reduce the infection rate—especially if we have not taken such precautions in the past.

To illustrate the cognitive mistake, consider a first-time skier. He goes out the first day and comes back soaked to the bone. Undeniably, it’s the snow that made him wet, but if he just shrugged his shoulders and said “Well, if I’m going to ski, there is going to be snow, so I guess I’ll just have to be soaked every day,” we would call him a fool. Of course the snow made him wet, but a simple pair of rubber ski pants will keep him dry. In the same way, even if humidity is a factor in transmissibility, so is droplet and aerosol spread. So you can limit transmissibility, even if you can’t change the humidity, by limited droplet and aerosol spread.

In giving the skier analogy, I was not trying to compare snow with viruses; I was demonstrating Rancourt’s logical mistake. The fact that some thing X is even the main cause of a problem Y doesn’t mean that the only way to solve Y is by removing or changing X; because causation is complex, usually the problem can be mitigated by taking some other precaution, or action, Z. For example, the fact that a river’s physical attributes are primarily what determine its speed doesn’t mean that you can stop it by building a dam. Likewise, even if a lack of humidity in the winter has been the main cause of the uptick in winter viral spread in the past (and you can’t change the humidity), that doesn’t mean that you can’t mitigate the spread of the virus by taking some other precaution (like mandating masks).

But if you would like a more direct analogy, suppose we tried to mitigate the spread of the flu by locking everyone in the world in their home, in separate rooms, for two months. This would, of course, be overly draconian, and a really bad idea for multiple reasons–but it undoubtedly would stop the spread, and indeed most likely wipe out the disease. It would run its course in all infected persons, either killing them or being killed by their immune systems, and then be done.

But notice how stupid someone would seem if they came out and said, “such efforts will have no effect at all on the spread of the disease at all because isolating people won’t affect the humidity.” Even if humidity is normally a major factor in transmission, there are other things at play: like how we are exposed to others who are infected. If we limit that exposure by locking everyone in their room—or, less drastically, we simply encourage people to social distance and wear masks—we will lessen the spread. even if the humidity levels are unaffected. So Rancourt’s argument here suffers from the most basic of logical flaws: he simply failed to recognize that there is more than one causal factor when it comes to viral spread. In logic, we call this the fallacy of oversimplified cause.[55] 

Problem 2: What’s Happened Since: Wide-spread Infection in Humid Months

The second problem with Rancourt’s humidity argument begins with realizing that Shaman himself has admitted that we don’t know enough about COVID to conclude that humidity is a factor in its transmission.[56] Others, like Rachel Baker, who studies how climate affects infectious disease for a living, has argued that it likely is not—at least, not yet. From the same article:

“Rachel Baker, lead author of a new article in Science and a researcher at Princeton University who studies how climate affects infectious disease, said the main conclusion is that in a pandemic like the one we’re in now, what decides how quickly the new virus spreads is how many people are susceptible, or not immune, to it. Climate would play a bigger role only as more people become immune.”[57]

And what has happened since Rancourt wrote his argument in April of 2020 seems to suggest that she is right. The infection rate in states that ignored social distancing and mask guidelines have skyrocketed in the hottest, most humid times and places (e.g., Florida and Texas in July).[58] So either humidity doesn’t affect COVID at all, or it does and we really need to start wearing masks—because this winter is going to be brutal!

Failed Argument 3: Particles that transmit the virus are too small to be blocked by masks.

The major premise of this argument is that the COVID virus, or more specifically the droplets that carry it, are aerosol particles that are too small to be blocked by cloth masks and thus masks cannot provide protection. He tries to establish this by claiming that aerosols can’t even be blocked by N95 masks; if that’s true, how could cloth masks possibly provide any protection? But, as you might have guessed, there are serious flaws with this argument too—flaws so severe that each renders it impotent. I will explain four of them.   

            Problem 1: It’s Not Just Aerosols (And Even If It Is, Masks Still Work)

Rancourt’s argument in this section relies on the assumption that practically the only method of transmission for COVID is aerosols. Indeed, in the video that accompanies his article, he says:

“We have known for a decade now that the main transmission route of all of these types of viral respiratory diseases, is very fine aerosol particles, that are supported as part of the fluid air. … It’s not about droplets, it’s not about spitballs, it’s not about surfaces, and fomites, and all that kind of stuff –that has nothing to do with it. It’s all about buildings where you have fine aerosol particles suspended in the air of the building—they can be measured, they are in high concentration—that’s where the transmission occurs.”

This is most likely false. We certainly have not known this “for a decade now.” The role of droplets, aerosols, and fomites in the transmission of the flu is still hotly debated, much less COVID. These things are difficult to study. As Fineberg put it, “for no respiratory virus is the exact proportion of infections due to air droplet, aerosol, or fomite transmission fully established,

and many individual factors and situations may contribute to the importance of each route of transmission.”[59] And there most certainly is no peer reviewed evidence (much less a RCT) that proves that aerosols even are a mode of transmission for COVID, much less the only one. As Dr. Josh Santarpia put it, “To my knowledge, there is no definitive evidence of transmission where aerosol was the only possible route.”

Now, there are some anecdotal studies which suggest that COVID might also be transmissible through aerosols. But first, those studies admit that it may only be to those who are susceptible—because the viral load in aerosols is so low. Only around 1 in 700 aerosols that leave an infected person’s mouth have a single virion in them.[60] What’s more, because the assumption that droplets only travel around six feet is based on outdated studies, these anecdotes could be explained by droplet exposure. [61]

On top of that, while it is true that, numerically speaking, aerosols likely make up the majority of the particles that exit your mouth, they only make up a tiny fraction of the material that leaves you mouth.[62] Most of that is droplets; that’s where most of the viral load is carried. Indeed, not do only 1 in 700 aerosols that leave an infected person’s mouth have even a single virus in them, but the only aerosols that could have more are those that started out as larger droplets (e.g., 50-100 microns, with a number higher virus load) that evaporated down (i.e., aerosolized) after they left your mouth. This is important because, as I explained in the first section, masks unquestionably capture such droplets.[63] So even if aerosols are the only mode of transmission, contrary to what Rancourt says in this section of his paper, masks would greatly reduce the number of aerosols in the air, and thus reduce the risk of infection.

Think of it this way. Even if 10 micron and lower aerosols are the only mode of transmission, masks can reduce risk. Why? According to Dr. Jeffry Martin, “persons who have a member of their household infected with the virus have a higher probability of getting infected with COVID …This tells us that close contact is the most important factor.”[64] If an infected person releasing aerosols is what makes such long personal interactions more risky, it would be because the more aerosols you are exposed to, the more likely you are to be infected—either because of increased viral load, or increased risk of inhalation. Since most masks can filter even the 10 micron particles to some degree, they reduce risk. And even if they can’t, they still block the larger more potent droplets and prevent them from evaporating and becoming more potent 10 micron aerosols. And since those particles would be what are carrying majority of the viral load, masks would still greatly reduce risk.[65]

To be clear, I’m not saying aerosols are not a mode of transmission. They likely are. But they are almost certainly not the only mode (such that, all other modes are irrelevant); and even if they were, masks would still help. This is contrary to all the assumptions that Rancourt makes on this issue.

Problem 2: Rancourt’s Argument for Aerosols Being The Main Mode is Faulty

If humidity affects the transmission of viruses, it’s not clear how it does so. Two possibilities that Rancourt mentions are “viable decay” and “physical loss.” If it is viable decay, flu spreads less in the summer because humid air deactivates viral-pathogen-carrying droplets more quickly than dry air. If it’s physical loss, then the humidity physically removes such drops from the air (by keeping them from evaporating and aerosolizing as quickly).

The reason this matters is because Rancourt himself admits that his argument that masks can’t filter particles infected with COVID (because they are too small) is dependent on the “physical loss” explanation.   

If my view of the mechanism is correct (i.e., “physical loss”), then Shaman’s work further necessarily implies that the dryness-driven high transmissibility (large R0) arises from small aerosol particles fluidly suspended in the air; as opposed to large droplets that are quickly gravitationally removed from the air.[66]

The humidity hypothesis itself doesn’t turn on which mechanism it is, but his argument that the primary mode of transmissibility is aerosols does. But there is no good reason to think the physical loss explanation is right.

First, the author of the study that Rancourt himself cites (Harper, 1961) argues for the “viable decay” hypothesis and regards the physical decay hypothesis to merely be possible.[67] And to think that something is true, merely because it is possible, is (cleverly called) the “appeal to possibility” fallacy.[68] Possible things might be true, but the fact that they are possible doesn’t entail they are.

Second, Rancourt doesn’t actually provide any evidence for the physical loss theory. He merely states that it “seems more plausible” to him, and that he finds it “difficult to understand” how the viable decay hypothesis could be true.[69] Needless to say, the fact that Rancourt can’t understand something is not a good reason to think that it is false. (By the way, thinking something is false because you can’t understand it is called the “appeal to personal incredulity” fallacy.[70])

So the assumption that Rancourt makes in this argument, that aerosols are the only significant mode of transmission for COVID—which, even if true, doesn’t mean that masks don’t work—is at best based on another unsupported assumption that the authors Rancourt himself cites consider implausible.

Problem 3: Either A Mistake in The Math or Basic Immunology  

Rancourt’s argument is not well organized or well written, and it is difficult to parse sometimes; but it seems that he has made a fundamental mathematical mistake that completely invalidates his argument. To begin to see why, recall that one of the major premises of his third argument is that not even N95 masks can block viruses. To establish this, he argues that the pores in N95 masks are too big to block the virus. He says.

“…indoor airborne virus concentrations have been shown to exist (in day-care facilities, health centers, and on board airplanes) primarily as aerosol particles of diameters smaller than 2.5 μm [microns]…Such small particles (< 2.5 μm) are part of air fluidity, are not subject to gravitational sedimentation, and would not be stopped by long-range inertial impact. This means that the slightest (even momentary) facial misfit of a mask or respirator renders the design filtration norm of the mask or respirator entirely irrelevant. In any case, the filtration material itself of N95 (average pore size ~0.3−0.5 μm) does not block virion penetration, not to mention surgical masks.[71]

Initially when I read this, I was confused. Clearly, a 2.5 μm particle is much bigger than a 0.3 (or 0.4, or 0.5) pore. So how can he possibly be claiming that the 0.3 μm pores in N95 masks are too big to block 2.5 μm particles? And then it dawned on me. Yes, 2.5 is greater than 0.3–but it’s less than 3! It seems he didn’t notice the decimal. He thinks that a 0.3 μm pore won’t block a 2.5 μm particle because 3 is a greater number than 2.5.

The only other possibility is that he is first saying that N95 masks can’t block particles smaller than 2.5 μm if they are misfit—which, of course is true; that’s why N95s are usually tested for proper fit. Then he makes a separate point that, even if they are properly fit, it doesn’t matter because the pore size of an N95 (which is approximately 0.3−0.5 microns) is bigger than the virus itself (which is about .125 microns). If so, there is no math error—but his point is entirely irrelevant because the virus never travels alone; it always travels in droplets! This is immunology 101. So either he is making a basic math error, or a basic immunology error.

What’s more, even a virus was traveling alone, N95s (and in fact cloth masks) would be exceedingly efficient at capturing them because of Brownian Motion. In other words, as I shall now show, Rancourt doesn’t even understand the physics behind how N95s work—which is ironic given that, if his academic training in physics is relevant to anything in this debate, it would be this.

Problem 4: Rancourt Doesn’t Understand How Masks Work

“Brownian Motion” refers to the erratic way that such small particles zig-zag around due to their interaction with the surrounding gas atoms and molecules in the air. Essentially, they are so light, that they are easily pushed around by such things. Since the motion of molecules and atoms in a gas is chaotic and random, particles smaller than 0.3 μm dance around in the air randomly as they interact with them.

This makes much easier to capture because they don’t travel in a straight line. If N95 masks were a woven porous sieve, and these particles just traveled in a straight line, yes they would be basically impossible to catch. But not only do they not travel in straight lines, N95 are not made sieve’s made of woven material; they are usually made of synthetic plastic fibers. Now, there are spaces between the fibers, but they are twisted and compressed together in such a way that it essentially creates a maze that most particles can’t pass through. Gasses, like 02 and CO2 can—that’s why you can still breathe while wearing one. But particles, especially those dominated by Brownian Motion, bouncing around like crazy, cannot.[72]

The hardest particles to catch are those that are just big enough to not be dominated by Brownian Motion—that is, the smallest particles that aren’t bouncing around like crazy but do generally travel in a straight line. They are around 0.3 microns. But still, N95s have been shown to capture 95% of such particles; that’s where the “95” in their name comes from. Surgical masks, which are not woven, can also capture particle 0.3 microns and below—although yes, less efficiently. And so can cloth masks. Single layer cotton cloth masks don’t do very well with particles that small, but layering the cloths creates similar convoluted pathways for the particles to travel through, especially when you combine them with non-woven fabric, like flannel. As I pointed out in the first section, Konda found that such masks filtered 80% of particles smaller than 0.3 microns and 90% of those larger.[73]

So Rancourt’s claim that the particles that the virus travel in are just too small to be stopped by a mask demonstrates a fundamental misunderstanding of the physics of how masks work. Thus it is a baseless claim.

Failed Argument 4: Masks Can’t Guarantee 0% Exposure, Thus They are Useless

In his final argument, Rancourt suggests that masks can’t work because they are not 100% effective at stopping infected droplets. Why must they do so? Because, he says, the minimal infective dose (MID) for COVID is really low; exposure to just one infected droplet, with only one virus in it, will make a person sick. And so, he says, “the studies that show partial stopping power of masks, or that show that masks can capture many large droplets produced by a sneezing or coughing mask-wearer…are irrelevant.”[74] But, again, his argument is fundamentally flawed. There are essentially three problems with his argument.

Problem 1: No Evidence for COVID’s Minimal Infective Dose (MID)

First of all, he provides no direct evidence for COVID’s MID. He, instead, cites a study from 2011 (by Yezli and Otter) about influenza.[75] But, as we have discussed, COVID is a very different disease that affects those it infects in many different ways (for example, it seems to affect blood vessels and cause blood clots). So influenza’s MID can really only point in the direction of COVID’s MID, at best.  

Second, he merely states that “It is believed that a single virion can be enough to induce illness in the host.”[76] But of course a belief is not evidence. He quotes Zwart et al. (2009), saying his study on a virus-insect system showed that “the action of a single virion can be sufficient to cause disease.”[77] However, the fact that something can be sufficient to cause something, doesn’t mean that it is or will in all or even most cases.

And the other evidence he provides, like from Baccam et al. (2006) and Brooke et al. (2013), only talk about how quickly or efficiently viruses reproduce in cells once they are infected–not the probability of cells becoming infected once exposed. So, once again, Rancourt is “interpreting” studies to make them show what they don’t.[78]

Problem 2: He Overestimates Viral Load and its Threat

Rancourt’s paper is so poorly written, it’s sometimes difficult to tell what exactly he is saying or suggesting. For example, to “point out the relevant features” for his statements about the MID of COVID, he provides a bulleted list from Yezli and Otter. But he does not provide page numbers or quotation marks, so it is impossible to tell whether these are direct quotes or summaries of their work. For example, point number six is just “For further background:” and then the next points mention other authors. Are these other authors mentioned by Yezli and Otter? Or is he just summarizing other sources? It’s impossible to tell.

So when he says, in point four of this list, that “There are typically 10 to 3rd power − 10 to 7th power virions per aerolized [sic] influenza droplet with diameter 1 μm − 10 μm,” it’s impossible to know whether he is quoting Yezli and Otter, summarizing them, or doing his own calculations based on information they provided. But in layman’s terms, this means that there are 1000 to 10 million viral particles, in each infected microdroplet 1 to 10 microns in size. And while it is a statistic about the flu, it is clear that we are meant to infer from it that roughly the same numbers hold for COVID. Not only is Rancourt adamant about how similar the two viruses are, but why else would he bring this statistic up? Indeed, it’s clear that he thinks that every droplet a COVID infected person emits is going to have at least 1000 viruses in it. Hey says that the information in this bulleted list means that, “If anything gets through (and it always does, irrespective of the mask), then you are going to be infected.” (emphasis added). The only way that is true is if every aerosolized droplet is potently infected.

But this is simply not true. Even when coming from an infected person, microdroplets of that size are mostly empty of viruses and contain at most a single viral particle. Why? Because it’s difficult to get coronavirus into a concentration much higher than 10 million per mL.[79] And a 10micron droplet is 0.167 picoliters (4/3 * 5^3 * 10^-18 m^3). A mL is 1 billion picoliters. So for every 1,000 micron droplets that an infected person spews out, only at most 2 (1.67) will have a single virion in it—that’s roughly 1 out of every 600 (which is quite close to the 1 out of every 700 number I cited before).[80] Granted, infected aerosols can hang in the air for a few hours, but given how few of them there are, a person’s mask inability to filter them all doesn’t entail that they “don’t work”—especially if we are talking about the low concentration of infected aerosols there would be in a public space. Add this to the fact that, according to Heneghan, the symptoms that someone suffers is likely proportional to the amount of their viral exposure, [81] and it becomes painfully clear that the amount that Rancourt is overstating worries about a single infected aerosol making it through is absurd.

Problem 3: The All or Nothing Fallacy

The all or nothing fallacy is a variety of the false dilemma fallacy.[82] One commits the false dilemma fallacy when one suggests that there are fewer options than there actually are. “You are either for us, or against us.” No, actually, I could just be neutral, or not care. The all or nothing fallacy presents a false dilemma by suggesting that there are only two options—either all or nothing—when in fact there are many more options in the middle ground between those two extremes.

The fallacy is very common when talking about the effectiveness of laws. Take seat belt laws, for example. Some people ignore them, and other times they are not enough to save the person’s life. But they undoubtably decrease the number fatal accidents. The same is true of speed limits. They do not prevent everyone from speeding and cannot eliminate all car crashes. But no one would argue that speed limits are useless and that we should not even bother with them because they do no good. They reduce the amount of speeding and thus make the roads safer. Or think again about our Kevlar vests. They are fall from perfect; they leave your head exposed, and can be pierced by “armor piercing bullets. That doesn’t mean they aren’t safe and effective, or that they don’t offer protection.

In the same way, masks cannot eliminate COVID infections; even if everyone is wearing a mask, some people will still get infected, because masks are not perfect. They do let some particles through. Some people will ignore the ordinance, or wear them improperly, for example, by leaving their nose hanging out the top. But if masks are mandated, more people will be wearing them, and wearing them properly. This will reduce the number of infected droplets in the air. And if you still happen to be exposed to one in the air, wearing one can reduce your chance of exposure (although it would depend on the mask). Thus, even though they cannot eliminate it, mask mandates will reduce the probability of infection, and thus the number of people infected.

Or to put it another way—covering your mouth when you sneeze is imperfect, too. Droplets will still escape. That doesn’t mean that you shouldn’t do it or that it doesn’t reduce the chance of infection.

Rancourt’s Concluding Arguments: Biases and Mask Risk 

Rancourt finishes his article by claiming that no “bias free” study could ever show that mask mandates are effective.[83] But that “bias free” phrase is doing a lot of work. Notice that, if any such study ever came out, he would just claim that it was biased and dismiss it. He has just built into his argument what logicians call an “ad hoc” excuse–an unfalsifiable way to excuse away any contrary evidence. It is a telltale sign of pseudoscience and irrationality.

Now if by “bias free” he just means RCT, as in any study that is not a RCT is biased, he is simply misunderstanding the nature of science and scientific reasoning. As I mentioned before, RCTs are neither needed or appropriate to answer all scientific questions. [84] Indeed, they have amazing limits, can be very misleading, and (as Rancourt has himself proved) they are also very easy to cherry pick in nefarious ways to make them seem like they support conclusions they don’t. [85] When it comes to things like masks and bullet proof vests, which we already know work, more RTC’s would be basically useless.

He also suggests that no such study could be done because “Mask-wearing is associated (correlated) with several other health behaviors” and “The results would not be transferable, because of differing cultural habits.” But, of course, these are simply things that such studies would have to take into account and control for. It does not mean they cannot be done. Indeed, you could say the same thing about cigarettes—but that doesn’t mean we can’t know that they increase the risk of cancer.

He also lists a number of “unknown risks” to mask wearing, suggesting that the risks of a mask mandate would outweigh its benefits. But not only are the supposed risks he lists miniscule compared to the tens of thousands of lives that mask mandates could save, and the enormous economic benefit that masks could generate by allowing businesses to open up without major risk; these worries are also completely unfounded.[86] In my debate, as evidence of their dangers, he mentioned a story he heard about someone passing out while driving and wearing a mask. For someone who demands RCT’s before believing anything, it certainly seems strange to trust such anecdotal evidence. (People pass out while driving everyday; with mask wearing now common, such a story is no surprise.) Essentially, his epistemic standards are backwards. He demands impossible evidence for what he doesn’t want to believe, and no evidence for what he does. This is like refusing to believe that Kevlar vests are safe and effective because no RCT’s have been performed, but then believing they are dangerous because you heard a story about a guy who died while wearing one. It’s absurd.

What’s more, his worries about mask dangers completely contradict his thesis. You can’t think masks are not effective but at the same time they are dangerous. Why? Because gases are finer than particles. If a mask is so porous or loose-fitting that it lets disease carrying aerosols into the air as freely as if you were not wearing it at all, there is no way that it can trap CO2 or keep you from taking in Oxygen. If it is so tight and non-porous that it traps CO2 and won’t let in oxygen, there is no way it is letting even a single aerosol into the air.

Ironically, Rancourt accuses those  advocating for masks of manipulating people’s fear. But, at the same time, he is arguing that having a cloth over your face is deadly and dangerous. There have been, as of this writing, 648,000 confirmed deaths from COVID worldwide. The real number is likely higher.[87] There have been zero confirmed deaths from people wearing masks. And healthcare workers have been wearing them, for hours a day, for a century. But Rancourt wants you to be afraid of masks? Who, I ask you, is stoking irrational fears?

Conclusion

Before the debate, I half expected Rancourt to argue that masks can’t help stop the pandemic because there is no pandemic. As he said in a YouTube video.[88]

This year, this winter, under COVID 19, there have not been more deaths than usual…Is something special happening? It’s not. That’s the first point I want to make. This is not a killer pathogen that is unusual in terms of how many deaths it causes.”

Of course, the fact that COVID didn’t really take off with gusto until the winter was almost over (for example, the first 100 deaths didn’t happen in the U.S. North America until March 17, and winter ends on March 20) makes his claim about there being no “winter burden” completely irrelevant to whether or not there truly is a pandemic. There was a huge winter burden, in places were the virus took hold early, and there was a huge number of excess deaths elsewhere in the spring. But that doesn’t keep him from concluding that…

Nothing special happened. It was a fake event, if you like, in the sense that it was given a special name and used in propaganda to frighten us to make us think that there was a particularly dangerous thing happening, that was very unusual, that was unseen previously. That’s all a big lie. I’m personally very convinced of this. I’ve looked at all the data…this has been a huge fabrication.

Now he is willing to admit there was a peak of deaths, in some places, after the pandemic was declared. This is what he calls “the COVID peak.” But about these peaks he says two things. First, it’s never big enough to actually make the total number of excess deaths rise.

“The area of the peak [of deaths] is not big, because it’s so narrow, so you don’t have a total number of extra deaths that’s significant.” 

According to Rancourt, a few people who would have died later just died a little bit sooner. So there is no pandemic.

What’s more, the peak was not due to COVID, but instead was the result of government lockdowns. We isolated them, stressed them out, and compromised their immune system. Never mind, of course, that states which didn’t do lockdowns are now seeing much worse outbreaks than those who did. Rancourt wants you to believe that the government only wants you to wear a mask to “hide its crimes.”

“How do you cover that up? You convince everyone that this was a really dangerous pandemic. What’s the best way to convince everyone that we really had a killer here?…well, convince them that they have to wear a face mask. If you as an individual are so frightened that you are going to put a face mask on in the middle of summer, you are personally investing in the belief of that lie. And that’s a powerful psychological way of convincing you that there was this danger….and [that] the government didn’t do anything wrong.”

Given the kind of thinker that such statements demonstrate Rancourt to be, I have no illusion about convincing him that that he is wrong. You can’t reason someone out of a position they didn’t reason themselves into. Doubting the scientific consensus is clearly part of his identity, and when a belief is tied to someone’s identity, presenting evidence against is likely just going to backfire.[89] Indeed, Rancourt seems to be the poster child for the Dunning-Kruger effect, and the fact that intelligence alone doesn’t make one adept at avoiding bad arguments–but instead, makes one better at creating fallacious (but seemingly convincing) arguments for false conclusions.[90] As an old philosophy professor once said of a fellow student of mine, “He’s just smart enough to be dangerous.” Indeed, I don’t want him to read this. All he will do is produce a whole list of ad hoc excuses to explain away his errors, or go on to mischaracterize a list of other studies.

My hope is simply that others will see this article, realize how clear cut the case for masks is, and how dishonest the arguments against them are—and then wear them until the pandemic is over. But if you are still not convinced, just think of it this way:

If you wear a mask but they don’t work, who have you hurt?

But if you don’t and they do—you are risking other people’s lives.

Don’t be that person.

Oh, and make sure your mask covers your nose.


[1] Denis G. Rancourt, “Masks Don’t Work: A Review of Science Relevant to COVID-19 Social Policy,” River Cities’ Reader, June 11, 2020, https://donotlink.it/OEv6x

[2] David Kyle Johnson, “Resolved: Public Mask Mandates Assist in Curbing the Spread of Covid-19,” Another Logical Take, July 24, 2020, https://davidkylejohnson.wordpress.com/2020/07/24/resolved-public-mask-mandates-assist-in-curbing-the-spread-of-COVID-19/.

[3] See Rick Kushman, “Your Mask Cuts Own Risk by 65 Percent,” UC Davis, July 6, 2020, https://www.ucdavis.edu/coronavirus/news/your-mask-cuts-own-risk-65-percent/. Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298  See WH Seto,et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6. and Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25, https://pubmed.ncbi.nlm.nih.gov/16014825/. Lijie Zhang, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseases 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765.  See Christian J. Kähler and Rainer Hain, “Fundamental Protective Mechanisms of Face Masks Against Droplet Infections,” Journal of Aerosol Science 148 (2020) https://doi.org/10.1016/j.jaerosci.2020.105617. C. Raina MacIntyre, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare 1Workers,” BMJ Open 5 no. 4, (2015) https://doi.org/10.1136/bmjopen-2014-006577.  This study suggested that 95% of viruses in aerosols could be blocked by homemade masks, and 97% could be blocked by surgical masks: Qing-Xia Ma, et al, “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805. This is a study out of Hong Kong which suggested that people wearing a mask was very effective at reducing transmission of alpha coronaviruses”; Nancy H. L. Leung, et al., “Respiratory Virus Shedding in Exhaled Breath and Efficacy of Face Masks,” Nature Medicine 26 (2020): 676-80, https://doi.org/10.1038/s41591-020-0843-2.

[4] See also WH Seto, et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6; see also Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25; Harvey Fineberg, Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020), (The National Academies Press, 2020), chapter 1 and 2, https://www.nap.edu/read/25769/chapter/1#2.

[5] Depending on your definition, aerosols range from around 100 microns to 0.1 micron. “Various sources will put the cutoff at 2 µm, 5 µm, 10 µm, 20 µm, or even 100 µm.” Justin Morgenstern, “Aerosols, Droplets, and Airborne Spread: Everything You Could Possibly Want to Know,” First10EM, April 6, 2020, https://first10em.com/aerosols-droplets-and-airborne-spread/. For simplicity, I’ll define aerosol as a droplet that is 10 µm in size. Brownian motion dominates in particles less than 0.3 µm in size. 

[6] Talib Dbouk and Dimitris Drikakis, “On Respiratory Droplets and Face Masks,” Physics of Fluids 32, no. 063303, published electronically June 16, 2020, https://doi.org/10.1063/5.0015044. Bhanu Bhakta Neupane, Sangita Mainali, Amita Sharma, and Basant Giri, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks,” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

[7] Cloth masks of only one material seem to have very little effectiveness: Samy Rengasamy, Benjamin Eimer, and Ronald E. Shaffer, “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles,” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044. This is why those who are just wearing bandanas or pulling their t-shirt over their mouth, are not doing anyone much good.

[8]  Both types “significantly reduced the number of microorganisms expelled by volunteers,” “the surgical mask was 3 times more effective.”) Anna Davies, et al., “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (August 2013): 413-8, https://doi.org/10.1017/dmp.2013.43;  Milton (2013) found that surgical masks decreased emission of large particles by 25 fold, and aerosols by 3 fold in flu patients. See Donald K Milton, et al., Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks,” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205.

[9] Aydin et al. (2020), suggests that layering greatly increases the filtering efficiency of cloth masks while also maintaining some breathability, Onur Aydin, et al., “Performance of Fabrics for Home-Made Masks Against the Spread of Respiratory Infections through Droplets: A Quantitative Mechanistic Study,” medRxiv,preprint, submitted July 8, 2020  https://doi.org/10.1101/2020.04.19.20071779.

            [10] Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

[11] “Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.” Konda, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks.”

[12] Dr. Marty, a professor of infectious diseases at Florida International University told Good Morning America “But if you add that filter, then you’re also adding a really good protection for yourself.” See Becky Worley, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe, “Face Masks With Filter add Another Layer of Protection, Experts Say,” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

[13] This is actually what N95 masks are named for; they protect their wearer by being 95% effective at filtering the air that a person breathes in. And because they often have unfiltered exhaust vents, they usually don’t filter the air a person breathes out. Combine that with the fact that they don’t even perform their intended function well unless they are perfectly fit, and you can realize why they should likely only be worn by health care workers in high risk environments.

[14] Some clarification here is useful. Technically, depending on how you classify “aerosols” (definitions range from 5 microns to 100 microns), most of  the particles you breath out could be classified as aerosols–and depending on their size, the mask will filter them with different efficiencies. Even cloth masks are very good at filtering down to 10 microns, pretty good down to 5 microns, but not great below 5. Neupane, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.”

In one way, this is concerning because according to Burch (2020), the average size for aerosols leaving your mouth is 3 microns.  The good news is, despite the fact that they make up the largest number, they only represent 0.00024% of the liquid leaving your mouth during a cough. Consequently, very few of them are infected (at worst 1 out of every 700). A full 99.99976% of the viruses sprayed during a cough are carried in droplets — not aerosols.’) So the majority of transmission happens from droplets.  What’s more, the deadliest aerosols are those that started out as droplets, but then evaporated down; they have higher concentrations of the virus. Masks catch those. So the inability of masks to filter out 0.3 micron particles does not greatly hinder their ability to keep infected particles out of the air, and thus does not prevent them from efficiently preventing the spread of COVID.
                Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” The Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

[15] From the abstract of: Richard O. J. H. Stutt, Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin, “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic,” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

[16] Wycliffe E Wei, Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee, ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020,” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

                [17]Anthony D Sung, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial,” Clin Infect Dis 63, no. 8 (October 2016): 999-1006, https://doi.org/10.1093/cid/ciw451. Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/ 10.1001/jama.2020.12897. In this study, cases of COVID-19 declined after mask mandates were put into effect in hospitals (that required all health care workers and patients to mask up). The study concluded that such mandates reduce the transmission of SARS-CoV-2.

[18] Timo Mitze, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde, “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach,” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

This study shows the impact of mask mandates in Germany. In Jena, for example, the first German city to enact such a mandate, COVID-19 cases fell by almost 25% in 20 days. The study concluded that similar mandates could ruse the daily growth rate by 40% in the long term, although it did acknowledge that, outside Germany, different norms and climatic conditions in other countries might result in different protective outcomes.

                [19] “HSC COVID-19 Report #5 – July 20, 2020,” University of North Texas Health Science Center at Fort Worth, https://www.scribd.com/presentation/469858261/COVID-19-Report-July-20-Updated?fbclid=IwAR1ta8C-x5yYfpqQ5eghmiPFr42ndbA6rYCmTv3WbcGU9tDt3a_RU1BOIL0.

[20] In those 15 US States, they likely prevented up to 450,000 cases in under two months. Wei Lyu and George L. Wehby, “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” Health Affair 39, no. 8 (2020): 1-7, https://doi.org/ 10.1377/hlthaff.2020.00818.

This was a retrospective analysis which examined the effects that different governmental orders to wear face masks had on COVID-19 growth rates, from April 9-May 15, 2020. It estimated that they prevented between 230,000 and 450,000 cases by May 22 (a reduction of 14-27%).

[21] Kasra Zarei and John Duchneskie, “Coronavirus Cases Rise in States with Relaxed Face Mask Policies,” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/COVID-19-coronavirus-face-masks-infection-rates-20200624.html.

                [22] American Thoracic Society, “Countries with Early Adoption of Face Masks Showed Modest COVID-19 Infection Rates,” Medical Xpress, June 24, 2020, https://medicalxpress.com/news/2020-06-countries-early-masks-modest-COVID-.html.

                [23] Joseph Berger, “Death Drops 27% With State’s Seat-belt Law, The New York Times, May 1, 1985, https://www.nytimes.com/1985/05/01/nyregion/death-drops-27-with-state-s-seat-belt-law.html.

                [24] Samantha M. Tracht, Sara Y. Del Valle, and James M. Hyman, “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1),” Plos One 5, no. 2 (February 2010): 1-12, doi.org/10.1371/journal.pone.0009018.

[25] Stutt, et al., “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.”

To keep the infection rate (R0) below 1.0, the authors argue for widespread use of face masks. “[F]acemask adoption by entire populations would have a significant impact on reducing COVID-19 spread.” “[I]n summary, our modelling analyses provide support for the immediate, universal adoption of facemasks by the public.”

[26] Derek K Chu, et al., “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-analysis,” The Lancet 395, no. 10242 (2020): 1973-87, https://doi.org/10.1016/S0140-6736(20)31142-9.

This was a review of 172 observational studies and 44 relevant comparative studies. The authors concluded “Face mask use could result in a large reduction in risk of infection.”

[27] Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley, “Reducing Transmission of SARS-CoV-2,” Science 368, no. 6498 (June 2020): 1422-24, https://doi.org/10.1126/science.abc6197. In this paper, aerosol chemists and an infectious disease specialist argue that, because “airborne spread from undiagnosed infections will continuously undermine the effectiveness of even the most vigorous testing, tracing and social distancing programs,” the widespread use of masks are necessary to help prevent the spread of COVID. Both analytical information about the virus and information about countries where masks are commonplace was used.

Catherine M. Clase, et al., “Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Annals of Internal Medicine, published electronically May 22, 2020, https://doi.org/10.7326/M20-2567. This study, done by an international research team of medical doctors and other medical specialists not only concluded that cloth masks worn by the public will reduce COVID-19 transmission rates but that the benefits of widespread mask use outweigh any risks that may be brought about by wearing masks (such as improper use).

                [28] M. Joshua Hendrix, Charles Walde, Kendra Findley, and Robin Trotman, “Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy – Springfield, Missouri, May 2020,” Weekly 69, no. 28 (July 1, 2020): 930-32, http://dx.doi.org/10.15585/mmwr.mm6928e2.

[29] “New IHME COVID-19 Model Projects Nearly 180,000 US Deaths,” IHME,June 24, 2020, http://www.healthdata.org/news-release/new-ihme-COVID-19-model-projects-nearly-180000-us-deaths.

[30] For the quote, see McCabe, “Face Masks Really Do Matter.” For the evidence behind it, see John T. Brooks, Jay C. Butler, Robert R. Redfield, “Universal Masking to Prevent SARS-CoV-2 Transmission – The Time is Now,” Jama, published online July 14, 2020, https://doi.org/10.1001/jama.2020.13107.

[31] For more such evidence, see “Face Masks – A Summary of Relevant Research Papers for COVID-19,” Sound Reason & More,June 11, 2020, https://soundreasonandmore.wordpress.com/2020/06/11/face-masks-a-summary-of-relevant-research-papers-for-COVID-19/.

[32] Leung et al. 2020. Respiratory virus shedding in exhaled breath and efficacy of

face masks. Under review. DOI: 10.21203/rs.3.rs-16836/v1.

                [33] Markus MacGill, “What is a Randomized Controlled Trial?” Medical News Today, December 4, 2018, https://www.medicalnewstoday.com/articles/280574.

                [34] Rebecca A. Clay, “More than One Way to Measure,” American Psychological Association 41, no. 8 (September 2010): 52, https://www.apa.org/monitor/2010/09/trials; Roger Mulder, et al., “The Limitations of Using Randomised Controlled Trials as a Basis for Developing Treatment Guidelines,” Evidence-Based Mental Health 21, no. 1 (2018): 4-6, http://dx.doi.org/10.1136/eb-2017-102701.

                [35] Ibid.

[36] See Sergey A. Grinshpun, et al., “Performance of an N95 Filtering Facepiece Particulate Respirator and a Surgical Mask During Human Breathing: Two Pathways for Particle Penetration,” Journal of Occupational and Environmental Hygiene 6, no. 10 (2009): 593-603, https://doi.org/10.1080/15459620903120086. See also C. Raina MacIntyre, et al., “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers,” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17, https://doi.org/10.1111/irv.12474. See also Mark Loeb, et al., “SARS among critical care nurses Toronto,” Emerg Infect Dis 10, no. 2 (Feb 2004):251-5, https://doi.org/10.3201/eid1002.030838; C. Raina MacIntyre and Abrar Ahmad Chughtai, “A Rapid Systematic Review of the Efficacy of Face Masks and Respirators Against Coronaviruses and Other Respiratory Transmissible Viruses for the Community, Healthcare Workers and Sick Patients,” Int J Nurs Stud, published online April 30, 3030, https://doi.org/10.1016/j.ijnurstu.2020.103629.

                [37] David Kyle Johnson, “Confirmation Bias,” in Bad Arguments: 100 of the Most Important Fallacies in Western Philosophy, eds. Robert Arp, Steven Barbone, and Michael Bruce (Wiley Online Library, May 2018), https://doi.org/10.1002/9781119165811.ch17.

                [38] Rancourt, “Masks Don’t Work.”

                [39] Ibid.

[40] See Sergey A. Grinshpun, et al., “Performance of an N95 Filtering Facepiece Particulate Respirator and a Surgical Mask During Human Breathing: Two Pathways for Particle Penetration,” Journal of Occupational and Environmental Hygiene 6, no. 10 (2009): 593-603, https://doi.org/10.1080/15459620903120086. See also MacIntyre, et al., “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers.” See also Loeb, “SARS among critical care nurses, Toronto.”

                [41] Ibid.

                [42] Adam Hayes, “Law of Diminishing Marginal Returns,” Investopedia, June 14, 2020, https://www.investopedia.com/terms/l/lawofdiminishingmarginalreturn.asp.

                [43] Jeffrey D. Smith, et al., “Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers from Acute Respiratory Infection: a Systematic Review and Meta-analysis,” CMAJ 188, no. 8 (May 2016): 567-74, https://doi.org/10.1503/cmaj.150835.

                [44] Vittoria Offedu, et al., “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis,” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42, https://doi.org/10.1093/cid/cix681.

                [45] Lewis J. Radonovich, Michael S. Simberkoff, and Mary T. Bessessen, “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial,” JAMA 322, no. 9 (2019): 824–833, https://doi.org/10.1001/jama.2019.11645.

                [46] Youlin Long, et al., “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis,” J Evid Based Med 13 (2020): 93-101, https://doi.org/0.1111/jebm.12381.

                [47] Faisal bin-Reza, Vicente Lopez Chavarrias, Angus Nicoll, Mary E. Chamberland, “The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence,” Influenza and Other Respiratory Viruses 6, no. 4 (December 2011): 257, https://do8i.org/ 0.1111/j.1750-2659.2011.00307.x.

                [48] Ibid.

[49] B.J. Cowling, Y. Zhou, D.K.M.Ip, G.M.Leung, and A.E. Aiello, “Face Masks to Prevent Transmission of Influenza Virus: A Systematic Review,” Epidemiology & Infection 138, no. 4 (January 2010): 449-56, https://doi.org/10.1017/S0950268809991658.

                [50] B.J. Cowling, et al., “Face Masks to Prevent Transmission of Influenza Virus: A Systematic Review.”.

                [51] You can find a very similar conclusion in this “study” on parachute effectiveness. Robert W Yeh, et al., “Parachute Use to Prevent Death and Major Trauma when Jumping from Aircraft: Randomized Controlled Trail,” BMJ 363 (December 2018) https://doi.org/10.1136/bmj.k5094.

                [52] Jeffrey Shaman, Virginia E. Pitzer, Cécile Viboud, Bryan T. Grenfell, and Marc Lipsitch, “Absolute Humidity and the Seasonal Onset of Influenza in the Continental United States,” PLOS Biology 8, no. 2 (February 2010) https://doi.org/10.1371/journal.pbio.1000316

                [53] Rancourt, “Masks Don’t Work.”

                [54] Ibid.

                [55] Bo Bennett, “Oversimplified Cause,” Logically Fallacious, https://www.logicallyfallacious.com/logicalfallacies/Oversimplified-Cause-Fallacy.

                [56] Quote from: Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/.

                [57] For her study on this, see Rachel E. Baker, Wenchang Yang, Gabriel A. Vecchi, C. Jessica E. Metcalf, and Bryan T. Grenfell, “Susceptible Supply Limits the Role of Climate in the Early SARS-CoV-2 Pandemic,” Science 369, no. 6501 (July 17, 2020): 315-19, https://doi.org/10.1126/science.abc2535.  

                [58] Derek Hawkins, Michael Birnbaum, Meryl Kornfield, Siobhán O’Grady, Kareem Copeland, Marisa Iati, and Felicia Sonmez, “Arizona, Florida, Texas are Latest Coronavirus Epicenters,” The Washington Post, June 29, 2020, https://www.washingtonpost.com/nation/2020/06/28/coronavirus-live-updates-us/.

[59] Harvey Fineberg, Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020), (The National Academies Press, 2020), chapter 1 and 2, https://www.nap.edu/read/25769/chapter/1#2.

                [60] Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

                [61] See Zeshan Qureshi, et al., “What is the Evidence to Support the 2-metre Social Distancing Rule to Reduce COVID-19 Transmission?” CEBM, June 22, 2020, https://www.cebm.net/COVID-19/what-is-the-evidence-to-support-the-2-metre-social-distancing-rule-to-reduce-COVID-19-transmission/.

                [62]  It is also important to understand that although the majority of the droplets produced by a cough may be small enough to stay airborne, their small size means that collectively they add up to only a tiny fraction of the volume produced (perhaps less than 0.1%), and therefore only a tiny fraction of the total virus spread.

                [63] Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-COVID-19-from-aerosols-6c97d023bb6d.

                [64] Tia Ghose, “How Are People Being Infected With COVID-19?” Live Science, April 7, 2020, https://www.livescience.com/how-COVID-19-spreads-transmission-routes.html.

                [65] Erin Bromage, “The Risks – Know Them – Avoid Them,” Erin Bromage, May 6, 2020, https://www.erinbromage.com/post/the-risks-know-them-avoid-them.

                [66] Rancourt, “Masks Don’t Work.”

                [67] Harper does not appear in his bibliography, so I was unable to verify if Rancourt was misrepresenting his research.

                [68] Bo Bennett, “Appeal to Possibility,” Logically Fallacious, https://www.logicallyfallacious.com/logicalfallacies/Appeal-to-Possibility.

                [69] Rancourt, “Masks Don’t Work.”

                [70] Tuomas W. Manninen, “Appeal to Personal Incredulity,” in Bad Arguments: 100 of the Most Important Fallacies in Western Philosophy, eds. Robert Arp, Steven Barbone, and Michael Bruce (Wiley Online Library, May 2018), doi: 10.1002/9781119165811.ch17.

                [71] Rancourt, “Masks Don’t Work.”

                [72] Eric Litke, “Fact Check: No, N95 Filters are Not Too Large to Stop COVID-19 Particles,” USA Today, June 11, 2020, https://www.usatoday.com/story/news/factcheck/2020/06/11/fact-check-n-95-filters-not-too-large-stop-COVID-19-particles/5343537002/.

[73] Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

                [74] Rancourt, “Masks Don’t Work.”

                [75] Saber Yezli and Jonathan A. Otter, “Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment” Food and Environmental Virology 3 (2011): 1-30, https://doi.org/10.1007/s12560-011-9056-7.

                [76] Ibid.

                [77] Mark P. Zwart, Lia Hemerik, Jenny S. Cory, J. Arjan G.M. de Visser, Felix J.J.A. Bianchi, Monique M. Van Oers, Just M. Vlak, Rolf F. Hoekstra, and Wopke Van der Werf, “An Experimental Test of the Independent Action Hypothesis in Virus– Insect Pathosystems,” Proceedings of the Royal Society B (March 2009) http://doi.org/10.1098/rspb.2009.0064.

                [78] Prasith Baccam, Catherine Beauchein, Catherine A Macken, Frederick G Hayden, and Alan S Perelson, “Kinetics of Influenza A Virus Infection in Humans,” Journal of Virology 80, no. 15 (August 2006): 7590-99, https://doi.org/ 10.1128/JVI.01623-05; Christopher B Brooke, William L Ince, Jens Wrammert, Rafi Ahmed, Patrick C Wilson, Jack R Bennink, and Jonathan W Yewdell, “Most Influenza A Virions Fail To Express at Least One Essential Viral Protein,” Journal of Virology 87, no. 6 (March 2013): 3155-62, https://doi.org/10.1128/JVI.02284-12.

                [79] Yinon M Bar-On, Avi Flamholz, Rob Phillips, and Ron Milo, “SARS-CoV-2 (COVID-19) by the Numbers,” eLife 9, publihsed online April 2, 2020, https://doi.org/10.7554/eLife.57309.

                [80] Burch, “A Microscopic Perspective on Airborne COVID-19.”

                [81] Carl Heneghan, Jon Brassey, and Tom Jefferson, “SARS-CoV-2 Viral Load and the Severity of COVID-19,” CEBM, March 26, 2020, https://www.cebm.net/COVID-19/sars-cov-2-viral-load-and-the-severity-of-COVID-19/.

                [82] Bo Bennett, “False Dilemma,” Logically Fallacious, https://www.logicallyfallacious.com/logicalfallacies/False-Dilemma.

                [83] Rancourt, “Masks Don’t Work.”

                [84] Angus Deaton and Nancy Cartwright, “The Limitations of Randomised Controlled Trials,” VoxEU CEPR, November 9, 2016, https://voxeu.org/article/limitations-randomised-controlled-trials; Dennis Zeilstra, Jessica A. Younes, Robert J. Brummer, and Michiel Kleerebezem, “Perspective: Fundamental Limitations of the Randomised Controlled Trial Method in Nutritional Research: The Example of Probiotics,” Advances in Nutrition 9, no. 5 (September 2018): 561-71, https://doi.org/10.1093/advances/nmy046.

                [85] Clay, “More than One Way to Measure”; Alexander Krauss, “Trials and Errors: The Limits of Randomised Controlled Trials,” Campbell Collaboration, May 16, 2018,https://campbellcollaboration.org/blog/trials-and-errors-the-limits-of-randomised-controlled-trials.html.

                [86] Holly Secon, ”If Everyone in the US Wears a Mask in Public, 33,000 Lives Could Be Saved Over the Next 3 Months, One Model Suggests,” Business Insider, June 26, 2020, https://www.businessinsider.com/wearing-face-masks-could-save-33000-us-lives-2020-6; Megan Cerullo, “Everyone Wearing Face Masks Could Save America From a $1 Trillion GDP Loss,” CBS News, July 9, 2020, https://www.cbsnews.com/news/face-mask-wearing-save-money/.

                [87] Steven Novella, “COVID-19 and Excess Deaths,” Science-Based Medicine, July 22, 2020, https://sciencebasedmedicine.org/COVID-19-and-excess-deaths/.

[88] https://donotlink.it/qgwv9

                [89] “Backfire Effect,” RationalWIki, https://rationalwiki.org/wiki/Backfire_effect.

                [90] “Dunning-Kruger Effect,” Rational Wiki, https://rationalwiki.org/wiki/Dunning-Kruger_effect/.

On Masks: Notes for Rebuttal

These are the responses to the arguments I suspected Rancourt would give in my argument with him about the effectiveness of mask mandates. This is not all proofed and formalized; but I share it in hopes that someone else can make use of these arguments and sources.

On Aerosols

Short version: Rancourt argument only even potentially works on the assumption that the smallest aerosols are the only method of infection, and that masks can’t block such aerosols. But these assumptions are baseless. First, as I showed in my opening argument, because of Brownian motion, even cloth masks can catch some of the smallest aerosols. And they only need to catch some to reduce risk and thus mitigate spread. After all, their virial load is the smallest. Second, the current evidence points to droplets being the main source of transmission, and there are no published peer-reviewed papers that clearly define the role of aerosols in transmission, much less that even argue that it is the main one. I am not ruling that aerosols play some role—but if they do, we know it’s probably not the main role, and we don’t know how major its role is. (If it was, it would probably be as contagious as the measles—and it’s not.) What’s more, even if these assumptions are true, and aerosols are the main source, masks still help a lot! Most importantly, they capture the larger droplets that would evaporate and become even more potent and infectious aerosols—which is where most of the virus expelled by the person in aerosol form would be. If Rancourt really thinks people inhaling aerosols does all the infecting, then he should love masks, because they prevent most droplets from being aerosolized. And even for those droplets that start out small (which only have a 1/700 chance of being infected anyway), even if masks don’t filter them, masks would generally keep them close to the person’s face while breathing, and from being propelled as far when coughing or sneezing. Thus Rancourt “it’s the aerosols stupid” argument fails utterly.

Rancourt is likely to claim that cloth masks’ ability to catch infected droplets is irrelevant to their ability to help prevent the spread of COVID because COVID is spread primarily, even solely, through aerosol transmission. There are 7 things to say in response to this, each of which separately defeats this argument entirely.

  • It is demonstrably false that COVID spreads solely through aerosol transmission; we know that it can spread through droplets.[1] Consequently, since masks capture droplets, masks do reduce the spread of COVID.
  • It’s entirely possible that droplets is the primary mode of transmission. According to Dr. Jeffry Martin, “persons who have a member of their household infected with the virus have a higher probability of getting infected with COVID …This tells us that close contact is the most important factor.” [2] And that suggests droplet transmission. [Although they have been a bit behind on the science, both the CDC[3] and WHO[4] agree.] And if it is, since cloth masks will greatly reduce the number of droplets “shared” during such an interaction, cloth masks will greatly reduce the chance of transmission.
  • And even if it is by sharing aerosols that infection is transferred in close interactions,[5] that doesn’t mean masks don’t help. The fact that longer interactions are more risky means that, if it is aerosols, the number of aerosols you are exposed to matter—either because of viral load or risk of exposure. Masks, by reducing the number of aerosols and the velocity by which they leave your mouth, will reduce the number of aerosols an infected person exposes others too—and thus reduce risk.
  • In fact, while there are some anecdotes which suggest that COVID might also be transmissible through aerosols,[6] it may only be to those who are susceptible (because the viral load is low in aerosols), and there are no reliable studies or evidence right now that clearly define the role of aerosols in the transmission of COVID. As Dr. Josh Santarpia put it, “To my knowledge, there is no definitive evidence of transmission where aerosol was the only possible route.”[7] (Indeed, Santarpia argues that, since the 6  foot rule is outdated and probably too conservative, the anecdotes could easily be explained by respiratory droplet transmission.[8]) I don’t mean to rule out that it has a role, and there should definitely be more study—but as it stands, there is literally no peer reviewed literature that clearly defines the role of aerosol transmission of COVID[9]—much less any proving that it is the primary or sole mechanism. Since Rancourt is so keen on demanding RCTs of everything, he needs them for his. Without them, since it’s an assumption upon which his entire argument relies, his argument fails.
  • While it is true that, numerically speaking, aerosols likely make up the majority of the particles that exit your mouth, they only make up a tiny fraction of the material that leaves you mouth.[10] Most of that is droplets. What’s more, given the way the viruses distribute in bodily fluids, even in worse case scenarios, a very small proportion of aerosols will be infected—only about 1 in every 700. (On average, each larger droplets contains 70.) And the deadliest areoles are those that start out big (and then evaporate), and thus have more virus in them—but because they start out big, they much more likely to be blocked by masks.[11] 
  • It’s false that masks don’t block aerosols. Depending on your definition, aerosols range from around 100 microns to 0.1 micron.[12] The studies I have cited show that even the worst masks do a pretty good job (are about 90% efficient) at filtering particles larger than 10 microns. Multi layered and mix fabric masks, and surgical masks, can do that well all the way down to 0.3 microns—and are still 80% effective with even smaller particles. (The same machines that measure HEPA filters are used for these tests.) Again, because particles that small are not likely to be infected, and won’t be very “potent” if they are, cloth masks being less efficient in this regard is practically irrelevant to their ability to reduce risk and thus mitigate the spread of COVID. Masks greatly reduce the amount of infected particles in the air, and thus greatly reduce the probability of infection.  
  • Think of it this way, even if 10 micron and lower aerosols are the only mode of transmission, masks can reduce risk. On that assumption, sharing aerosols is what makes long personal interactions more risky, and the reason they would be more risky is because the more aerosols you are exposed to, the more likely you are to be infected—either because of increased viral load, or increased risk of inhalation. Since most masks can filter even the 10 micron particles to some degree, they reduce risk. And even if they can’t, they still block the larger more potent droplets and prevent them from evaporating and becoming more potent 10 micron aerosols. And since those particles are what are carrying majority of the viral load, masks would still greatly reduce risk.[13]

On Brownian Motion

Rancourt claims that masks can’t filter smaller particles because they are too small to be caught by the pores in masks—even N95 masks. This demonstrates an ironic fundamental misunderstanding of the physics involved. Because of the way the way they interact with atom and molecules in the air, particles that are smaller than 0.3 mirons don’t travel in straight lines—they are bounced around wildly. Consequently, when they try to go through a mask, they can’t get through… they bounce around inside the material of the mask until they are caught. This is definitely true of N95 masks, but even single layer woven cotton masks with pores. More, of course, will get through…but many of them are trapped.

It’s the particles that are 0.3 microns that are hardest to capture; they are the smallest particle not dominated by Brownian motion. So they will travel in a straight line, and have a better chance at making it through the mask. This is why having non-woven, or multi-layered material, is so important. It makes the pathways the particles must travel more convoluted, and thus makes them more likely to not be able to get through and be captured. Cloth masks designed in this way gave been shown to capture around 80% of such particles; which is not as good as N95 masks, but is more than enough to be beneficial.

As a friend told me, “[Rancourt] is thinking as if the mask was working like a sieve and he should know better. Physics is not intuitive outside the scale at which we have developed our intuition about physics, the human scale, measured in meters. At the microscopic level, it is very different. The masks are tested with 0.3 µm particles because at the atmospheric pressure, fluid mechanics tells us it is the size that will follow the movement of air through the mask and thus these particles can go through, but inefficiently (blocked > 95%). Together with ballistic for larger droplet and brownian motion for smaller one, the other sizes hit the mask fibers. If these fibers are paper or similar material, the liquid gets absorbed and the virus stuck on the fiber, if pure plastic, the water gets dispersed differently but the virus sticks to the mask. If the droplet has dried and you have a dry nuclei, Van der Waals force or electrostatic force will keep the virus stuck to the fibers.

Humidity Argument (4 min)

Short version (1:30). Rancourt uses Shaman to argue that lower humidity in the winter explains season variation in the flu, and concluded from this that masks can’t help mitigate the spread of COVID. But (1) Shaman has said it’s too early to how humidity affects COVID, and Princeton University’s Rachel Baker, who studies how climate affects infection disease for a living, published a paper in Science which says that, “in a pandemic like the one we’re in now, what decides how quickly the new virus spreads is how many people are susceptible, or not immune, to it. Climate would play a bigger role only as more people become immune.”[14]  (2) The fact that COVID is spreading like wildfire in Texas and Florida in July is pretty much proof that she is right. And if she’s not, and humidity is a major factor, we need to wear masks even more! As The humidity drops, masks will be even more important—because large and larger droplets will become aerosolized, and masks catch those. (2) Rancourt’s argument relies on false assumptions about aerosols being the only mode of infection, and masks being unable to block them. And (3) Rancourt is committing the oversimplified cause fallacy. The fact that humidity plays a role in transmission doesn’t mean that it is the only cause, and thus doesn’t mean that changes in humidity are the only thing that can affect transmissibility. To illustrate the fallacy, imagine if we decided to lock everyone in their room for a month to mitigate the spread. That would be a bad idea for many reasons—but it would mitigate spread. Now imagine someone said it won’t because it doesn’t change the humidity. … Rancourt’s “it’s the humidity stupid” argument is fundamentally flawed.

Rancourt argues that if lower humidity in the winter is what explains season variation in the flu, masks can’t help mitigate the spread of COVID. There are 3 major flaws with this argument.

  • He only mentions one study: Shaman 2010. He would need to show that this theory has become the consensus view among the relevant scientists to meet the burden of proof to even get this argument off the ground; he has not.
  • Again, Shaman himself has admitted (in an article for PBS’s WHYY) that we don’t know enough about COVID to conclude that humidity is a factor in its transmission. Others have argued that it likely is not—at least, not yet. From the article:

“Rachel Baker, lead author of a new article in Science and a researcher at Princeton University who studies how climate affects infectious disease, said the main conclusion is that in a pandemic like the one we’re in now, what decides how quickly the new virus spreads is how many people are susceptible, or not immune, to it. Climate would play a bigger role only as more people become immune.”

The fact that COVID is spreading like wildfire in humid Texas and Florida (and non-humid Arizona) in July, seems to show that she is exactly right. But even if aerosols and humidity is a major factor in transmission at this point, then we have even more reason to wear masks because, not only do they filter aerosols, BUT LOOK AT HOW INFECTIOUS IT IS EVEN IN THE HUMID SUMMER! We have to do everything we can to mitigate the spread in the coming non-humid winter months.

  • This argument only works on the assumptions that COVID spreads solely via aerosols and masks don’t filter them; only then would adjusting the humidity (and thus the number of infected aerosols in the air) be the only way to slow spread. But both of these assumptions are false. I explained in my opening statement about how masks block aerosols; I can say more later. But humidity’s effect on aerosols being the explanation for seasonal variation of the flu wouldn’t entail that illness only spreads through aerosols. Such illnesses are transmitted many ways, like through close contact and droplets, all year round. There will be a baseline of infection due to that. The humidity affecting other modes of infection, like aerosols, would bring the number of infections above baseline at certain times of years—but that doesn’t mean it’s the only mode on infection. What’s more, if you can bring down the baseline by mitigating the other ways it spreads (e.g., by wearing masks), you will bring down the total number of infections—even if you can’t keep it from raising above that baseline when the humidity drops. As the WHYY article put it:

The spread of a virus depends on both environmental conditions like temperature and humidity and the mechanism of people who are infected spreading it to people who are susceptible. The new paper in Science takes both things into account, to lead to a more biological and realistic view of how COVID-19 could spread, said Pamela Martinez, postdoctoral research fellow at … the Harvard School of Public Health. “When you observe the dynamics, the long-term temporal changes, of these diseases, you will observe a mix of what is happening in terms of: the number of susceptible, the number of infected, their behavior, how they are contacting; but also how the environment is playing into a role in this transmission rate.”

In other words, this argument commits the “oversimplified cause” fallacy—it wrongly concludes that a mere “contributing factor” is “the only factor” and thus the cause. Take a first-time skier, for example. He goes out the first day and comes back soaked to the bone. Undeniably, the snow made him wet. But if he just shrugged his shoulders and said “Well, if I’m going to ski, there is going to be snow, so I guess I’ll just have to be soaked every day,” we would call him a fool. A simple pair of rubber ski pants will keep him dry. The snow is not the only reason he got wet. Wearing clothes that soak up water was too. In the same way, low humidity may make aerosols worse in the winter, and cause seasonal spokes, but that’s not the only mode of transmission; droplets are too. So restricting them with masks can reduce transmission. Add to that the fact that masks can block aerosols, and Rancourt’s “It’s the humidity stupid” argument is transparently shortsighted and naive.

Debunking the Humidity Argument Again (2 min)

Another way to put it/More direct analogy: When I drew the analogy about the skier, I was not trying to compare snow with viruses; I was demonstrating Rancourt’s logical mistake. The fact that some thing X is even the main cause of a problem Y doesn’t mean that the only way to solve Y is by removing or changing X; because causation is complex, usually the problem can be mitigated by taking some other precaution, or action, Z. For example, the fact that a river’s physical attributes are primarily what determine its speed doesn’t mean that you can stop it by building a dam.  Likewise, even if a lack of humidity in the winter has been the main cause of winter viral spread in the past (and you can’t change the humidity), that doesn’t mean that you can’t mitigate the spread of the virus by taking some other precaution (like mandating masks).

To use a more direct analogy, suppose we tried to mitigate the spread of the flu by locking everyone in the world in their home, in separate rooms, for two months. This would of course be overly draconian, and a really bad idea for multiple reasons–but it undoubtedly would stop the spread, and indeed mostly likely wipe out the disease. It would run its course in all infected persons, either killing them or being killed by their immune systems, and then be done. Right? Of course!

But notice how stupid someone would seem if they came out and said, “such efforts will have no effect at all on the spread of the disease at all because isolating people won’t affect the humidity.” Even if humidity is normally a major factor in transmission, and explains seasonal variation, there are other things at play: like how we are exposed to others who are infected. If we limit that exposure by locking everyone in their room–or, less drastically, we simply encourage people to social distance and wear masks–we will lessen the spread–even if the humidity levels are unaffected. So Rancourt’s argument here suffers from the most basic of logical flaws: he simply failed to recognize that there is more than one causal factor when it comes to viral spread. In logic, we call this the fallacy of oversimplified cause.[15]

“Protect the Wearer” studies. (inhale= exhale)

Short version: Rancourt argues that his studies that prove masks don’t protect the health care workers (by filtering inhalations) entails that they can’t prevent source spread (by filtering exhalations). But (1) Some newer studies (Wang, 2020 suggest that masks do provide a modest protective benefit.[16] (2) The studies Rancourt cites don’t prove masks can’t protect health care workers; they only showed that the studies reviewed, which were usually flawed, don’t prove they do. Some such reviews (Xiao) were also unable to find proof that handwashing is effective; but I’m not going to stop washing my hands! (3) Studies can only show what they were designed to show. A study on whether a mask filters inhaled air might motivate one that studies how it filters exhaled air—but it cannot prove anything about how it filters exhaled air. (4) the air in health care settings is very different than the air in an enclosed public place, and thus the results cannot be transferred. 

Objection: The studies that show masks can’t protect their wearer entail that they also can’t filter breath.

In my opening statements, I pointed out that the studies that Rancourt cited, which suggest that surgical masks don’t offer enough protection to health care workers in high risk environments (by adequately filtering the air they breathe in), is irrelevant to whether or not cloth masks can adequately filter the air a person breathes out in the public. In reply, Rancourt might suggest that studies which show that masks can’t “filter in” also show that they can’t “filter out,” because “it’s just all about air flow through the mask in either direction.” This argument has 3 major flaws.

  1. Some newer studies suggest that masks do provide a modest protective benefit. [17] 
  2. Scientific studies cannot show anything beyond what they were designed to show. If a study is meant to test whether a mask can protect its wearer, then whether it does is the only conclusion one can draw. After all, the reason it can’t offer such protection may or may not be due to its “filtering in” capabilities. But even if it is, a separate study would be needed to determine it’s “filtering out” capabilities. A “filter in” study could “motivate” one to perform a “filter out” study, but it cannot be used to draw conclusions about whether masks can filter outgoing air. This is just basic philosophy of science; it is unscientific to claim that a study proves anything beyond what it was intended to demonstrate. 

To help illustrate Rancourt’s mistake, consider an analogy. Suppose you claim that condoms help prevent pregnancy. I say you’re wrong and cite a study that shows that the pregnancy rate among males who wear condoms is the same as in those who don’t. The results of that study are no doubt accurate, but they are also completely irrelevant to the issue at hand. By saying condoms help prevent pregnancy, you were saying that it helps prevent pregnancy in women. A study about the pregnancy rate in men is irrelevant. Similarly, if public health officials say that you wearing a mask helps protect others, citing a study saying that you wearing a mask doesn’t protect you, is irrelevant. In logic, we call this a non-sequitur.

  • Second, the air in a health care setting is considerably different than the air coming out of someone’s mouth. The air in, say, a hospital—given the number of infected people around—is much more likely to have many more infected small aerosol particles in it. Even if a mask can filter those with 80% efficiency, there will be enough to pose a significant risk. The spray coming out of an infected person’s mouth, however, is very different. Most of the virus is contained in droplets the mask will catch, and only 1 out of 700 aerosols in it are infected. Thus, even if masks can’t protect health care workers from being infected, they can and do help prevent an infected person from infecting others.

N95 vs Surgical Mask Studies

Short Version: Rancourt says that studies which show N95 masks to be equivalent to surgical masks entails that the very concept of masks as filters is flawed because, if there were any benefit, N95 would work better. But (1) There are plenty of studies that show they do work better, and (2) even if they don’t, that doesn’t mean that masks have no filter capabilities. With any protective equipment, there reaches a point where additional “layers” of protection are ineffective. For example, a 7mm think Kevlar vest will likely be just as effective as a 15mm one—that’s why they don’t make the latter. But that doesn’t mean that 1mm vests offer no protection, or that the concept of Kevlar as a bullet stopping material is flawed. And, again, (3) this is only about mask ability to filter inhaled air, not exhaled—they are not about source control—and so it is irrelevant.

In my opening statement I pointed out how the studies that Rancourt cites on whether N95 masks offer the same protection to their wearer as Surgical Masks are irrelevant to whether or not cloth masks can filter droplets and aerosols, and thus irrelevant to whether masks can help mitigate the spread of COVID 19. In his paper, however, he states:

if there were any benefit to wearing a mask, because of the blocking power against droplets and aerosol particles, then there should be more benefit from wearing a respirator (N95) compared to a surgical mask, yet several large meta-analyses, and all the RCT, prove that there is no such relative benefit.

If that conditional were true, the studies—while they still wouldn’t prove anything—would at least be relevant. But it is not. I explained this a bit in my opening statement; but let me elaborate more.

With most protective gear, as you increase the quality or quantity of the gear, there is a gradual increase in its effectiveness. But once you reach a certain point, increases in effectiveness slow and eventually become insignificant, such that there is no longer a benefit to having even higher quality. (It’s a bit like, but not exactly like, diminishing returns.[18]) So if the quality of masks levels off at a certain point, in such a way that N95 masks don’t offer that much more protection than surgical masks, that would not be surprising–and it certainly wouldn’t show that cloth masks provide no protection.

To illustrate this logical error, consider bullet proof vests. A vest with Kevlar that is, say, 1mm thick will clearly be less effective than one with Kevlar 2mm thick; and 2mm will be less effective than 3mm, etc. But at some point, continuing to increase the thickness will be unhelpful. For example, 7mm of Kevlar will likely stop all the same bullets as 15cm. A study that showed that 7mm and 10mm thick vests offer the same protection would not be surprising; but more importantly, such a study certainly wouldn’t entail that there is no protective benefit to wearing a bulletproof vest. It shouldn’t show that the very concept that “Kevlar offering protection” to be flawed. In the same way, a study that shows N95 and surgical masks offer around the same amount of protection doesn’t indicate that there is no protective benefit to wearing a cloth mask, or that the very concept that masks can capture particles is flawed.

N95 effectiveness

Rancourt’s third argument suggests that infected droplets are too small to be blocked by N95 masks, much less cloth masks. But, again, (1) he relies on false assumptions about aerosols. (2) Rancourt relies on admits his argument relies on the “physical removal” explanation for why humidity explains season variation, and even the authors Rancourt cites doubts that explanation. (3) The only reasons Rancourt gives for the physical removal theory is that it “seems more plausible” to him, and that he finds it “difficult to understand” how the other is true. In logic we call this “fallacious appeal to personal incredulity.” (4) He doesn’t understand how N95 masks work; for example, contrary to what Rancourt claims, because of Brownian motion, N95 filters are actually more efficient at filtering particles smaller than 0.3 microns. They, like even most kinds of cloth masks, are not sieves.[19] And (5) his argument is only relevant to whether masks filter the air you inhale, not the air you exhale—and it’s the latter that matters.

Mask’s aren’t 100% effective; MID; All or Nothing

Short Version: Rancourt argues that, because masks can’t guarantee 0% exposure, they are useless. But (1) this argument makes assumptions about the minimal infective dose of COVID that are not yet verified. At best we can only guess based on influence or SARS. Erin Bromage has good stuff on this. (2) He misrepresents some of the evidence he presents in this section too. I can elaborate if you want. (3) The argument fails to recognize that, even if one infected droplet is enough to infect you, the severity of symptoms could be proportional to the amount of exposure. There is good evidence (Henegan, 2020) that points in this direction.[20] And (4) the argument commits the “all or nothing fallacy.” Masks need not be 100% effective to slow the spread of COVID. To completely stop it—yes, they would have to be 100% effective, and everyone would have to wear one properly. But mask mandates do cause more people to wear them properly; this reduces the amount of infected droplets in public places, and that reduces spread.[21] Think in terms of speed limits. They cannot eliminate all accidents; some people will ignore them, and accident will happen. But they can and do reduce the number of accidents by reducing risk. Masks do the same thing.

On his research on MID

First of all, he provides no direct evidence for COVID’s MID. He, instead, cites a study from 2011 (by Yezli and Otter) about influenza.[22] But COVID is a different disease that affects those it infects in many different ways (for example, it seems to affect blood vessels and cause blood clots). So influenza’s MID can only point in the direction of COVID’s MID, at best.

Second, he merely states that “It is believed that a single virion can be enough to induce illness in the host.”[23] But of course a belief is not evidence. He quotes Zwart et al. (2009), saying his study on a virus-insect system showed that “the action of a single virion can be sufficient to cause disease.”[24] However, that statement is not specific to COVID, and the fact that something can be sufficient to cause something, doesn’t mean that it is or will in all or even most cases.

Third, even the evidence he provides for influenza doesn’t show that one infected droplet will make a person sick. According to Rancourt himself, Yezli and Otter’s study only suggests that the “50-percent probability MID easily fits into a single (one) aerolized [sic] droplet.”[25] That only means that one droplet making its way into your system means that you are about 50% likely to get sick. So, it’s “enough” in the sense that it could make you ill, but it’s not “enough” in the sense that it is guaranteed to make you ill. Again, he seems to be equivocating–this time on the word “enough.”

And the other evidence he provides, like from Baccam et al. (2006) and  Brooke et al. (2013), only talk about how quickly or efficiently viruses reproduce in cells once they are infected–not the probability of cells becoming infected once exposed.[26]

What’s more, he makes a mathematical error that greatly overestimates how many viruses would be in an aerosolized droplet. He says that “there are 1000 to 10 million viral particles, in each microdroplet 1 to 10 microns in size.” But, in fact, microdroplets of that size are mostly empty of virus and contain at most a single viral particle. Why? Because it’s difficult to get coronavirus into a concentration much higher than 10 million per mL (plaque forming units per milliliter)[27]; and a 10 micron droplet is (4/3 * 5^3 * 10^-18 m^3 =) 0.167 picoliter. A ml is 1 billion picoliters. So for every 1,000 10 micron droplets, only at most 2 (1.67) will have even a single virus in it—that’s roughly 1 out of every 600. So he is making an mathematical error of a factor of at least 10 million here. (My thanks to MW and my wife for the math here!) And since it is far from established that one virus is sufficient for an infection, much less a severe on, his argument here is based on nothing.

The All or Nothing Fallacy

The all or nothing fallacy is a variety of the false dilemma fallacy.[28] One commits the false dilemma fallacy when one suggests that there are fewer options than there actually are. “You are either for us, or against us.” No, actually, I could just be neutral, or not care. The all or nothing fallacy presents a false dilemma by suggesting that there are only two options—either all or nothing—when in fact there are many more options in the middle ground between those two extremes.

The fallacy is very common when talking about the effectiveness of laws. Notice that speed limits cannot prevent everyone from speeding and cannot eliminate all car crashes. But not one would argue that speed limits are useless and that we should not even bother with them. They reduce the amount of speeding and thus make the roads safer.

In the same way, masks cannot eliminate COVID infections; even if everyone is wearing a mask, some people will still get infected, because masks are not perfect. They cannot guarantee no transmission. But if everyone is wearing them, they can make the number of infected droplets in the air far fewer. And if you still happen to be exposed to one in the air, they can reduce the chance of exposure (by up to 84%!). Thus, even though they cannot eliminate it, mask mandates will reduce the probability of infection, and thus the number of people infected.

This also applies to the fact that some people will use their masks improperly–by, say, hanging their nose out of the top. No, their mask is not effective. But by mandating mask use, the number of infected people wearing them properly raises, and thus the probability of healthy people becoming infected drops.

There is no bias free study

Rancourt finishes his article by claiming that no “bias free” study could ever show that mask mandates are effective.[29] But that “bias free” phrase is doing a lot of work. Notice that, if any such study ever came out, he would just claim that it was biased and dismiss it. He has just built into his argument what logicians call an “ad hoc” excuse–an unfalsifiable way to excuse away any contrary evidence. It is a telltale sign of pseudoscience and irrationality.

No Study Can Be Done

He also suggests that no such study could be done because “Mask-wearing is associated (correlated) with several other health behaviors” and “The results would not be transferable, because of differing cultural habits.” But, of course, these are simply things that such studies would have to take into account and control for. It does not mean they cannot be done.

Masks are Risky

He also lists a number of “unknown risks” to mask wearing, suggesting that the risks of a mask mandate would outweigh its benefits. But (1) this is irreverent to whether mandates mitigate the spread—which is the topic of this debate. A drug can still cure something, even if it has side effects. (2) The supposed risks he lists are miniscule compared to the tens of thousands of lives the evidence suggests that mask mandates would save, and the enormous economic benefit that masks could generate by allowing businesses to open up without major risk. And (3) he provides no evidence that these risks are any real concern.[30] He’s just listing as many concerns as he can make up. Notice what he is doing: He is asking us to take all the scientifically proven evidence for the benefits of masks and completely ignore it, but take seriously, as if they are proven, all these “risks” that he is just essentially creating out of whole cloth. His epistemic standards are backwards. When it comes to masks working, he demands RTC when observation evidence will do just fine—but when it comes mask risks, he’s willing to accept them based on no evidence at all. This would be like, I don’t know, not putting a cast on your broken leg because your friend says “Hey, there could be asbestos in those casts; you don’t know.” Yeah, maybe–I guess? But until I have good reason to think such a thing is an actual risk, and that the risk outweighs the benefit, I’m going to do what has been proven to work. 

On Specific Risks

There are major problems with this argument.

  • Even if they did, they could still help prevent the spread of COVID—and that is the topic of this debate.
  • They are not dangerous. They do not trap CO2 in; they do not lock 02 out. They are designed to less gasses in and out, but trap droplets and particles. That is the very definition of a filter. Decades of use in the health care settings have proved this, as have numerous people showing their O2 levels while wearing a mask.
  • There are very few medical conditions that restrict mask use.
  • Evidence suggests they do not promote more face touching,[31] in fact they likely reduce it.
  • There is no evidence that a false sense of security causing risk compensation is a real concern. ON the flip side, mask mandates could just as easily make people take the threat more seriously. What’s more, this is a disingenuous concern that can be mitigated with simple education. If Rancourt is really concerned about this, he should be spreading information about how properly use a mask and the need for additional measures—like social distancing—not spreading pseudoscience about mask ineffectiveness.
  • They cannot cause you to infect yourself; that “plandemic” claim is baseless. You can’t “reinfect yourself with your own viral expressions.”
  • And any infections caused by improper use can (a) be deterred by education and (b) would not outweigh the number of infections caused. (If you become infected by touching your mask after using it, you probably would have been infected had you not been wearing it.)
  • The CDC did not fail to recommend wearing masks before because they were dangerous; they just didn’t think they were effective to protect their wearer. They were not considering the “protect others” angle. (This is why they recommended them for the venerable, and not everyone else.)
  • The study by Zhiging Rancourt cites in an interview about mask contamination is about contamination of surgical masks during surgery—not public use.
  • All other “worries” are fabricated, and have no evidence, and could not outweigh the benefit of their use. It’s like not getting a cast for a broken leg b/c your friend says it might have asbestos in it. Maybe…but until I have good reason not think it does, I’m going to stick with what I know works.

Masks Just Distribute Air Differently

In his rebuttal, Rancourt argued that cloth masks can’t prevent infected droplets from entering the air we breathe out, and thus don’t help curb the spread, because the air we breathe just leaks out of the edges of the mask; that why your glasses fog up. But there are two very simple replies:

  • While some of the air you breathe can leak out the edges, the momentum of your breathe pushes most of it through the mask, and thus most of the air is being filtered. Thus, even with leakage, masks reduce the number of infected droplets in the air, and thus reduce spread. And to think that it has to catch it all commits the all or nothing fallacy. (Speed limits don’t eliminate crashes, but they do help reduce them.)  
  • The breath that does leak out the edges still stays closer to you than it would without the mask. Since a major mode of transmission is people exhaling or spitting particles out into the air—onto objects or people—by keeping your air close to you, the mask also helps prevent the spread.  

Surgical Masks don’t prevent patient infection.[32]

What about Brosseau’s article?

Lisa Brosseau and Margaret Sietsema authored a very thoughtful piece on masks which Rancourt might use to try to support his case. There are 5 things to say about this article.

Short version: First, it supports my thesis; they just think masks mandates help a little. Second, is concern about risk compensation is overruled by the benefits. Third, it riles on aerosols being the primary mode of infection. Fourth, the argument against the filter measurement studies is weak. And five, it ends by committing the “all or nothing” fallacy.

  1. It actually supports my thesis in this debate, in admitting that universal mask use could help prevent the spread of COVID. Where Brosseau differs from me and the general medical community is regarding how much masks could help prevent spread. “…cloth masks and face coverings are likely to have limited impact on lowering COVID-19 transmission.” Limited is not none. And by negating the resolution, Rancourt is maintaining that mask mandates will have no effect at all—thus he cannot use Brosseau’s article to support his argument. What’s more, this part of the argument seems to be based a bit on the “all or nothing fallacy.” Not everyone will wear their mask perfectly, but this need not be the case to mitigate spread. More on that in a moment.
  2. Brosseau raises important concerns about misunderstandings leading to mask misuse, and misinformation about masks leading to risk compensation—people thinking that, because they are wearing masks, they don’t have to socially distance or take other precautions. But this is not a reason to think mask mandates can’t mitigate spread; it a reason to combat misinformation about masks. (Also, mask mandates could just as easily foster solidarity.) Fortunately, Brosseau mostly does this in her article. Rancourt is doing the opposite.
  3. Brosseau’s entire argument stems on aerosols being the primary mode on infection; while there are some anecdotes which suggest that COVID might also be transmissible through aerosols,[33] it may only be to those who are susceptible (because the viral load is low in aerosols), and there are no reliable studies or evidence right now that clearly define the role of aerosols in the transmission of COVID. As Dr. Josh Santarpia put it, “To my knowledge, there is no definitive evidence of transmission where aerosol was the only possible route.”[34] (Indeed, Santarpia argues that, since the 6  foot rule is outdated and probably too conservative, the anecdotes could easily be explained by respiratory droplet transmission.) I don’t mean to rule out that it has a role, and there should definitely be more study—but as it stands, there is literally no peer reviewed literature that clearly defines the role of aerosol transmission of COVID[35]—much less any proving that it is the primary or sole mechanism.
  4. Brosseau’s argument that masks can’t filter aerosols also seems weak. It relies uncritically on one study, and then nickpick the 8 studies where measurements contradict their conclusion. These measurements are generally done with machines that test HEPA filters. They are reliable.
  5. It commits the “all or nothing” fallacy at the end. “If masks had been the solution in Asia, shouldn’t they have stopped the pandemic before it spread elsewhere?” No, because no one is claiming that masks alone can wipe out the disease. It can slow the spread. And the degree to which it has slowed in Asian countries that wear masks, when compared to countries that did not, is evidence itself that Brosseau’s argument is invalid.

The Science Isn’t Good Enough

Rancourt is likely to object that the evidence I have presented, regarding masks ability to filter, and the efficacy of mask mandates, is not good enough because they are not RTC (randomly controlled trials). They are “substandard.” This is where my expertise in philosophy of science is relevant. There are 6 things wrong with this argument.

Short version: Rancourt’s standards of evidence are backwards. He demands RTC for the effectiveness of masks when (a) such trials cannot be ethically performed, (b) other kinds of studies (measurements, observational, and correlative) and the understanding of the physics of how they work is enough to know that they do. Notice that he demands absolutely no evidence to think that masks are risky and that their negative consequences outweigh. In reality, while RTCs are needed for drugs b/c of possible side effects etc., they are not really needed for masks. They have been used for decades, safely. Even if they are quickly done, because we need quick information, studies showing them effective are good evidence they work.

  1. RTC are necessary when dealing with drugs, because of possible side effects—but they are not necessary with many other things, especially when the mechanics and physics makes sense. You don’t need a RTC to know that parachutes protect you from hitting the ground when you jump out of a plane. Rancourt is just selectively raising the standard of evidence so he can discount the evidence that doesn’t say what he likes. (Notice he requires no evidence to think that masks are risky, but demands an RTC to know that they filter air.)
  2. RTC are very hard to pull off for anything but drug trials; when dealing with what can or cannot transmit a disease, they are unethical. If someone already has a disease, you can give them a placebo instead of a drug that may or may not work, as part of a trial if they agree. You cannot put someone in a situation where they may or may not contract a deadly disease. The kind of RTC’s that Rancourt is calling for here to prove that masks can mitigate spread cannot exist; so the fact that they do not, doesn’t prove that they don’t.
  3. Essentially, Rancourt is appealing to ignorance here. In logic, a fallacious appeal to ignorance happens when a person says something is false because it has not been proven true. Rancourt does this when he cites studies that simply “do not find that masks work” and says that means “they don’t work.” But the fallacy is even more egregious when studies you are calling for literally can’t be performed, and you then you cite their non-existence as proof of something.
  4. There are 3 other kinds of evidence you can have: (a) measuring what they can block. (b) observing what happens when you wear them (photography, hairstylist) (c) corelative studies about public health. The accumulation of these kinds of evidence can eventually make the need for RTC studies unnecessary; sure, it would be nice if they could ethically be performed—but if they can’t, a collection of non RTC studies all pointing in the same direction can be enough reason to draw an such a conclusion. (If it were a drug, that would be different story; because of potential side effects, you’d need RTCs, to make sure the risk is worth the benefit. But it’s not; it’s a mask. They have been used for years; we know that there are no potential dangers.)
  5. Rancourt might argue that they are just correlational; “mask mandate followed by reduce in spread”…and that correlation doesn’t not entail causation. But this is a misuse of the phrase. A single instance of correlation does not prove causation, this is true. But repeated correlation, in different circumstances, over and over, strongly implies it—so much so that concluding that causation is at work is justified. Continued disbelief in the light of such evidence is just pigheadedness, not careful scientific skepticism.
  6. Indeed, the evidence from cities, states, and countries where mask mandates slow the spread is so solid, that to win this debate I need not even rely on my arguments for the filter efficiency of masks. Maybe mandates work because people stay home more because they would rather not wear a mask. The mechanism doesn’t matter. What matters is whether rates on infection consistently slowed after mask mandates; since they did, clearly they help mitigate the spread.

Evidence shows masks don’t work/Airplane Example

This is not true. (1) Most of the evidence Rancourt cites is about whether N95 masks are as effective as surgical masks at protecting their wearer, or whether cloth masks protect their wearer; such studies have nothing to do with whether cloth masks can filter exhaled air and be a method of source control. (2) Most of the time he is misrepresenting their findings. And (3) at best, the studies just say they couldn’t find an effect in the experiments they looked at. But being unable to find something does not mean doesn’t exist–that’s just an appeal ignorance—especially when the studies say the experiments were limited.

These studies remind me of these studies that were unable to conclude that parachutes don’t prevent injuries when jumping out of planes. They looked at the evidence and said “there was not a significant difference in the number of injuries and deaths in the groups with or without parachutes; but these studies were limited and more research was needed.” The studies had people jumping out of airplanes that were still on the ground. These are the kinds of studies that Rancourt is relying on; RTC’s are not always the golden standard of evidence Rancourt makes them out to be.

The Xiao Study

In the interview he quotes: “Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza.”

  1. The study itself admits that the trials in looked at were flawed, and conclusions can’t be drawn from them.
  2. They must be flawed because they said there was no benefit to handwashing! Are we going to say start saying that people don’t need to wash their hands too? Unless he does, Rancourt cannot tout this study as evidence for his view.
  3. If Rancourt has read past the abstract, he would have seen that it says: “There are still few uncertainties in the practice of face mask use, such as who should wear the mask and how long it should be used for. In theory, transmission should be reduced the most if both infected members and other contacts wear masks, but compliance in uninfected close contacts could be a problem (12,34). Proper use of face masks is essential because improper use might increase the risk for transmission (39). Thus, education on the proper use and disposal of used face masks, including hand hygiene, is also needed.” The authors of this study are recommending the use of facemasks!
  4. This is kind of like one of those trials where they have people jump out a parked airplane and find no collection between survival and parachutes. You need better tests!

Covid Doesn’t Exist

Short version: Rancourt as argues elsewhere that COVID doesn’t exist. This is not on topic—we are talking about masks mandates, not conspiracy theories. I’m not going to let him shift the topic to something else because he has already lost the mask debate. I will say this… if there was such a conspiracy, it would have already broken down by now. but if you would like me to debunk it. Grimes (2016) showed that how fast conspiracies break down and are leaked is proportional to how many people it would take to keep them a secret.[36] Since basically the whole world would have to be involved in a conspiracy that made it seem like COVID was real when it wasn’t, the idea that one exists is absurd. And that is all I will say now. If some wants to ask about it, I’ll gladly debunk it.

Quick debunk: The argument relies on the assumption that doctors can’t tell when a patent dies of COVID; that’s false. It suggests that there has been no increase in excess morbidity; that’s false. And COVID are likely higher than reported. And it says that places that didn’t follow government guidelines for dealing with COVID, like Texas, didn’t see spikes—and that’s false.

  1. This would require a vast conspiracy of so many people that it could only last a few days; Grimes (2016) showed that how fast conspiracies break down and are leaked is proportional to how many people it would take to keep them a secret.[37] Since basically the whole world would have to be involved in a conspiracy that made it seem like COVID was real, the idea that one exists is absurd.
  2. I’ve heard him give his argument, and it relies on the false assumption that every time a doctor declares the cause of death, it is “political,” to we can’t trust the reports of COVID deaths.[38] But not only would such a conspiracy break down in two seconds…it is absurd to think that doctors cannot rationally determine the cause of death, or to determine cause of death with COVID.[39] There are certainly some difficult cases, but most a clear. When someone dies in a car wreck, we know the impact killed them. When someone tests positive for COVID, and they die because they can’t breathe or other such complications, we know that COVID killed them. To think that all such deaths are a political declaration (or that it is impossible to tell when COVID has killed someone) commits what is known as the continuum fallacy (the idea that “two states or conditions cannot be considered distinct (or do not exist at all) because between them there exists a continuum of states.” Some cases may be difficult; but most are clear cut. Death is this way too; there is not a clear demarcation for when someone dies. But that doesn’t mean there is no such thing as death.

Steve Novella, MD: There is little reason to think there is any significant overcounting of COVID-19 deaths. If someone is very ill from COVID-19 and they die, it is highly likely they would not have died if they were not sick from the virus. And during a pandemic, if you have an illness that clinically looks like the pandemic illness, statistically it’s a good bet that is what you have. So while it is possible there may be some overcounting, it is likely minimal and dwarfed by the underreporting. This is why most experts agree that, if anything, we are underestimating the death toll from this pandemic.[40]

  • The fact that there is academic “reward” to discovering a virus doesn’t mean that it is made up. This is the genetic fallacy.
  • His argument relies on his false assumption that there was no increase of in the overall death rate due to COVID. While there may not have been a significant extra “winter burden” worldwide during the winter months, there was in specific places (where there were COVID outbreaks), like Wuhan. What’s more, since the winter, there has been a grandiose amount of excess deaths—in the spring, and now the summer.[41] The only reasonable explanation for is COVID.

Again Novella: “One study published in JAMA, for example, found that in the US: …the number of deaths due to any cause increased by approximately 122 000 from March 1 to May 30, 2020, which is 28% higher than the reported number of COVID-19 deaths.”

He thinks the overall death rate entails that COVID doesn’t exist? It actually proves that COVID not only exist, but that it is much more deadly than the official confirmed COVID death count suggests.

  • Now Rancourt will tell you that the sudden spike in deaths in places where COVID hit wasn’t actually due to COVID—but it was “man made”…it was due states dealing with COVID with lock down orders and preparing hospitals. So, on his view, people were dying of loneliness, or because they couldn’t go outside, and hospitals were sending people home who were on ventilators. But not only can lockdowns not kill en mass, and not only did hospitals not send people home to their deaths… and not only have the vast majority of excess deaths being confirmed to be due to COVID—but his entire argument on this point relies on statement like “look at Texas and California; they didn’t follow the government mandates, and then didn’t see a spike.” Well, guess what’s happened in Texas and California since he made those statements? Cases have gone through the roof. He, will of course, make up excuses for why—despite the fact that his theory directly entails this wouldn’t happen, it did—but this just proves he is a pseudoscientist. This is called making up an ad hoc excuse—an unfalsifiable way to avoid being proven wrong by the evidence. (It’s like creationists saying the devil planted the dinosaur fossils.) It’s a telltale sign of irrational argument. Real scientists admit when they are wrong, and change their view.  
  • He says “nothing has ever caused this sharp of a peak before.” How long have records been kept? …covid is new, and its contagious. That’s why .

Why did the CDC and WHO Change Their Recommendation?

Rancourt argues that CDC and WHO changing their recommendation on masks entails that masks don’t work. This does not follow.

The AAPS (Association of American Physicians and Surgeons) statement.[42]

  1. It is old, and reflects old guidance form the CDC and WHO.
  2. The association has promoted a range of scientifically discredited hypotheses, including the belief that HIV does not cause AIDS, that being gay reduces life expectancy, that there is a link between abortion and breast cancer, and that there is a causal relationship between vaccines and autism. It is opposed to the Affordable Care Act and other forms of universal health insurance. It is not a reliable source of information.

“I’m a scientist; he is not.”

He claims that his science degree makes him more qualified to talk about this than my philosophy degree. But since his physics concentration is it metals, but my concentrations on medical reasoning and medical pseudoscience, I am actually more qualified on this issue. Indeed the only subject on which his physics degree is relevant to this debate is Brownian motion—how interaction with air makes the smallest particle move randomly and easier to capture—and he not only doesn’t mention it in his online articles, but he doesn’t even seem to understand it. When I talked to the physicists and engineers at my university, they were astounded by his ignorance. Indeed, by endorsing thing like climate change denial in the past, and saying thing like COVID is a hoax (when he defends the anti-mask position), Rancourt has made his degree irrelevant. He is not a scientist anymore; he is a pseudoscientist—on par with those who claim to be psychics and think that vaccines cause autism. The average college grad with a liberal arts degree is much more qualified to talk about this than he is.

That Kid Wearing The Mask

On Highwire, a conspiracy theory talk show on which Rancourt has spouted his biased opinions and research on masks unchallenged, an experiment was performed where a kid wears a mask, the host puts a CO2 detector inside it, and the reading go off the chart. This is supposed to prove that masks are dangerous—that they cause CO2 poisoning. This is ridiculous.

  1. First, this is irrelevant, because the issue is whether masks help prevent the spread of coved, not whether they have side effects. A drugs can have side effects, but still be effective. So can masks.
  2. This is a kid and a talk show host; not trained scientists. This is a perfect example of “double standards” when it comes to evidence—regarding Rancourt and the anit-mask crowed in general. A kid on a right wing talk show does not outweigh the consensus of scientific experts.
  3. A real test would measure the amont of CO2 vs. O2 in his blood—that’s what matters. And there are tons of people who have done this with pulse-socks and show that masks have no effect.
  4. There is no control; if you breathed on this kind of CO2 censor without a mask, the CO2 readings would go off the chart. They are used to detect slight increases in public spaces or basements over time, not what’s coming directly out of your mouth.
  5. If this proves anything it’s that masks are harmless and all the worries about CO2 poisoning are non-sense; because while the reading was off the chart, the kid was sitting there breathing comfortably, no side effects no nothing. If what they say is happening, was happening, that kid would be dead. Whatever a mask does with the CO2 leaving your mouth, it clearly doesn’t harm you.
  6. Rancourt can’t have it both ways. He wants to say masks are so porous that they just let droplets and aresols pass right through them. But then they are so non-porous that they can’t even let gases, like CO2, through and you will choke to death. Since, gases are finer than droplets and aerosols, this is impossible. Masks can’t both capture all your breath and keep it from escaping, but also not capture your breath and let it escape into the environment. This kind of contradictory non-sense is what get with confirmation bias—when you tout the bad evidence for your theory, and ignore the good evidence against it.

Rancourt is a pseudoscientist

If you look back at his arguments, he made specific predictions that all turns out wrong. His humidity argument predicted that it would go away in the summer because of humidity; it did not. He said there was not and would not be any overall excess deaths; there have been. Nevertheless, despite being proven wrong, he has just made up excuses to get himself out of the evidence, so he can continue to believe what he wants. This is giant red flag “I’m a pseudoscientist” signals. I’m not sure how you could be, but if you are still confused by the evidence—consider the source of the arguments. I have shown you how he misreports the evidence and give fallacious invalid arguments. I am honest about what the evidence shows, and try to draw the most rational conclusion. I have changed my mind on this issue given the evidence. Rancourt has not. Who do you think is more trustworthy here?

And if you are still having trouble figuring out whether to wear a mask, do something like Pascal’s wager:

You ever know if you are infected or not

            If you wear a mask, and they work, you’ve help saved lives. If not… how has it harmed you?

            If you don’t, and they don’t work—what have you gained? But if they do, you have put others at risk.

It’s a no loss bet; wear the mask.

Given how keen Rancourt seems to be overturn the scientific consensus, and buck the establishment, I’m kind of surprised by the fact that he is on the side of the debate he is on. The consensus majority view was that healthy people should not wear masks. The CDC said that for years. That view was challenged—and then overturned! A little mini-scientific revolution happened, right in front of our eyes. As a climate change skeptic, I’d expect Rancourt to be saying “See, the consensus was wrong about masks—and now they admit it! What else might they be wrong about?”

COVID FACTS; herd immunity

Covid R naught is 3. That means we have ot have 70% for herd immunity.

Closing Argument

The argument that masks work to prevent the spread of COVID is simple.

  1. COVID spreads through infected persons exhaling droplets and aerosols.
  2. Masks block the majority of exhaled droplets and aerosols. 
  3. Thus infected persons wearing masks greatly reduce the risk of infecting others.
  4. Public mask mandates increase the number of infected persons wearing masks.
  5. Thus public mask mandates help mitigate the spread of COVID.  

This argument is valid: if the premises are true, the conclusion would follow—and all the premises are supported by solid evidence. It is as simple as that.

Now, in making his argument, Rancourt assumes that all infections are caused by aerosols and that masks can’t block them, at all. Now, let me clear: Both of those assumptions are false. While aerosols likely are a mode of transmission, droplets also are —indeed, they are most likely the main mode. And even if, instead, aerosols are the main mode, the most potent ones are those that start out as droplets (e.g., 100 microns) and evaporate to become aerosols—and masks definitely block those. What’s more, thanks to Brownian Motion (the random way that they move), even the tiniest (0.1 microns) aerosols can be blocked by masks. This doesn’t matter much, because like only 1 in every 700 such droplets has even a single virus in it…but still. It can block them. So whether COVID is spread by droplets, or aerosols, or both, masks help reduce the number of infected particles in the environment, and thus mask mandates help reduce the spread of COVID.

But let’s pretend, just for argument’s sake, that masks can’t block the hardest aerosols to block—those that are 0.3 microns. And, let’s even pretend that the coronavirus is smart; it knows what size particles can go through a mask, and so it chooses to place itself in all and only aerosols that are 0.3 microns, and they all just go right through the mask.. Both ways. These infected particles just roam wherever they please.

Even given those ridiculously generous assumptions, the evidence still suggests that mask mandates help mitigate the spread of COVID. Obviously not by masks filtering particles—but we still know mask mandates help. How can I say this?

Recall the evidence I mentioned in my opening about the effect of mask mandates. In cities, states, and counties, all over the world, infection rates dropped about two weeks after the mask mandates went into effect. And the mandates went into early in some places, later in others—but they are always followed by a reduction in spread. If it was just a couple of places—maybe, yeah, that could be a coincidence—a case where “correlation does not entail causation.” But given the monumental number and variety of times this has happened, there is no other reasonable explanation. Mask mandates help reduce the spread of COVID. The most likely do it because masks filter—but even if they don’t, they must be doing it in some other way. Maybe mask mandates make people stay home because they don’t want to go out wearing a mask. I don’t know. What I do know, is the data is very clear: mask mandates help prevent the spread of COVID 19—and that is all I have to establish to win this debate—and I have done so without question.

Of course I am not a doctor, but my argument does not rely on medical expertise. It relies on my expertise in argument summary and evaluation, and pseudoscience recognition. What’s more, it would be fallacious to dismiss my argument simply because I do not have a medical degree; either my argument is valid and its premises are true, or not. To think they are wrong simply because I am this or that kind of academic would commit the ad hominem or genetic fallacy—to attack an argument based on its origin. My argument should stand or fall on the evidence I presented.

But what is not fallacious is to doubt the premises of an argument based on the reliability of its source. And in my opening argument, I clearly showed—not only that Rancourt does not understand how masks work—but that you have good reason to doubt the premises of his argument. Rancourt methodically and consistently misrepresents the studies he selectively cites. They do not show what he says they do. He makes basic but grandiose mathematical errors, and commits countless logical fallacies. They invalidate his arguments. He makes unsupported assumptions, and touts irrelevant evidence. Even if you think the things he said today sounded convincing, you should only take them with a grain of salt.

In videos, I’ve seen him say that “Coronavirus Has Been a Huge Fabrication.” That there are no excess deaths. That the government just wants you to believe masks works so it can cover up its crimes—on sites that say Bill Gates is a secret Nazi. In my professional opinion, he’s clearly a conspiracy theorist and pseudoscientist. Before you believe what he tells you …consider the source.

And lastly…consider this: If you wear a mask but they don’t work…Who have you hurt? But if you don’t and they do—you are risking other people’s lives. Don’t be that person…oh, and make sure your mask covers your nose.


                [1] “How it Spreads,” BC Centre for Disease Control,http://www.bccdc.ca/health-info/diseases-conditions/covid-19/about-covid-19/how-it-spreads.

                [2] Tia Ghose, “How Are People Being Infected With COVID-19?” Live Science, April 7, 2020, https://www.livescience.com/how-covid-19-spreads-transmission-routes.html.

                [3] “What You Should Know About COVID-19 to Protect Yourself and Others,” CDC, https://www.cdc.gov/coronavirus/2019-ncov/downloads/2019-ncov-factsheet.pdf#:~:text=COVID%2D19%20is%20primarily,nose%2C%20or%20eyes.

                [4]“Modes of Transmission of Virus Causing COVID-19: Implications for IPC Precaution Recommendations,” World Health Organization, March 29, 2020, updated July 9, 2020, https://www.who.int/news-room/commentaries/detail/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations.

[5] Roxanne Khamsi, “They Say Coronavirus Isn’t Airborne – But It’s Definitely Borne By Air,” Wired, March 14, 2020, https://www.wired.com/story/they-say-coronavirus-isnt-airborne-but-its-definitely-borne-by-air/.

                [6] Mahesh Jayaweera, Hasini Perera, Buddhika Gunawardana, and Jagath Manatunge, “Transmission of COVID-19 Virus by Droplets and Aerosols: A Critical Review on the Unresolved Dichotomy,” Environ Res 188, no. 109819, published online June 13, 2020, https://doi.org/10.1016/j.envres.2020.109819.

                [7] Ghose, “How are People Being Infected with COVID-19?”

[8] See also Zeshan Qureshi, et al., “What is the Evidence to Support the 2-metre Social Distancing Rule to Reduce COVID-19 Transmission?” CEBM, June 22, 2020, https://www.cebm.net/covid-19/what-is-the-evidence-to-support-the-2-metre-social-distancing-rule-to-reduce-covid-19-transmission/.

                [9] Tanya Lewis, “How Coronavirus Spreads through the Air: What We Know So Far,” Scientific American, May 12, 2020, https://www.scientificamerican.com/article/how-coronavirus-spreads-through-the-air-what-we-know-so-far1/.

                [10]  It is also important to understand that although the majority of the droplets produced by a cough may be small enough to stay airborne, their small size means that collectively they add up to only a tiny fraction of the volume produced (perhaps less than 0.1%), and therefore only a tiny fraction of the total virus spread.

                [11] Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-covid-19-from-aerosols-6c97d023bb6d.

                [12] “Various sources will put the cutoff at 2 µm, 5 µm, 10 µm, 20 µm, or even 100 µm.” Justin Morgenstern, “Aerosols, Droplets, and Airborne Spread: Everything You Could Possibly Want to Know,” First10EM, April 6, 2020, https://first10em.com/aerosols-droplets-and-airborne-spread/.

                [13] Erin Bromage, “The Risks – Know Them – Avoid Them,” Erin Bromage, May 6, 2020, https://www.erinbromage.com/post/the-risks-know-them-avoid-them.

                [14] Quote from: Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/. Here is the study: Rachel E. Baker, Wenchang Yang, Gabriel A. Vecchi, C. Jessica E. Metcalf, and Bryan T. Grenfell, “Susceptible Supply Limits the Role of Climate in the Early SARS-CoV-2 Pandemic,” Science 369, no. 6501 (July 17, 2020): 315-19, https://doi.org/10.1126/science.abc2535.   

                [15] Bo Bennett, “Oversimplified Cause,” Locially Fallacious, https://www.logicallyfallacious.com/logicalfallacies/Oversimplified-Cause-Fallacy.

                [16] Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298; Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/ 10.1001/jama.2020.12897.  And Scott Alexander, “Face Masks: Much More Than You Wanted to Know,” Slate Star Codex, March 23, 2020, https://slatestarcodex.com/2020/03/23/face-masks-much-more-than-you-wanted-to-know/.

                [17] Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing.” 

                [18] Adam Hayes, “Law of Diminshing Marginal Returns,” Investopedia, June 14, 2020, https://www.investopedia.com/terms/l/lawofdiminishingmarginalreturn.asp.

[19] Just below 0.3 microns is where Brownian Motion starts, so 0.3 micron particles are actually the hardest to capture. N95 masks are so named because they are 95% efficient at capturing such particles. They are actually more efficient at capturing particles both larger and small than that.  – find a better source: “N95s – Sufficient Protection for Covid19?” https://www.sphosp.org/wp-content/uploads/2020/04/Letter-in-response-to-N-95-use-RA-Final.pdf.

                [20] Carl Heneghan, Jon Brassey, and Tom Jefferson, “SARS-CoV-2 Viral Load and the Severity of COVID-19,” CEBM, March 26, 2020, https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/.

[21] Think of it this way; speed limits aren’t perfect. Some people will break the law; accidents will still happen. But that doesn’t mean speed limits don’t reduce the number of accidents. In the same way, although they won’t eliminate it, mask mandates will assist in curbing the spread of Covid-19.

[22] Saber Yezli and Jonathan A. Otter, “Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment” Food and Environmental Virology 3 (2011): 1-30, https://doi.org/10.1007/s12560-011-9056-7.

[23] Ibid.

[24] Mark P. Zwart, Lia Hemerik, Jenny S. Cory, J. Arjan G.M. de Visser, Felix J.J.A. Bianchi, Monique M. Van Oers, Just M. Vlak, Rolf F. Hoekstra, and Wopke Van der Werf, “An experimental test of the independent action hypothesis in virus– insect pathosystems,” Proceedings of the Royal Society B (March 2009), http://doi.org/10.1098/rspb.2009.0064.

[25] Rancourt, “Masks Don’t Work.”

[26] Prasith Baccam, Catherine Beauchein, Catherine A Macken, Frederick G Hayden, and Alan S Perelson, “Kinetics of Influenza A Virus Infection in Humans,” Journal of Virology 80, no. 15 (August 2006): 7590-9, https://doi.org/ 10.1128/JVI.01623-05; Christopher B Brooke, William L Ince, Jens Wrammert, Rafi Ahmed, Patrick C Wilson, Jack R Bennink, and Jonathan W Yewdell, “Most Influenza A Virions Fail To Express at Least One Essential Viral Protein,” Journal of Virology87, no. 6 (March 2013): 3155-62, https://doi.org/ 10.1128/JVI.02284-12.

[27] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7224694/

[28] Bo Bennett, “False Dilemma,” Logically Fallacious, https://www.logicallyfallacious.com/logicalfallacies/False-Dilemma.

[29] Rancourt, “Masks Don’t Work.”

[30] Holly Secon, ”If Everyone in the US Wears a Mask in Public, 33,000 Lives Could Be Saved Over the Next 3 Months, One Model Suggests,” Business Insider, June 26, 2020, https://www.businessinsider.com/wearing-face-masks-could-save-33000-us-lives-2020-6; Megan Cerullo, “Everyone Wearing Face Masks Could Save America From a $1 Trillion GDP Loss,” CBS News, July 9, 2020, https://www.cbsnews.com/news/face-mask-wearing-save-money/.

[31] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7362106/

[32] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480558/ and https://pubmed.ncbi.nlm.nih.gov/16295987/

[33] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7293495/

[34] https://www.livescience.com/how-covid-19-spreads-transmission-routes.html

[35] https://www.scientificamerican.com/article/how-coronavirus-spreads-through-the-air-what-we-know-so-far1/

[36] https://phys.org/news/2016-01-equation-large-scale-conspiracies-quickly-reveal.html

[37] https://phys.org/news/2016-01-equation-large-scale-conspiracies-quickly-reveal.html

[38] https://alternative-news-source.com/2020/07/13/denis-rancourt-epidemiologist-this-has-been-a-huge-fabrication/?fbclid=IwAR3h4qwoLN7K6n2kLXPGljw5UZ6GdcPK_jVAxpy4pu_Zt2mW1N5wVv5aYGw

[39] https://alternative-news-source.com/2020/07/13/denis-rancourt-epidemiologist-this-has-been-a-huge-fabrication/?fbclid=IwAR3h4qwoLN7K6n2kLXPGljw5UZ6GdcPK_jVAxpy4pu_Zt2mW1N5wVv5aYGw

[40] https://sciencebasedmedicine.org/covid-19-and-excess-deaths/?fbclid=IwAR1-m2gmkzQKnu5So5YOujPiJQQrnGZUdxGTodb8X9nIn6tKBUNf94aBZnc

[41][41] https://sciencebasedmedicine.org/covid-19-and-excess-deaths/?fbclid=IwAR1-m2gmkzQKnu5So5YOujPiJQQrnGZUdxGTodb8X9nIn6tKBUNf94aBZnc And https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm?fbclid=IwAR39CnPCZbKAGkogP0PnVCznpAb1veqnpEoQ640gVoTz13vK4gPDEAB5rNE

[42] https://aapsonline.org/mask-facts/?fbclid=IwAR1mS2h6gSv4Eu-AB8wWFgKgGlLR1YR7D2Uwdx8mERugRZ4QUqPsQxMagsk

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Ma, Qing-Xia, Hu Shan, Hong-Liang Zhang, Gui-Mei Li, Rui-Mei Yang, and Ji-Ming Chen. “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2.” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805.

MacIntyre, C Raina, Holly Seale, Tham Chi Dung, Nguyen Tran Hien, Phan Thi Nga, Abar Ahmad Chughtai, Bayzidur Rahman, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare Workers.” BMJ Open 5, no. 4 (2015) https://doi.org/10.1136/bmjopen-2014-006577.

MacIntyre, C Raina, Abrar Ahmad Chughtai, Bayzidur Rahman, Yang Peng, Yi Zhang, Holly Seale, Xiaoli Wang, et al. “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers.” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17. https://doi.org/10.1111/irv.12474.

McCabe, Caitlin. “Face Masks Really Do Matter. The Scientific Evidence Is Growing.” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298.

Mitze, Timo, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde. “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach.” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

            “Modes of Transmission of Virus Causing COVID-19: Implications for IPC Precaution Recommendations,” World Health Organization, March 29, 2020, updated July 9, 2020, https://www.who.int/news-room/commentaries/detail/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations.

            Morgenstern, Justin. “Aerosols, Droplets, and Airborne Spread: Everything You Could Possibly Want to Know.” First10EM, April 6, 2020, https://first10em.com/aerosols-droplets-and-airborne-spread/.

            Neupane, Bhanu Bhakta, Sangita Mainali, Amita Sharma, and Basant Giri. “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

“New IHME COVID-19 Model Projects Nearly 180,000 US Deaths.” IHME,June 24, 2020. http://www.healthdata.org/news-release/new-ihme-covid-19-model-projects-nearly-180000-us-deaths.

“N95s – Sufficient Protection for Covid19?” https://www.sphosp.org/wp-content/uploads/2020/04/Letter-in-response-to-N-95-use-RA-Final.pdf.

Offedu, Vittoria, Chee Fu Yung, Mabel Sheau Fong Low, and Clarence C Tam. “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis.” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42. https://doi.org/10.1093/cid/cix681.

Prather, Kimberly A., Chia C. Wang, and Robert T. Schooley. “Reducing Transmission of SARS-CoV-2.” Science 368, no. 6498 (June 2020): 1422-24. https://doi.org/10.1126/science.abc6197.

            Qureshi, Zeshan, Nicholas Jones, Robert Temple, Jessica PJ Larwood, Trisha Greenhalgh, and Lydia Bourouiba. “What is the Evidence to Support the 2-metre Social Distancing Rule to Reduce COVID-19 Transmission?” CEBM, June 22, 2020, https://www.cebm.net/covid-19/what-is-the-evidence-to-support-the-2-metre-social-distancing-rule-to-reduce-covid-19-transmission/.

Radonovich, Lewis J., Michael S. Simberkoff, and Mary T. Bessessen. “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial.” JAMA 322, no. 9 (2019): 824–833. https://doi.org/10.1001/jama.2019.11645.

Rengasamy, Samy, Benjamin Eimer, and Ronald E. Shaffer. “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles.” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044.

Smith, Jeffrey D., Colin C. MacDougall, Jennie Johnstone, Ray A. Copes, Brain Schwartz, and Gary E. Garber. “Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers from Acute Respiratory Infection: a Systematic Review and Meta-analysis.” CMAJ 188, no. 8 (May 2016): 567-74. https://doi.org/10.1503/cmaj.150835.

Stutt, Richard O. J. H., Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin. “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

Wang, Xiaowen, Enrico G. Ferro, Guohai Zhou, et al. “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers.” JAMA.Published electronically July 14, 2020. https://doi.org/ 10.1001/jama.2020.12897.

            Weaver, G. H. “The Value of the Face Mask and Other Measures.” The Journal A. M. A.70, no. 2 (January 12, 1918): 76-78. https://doi.org/10.1001/jama.1918.02600020010005.

Wei, Wycliffe E., Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee. ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020.” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

            “What You Should Know About COVID-19 to Protect Yourself and Others,” CDC, https://www.cdc.gov/coronavirus/2019-ncov/downloads/2019-ncov-factsheet.pdf#:~:text=COVID%2D19%20is%20primarily,nose%2C%20or%20eyes.

Worley, Becky, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe. “Face Masks With Filter add Another Layer of Protection, Experts Say.” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

Yu, Alan. “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/.

Zarei, Kasra, and John Duchneski. “Coronavirus Cases Rise in States with Relaxed Face Mask Policies.” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/covid-19-coronavirus-face-masks-infection-rates-20200624.html.

Resolved: public mask mandates assist in curbing the spread of Covid-19

I Took the Affirmative in a debate on this issue. This is my opening statement. The endnotes contain all the evidence that Rancourt mis-summarizes and misrepresents the studies he cites. It also explains the many errors that he makes in his argument, and the fallacies he commits.

Thanks Petar

While I do appreciate this opportunity, I’d like to begin by expressing my reservation about participating in this debate. Anyone curious about the effectiveness of mask mandates should listen to current medical and public health experts—epidemiologists and immunologists—not a debate between a philosopher/logician and a physicist who specialized in metals but no longer works or publishes in academia.

What’s more, there is really no debate to be had on this issue. There was a debate, in the scientific community, a few months ago—but it was settled very quickly once the evidence was laid out. Indeed, initially, I thought that public mask wearing was overkill. But then I learned how COVID spreads, and how prevalent asymptomatic spread of COVID is. To help curb its spread, all masks have to do is reduce the number of infected particles that exit an infected person’s mouth—and good evidence suggests they do. Since I am willing to update my beliefs in light of new evidence, I changed my mind.

This, Petar, is why you couldn’t find any medical experts for this debate; they’ve already had it. And engaging with pseudoscientific arguments risks legitimizing them. But I engage with pseudoscience for a living. And since this is one of those times that pseudoscience can kill, I decided to take this opportunity to (1) communicate the scientific argument on this issue to a broader audience and (2) debunk the pseudoscience. Fortunately, as a philosopher and logician, who teaches and publishes on logic, argumentation, philosophy of science, medical diagnosis, and medical pseudoscience—I am especially qualified to do these two things.  

Ok, so first: how and why masks assist in curbing the spread of Covid-19.

The explanation is simple, but misinformation has confused the issue. It’s commonly believed that masks simply protect their wearer from becoming infected by filtering the air that a person inhales. But while there is some evidence that cloth masks maybe offer some protection to their wearer in this regard,[1],[2] the primary way they help mitigate the spread is by filtering the air a person exhales—by [click] sneezing, coughing, speaking, or breathing.

Why are masks effective in filtering viruses from the exhaled air? Because a virus doesn’t travel by itself; it travels in droplets of moisture propelled from the mouth that can be captured. The largest droplets are intercepted by the surface of the mask; smaller ones are stopped by impaction as they try to make it through the mask; and the smallest, including aerosols, are diffused by the mask because of something called Brownian motion–the erratic way they move. This lowers the number of infected droplets in the air, and thus reduces the risk of exposure for other people.[3] [4]

Now, it’s important to note that, while all masks filter exhalations,[5] certain kinds of masks are better than others.[6] The early woven cloth masks were effective, but not as effective as later non-woven ones—what we today call “medical” or “surgical masks.” (According to Davies (et al, 2013), while both types are effective, surgical masks are about three times more effective. [7] [8] But different kinds of cloth, layered or combined, can offer better filtration, by making the pathway particles would have to travel to get through the mask more convoluted. Aydin (et al, 2020) found that layering cotton fabrics can make homemade masks almost as effective as surgical masks,[9] and Konda (et al, 2020) found that layering different kinds of fabrics (like cotton with flannel) could also increase their efficacy.  Such masks filtered 80% of particles smaller than 300 nanometers (0.3 microns) and 90% of those larger. [10] Filters can also improve mask efficacy.[11]

Now if an infected droplet is already in the air that a masked person is about to inhale, the mask will be less likely to catch that particle. That might make one question how cloth masks can filter the air that someone exhales. But that question is easily answered. Part of it is due to air flow; when you are breathing in, you are not pushing the air directly through the mask. But also–the longer a droplet is in the air, the more opportunity it has to evaporate and become smaller (and even aerosolize)—and (unless it’s smaller than 0.3 microns) the smaller it is, the less likely a particle is to be caught by a mask.[12] So infected droplets in the air that an unmasked person has exhaled has a better chance at making it through your mask. But most of the infected droplets exiting your mouth won’t, since they have not yet had a chance to evaporate.[13] [14]

In other words, masks unquestionably filter droplets (on the right), including most of them that would become aerosols (in the middle) And they can even capture those that start out small (on the far left), just less efficiently.

So, if you are in a room with a non-masked infected person, you are pretty likely to be infected even if you are wearing a cloth mask. However, if that infected person is wearing a cloth mask, you are much less likely to be infected—even if you are not wearing a mask. This is why it is said “My mask protects you, your mask protects me.”[15] Your choice to not wear a mask does not put you at risk; it puts others at risk.

Now, since the fact that the majority of the work that masks do in curbing the spread of COVID is done by the masks that infected persons are wearing, one might wonder …

… why we don’t just have infected people wear them. Indeed, this was part of the reasoning behind the traditional ], years long, CDC and WHO recommendations that said mask wearing is not necessary for seemingly healthy individuals. With many diseases it is not. But then experts realized just how long a person could be infected with COVID without knowing it, and even that many infected never have any symptoms.[16] Consequently, public mask mandates are the only way to ensure that infected persons—including those who are pre- or asymptomatic—are wearing a mask. Such mandates would thus reduce the number of infected people without masks, thus reduce the number of infected particles in the air, and thus reduce the probability of transmission. Once we realized this, mask wearing was recommended. Granted, the CDC and WHO lagged behind the experts in this regard. But scientists change their mind based on evidence all the time. That’s not unusual. It’s just usually not that public.

So given what we know masks do, the fact that mandating them helps curb the spread of COVID is just common sense. But the evidence also bears this out. Now you can’t do a direct, controlled experiment where you blindly throw non-infected people into rooms with masked or un-masked infected persons, and see if they get sick. That’s unethical. But all the ethical ways to study this question indirectly indicate that cloth masks curb the spread.

For example, transmission rates slowed in hospitals (Sung (2016)[17] Wang, et. al., 2020),[18] German cities (Mitz, et. al 2020),[19] North Texas (Nandy, 2020),[20] and in US states (Lyu & Wehby, 2020),[21] after mandates went into effect. (In Germany, they reduced growth rates by 40%.) What’s more, U.S. States with mandates have seen much less spread than those without, [22] as have countries where mask use is popular.[23] Modeling has also confirmed the effectiveness of mask mandates.[24] According to Stutt (et. al., 2020)[25] and Eikenberry (et. al., 2020), if masks are just 50% effective, they could help bring down infection rates to non-epidemic levels and reduce the death rate by as much as 45%. Large reviews of observational and comparative studies have also concluded that mask mandates are highly effective,[26] as have collections of collaborating experts.[27] And, of course, there were those infected hairstylists in Missouri who didn’t pass it on to 140 of their clients because they were wearing a mask.[28]

The IHME found that mask mandates could save 33,000 by October 1st,[29] and (according to Brooks, 2020) if everyone worse a mask, we could get the pandemic under control in four to eight weeks.[30] None of this is as good evidence as the above described unethical blinded study would provide, but it is literally as good as one could reasonably expect.[31] Indeed, because we are not dealing with a drug, this evidence makes randomized controlled trials unnecessary.

Now, Rancourt self-published an article he titled “Masks Don’t Work” where he suggests that the science indicates otherwise—but that brings me to the second part of my opening argument: debunking the pseudoscience.

In his article “Masks Don’t Work,” Rancourt offers a survey of seven (7) studies which he says prove that “masks don’t work.” But…

First, it’s not a true survey of the literature. Rancourt just combed through studies to find the ones he thinks support his position, and ignored the rest.  In logic, we call this “confirmation bias.” At best, it only proves some people can find some evidence for anything.”

Second, the majority of the studies he cites, like Smith (et. al. 2016) are irrelevant to his claim. They are about whether N95 masks protect their wearer better than surgical masks, not about whether cloth masks filter exhaled air. So he’s equivocating on the word “mask” and what it means for a mask “to work.” What’s more, although it is very unlikely that a surgical mask offers just as much protection as (properly sealed) N95 masks[32]even if they did, that wouldn’t even prove that cloth masks can’t filter inhaled air, much less exhaled air. With all protective equipment, you are bound to reach an upper limit, where adding more protection is just overkill.

Third, the other studies he mentions simply don’t say what he claims they do. For example, his quote from bin-Reza (2012) read “None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.” This implies that the study concluded that there is no benefit to wearing masks or respirators. In reality, however, the slash in the “mask/respirator” phrase is meant to indicate a comparison between the two—the study is actually saying that they are equally effective, not lumping them together and declaring them both ineffective. Several of the sentences before and after the one he quote mines demonstrate this. 

“Eight of nine retrospective observational studies found that mask and ⁄ or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS).”

And SARS, by the way, is the most analogous disease to COVID-19.

The text accompanying the other studies contain similarly misleading quotes or summaries.  As Jacobs (2009) said to me in correspondence,

Dr. Rancourt’s opinion piece mischaracterizes the research findings I reported in my 2009 peer-reviewed article…. It was not designed to examine mask effectiveness of preventing the mask-wearer from spreading a respiratory infection. My study has no bearing on addressing that recommendation…. [and] The mask used was a typical surgical (disposable paper) mask, not an N-95 respirator mask as [Rancourt] states in his article.

And the conclusions of others just outright contradict his thesis.

“There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission.” Cowling (et. al., 2010)

In other words, Rancourt scoured the literature, and the best he could do is find studies that don’t actually support his thesis, but which he could misquote or mis-summarize to make it look like they do.[33]

The second argument he presents cites Shaman’s 2010 article which suggests that humidity is responsible for seasonal variation in flu infections. From this he somehow concludes that masks cannot mitigate the spread. But (1) Shaman himself has said that we don’t know enough about COVID to conclude that humidity is a factor in its transmission[34]—and the fact that COVID is spreading like wildfire in Florida and Texas in July seems to indicate that it is not. Indeed, experts agree, that with new diseases, it’s not. [35] (2) This argument relies on the assumptions that COVID spreads solely via aerosols and masks don’t prevent aerosols from existing in the air; both of these assumptions are false. And (3) humidity causing seasonal variation wouldn’t mean that masks don’t work because humidity is not the only causal factor in transmission. There also is contact and contamination; thus, measures restricting those, like masks, would mitigate spread. In my logic class, we would call Rancourt’s error here “the fallacy of oversimplified cause.”[36]

Rancourt’s third argument suggests that infected droplets are too small to be blocked by N95 respirators, much less cloth masks. But here, he is not only (1) talking about inhalation not exhalation, (2) making false assumptions about aerosols and transmissibility, and (3) fallaciously appealing to incredulity to favor dubious theories, but (4) he doesn’t understand how N95 masks work; contrary to what he claims, because of Brownian motion, N95 filters are actually more efficient at filtering particles smaller than 0.3 microns. They are not sieves. Neither are most cloth masks.[37]

Lastly, Rancourt argues that, because masks can’t guarantee 0% exposure, they are useless. But here, he not only, again, (1) misrepresents the evidence[38] (2) makes unsupported assumptions about the minimal infective dose of COVID and a mathematical error that exaggerates the infectious potency of aerosols 10-million-fold,[39] and (3) fails to recognize that symptom severity could be proportional to the amount of viral exposure[40]—but (4) his argument is a prime example of the “all or nothing fallacy.” Yes, masks would need to 100% effective to completely stop the spread of COVID—but not to slow it. By merely reducing the amount of infected droplets in public places, they reduce spread.[41] Seatbelt laws are not 100% effective; some people still speed and accidents still happen. That doesn’t mean speed limits don’t reduce accidents.

Now, I do not expect any of this to have any effect on Rancourt or those in his echo chamber. They think otherwise for ideological reasons, not evidence based scientific ones. And you cannot reason someone out of a position that they did not reason themselves into. But what I have presented here is enough to convince any fair, open-minded person that, yes, indeed, public mask mandates assist in curbing the spread of Covid-19. Indeed, for them to do so, masks only need to do what we already knew they do: catch droplets. If they were unable to do this, the successful use of HEPA filters (which operate on the same principles as mask) in nearly every segment of the economy, and in your vacuum cleaner, would just be a giant coincidence. The burden of proof is thus on Rancourt to show otherwise. Needless to say, misrepresenting the scientific evidence and offering fallacious arguments does not meet that burden. 


[1] The cloth masks do somewhat filter the air we breathe in, but not enough to be effective in high risk environments. According to this article, some researchers are starting to suspect that they offer some protection to wearers in low-risk public environments, and studies to test this are hopefully coming soon. Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298  On whether medical/surgical (non-woven) masks are effective at protecting their wearer in high risk environment, the evidence seems to be mixed. MacIntyre (et al., 2014) showed that, while medical (surgical) masks provided some protection to the wearer in such environments, cloth masks provided almost none. See C. Raina MacIntyre, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare 1Workers,” BMJ Open 5 no. 4, (2015) https://doi.org/10.1136/bmjopen-2014-006577. The results in Seto (2003) and (Nishiura , 2005) also suggested that surgical masks do work to protect health care workers.  WH Seto,et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6. and Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25, https://pubmed.ncbi.nlm.nih.gov/16014825/. And Zhang (2009) suggests that they can protect even the general public. Lijie Zhang, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseaes 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765. But then Kähler (et al., 2020) seems to suggest that surgical (or similar) masks probably don’t provide sufficient protection for the wearer against droplet infection; only property fitted particle-filtering (e.g., N95) masks can do that. But all such studies are plagued by things like recall bias.
                When it comes to protecting others by filtering the air that a person breathes out, the study found that a simple mouth and nose cover is enough. Such masks are effective at limiting droplet emission when coughing, sneezing, speaking, singing, or breathing. Face coverings significantly reduce the spread of viruses and thus public mask wearing is “a very useful contribution to contain a pandemic.”  See Christian J. Kähler and Rainer Hain, “Fundamental Protective Mechanisms of Face Masks Against Droplet Infections,” Journal of Aerosol Science 148 (2020) https://doi.org/10.1016/j.jaerosci.2020.105617.

                [2] See also Rick Kushman, “Your Mask Cuts Own Risk by 65 Percent,” UC Davis, July 6, 2020, https://www.ucdavis.edu/coronavirus/news/your-mask-cuts-own-risk-65-percent/

[3] Talib Dbouk and Dimitris Drikakis, “On Respiratory Droplets and Face Masks,” Physics of Fluids 32, no. 063303, published electronically June 16, 2020, https://doi.org/10.1063/5.0015044.

[4] Bhanu Bhakta Neupane, Sangita Mainali, Amita Sharma, and Basant Giri, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks,” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

[5] Two more studies on mask effectiveness:
Qing-Xia Ma, et al, “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805.

This study suggested that 95% of viruses in aerosols could be blocked by homemade masks, and 97% could be blocked by surgical masks.

Nancy H. L. Leung, et al., “Respiratory Virus Shedding in Exhaled Breath and Efficacy of Face Masks,” Nature Medicine 26 (2020): 676-80, https://doi.org/10.1038/s41591-020-0843-2.
This is a study out of Hong Kong which suggested that people wearing a mask was very effective at reducing transmission of alpha coronaviruses.

[6] Cloth masks of only one material seem to have very little effectiveness: Samy Rengasamy, Benjamin Eimer, and Ronald E. Shaffer, “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles,” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044. This is why those who are just wearing bandanas, or pulling their t-shirt over their mouth, are not doing anyone any good.

[7]  Both types “significantly reduced the number of microorganisms expelled by volunteers,” the “the surgical mask was 3 times more effective.”) Anna Davies, et al., “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (August 2013): 413-8, https://doi.org/10.1017/dmp.2013.43.

                [8] Milton (2013) found that surgical masks decreased emission of large particles by 25 fold, and aerosols by 3 fold in flu patients. See Donald K Milton, et al., Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks,” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205. 5

[9] Aydin et al, 2020, suggests that layering great increases the filtering efficiency of cloth masks while also maintaining some breathability, Onur Aydin, et al., “Performance of Fabrics for Home-Made Masks Against the Spread of Respiratory Infections through Droplets: A Quantitative Mechanistic Study,” medRxiv,preprint, submitted July 8, 2020  https://doi.org/10.1101/2020.04.19.20071779.

[10] “Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.” Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

[11] Dr. Marty, a professor of infectious diseases at Florida International University told “Good Morning America.” “But if you add that filter, then you’re also adding a really good protection for yourself.” See Becky Worley, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe, “Face Masks With Filter add Another Layer of Protection, Experts Say,” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

[12] That’s not quite accurate. Particles around .3 microns are actually the hardest to catch. Those smaller are easier to catch because of Brownian motion. But this actually helps my thesis, so for simplicity I shall leave this nuanced point to the side.

[13] This is actually what N95 masks are for; they protect their wearer by being 95% effective at filtering the air that a person breathes in. And because they often have unfiltered exhaust vents, they usually don’t filter the air a person breathes out. Combine that with the fact that they don’t even perform their intended function well unless they are perfectly fit, and you can realize why they should likely only be worn by health care workers in high risk environments. It’s my estimation that the use of N95 masks by the general public likely wouldn’t help curb the spread of COVID-19 as well as the use of cloth masks.  But I’m happy to be corrected on that point.

[14] Some clarification here is useful. Technically, depending on how you classify “aerosoles” (definitions range from 5 microns to 100 microns), most of  the particles you breath out could be classified as arisoles–and depending on their size, the mask will filter them with different efficiencies. Even cloth masks are very good at filtering down to 10 microns, pretty good down to 5 microns, but not great below 5. Neupane, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.”

In one way, this is concerning because (according to Burch (2020), the average size for aerosoles leaving your mouth is 3 microns.  The good news is, despite the fact that they make up the largest number, they only represent 0.00024% of the liquid leaving your mouth during a cough. Consequently, very few of them are infected (at worst 1 out of every 700). A full “ 99.99976% of the viruses sprayed during a cough are carried in droplets — not aerosols.’) So the majority of transmission happens from droplets.  What’s more, the deadliest aerosoles are those that started out as droplets, but then evaporated down; they have higher concentrations of the virtus. Masks catch those.  Sso the inability of masks to filter out 3 micron arisles does not greatly hinder their ability to keep infected particles out of the air, and thus does not prevent them from efficiently preventing the spread of covid.
                Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” The Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-covid-19-from-aerosols-6c97d023bb6d.

[15] From the abstract of: Richard O. J. H. Stutt, Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin, “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic,” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

[16] Wycliffe E Wei, Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee, ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020,” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

                [17]Anthony D Sung, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial,”  Clin Infect Dis 63, no. 8 (October 2016): 999-1006, https://doi.org/10.1093/cid/ciw451.

[18] Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/ 10.1001/jama.2020.12897. In this study, cases of COVID-19 declined after mask mandates were put into effect in hospitals (that required all health care workers and patients to mask up). The study concluded that such mandates  reduce the transmission of SARS-CoV-2.

[19] Timo Mitze, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde, “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach,” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

This study shows the impact of mask mandates in Germany. In Jena, for example, the first German city to enact such a mandate, COVID-19 cases fell by almost 25% in 20 days. The study concluded that similar mandidats could ruse the daily growth rate by 40% in the long term, although it did acknowledge that, outside Germany, different norms and climatic conditions in other countries might result in different protective outcomes.

                [20] “HSC COVID-19 Report #5 – July 20, 2020,” University of North Texas Health Science Center at Fort Worth, https://www.scribd.com/presentation/469858261/COVID-19-Report-July-20-Updated?fbclid=IwAR1ta8C-x5yYfpqQ5eghmiPFr42ndbA6rYCmTv3WbcGU9tDt3a_RU1BOIL0.

[21] In those 15 US States, they likely prevented up to 450,000 cases in under two months. Wei Lyu and George L. Wehby, “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” Health Affair 39, no. 8 (2020): 1-7, https://doi.org/ 10.1377/hlthaff.2020.00818.

This was a retrospective analysis which examined the effects that different governmental orders to wear face masks had on COVID-19 growth rates, from April 9-May 15, 2020. It estimated that they prevated between 230,000 and 450,000 cases by May 22 (a reduction of 14-27%).

[22] Kasra Zarei and John Duchneskie, “Coronavirus Cases Rise in States with Relaxed Face Mask Policies,” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/covid-19-coronavirus-face-masks-infection-rates-20200624.html.

                [23] American Thoracic Society, “Countries with Early Adoption of Face Masks Showed Modest COVID-19 Infection Rates,” Medical Xpress, June 24, 2020, https://medicalxpress.com/news/2020-06-countries-early-masks-modest-covid-.html.

                [24] Samantha M. Tracht, Sara Y. Del Valle, and James M. Hyman, “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1),” Plos One 5, no. 2 (February 2010): 1-12, doi.org/10.1371/journal.pone.0009018.

[25] Stutt, et al.,“A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.”

To keep the infection rate (R0) below 1.0, the authors argue for widespread use of face masks. “[F]acemask adoption by entire populations would have a significant impact on reducing COVID-19 spread.” “[I]n summary, our modelling analyses provide support for the immediate, universal adoption of facemasks by the public.”

[26] Derek K Chu, et al., “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-analysis,” The Lancet 395, no. 10242 (2020): 1973-87, https://doi.org/10.1016/S0140-6736(20)31142-9.

This was a review of 172 observational studies and 44 relevant comparative studies. The authors concluded “Face mask use could result in a large reduction in risk of infection.”

[27] Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley, “Reducing Transmission of SARS-CoV-2,” Science 368, no. 6498 (June 2020): 1422-24, https://doi.org/10.1126/science.abc6197. In this paper, aerosol chemists and an infectious disease specialist argue that, because “airborne spread from undiagnosed infections will continuously undermine the effectiveness of even the most vigorous testing, tracing and social distancing programs,” the widespread use of masks are necessary to help prevent the spread of COVID. Both analytical information about the virus and information about countries where masks are commonplace was used.

Catherine M. Clase, et al., “Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Annals of Internal Medicine, published electronically May 22, 2020, https://doi.org/10.7326/M20-2567. This study, done by an international research team of medical doctors and other medical specialists not only concluded that cloth masks worn by the public will reduce COVID-19 transmission rates, but that the benefits of widespread mask use outweigh any risks that may be brought about by wearing masks (such as improper use).

                [28] M. Joshua Hendrix, Charlse Walde, Kendra Findley, and Robin Trotman, “Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy – Springfield, Missouri, May 2020,” Weekly 69, no. 28 (July 1, 2020): 930-32, http://dx.doi.org/10.15585/mmwr.mm6928e2external icon.

[29] “New IHME COVID-19 Model Projects Nearly 180,000 US Deaths,” IHME,June 24, 2020, http://www.healthdata.org/news-release/new-ihme-covid-19-model-projects-nearly-180000-us-deaths.

[30] For the quote, see McCabe, “Face Masks Really Do Matter.” For the evidence behind it, see  John T. Brooks, Jay C. Butler, Robert R. Redfield, “Universal Masking to Prevent SARS-CoV-2 Transmission – The Time is Now,” Jama, published online July 14, 2020, https://doi.org/10.1001/jama.2020.13107.

[31] for more such evidence, see “Face Masks – A Summary of Relevant Research Papers for COVID-19,” Sound Reason & More,June 11, 2020, https://soundreasonandmore.wordpress.com/2020/06/11/face-masks-a-summary-of-relevant-research-papers-for-covid-19/.

[32] See Sergey A. Grinshpun, et al., “Performance of an N95 Filtering Facepiece Particulate Respirator and a Surgical Mask During Human Breathing: Two Pathways for Particle Penetration,” Journal of Occupational and Environmental Hygiene 6, no. 10 (2009): 593-603, https://doi.org/10.1080/15459620903120086. See also C Raina MacIntyre, et al., “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers,” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17, https://doi.org/10.1111/irv.12474. See also Loeb M, McGeer A, Henry B, et al. “SARS among critical care nurses,” Toronto. Emerg Infect Dis 2004 Feb;10(2):251-5.

[33] Here is a full rundown of how Rancourt misrepresents the studies he cites, and how they are either irrelevant to his thesis, or actually contradict it.

Joshua L. Jacobs, et al., “Use of Surgical Face Masks to Reduce the Incidence of the Common Cold Among health Care Workers in Japan: A Randomized Controlled Trial,” Am J Infect Control 37, no. 5 (June 2009): 417-19, https://doi.org/ 10.1016/j.ajic.2008.11.002.

This study showed that N95 masks cause headaches in some, and that (surgical) facemasks don’t protect their wearer. This only tells us what we already know: Wearing a tight banded mask on your face for 12 hours is bound to cause headache, and surgical masks don’t provide adequate protection in high risk environments. And since both findings are irrelevant to whether cloth masks filter outgoing particles, this study is irrelevant to his thesis.

B.J. Cowling, Y. Zhou, D.K.M.Ip, G.M.Leung, and A.E. Aiello, “Face Masks to Prevent Transmission of Influenza Virus: A Systematic Review,” Epidemiology & Infection 138, no. 4 (January 2010): 449-456, https://doi.org/10.1017/S0950268809991658.

The part of the study that Rancourt mentions is about whether masks (in this case, cloth masks) protect their wearer from infection, not whether they filter exhaled air and thus protect others. So it is irrelevant to his thesis. What’s more, the authors admit that the body of evidence they are examining is not sufficient to draw a conclusion, but also suggest that the evidence that does exist at least suggests that cloth masks do provide some protection for their wearer—probably not enough for a healthcare setting, but maybe enough for household use. They recommend further study on this topic. The part of the study that Rancourt doesn’t mention is the part that examines whether cloth provides protection to others by filtering air, and they conclude that they do. Rancourt is engaged in major confirmation bias here, by just leaving that part out.

Faisal bin-Reza, Vicente Lopez Chavarrias, Angus Nicoll, Mary E. Chamberland, “The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence,” Influenza and Other Respiratory Viruses 6, no. 4 (December 2011): 257, https://do8i.org/ 0.1111/j.1750-2659.2011.00307.x.

As I mentioned in my opening statement, Rancourt uses a misleading quote from this one to imply that it found that “mask/respirators” don’t work, when in fact it found that they work equally well. What’s more, the part of the study Rancourt cities is about influenza, not COVID—and the authors themselves specifically state that their findings about influenza cannot be extrapolated to SARS-CoV-1 (“SARS is an unusual acute viral respiratory infection with a very different epidemiology to almost all other respiratory viral infections. It is fundamentally different from human influenza.”) But SARS-CoV-1 is very similar to SARS-CoV-2 (the cause of COVID-19), and about SARS-CoV-1 this study “found that mask and ⁄or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome.”

Jeffrey D. Smith, et al., “Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers from Acute Respiratory Infection: a Systematic Review and Meta-analysis,” CMAJ 188, no. 8 (May 2016): 567-74, https://doi.org/10.1503/cmaj.150835.

This study compares the effectiveness of N95 and surgical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. What more, it admits that it doesn’t prove that they do offer equal protection; just that the available evidence so far is inadequate for proving that N95 masks offer more protection in a clinical setting. “Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.” However, even though it was not enough to prove they were superior, they did find that “In general, compared with surgical masks, N95 respirators showed less filter penetration, less face-seal leakage and less total inward leakage under the laboratory experimental conditions described.” So this is far from proof that N95’s don’t work better than masks.

Vittoria Offedu, et al., “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis,” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42, https://doi.org/10.1093/cid/cix681.

Again, this study is about whether N95 and surgical masks protect their wearer—specifically healthcare workers in high risk settings. It is not about whether cloth masks protect others by catching expelled droplets of COVID. So it is irrelevant to the issue. (It found that N95 masks do protect better than surgical masks against clinical respiratory illness, but that N95 and surgical masks protect against viral infections and influenza-like illness equally well. Rancourt takes the quote about this (“Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant” out of context to make it seem like it is about the effectiveness of masks.) What’s more, it specifically found that masks and respirators do protect against SARS (which, again, is the closest thing to Covid-19). Indeed, it specifically stated that “This systematic review and meta-analysis supports the use of respiratory protection.”

Lewis J. Radonovich, Michael S. Simberkoff, and Mary T. Bessessen, “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial,” JAMA 322, no. 9 (2019): 824–833, https://doi.org/10.1001/jama.2019.11645.

Again, this study compares the effectiveness of N95 and medical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. What’s more, it’s about the flu—not SARS, so its findings really can’t be transferred over to COVID. Also, the non-difference could just be due to the N95’s not being properly sealed or used.

Youlin Long, et al., “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis,” J Evid Based Med 13 (2020): 93-101, https://doi.org/0.1111/jebm.12381.

Again, this study compares the effectiveness of N95 and medical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. And again, it’s about the flu—not SARS, so its findings really can’t be transferred over to COVID. It merely suggests that N95 masks should be reserved for health care workers in the most high risk situations—not that cloth masks can’t filter out droplets.

For this rundown, I partially relied on information provided here:  “Confirmation Bias Masks Truth OR Confirmation Bias, Masks, Truth,” Sound Reason & More,June 30, 2020, https://soundreasonandmore.wordpress.com/2020/06/30/confirmation-bias-masks-truth-or-confirmation-bias-masks-truth/?fbclid=IwAR38Vw0Ev6l5CU8bdn3f5uLsgPSkJErKyj07WPZiad-q0IcHxTl8mdH10o8.
                In other notes, I also relied on some information provided here: “Face Masks – A Summary of Relevant Research Papers for COVID-19.”

[34] Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, http://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer 

                [35] Quote from: Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/. Here is the study: Rachel E. Baker, Wenchang Yang, Gabriel A. Vecchi, C. Jessica E. Metcalf, and Bryan T. Grenfell, “Susceptible Supply Limits the Role of Climate in the Early SARS-CoV-2 Pandemic,” Science 369, no. 6501 (July 17, 2020): 315-19, https://doi.org/10.1126/science.abc2535.   

[36] To illustrate this fallacy, imagine that we forcibly locked everyone in a separate room for two months to mitigate the spread of the flu. This would be a bad idea for multiple reasons, but that level of isolation would obviously mitigate the spread. No physical contact means no spread. But now imagine someone said, “It won’t mitigate the spread at all because humidity explains seasonal variation.” Wouldn’t we laugh them out of the room. Even if humidity is normally a major factor, that doesn’t mean physical contact is not also a factor—and so it doesn’t mean that keeping people from being in contact wouldn’t mitigate the spread. Of course it would. In the same way, so would reducing the number of infected droplets in the air with masks.

[37] Just below 0.3 microns is where Brownian Motion starts, so 0.3 micron particles are actually the hardest to capture. N95 masks are so named because they are 95% efficient at capturing such particles. They are actually more efficient at capturing particles both larger and small than that.  “N95s – Sufficient Protection for Covid19?” https://www.sphosp.org/wp-content/uploads/2020/04/Letter-in-response-to-N-95-use-RA-Final.pdf. See also Olof Gustafsson, Simon Gustafsson, Levon Manukyan, and Albert Mihranyan, “Significance of Brownian Motion for Nanoparticle and Virus Capture in Nanocellulose-Based Filter Paper,” Membranes 8, no. 4, published online October 5, 2018, https://doi/org/10.3390/membranes8040090.  

                [38] Prasith Baccam, Catherine Beauchein, Catherine A Macken, Frederick G Hayden, and Alan S Perelson, “Kinetics of Influenza A Virus Infection in Humans,” Journal of Virology 80, no. 15 (August 2006): 7590-9, https://doi.org/ 10.1128/JVI.01623-05 and Christopher B Brooke, William L Ince, Jens Wrammert, Rafi Ahmed, Patrick C Wilson, Jack R Bennink, and Jonathan W Yewdell, “Most Influenza A Virions Fail To Express at Least One Essential Viral Protein,” Journal of Virology87, no. 6 (March 2013): 3155-62, https://doi.org/ 10.1128/JVI.02284-12 They only talk about how quickly or efficiently viruses reproduce in cells once they are infected–not the probability of cells becoming infected once exposed.

[39] What’s more, he makes a mathematical error that greatly overestimates how many viruses would be in an aerosolized droplet. He says that “there are 1000 to 10 million viral particles, in each microdroplet 1 to 10 microns in size.” But, in fact, microdroplets of that size are mostly empty of virus and contain at most a single viral particle. Why? Because it’s difficult to get coronavirus into a concentration much higher than 10 million per mL (plaque forming units per milliliter)[39]; and a 10 micron droplet is (4/3 * 5^3 * 10^-18 m^3 =) 0.167 picoliter. A ml is 1 billion picoliters. So for every 1,000 10 micron droplets, only at most 2 (1.67) will have even a single virus in it—that’s roughly 1 out of every 600. So he is making an mathematical error of a factor of at least 10 million here. (My thanks to MW and my wife for the math!) And since it is far from established that one virus is sufficient for an infection, much less a severe on, his argument here is based on nothing. Source: Yinon M Bar-On, Avi Flamholz, Rob Phillps, and Ron Milo, “SARS-CoV-2 (COVID-19) By the Numbers,” eLIfe 9, no. e57309, published online April 2, 2020, https://doi.org/10.7554/eLife.57309.  

                [40] Carl Heneghan, Jon Brassey, and Tom Jefferson, “SARS-CoV-2 Viral Load and the Severity of COVID-19,” CEBM, March 26, 2020, https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/.

[41] Think of it this way; speed limits aren’t perfect. Some people will break the law; accidents will still happen. But that doesn’t mean speed limits don’t reduce the number of accidents. In the same way, although they won’t eliminate it, mask mandates will assist in curbing the spread of Covid-19.

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Long, Youlin, Tengyue Hu, Liqin Liu, Rui Chen, Qiong Guo, Liu Yang, Yifan Cheng, Jin Huang, et al. “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis.” J Evid Based Med 13 (2020): 93-101. https://doi.org/0.1111/jebm.12381.

Lyu, Wei, and George L. Wehby. “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US.” Health Affair 39, no. 8 (2020): 1-7. https://doi.org/ 10.1377/hlthaff.2020.00818.

Ma, Qing-Xia, Hu Shan, Hong-Liang Zhang, Gui-Mei Li, Rui-Mei Yang, and Ji-Ming Chen. “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2.” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805.

MacIntyre, C Raina, Holly Seale, Tham Chi Dung, Nguyen Tran Hien, Phan Thi Nga, Abar Ahmad Chughtai, Bayzidur Rahman, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare Workers.” BMJ Open 5, no. 4 (2015) https://doi.org/10.1136/bmjopen-2014-006577.

MacIntyre, C Raina, Abrar Ahmad Chughtai, Bayzidur Rahman, Yang Peng, Yi Zhang, Holly Seale, Xiaoli Wang, et al. “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers.” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17. https://doi.org/10.1111/irv.12474.

McCabe, Caitlin. “Face Masks Really Do Matter. The Scientific Evidence Is Growing.” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298.

            Milton, Donald K., M> Patricia Fabian, Benjamin J. Cowling, Michael L Grantham, and James J. McDevitt.Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks.” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205.

Mitze, Timo, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde. “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach.” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

            Neupane, Bhanu Bhakta, Sangita Mainali, Amita Sharma, and Basant Giri. “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

“New IHME COVID-19 Model Projects Nearly 180,000 US Deaths.” IHME,June 24, 2020. http://www.healthdata.org/news-release/new-ihme-covid-19-model-projects-nearly-180000-us-deaths.

            Nishiura, Hiroshi, Tadatoshi Kuratsuji, Tan Quy, Nguyen Chi Phi, Vo Van Ban, L E Dang Ha, Hoang Thuy Long, et al. “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam.” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25. https://pubmed.ncbi.nlm.nih.gov/16014825/.

“N95s – Sufficient Protection for Covid19?” https://www.sphosp.org/wp-content/uploads/2020/04/Letter-in-response-to-N-95-use-RA-Final.pdf.

Offedu, Vittoria, Chee Fu Yung, Mabel Sheau Fong Low, and Clarence C Tam. “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis.” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42. https://doi.org/10.1093/cid/cix681.

Prather, Kimberly A., Chia C. Wang, and Robert T. Schooley. “Reducing Transmission of SARS-CoV-2.” Science 368, no. 6498 (June 2020): 1422-24. https://doi.org/10.1126/science.abc6197.

Radonovich, Lewis J., Michael S. Simberkoff, and Mary T. Bessessen. “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial.” JAMA 322, no. 9 (2019): 824–833. https://doi.org/10.1001/jama.2019.11645.

Rengasamy, Samy, Benjamin Eimer, and Ronald E. Shaffer. “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles.” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044.

            Seto, WH, D Tsang, RWH Yung, TY Ching, TK Ng, M Ho, LM Ho, et al. “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS).” The Lancet 361, no 9368 (May 3, 2003): 1519-20. https://doi.org/10.1016/S0140-6736(03)13168-6.

Smith, Jeffrey D., Colin C. MacDougall, Jennie Johnstone, Ray A. Copes, Brain Schwartz, and Gary E. Garber. “Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers from Acute Respiratory Infection: a Systematic Review and Meta-analysis.” CMAJ 188, no. 8 (May 2016): 567-74. https://doi.org/10.1503/cmaj.150835.

Stutt, Richard O. J. H., Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin. “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.        

Sung, Anthony D, Julia A. M. Sung, Samantha Thomas, Terry Hyslop, Cristina Gasparetto, Gwynn Long, David Rizzieri, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial.” Clin Infect Dis 63, no. 8 (October 2016): 999-1006. https://doi.org/10.1093/cid/ciw451.

            Tracht, Samantha M., Sara Y. Del Valle, and James M. Hyman. “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1).” Plos One 5, no. 2 (February 2010): 1-12. doi.org/10.1371/journal.pone.0009018.

Wang, Xiaowen, Enrico G. Ferro, Guohai Zhou, et al. “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers.” JAMA.Published electronically July 14, 2020. https://doi.org/ 10.1001/jama.2020.12897.

            Weaver, G. H. “The Value of the Face Mask and Other Measures.” The Journal A. M. A.70, no. 2 (January 12, 1918): 76-78. https://doi.org/10.1001/jama.1918.02600020010005.

Wei, Wycliffe E., Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee. ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020.” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

Worley, Becky, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe. “Face Masks With Filter add Another Layer of Protection, Experts Say.” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

Yu, Alan. “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/.

Zarei, Kasra, and John Duchneski. “Coronavirus Cases Rise in States with Relaxed Face Mask Policies.” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/covid-19-coronavirus-face-masks-infection-rates-20200624.html.

            Zhang, Lijie, Zhibin Peng, Jianming Ou, Guang Zeng, Robert E. Fontaine, Mingbin Liu, Fuqiang Cui, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseaes 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765.

Thanks Petar

While I do appreciate this opportunity, I’d like to begin by expressing my reservation about participating in this debate. Anyone curious about the effectiveness of mask mandates should listen to current medical and public health experts—epidemiologists and immunologists—not a debate between a philosopher/logician and a physicist who specialized in metals but no longer works or publishes in academia.

What’s more, there is really no debate to be had on this issue. There was a debate, in the scientific community, a few months ago—but it was settled very quickly once the evidence was laid out. Indeed, initially, I thought that public mask wearing was overkill. But then I learned how COVID spreads, and how prevalent asymptomatic spread of COVID is. To help curb its spread, all masks have to do is reduce the number of infected particles that exit an infected person’s mouth—and good evidence suggests they do. Since I am willing to update my beliefs in light of new evidence, I changed my mind.

This, Petar, is why you couldn’t find any medical experts for this debate; they’ve already had it. And engaging with pseudoscientific arguments risks legitimizing them. But I engage with pseudoscience for a living. And since this is one of those times that pseudoscience can kill, I decided to take this opportunity to (1) communicate the scientific argument on this issue to a broader audience and (2) debunk the pseudoscience. Fortunately, as a philosopher and logician, who teaches and publishes on logic, argumentation, philosophy of science, medical diagnosis, and medical pseudoscience—I am especially qualified to do these two things.  

SLIDE 2

Ok, so first: how and why masks assist in curbing the spread of Covid-19.

The explanation is simple, but misinformation has confused the issue. It’s commonly believed that masks simply protect their wearer from becoming infected by filtering the air that a person inhales. But while there is some evidence that cloth masks maybe offer some protection to their wearer in this regard,[1],[2] the primary way they help mitigate the spread is by filtering the air a person exhales—by [click] sneezing, coughing, speaking, or breathing.

SLIDE 3

Why are masks effective in filtering viruses from the exhaled air? Because a virus doesn’t travel by itself; it travels in droplets of moisture propelled from the mouth that can be captured. The largest droplets are intercepted by the surface of the mask; smaller ones are stopped by impaction as they try to make it through the mask; and the smallest, including aerosols, are diffused by the mask because of something called Brownian motion–the erratic way they move. This lowers the number of infected droplets in the air, and thus reduces the risk of exposure for other people.[3] [4]

SLIDE 4

Now, it’s important to note that, while all masks filter exhalations,[5] certain kinds of masks are better than others.[6] The early woven cloth masks were effective, but not as effective as later non-woven ones—what we today call “medical” or “surgical masks.” (According to Davies (et al, 2013), while both types are effective, surgical masks are about three times more effective. [7] [8] But different kinds of cloth, layered or combined, can offer better filtration, by making the pathway particles would have to travel to get through the mask more convoluted. Aydin (et al, 2020) found that layering cotton fabrics can make homemade masks almost as effective as surgical masks,[9] and Konda (et al, 2020) found that layering different kinds of fabrics (like cotton with flannel) could also increase their efficacy.  Such masks filtered 80% of particles smaller than 300 nanometers (0.3 microns) and 90% of those larger. [10] Filters can also improve mask efficacy.[11]

SLIDE 5

Now if an infected droplet is already in the air that a masked person is about to inhale, the mask will be less likely to catch that particle. That might make one question how cloth masks can filter the air that someone exhales. But that question is easily answered. Part of it is due to air flow; when you are breathing in, you are not pushing the air directly through the mask. But also–the longer a droplet is in the air, the more opportunity it has to evaporate and become smaller (and even aerosolize)—and (unless it’s smaller than 0.3 microns) the smaller it is, the less likely a particle is to be caught by a mask.[12] So infected droplets in the air that an unmasked person has exhaled has a better chance at making it through your mask. But most of the infected droplets exiting your mouth won’t, since they have not yet had a chance to evaporate.[13] [14]

SLIDE 6

In other words, masks unquestionably filter droplets (on the right), including most of them that would become aerosols (in the middle) And they can even capture those that start out small (on the far left), just less efficiently.

So, if you are in a room with a non-masked infected person, you are pretty likely to be infected even if you are wearing a cloth mask. However, if that infected person is wearing a cloth mask, you are much less likely to be infected—even if you are not wearing a mask. This is why it is said “My mask protects you, your mask protects me.”[15] Your choice to not wear a mask does not put you at risk; it puts others at risk.

Now, since the fact that the majority of the work that masks do in curbing the spread of COVID is done by the masks that infected persons are wearing, one might wonder …

SLIDE 7

… why we don’t just have infected people wear them. Indeed, this was part of the reasoning behind the traditional ], years long, CDC and WHO recommendations that said mask wearing is not necessary for seemingly healthy individuals. With many diseases it is not. But then experts realized just how long a person could be infected with COVID without knowing it, and even that many infected never have any symptoms.[16] Consequently, public mask mandates are the only way to ensure that infected persons—including those who are pre- or asymptomatic—are wearing a mask. Such mandates would thus reduce the number of infected people without masks, thus reduce the number of infected particles in the air, and thus reduce the probability of transmission. Once we realized this, mask wearing was recommended. Granted, the CDC and WHO lagged behind the experts in this regard. But scientists change their mind based on evidence all the time. That’s not unusual. It’s just usually not that public.

SLIDE 8

So given what we know masks do, the fact that mandating them helps curb the spread of COVID is just common sense. But the evidence also bears this out. Now you can’t do a direct, controlled experiment where you blindly throw non-infected people into rooms with masked or un-masked infected persons, and see if they get sick. That’s unethical. But all the ethical ways to study this question indirectly indicate that cloth masks curb the spread.

For example, transmission rates slowed in hospitals (Sung (2016)[17] Wang, et. al., 2020),[18] German cities (Mitz, et. al 2020),[19] North Texas (Nandy, 2020),[20] and in US states (Lyu & Wehby, 2020),[21] after mandates went into effect. (In Germany, they reduced growth rates by 40%.) What’s more, U.S. States with mandates have seen much less spread than those without, [22] as have countries where mask use is popular.[23] Modeling has also confirmed the effectiveness of mask mandates.[24] According to Stutt (et. al., 2020)[25] and Eikenberry (et. al., 2020), if masks are just 50% effective, they could help bring down infection rates to non-epidemic levels and reduce the death rate by as much as 45%. Large reviews of observational and comparative studies have also concluded that mask mandates are highly effective,[26] as have collections of collaborating experts.[27] And, of course, there were those infected hairstylists in Missouri who didn’t pass it on to 140 of their clients because they were wearing a mask.[28]

The IHME found that mask mandates could save 33,000 by October 1st,[29] and (according to Brooks, 2020) if everyone worse a mask, we could get the pandemic under control in four to eight weeks.[30] None of this is as good evidence as the above described unethical blinded study would provide, but it is literally as good as one could reasonably expect.[31] Indeed, because we are not dealing with a drug, this evidence makes randomized controlled trials unnecessary.

Now, Rancourt self-published an article he titled “Masks Don’t Work” where he suggests that the science indicates otherwise—but that brings me to the second part of my opening argument: debunking the pseudoscience.

SLIDE 9

In his article “Masks Don’t Work,” Rancourt offers a survey of seven (7) studies which he says prove that “masks don’t work.” But…

First, it’s not a true survey of the literature. Rancourt just combed through studies to find the ones he thinks support his position, and ignored the rest.  In logic, we call this “confirmation bias.” At best, it only proves some people can find some evidence for anything.”

Second, the majority of the studies he cites, like Smith (et. al. 2016) are irrelevant to his claim. They are about whether N95 masks protect their wearer better than surgical masks, not about whether cloth masks filter exhaled air. So he’s equivocating on the word “mask” and what it means for a mask “to work.” What’s more, although it is very unlikely that a surgical mask offers just as much protection as (properly sealed) N95 masks[32]even if they did, that wouldn’t even prove that cloth masks can’t filter inhaled air, much less exhaled air. With all protective equipment, you are bound to reach an upper limit, where adding more protection is just overkill.

SLIDE 10

Third, the other studies he mentions simply don’t say what he claims they do. For example, his quote from bin-Reza (2012) read “None of the studies established a conclusive relationship between mask/respirator use and protection against influenza infection.” This implies that the study concluded that there is no benefit to wearing masks or respirators. In reality, however, the slash in the “mask/respirator” phrase is meant to indicate a comparison between the two—the study is actually saying that they are equally effective, not lumping them together and declaring them both ineffective. Several of the sentences before and after the one he quote mines demonstrate this. 

“Eight of nine retrospective observational studies found that mask and ⁄ or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome (SARS).”

And SARS, by the way, is the most analogous disease to COVID-19.

The text accompanying the other studies contain similarly misleading quotes or summaries.  As Jacobs (2009) said to me in correspondence,

Dr. Rancourt’s opinion piece mischaracterizes the research findings I reported in my 2009 peer-reviewed article…. It was not designed to examine mask effectiveness of preventing the mask-wearer from spreading a respiratory infection. My study has no bearing on addressing that recommendation…. [and] The mask used was a typical surgical (disposable paper) mask, not an N-95 respirator mask as [Rancourt] states in his article.

And the conclusions of others just outright contradict his thesis.

“There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission.” Cowling (et. al., 2010)

In other words, Rancourt scoured the literature, and the best he could do is find studies that don’t actually support his thesis, but which he could misquote or mis-summarize to make it look like they do.[33]

SLIDE 11

The second argument he presents cites Shaman’s 2010 article which suggests that humidity is responsible for seasonal variation in flu infections. From this he somehow concludes that masks cannot mitigate the spread. But (1) Shaman himself has said that we don’t know enough about COVID to conclude that humidity is a factor in its transmission[34]—and the fact that COVID is spreading like wildfire in Florida and Texas in July seems to indicate that it is not. Indeed, experts agree, that with new diseases, it’s not. [35] (2) This argument relies on the assumptions that COVID spreads solely via aerosols and masks don’t prevent aerosols from existing in the air; both of these assumptions are false. And (3) humidity causing seasonal variation wouldn’t mean that masks don’t work because humidity is not the only causal factor in transmission. There also is contact and contamination; thus, measures restricting those, like masks, would mitigate spread. In my logic class, we would call Rancourt’s error here “the fallacy of oversimplified cause.”[36]

SLIDE 12

Rancourt’s third argument suggests that infected droplets are too small to be blocked by N95 respirators, much less cloth masks. But here, he is not only (1) talking about inhalation not exhalation, (2) making false assumptions about aerosols and transmissibility, and (3) fallaciously appealing to incredulity to favor dubious theories, but (4) he doesn’t understand how N95 masks work; contrary to what he claims, because of Brownian motion, N95 filters are actually more efficient at filtering particles smaller than 0.3 microns. They are not sieves. Neither are most cloth masks.[37]

SLIDE 13

Lastly, Rancourt argues that, because masks can’t guarantee 0% exposure, they are useless. But here, he not only, again, (1) misrepresents the evidence[38] (2) makes unsupported assumptions about the minimal infective dose of COVID and a mathematical error that exaggerates the infectious potency of aerosols 10-million-fold,[39] and (3) fails to recognize that symptom severity could be proportional to the amount of viral exposure[40]—but (4) his argument is a prime example of the “all or nothing fallacy.” Yes, masks would need to 100% effective to completely stop the spread of COVID—but not to slow it. By merely reducing the amount of infected droplets in public places, they reduce spread.[41] Seatbelt laws are not 100% effective; some people still speed and accidents still happen. That doesn’t mean speed limits don’t reduce accidents.

SLIDE 14: BIBLIO

Now, I do not expect any of this to have any effect on Rancourt or those in his echo chamber. They think otherwise for ideological reasons, not evidence based scientific ones. And you cannot reason someone out of a position that they did not reason themselves into. But what I have presented here is enough to convince any fair, open-minded person that, yes, indeed, public mask mandates assist in curbing the spread of Covid-19. Indeed, for them to do so, masks only need to do what we already knew they do: catch droplets. If they were unable to do this, the successful use of HEPA filters (which operate on the same principles as mask) in nearly every segment of the economy, and in your vacuum cleaner, would just be a giant coincidence. The burden of proof is thus on Rancourt to show otherwise. Needless to say, misrepresenting the scientific evidence and offering fallacious arguments does not meet that burden. 


[1] The cloth masks do somewhat filter the air we breathe in, but not enough to be effective in high risk environments. According to this article, some researchers are starting to suspect that they offer some protection to wearers in low-risk public environments, and studies to test this are hopefully coming soon. Caitlin McCabe, “Face Masks Really Do Matter. The Scientific Evidence Is Growing,” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298  On whether medical/surgical (non-woven) masks are effective at protecting their wearer in high risk environment, the evidence seems to be mixed. MacIntyre (et al., 2014) showed that, while medical (surgical) masks provided some protection to the wearer in such environments, cloth masks provided almost none. See C. Raina MacIntyre, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare 1Workers,” BMJ Open 5 no. 4, (2015) https://doi.org/10.1136/bmjopen-2014-006577. The results in Seto (2003) and (Nishiura , 2005) also suggested that surgical masks do work to protect health care workers.  WH Seto,et al., “Effectiveness of Precautions Against Droplets and Contact in Prevention of Nosocomial Transmission of Severe Acute Respiratory Syndrome (SARS),” The Lancet 361, no 9368 (May 3, 2003): 1519-20, https://doi.org/10.1016/S0140-6736(03)13168-6. and Hiroshi Nishiura, et al., “Rapid Awareness and Transmission of Severe Acute Respiratory Syndrome in Hanoi French Hospital, Vietnam,” Am J Trop Med Hyg 73, no. 1 (July 2005): 17-25, https://pubmed.ncbi.nlm.nih.gov/16014825/. And Zhang (2009) suggests that they can protect even the general public. Lijie Zhang, et al., “Protection by Face Masks against Influenza A(H1N1)pdm09 Virus on Trans-Pacific Passenger Aircraft, 2009,” Emerging Infectious Diseaes 19, no. 9 (September 2013): 1403-10, https://doi.org/10.3201/eid1909.121765. But then Kähler (et al., 2020) seems to suggest that surgical (or similar) masks probably don’t provide sufficient protection for the wearer against droplet infection; only property fitted particle-filtering (e.g., N95) masks can do that. But all such studies are plagued by things like recall bias.
                When it comes to protecting others by filtering the air that a person breathes out, the study found that a simple mouth and nose cover is enough. Such masks are effective at limiting droplet emission when coughing, sneezing, speaking, singing, or breathing. Face coverings significantly reduce the spread of viruses and thus public mask wearing is “a very useful contribution to contain a pandemic.”  See Christian J. Kähler and Rainer Hain, “Fundamental Protective Mechanisms of Face Masks Against Droplet Infections,” Journal of Aerosol Science 148 (2020) https://doi.org/10.1016/j.jaerosci.2020.105617.

                [2] See also Rick Kushman, “Your Mask Cuts Own Risk by 65 Percent,” UC Davis, July 6, 2020, https://www.ucdavis.edu/coronavirus/news/your-mask-cuts-own-risk-65-percent/

[3] Talib Dbouk and Dimitris Drikakis, “On Respiratory Droplets and Face Masks,” Physics of Fluids 32, no. 063303, published electronically June 16, 2020, https://doi.org/10.1063/5.0015044.

[4] Bhanu Bhakta Neupane, Sangita Mainali, Amita Sharma, and Basant Giri, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks,” PeerJ 7,no. e7142 (2019), https://doi.org/10.7717/peerj.7142.

[5] Two more studies on mask effectiveness:
Qing-Xia Ma, et al, “Potential Utilities of Mask-Wearing and Instant Hand Hygiene for Fighting SARS-CoV-2” Journal of Medical Virology (2020) https://doi.org/10.1002/jmv.25805.

This study suggested that 95% of viruses in aerosols could be blocked by homemade masks, and 97% could be blocked by surgical masks.

Nancy H. L. Leung, et al., “Respiratory Virus Shedding in Exhaled Breath and Efficacy of Face Masks,” Nature Medicine 26 (2020): 676-80, https://doi.org/10.1038/s41591-020-0843-2.
This is a study out of Hong Kong which suggested that people wearing a mask was very effective at reducing transmission of alpha coronaviruses.

[6] Cloth masks of only one material seem to have very little effectiveness: Samy Rengasamy, Benjamin Eimer, and Ronald E. Shaffer, “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles,” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044. This is why those who are just wearing bandanas, or pulling their t-shirt over their mouth, are not doing anyone any good.

[7]  Both types “significantly reduced the number of microorganisms expelled by volunteers,” the “the surgical mask was 3 times more effective.”) Anna Davies, et al., “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?” Disaster Medicine and Public Health Preparedness 7, no. 4 (August 2013): 413-8, https://doi.org/10.1017/dmp.2013.43.

                [8] Milton (2013) found that surgical masks decreased emission of large particles by 25 fold, and aerosols by 3 fold in flu patients. See Donald K Milton, et al., Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks,” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205. 5

[9] Aydin et al, 2020, suggests that layering great increases the filtering efficiency of cloth masks while also maintaining some breathability, Onur Aydin, et al., “Performance of Fabrics for Home-Made Masks Against the Spread of Respiratory Infections through Droplets: A Quantitative Mechanistic Study,” medRxiv,preprint, submitted July 8, 2020  https://doi.org/10.1101/2020.04.19.20071779.

[10] “Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.” Abhiteja Konda, Abhinav Prakash, Gregory A. Moss, Michael Schmoldt, Gregory D. Grant, and Supratik Guha, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano 14, no. 5 (2020): 6339-47, https://doi.org/10.1021/acsnano.0c03252.

[11] Dr. Marty, a professor of infectious diseases at Florida International University told “Good Morning America.” “But if you add that filter, then you’re also adding a really good protection for yourself.” See Becky Worley, Anthon Kane, Robyn Weil, and Angeline Jane Bernabe, “Face Masks With Filter add Another Layer of Protection, Experts Say,” GMA, July 16, 2020, https://abcnews.go.com/GMA/Wellness/face-masks-filters-add-layer-protection-experts/story?id=71811792.

[12] That’s not quite accurate. Particles around .3 microns are actually the hardest to catch. Those smaller are easier to catch because of Brownian motion. But this actually helps my thesis, so for simplicity I shall leave this nuanced point to the side.

[13] This is actually what N95 masks are for; they protect their wearer by being 95% effective at filtering the air that a person breathes in. And because they often have unfiltered exhaust vents, they usually don’t filter the air a person breathes out. Combine that with the fact that they don’t even perform their intended function well unless they are perfectly fit, and you can realize why they should likely only be worn by health care workers in high risk environments. It’s my estimation that the use of N95 masks by the general public likely wouldn’t help curb the spread of COVID-19 as well as the use of cloth masks.  But I’m happy to be corrected on that point.

[14] Some clarification here is useful. Technically, depending on how you classify “aerosoles” (definitions range from 5 microns to 100 microns), most of  the particles you breath out could be classified as arisoles–and depending on their size, the mask will filter them with different efficiencies. Even cloth masks are very good at filtering down to 10 microns, pretty good down to 5 microns, but not great below 5. Neupane, “Optical Microscopic Study of Surface Morphology and Filtering Efficiency of Face Masks.”

In one way, this is concerning because (according to Burch (2020), the average size for aerosoles leaving your mouth is 3 microns.  The good news is, despite the fact that they make up the largest number, they only represent 0.00024% of the liquid leaving your mouth during a cough. Consequently, very few of them are infected (at worst 1 out of every 700). A full “ 99.99976% of the viruses sprayed during a cough are carried in droplets — not aerosols.’) So the majority of transmission happens from droplets.  What’s more, the deadliest aerosoles are those that started out as droplets, but then evaporated down; they have higher concentrations of the virtus. Masks catch those.  Sso the inability of masks to filter out 3 micron arisles does not greatly hinder their ability to keep infected particles out of the air, and thus does not prevent them from efficiently preventing the spread of covid.
                Adrien Burch, “A Microscopic Perspective on Airborne COVID-19,” The Medium, March 31, 2020, https://medium.com/better-humans/should-you-be-worried-about-catching-covid-19-from-aerosols-6c97d023bb6d.

[15] From the abstract of: Richard O. J. H. Stutt, Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin, “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic,” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.

[16] Wycliffe E Wei, Zongbin Li, Calvin J Chiew, Sarah E Yong, Matthias P Toh, and Vernon J Lee, ”Presymptomatic Transmission of SARS-CoV-2-Singapore, January 23-March 16, 2020,” MMWR Morb Mortal Wkly Rep. 69, no. 14 (April 2020): 411-5, https://doi.org/10.15585/mmwr.mm6914e1.

                [17]Anthony D Sung, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial,”  Clin Infect Dis 63, no. 8 (October 2016): 999-1006, https://doi.org/10.1093/cid/ciw451.

[18] Xiaowen Wang, Enrico G. Ferro, Guohai Zhou, et al., “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers,” JAMA,published electronically July 14, 2020, https://doi.org/ 10.1001/jama.2020.12897. In this study, cases of COVID-19 declined after mask mandates were put into effect in hospitals (that required all health care workers and patients to mask up). The study concluded that such mandates  reduce the transmission of SARS-CoV-2.

[19] Timo Mitze, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde, “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach,” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

This study shows the impact of mask mandates in Germany. In Jena, for example, the first German city to enact such a mandate, COVID-19 cases fell by almost 25% in 20 days. The study concluded that similar mandidats could ruse the daily growth rate by 40% in the long term, although it did acknowledge that, outside Germany, different norms and climatic conditions in other countries might result in different protective outcomes.

                [20] “HSC COVID-19 Report #5 – July 20, 2020,” University of North Texas Health Science Center at Fort Worth, https://www.scribd.com/presentation/469858261/COVID-19-Report-July-20-Updated?fbclid=IwAR1ta8C-x5yYfpqQ5eghmiPFr42ndbA6rYCmTv3WbcGU9tDt3a_RU1BOIL0.

[21] In those 15 US States, they likely prevented up to 450,000 cases in under two months. Wei Lyu and George L. Wehby, “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US,” Health Affair 39, no. 8 (2020): 1-7, https://doi.org/ 10.1377/hlthaff.2020.00818.

This was a retrospective analysis which examined the effects that different governmental orders to wear face masks had on COVID-19 growth rates, from April 9-May 15, 2020. It estimated that they prevated between 230,000 and 450,000 cases by May 22 (a reduction of 14-27%).

[22] Kasra Zarei and John Duchneskie, “Coronavirus Cases Rise in States with Relaxed Face Mask Policies,” The Philadelphia Inquirer, June 24, 2020, https://www.inquirer.com/health/coronavirus/covid-19-coronavirus-face-masks-infection-rates-20200624.html.

                [23] American Thoracic Society, “Countries with Early Adoption of Face Masks Showed Modest COVID-19 Infection Rates,” Medical Xpress, June 24, 2020, https://medicalxpress.com/news/2020-06-countries-early-masks-modest-covid-.html.

                [24] Samantha M. Tracht, Sara Y. Del Valle, and James M. Hyman, “Mathematical Modeling of the Effectiveness of Facemasks in Reducing the Spread of Novel Influenza A (H1N1),” Plos One 5, no. 2 (February 2010): 1-12, doi.org/10.1371/journal.pone.0009018.

[25] Stutt, et al.,“A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.”

To keep the infection rate (R0) below 1.0, the authors argue for widespread use of face masks. “[F]acemask adoption by entire populations would have a significant impact on reducing COVID-19 spread.” “[I]n summary, our modelling analyses provide support for the immediate, universal adoption of facemasks by the public.”

[26] Derek K Chu, et al., “Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-analysis,” The Lancet 395, no. 10242 (2020): 1973-87, https://doi.org/10.1016/S0140-6736(20)31142-9.

This was a review of 172 observational studies and 44 relevant comparative studies. The authors concluded “Face mask use could result in a large reduction in risk of infection.”

[27] Kimberly A. Prather, Chia C. Wang, and Robert T. Schooley, “Reducing Transmission of SARS-CoV-2,” Science 368, no. 6498 (June 2020): 1422-24, https://doi.org/10.1126/science.abc6197. In this paper, aerosol chemists and an infectious disease specialist argue that, because “airborne spread from undiagnosed infections will continuously undermine the effectiveness of even the most vigorous testing, tracing and social distancing programs,” the widespread use of masks are necessary to help prevent the spread of COVID. Both analytical information about the virus and information about countries where masks are commonplace was used.

Catherine M. Clase, et al., “Cloth Masks May Prevent Transmission of COVID-19: An Evidence-Based, Risk-Based Approach,” Annals of Internal Medicine, published electronically May 22, 2020, https://doi.org/10.7326/M20-2567. This study, done by an international research team of medical doctors and other medical specialists not only concluded that cloth masks worn by the public will reduce COVID-19 transmission rates, but that the benefits of widespread mask use outweigh any risks that may be brought about by wearing masks (such as improper use).

                [28] M. Joshua Hendrix, Charlse Walde, Kendra Findley, and Robin Trotman, “Absence of Apparent Transmission of SARS-CoV-2 from Two Stylists After Exposure at a Hair Salon with a Universal Face Covering Policy – Springfield, Missouri, May 2020,” Weekly 69, no. 28 (July 1, 2020): 930-32, http://dx.doi.org/10.15585/mmwr.mm6928e2external icon.

[29] “New IHME COVID-19 Model Projects Nearly 180,000 US Deaths,” IHME,June 24, 2020, http://www.healthdata.org/news-release/new-ihme-covid-19-model-projects-nearly-180000-us-deaths.

[30] For the quote, see McCabe, “Face Masks Really Do Matter.” For the evidence behind it, see  John T. Brooks, Jay C. Butler, Robert R. Redfield, “Universal Masking to Prevent SARS-CoV-2 Transmission – The Time is Now,” Jama, published online July 14, 2020, https://doi.org/10.1001/jama.2020.13107.

[31] for more such evidence, see “Face Masks – A Summary of Relevant Research Papers for COVID-19,” Sound Reason & More,June 11, 2020, https://soundreasonandmore.wordpress.com/2020/06/11/face-masks-a-summary-of-relevant-research-papers-for-covid-19/.

[32] See Sergey A. Grinshpun, et al., “Performance of an N95 Filtering Facepiece Particulate Respirator and a Surgical Mask During Human Breathing: Two Pathways for Particle Penetration,” Journal of Occupational and Environmental Hygiene 6, no. 10 (2009): 593-603, https://doi.org/10.1080/15459620903120086. See also C Raina MacIntyre, et al., “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers,” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17, https://doi.org/10.1111/irv.12474. See also Loeb M, McGeer A, Henry B, et al. “SARS among critical care nurses,” Toronto. Emerg Infect Dis 2004 Feb;10(2):251-5.

[33] Here is a full rundown of how Rancourt misrepresents the studies he cites, and how they are either irrelevant to his thesis, or actually contradict it.

Joshua L. Jacobs, et al., “Use of Surgical Face Masks to Reduce the Incidence of the Common Cold Among health Care Workers in Japan: A Randomized Controlled Trial,” Am J Infect Control 37, no. 5 (June 2009): 417-19, https://doi.org/ 10.1016/j.ajic.2008.11.002.

This study showed that N95 masks cause headaches in some, and that (surgical) facemasks don’t protect their wearer. This only tells us what we already know: Wearing a tight banded mask on your face for 12 hours is bound to cause headache, and surgical masks don’t provide adequate protection in high risk environments. And since both findings are irrelevant to whether cloth masks filter outgoing particles, this study is irrelevant to his thesis.

B.J. Cowling, Y. Zhou, D.K.M.Ip, G.M.Leung, and A.E. Aiello, “Face Masks to Prevent Transmission of Influenza Virus: A Systematic Review,” Epidemiology & Infection 138, no. 4 (January 2010): 449-456, https://doi.org/10.1017/S0950268809991658.

The part of the study that Rancourt mentions is about whether masks (in this case, cloth masks) protect their wearer from infection, not whether they filter exhaled air and thus protect others. So it is irrelevant to his thesis. What’s more, the authors admit that the body of evidence they are examining is not sufficient to draw a conclusion, but also suggest that the evidence that does exist at least suggests that cloth masks do provide some protection for their wearer—probably not enough for a healthcare setting, but maybe enough for household use. They recommend further study on this topic. The part of the study that Rancourt doesn’t mention is the part that examines whether cloth provides protection to others by filtering air, and they conclude that they do. Rancourt is engaged in major confirmation bias here, by just leaving that part out.

Faisal bin-Reza, Vicente Lopez Chavarrias, Angus Nicoll, Mary E. Chamberland, “The use of masks and respirators to prevent transmission of influenza: a systematic review of the scientific evidence,” Influenza and Other Respiratory Viruses 6, no. 4 (December 2011): 257, https://do8i.org/ 0.1111/j.1750-2659.2011.00307.x.

As I mentioned in my opening statement, Rancourt uses a misleading quote from this one to imply that it found that “mask/respirators” don’t work, when in fact it found that they work equally well. What’s more, the part of the study Rancourt cities is about influenza, not COVID—and the authors themselves specifically state that their findings about influenza cannot be extrapolated to SARS-CoV-1 (“SARS is an unusual acute viral respiratory infection with a very different epidemiology to almost all other respiratory viral infections. It is fundamentally different from human influenza.”) But SARS-CoV-1 is very similar to SARS-CoV-2 (the cause of COVID-19), and about SARS-CoV-1 this study “found that mask and ⁄or respirator use was independently associated with a reduced risk of severe acute respiratory syndrome.”

Jeffrey D. Smith, et al., “Effectiveness of N95 Respirators Versus Surgical Masks in Protecting Health Care Workers from Acute Respiratory Infection: a Systematic Review and Meta-analysis,” CMAJ 188, no. 8 (May 2016): 567-74, https://doi.org/10.1503/cmaj.150835.

This study compares the effectiveness of N95 and surgical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. What more, it admits that it doesn’t prove that they do offer equal protection; just that the available evidence so far is inadequate for proving that N95 masks offer more protection in a clinical setting. “Although N95 respirators appeared to have a protective advantage over surgical masks in laboratory settings, our meta-analysis showed that there were insufficient data to determine definitively whether N95 respirators are superior to surgical masks in protecting health care workers against transmissible acute respiratory infections in clinical settings.” However, even though it was not enough to prove they were superior, they did find that “In general, compared with surgical masks, N95 respirators showed less filter penetration, less face-seal leakage and less total inward leakage under the laboratory experimental conditions described.” So this is far from proof that N95’s don’t work better than masks.

Vittoria Offedu, et al., “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis,” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42, https://doi.org/10.1093/cid/cix681.

Again, this study is about whether N95 and surgical masks protect their wearer—specifically healthcare workers in high risk settings. It is not about whether cloth masks protect others by catching expelled droplets of COVID. So it is irrelevant to the issue. (It found that N95 masks do protect better than surgical masks against clinical respiratory illness, but that N95 and surgical masks protect against viral infections and influenza-like illness equally well. Rancourt takes the quote about this (“Evidence of a protective effect of masks or respirators against verified respiratory infection (VRI) was not statistically significant” out of context to make it seem like it is about the effectiveness of masks.) What’s more, it specifically found that masks and respirators do protect against SARS (which, again, is the closest thing to Covid-19). Indeed, it specifically stated that “This systematic review and meta-analysis supports the use of respiratory protection.”

Lewis J. Radonovich, Michael S. Simberkoff, and Mary T. Bessessen, “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial,” JAMA 322, no. 9 (2019): 824–833, https://doi.org/10.1001/jama.2019.11645.

Again, this study compares the effectiveness of N95 and medical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. What’s more, it’s about the flu—not SARS, so its findings really can’t be transferred over to COVID. Also, the non-difference could just be due to the N95’s not being properly sealed or used.

Youlin Long, et al., “Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis,” J Evid Based Med 13 (2020): 93-101, https://doi.org/0.1111/jebm.12381.

Again, this study compares the effectiveness of N95 and medical masks; as I explain in the main text of my opening statement, this makes it irrelevant to his thesis. And again, it’s about the flu—not SARS, so its findings really can’t be transferred over to COVID. It merely suggests that N95 masks should be reserved for health care workers in the most high risk situations—not that cloth masks can’t filter out droplets.

For this rundown, I partially relied on information provided here:  “Confirmation Bias Masks Truth OR Confirmation Bias, Masks, Truth,” Sound Reason & More,June 30, 2020, https://soundreasonandmore.wordpress.com/2020/06/30/confirmation-bias-masks-truth-or-confirmation-bias-masks-truth/?fbclid=IwAR38Vw0Ev6l5CU8bdn3f5uLsgPSkJErKyj07WPZiad-q0IcHxTl8mdH10o8.
                In other notes, I also relied on some information provided here: “Face Masks – A Summary of Relevant Research Papers for COVID-19.”

[34] Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, http://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer 

                [35] Quote from: Alan Yu, “What Happens to the Coronavirus When It Gets Warmer?” Whyy, May 20, 2020, https://whyy.org/articles/what-happens-to-the-coronavirus-when-it-gets-warmer/. Here is the study: Rachel E. Baker, Wenchang Yang, Gabriel A. Vecchi, C. Jessica E. Metcalf, and Bryan T. Grenfell, “Susceptible Supply Limits the Role of Climate in the Early SARS-CoV-2 Pandemic,” Science 369, no. 6501 (July 17, 2020): 315-19, https://doi.org/10.1126/science.abc2535.   

[36] To illustrate this fallacy, imagine that we forcibly locked everyone in a separate room for two months to mitigate the spread of the flu. This would be a bad idea for multiple reasons, but that level of isolation would obviously mitigate the spread. No physical contact means no spread. But now imagine someone said, “It won’t mitigate the spread at all because humidity explains seasonal variation.” Wouldn’t we laugh them out of the room. Even if humidity is normally a major factor, that doesn’t mean physical contact is not also a factor—and so it doesn’t mean that keeping people from being in contact wouldn’t mitigate the spread. Of course it would. In the same way, so would reducing the number of infected droplets in the air with masks.

[37] Just below 0.3 microns is where Brownian Motion starts, so 0.3 micron particles are actually the hardest to capture. N95 masks are so named because they are 95% efficient at capturing such particles. They are actually more efficient at capturing particles both larger and small than that.  “N95s – Sufficient Protection for Covid19?” https://www.sphosp.org/wp-content/uploads/2020/04/Letter-in-response-to-N-95-use-RA-Final.pdf. See also Olof Gustafsson, Simon Gustafsson, Levon Manukyan, and Albert Mihranyan, “Significance of Brownian Motion for Nanoparticle and Virus Capture in Nanocellulose-Based Filter Paper,” Membranes 8, no. 4, published online October 5, 2018, https://doi/org/10.3390/membranes8040090.  

                [38] Prasith Baccam, Catherine Beauchein, Catherine A Macken, Frederick G Hayden, and Alan S Perelson, “Kinetics of Influenza A Virus Infection in Humans,” Journal of Virology 80, no. 15 (August 2006): 7590-9, https://doi.org/ 10.1128/JVI.01623-05 and Christopher B Brooke, William L Ince, Jens Wrammert, Rafi Ahmed, Patrick C Wilson, Jack R Bennink, and Jonathan W Yewdell, “Most Influenza A Virions Fail To Express at Least One Essential Viral Protein,” Journal of Virology87, no. 6 (March 2013): 3155-62, https://doi.org/ 10.1128/JVI.02284-12 They only talk about how quickly or efficiently viruses reproduce in cells once they are infected–not the probability of cells becoming infected once exposed.

[39] What’s more, he makes a mathematical error that greatly overestimates how many viruses would be in an aerosolized droplet. He says that “there are 1000 to 10 million viral particles, in each microdroplet 1 to 10 microns in size.” But, in fact, microdroplets of that size are mostly empty of virus and contain at most a single viral particle. Why? Because it’s difficult to get coronavirus into a concentration much higher than 10 million per mL (plaque forming units per milliliter)[39]; and a 10 micron droplet is (4/3 * 5^3 * 10^-18 m^3 =) 0.167 picoliter. A ml is 1 billion picoliters. So for every 1,000 10 micron droplets, only at most 2 (1.67) will have even a single virus in it—that’s roughly 1 out of every 600. So he is making an mathematical error of a factor of at least 10 million here. (My thanks to MW and my wife for the math!) And since it is far from established that one virus is sufficient for an infection, much less a severe on, his argument here is based on nothing. Source: Yinon M Bar-On, Avi Flamholz, Rob Phillps, and Ron Milo, “SARS-CoV-2 (COVID-19) By the Numbers,” eLIfe 9, no. e57309, published online April 2, 2020, https://doi.org/10.7554/eLife.57309.  

                [40] Carl Heneghan, Jon Brassey, and Tom Jefferson, “SARS-CoV-2 Viral Load and the Severity of COVID-19,” CEBM, March 26, 2020, https://www.cebm.net/covid-19/sars-cov-2-viral-load-and-the-severity-of-covid-19/.

[41] Think of it this way; speed limits aren’t perfect. Some people will break the law; accidents will still happen. But that doesn’t mean speed limits don’t reduce the number of accidents. In the same way, although they won’t eliminate it, mask mandates will assist in curbing the spread of Covid-19.

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Lyu, Wei, and George L. Wehby. “Community Use of Face Masks and COVID-19: Evidence from a Natural Experiment of State Mandates in the US.” Health Affair 39, no. 8 (2020): 1-7. https://doi.org/ 10.1377/hlthaff.2020.00818.

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MacIntyre, C Raina, Holly Seale, Tham Chi Dung, Nguyen Tran Hien, Phan Thi Nga, Abar Ahmad Chughtai, Bayzidur Rahman, et al. “A Cluster Randomised Trial of Cloth Masks Compared with Medical Masks in Healthcare Workers.” BMJ Open 5, no. 4 (2015) https://doi.org/10.1136/bmjopen-2014-006577.

MacIntyre, C Raina, Abrar Ahmad Chughtai, Bayzidur Rahman, Yang Peng, Yi Zhang, Holly Seale, Xiaoli Wang, et al. “The Efficacy of Medical Masks and Respirators Against Respiratory Infection in Healthcare Workers.” Influenza and Other Respir Viruses 11, no. 6 (November 2017): 511-17. https://doi.org/10.1111/irv.12474.

McCabe, Caitlin. “Face Masks Really Do Matter. The Scientific Evidence Is Growing.” The Wall Street Journal, July 18, 2020, https://www.wsj.com/articles/face-masks-really-do-matter-the-scientific-evidence-is-growing-11595083298.

            Milton, Donald K., M> Patricia Fabian, Benjamin J. Cowling, Michael L Grantham, and James J. McDevitt.Influenza Virus Aerosols in Human Exhaled Breath: Particle Size, Culturability, and Effect of Surgical Masks.” PLoS Pathogens 9, no. 3 (March 2013): 1-7, https://doi.org/10.1371/journal.ppat.1003205.

Mitze, Timo, Reinhold Kosfeld, Johannes Rode, and Klaus Wälde. “Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach.” IZA (June 2020) http://ftp.iza.org/dp13319.pdf.

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“New IHME COVID-19 Model Projects Nearly 180,000 US Deaths.” IHME,June 24, 2020. http://www.healthdata.org/news-release/new-ihme-covid-19-model-projects-nearly-180000-us-deaths.

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Offedu, Vittoria, Chee Fu Yung, Mabel Sheau Fong Low, and Clarence C Tam. “Effectiveness of Masks and Respirators Against Respiratory Infections in Healthcare Workers: A Systematic Review and Meta-Analysis.” Clinical Infectious Diseases 65 no. 11, (December 2017): 1934–42. https://doi.org/10.1093/cid/cix681.

Prather, Kimberly A., Chia C. Wang, and Robert T. Schooley. “Reducing Transmission of SARS-CoV-2.” Science 368, no. 6498 (June 2020): 1422-24. https://doi.org/10.1126/science.abc6197.

Radonovich, Lewis J., Michael S. Simberkoff, and Mary T. Bessessen. “N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial.” JAMA 322, no. 9 (2019): 824–833. https://doi.org/10.1001/jama.2019.11645.

Rengasamy, Samy, Benjamin Eimer, and Ronald E. Shaffer. “Simple Respiratory Protection – Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20-1000 nm Size Particles.” Annals of Occupational Hygiene 54, no. 7 (October 2010): 789-98, https://doi.org/10.1093/annhyg/meq044.

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Stutt, Richard O. J. H., Renata Retkute, Michael Bradley, Christopher A. Gilligan, and John Colvin. “A Modelling Framework to Assess the Likely Effectiveness of Facemasks in Combination with ‘Lock-down’ in Managing the COVID-19 Pandemic.” Proceedings of the Royal Society A (2020) https://doi.org/10.1098/rspa.2020.0376.        

Sung, Anthony D, Julia A. M. Sung, Samantha Thomas, Terry Hyslop, Cristina Gasparetto, Gwynn Long, David Rizzieri, et al. “Universal Mask Usage for Reduction of Respiratory Viral Infections after Stem Cell Transplant: a Prospective Trial.” Clin Infect Dis 63, no. 8 (October 2016): 999-1006. https://doi.org/10.1093/cid/ciw451.

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Wang, Xiaowen, Enrico G. Ferro, Guohai Zhou, et al. “Association Between universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers.” JAMA.Published electronically July 14, 2020. https://doi.org/ 10.1001/jama.2020.12897.

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Is the Cure Worse Than the Problem?

Could social distancing create more of a problem than COVID-19 itself?

David Kyle Johnson/Twitter

Around midnight last night, an all-caps tweet raised a question that’s likely been on everyone’s mind: Could the cure be worse than the problem?

Across America, in an effort to save lives by preventing the spread of the COVID-19 virus, many people have been practicing “social distancing”—the practice of people eschewing crowds and staying (and working from) home to avoid others as much as possible. To encourage this, nearly all schools have either canceled or moved online, and businesses have closed—sometimes voluntarily and sometimes by order of a state government. But this has hit the economy hard: The stock market has lost all the gains since January 2016, by some estimates unemployment could reach 20 percent, and many (most?) restaurants (especially local ones) could close forever.

Are we shooting ourselves in the foot here? Or maybe, for a better analogy—are we shooting ourselves in the head to prevent stepping on a nail?

To answer this question, we need to answer three others:

1. Is social distancing really necessary to prevent the spread of COVID-19?

2. How many lives will preventing the spread of COVID-19 save?

3. What will the costs of a wrecked economy be?

Let’s ask each in turn.

Is social distancing really necessary to prevent the spread of COVID-19?

Wikimedia Commons/Wikipedia

What it means to flatten the curveSource: Wikimedia Commons/Wikipediaupdownedit

The effectiveness of social distancing in reducing the speed at which a disease spreads is well documented and easily  explained. It’s been proven by past examples (like when the Spanish flu spread slower in St. Louis than in Philadelphia) and by present examples (compare Kentucky to Tennessee, and China and Japan to most places in Europe.) But it’s also just common sense. The less that people interact with each other, the less often the infection will be spread to others. Social distancing “flattens the curve” by spreading out the number of infections over time.

To be fair, South Korea flattened their “COVID-curve” without extreme social distancing by relying on extensive testing. So, strictly speaking, social distancing is not necessary to curb the spread of  COVID-19. But, despite repeated promises from the federal government, the U.S. still has not seen widespread testing. South Korea tested 5,200 tests per million inhabitants, the U.S. only 74 per million (source). So social distancing is, as of this writing, necessary in the U.S. to help curtail the spread of COVID-19. We have to make up for the fact that tests aren’t available by all acting as if we are infected.

Some have suggested that flattening the curve with COVID-19 is not necessary because it’s just another exaggerated fear about the end of the world. But as I explained in a previous post, that argument doesn’t hold water. Most importantly, there were never solid scientific predictions that Ebola would become a worldwide pandemic because the U.S. dispersed pandemic response teams around the globe to deal with it. There were such scientific predictions about COVID-19 at least partly because those U.S. pandemic response teams were fired in 2018, and thus the warning signs about COVID-19 went unheeded

Still others suggested that it was all “media hoax,” something being exaggerated for ratings or  political gain. But not only was this demonstrably false at the time—the media was simply reporting the predictions of experts—but those who claimed this (in January and February), like Fox News, subsequently flip-flopped on the issue and admitted the situation’s severity (in March).

Lastly, people claimed COVID-19 is “no worse than the flu.” But while it was true (in late February/early Mach) that the flu had killed more Americans (18,000) than COVID-19 had (around 15) up to that point in 2020, ways COVID-19 is different made it very likely that it would eventually kill far more. Its mortality rate is higher, it’s infectious before symptoms show in the host and for longer (two weeks vs. a few days), and humans have no immunity or vaccine (source). According to the COVID-19 response team at the Imperial College in London, if we went on with business as usual, 80 percent of Americans would get it, and 2.2 million of them would die (in 6 months, compared to 30,000 from the flu in a year).

And that brings us to our second question:

How many lives will preventing the spread of COVID-19 save?

Stanford’s John P.A. Ioannidis would likely argue such estimates are too high. He suggests that the mortality rate for COVID-19 that is often cited in the media, 3.4 percent, is far too high. That’s only among confirmed cases; factoring in the mild and thus unreported cases would make that number drop.

Wikimedia Commons/Wikipedia

An early outbreak happened on The Diamond PrincessSource: Wikimedia Commons/Wikipediaupdownedit

But Ioannidis’s evidence for his extremely low number, 0.125 percent, seems to be flimsy. He merely took the mortality rate among the elderly on the Diamond Princess (1 percent) and extrapolated to the general U.S. population (which has more younger people). But that is only one small sample; its mortality rate could be low because of other factors, and COVID-19 might affect all ages groups more equally than Ioannidis assumed.

Indeed, recent reports suggest that blood type might be a factor, and that younger people might be more susceptible than previously thought. In fact, Ioannidis himself admits that the mortality rate could be as high as 1 percent, and 0.9 percent is the mortality rate the Imperial College assumed to arrive at their 2.2 million figure. (Scarily, if you only look at “closed cases,” the mortality rate is more like 10-13 percent.)

 Wikimedia Commons/Wikipedia

Not flattening the curve could overwhelm the health care systemSource: Wikimedia Commons/Wikipediaupdownedit

To make matters worse, the current mortality rate is not the only relevant factor. If too many people are infected all at once, it will overwhelm our health care system. If that happens, not only will many COVID-19 patients be unable to get the care they need—which would spike the mortality rate–no one else would be able to get the care they need either. Broken leg? Heart attack? “Sorry, we’re full.”

Factoring this in, the Imperial College projects that “life as normal” would generate 4 million American deaths–more than the civil war. Even with preventive measures, like isolating the known infected, without social distancing, 2 million Americans would still die. (Worldwide: 45 million. That’s “Black Death” numbers.)

But could the economic effects of social distancing be worse? That brings us to our final question:

Wikimedia Commons/Wikipedia

A run on the American Union Bank during the Great DepressionSource: Wikimedia Commons/Wikipediaupdownedit

What will the costs of a wrecked economy really be?

The economic effects of social distancing could be dire–maybe even another Great Depression. Could that cost more lives than social distancing will save? It’s sometimes said that the Great Depression caused 7 million Americans to starve to death. Since 7 million is more than 4 million, one might argue that the cure is worse, and that we should just accept the death of 4 million Americans as the lesser of two evils. 

But there are essentially three things wrong with this argument.

First, it relies on a strict utilitarian calculation—maximize happiness for the most amount of people—and that is only one of many ethical theories. Kantians, for example, would argue that it’s morally wrong to just go about willingly spreading a disease that you know will kill millions, regardless of whether the consequences of not doing so would be worse.

Second, the projections for the death rates of COVID-19 are based on scientific evidence. Projections about a COVID-19 economic downturn death rate are not. Clearly, we should take the more certain threat seriously.  

And third, that “7 million deaths” statistic seems to just be old Russian anti-capitalist propaganda.  The evidence suggests that here wasn’t a dip in the death rate of Americans during the Great Depression, and some recent research has even suggested that the effect of economic downturns (on mortality rates) might be positive.

 Wikimedia Commons/Wikipedia

Free coffee and donuts for the unemployedSource: Wikimedia Commons/Wikipediaupdownedit

Now, to be fair, the reason the Depression didn’t cause people to starve to death is  massive social programs (that were a part of FDR’s new deal) which gave money and food to the unemployed. So, if we continue to do social distancing, but don’t couple it with an economic stimulus package that either keeps people working or gives them money for food and rent, perhaps we could see more than 4 million deaths. But that’s not an argument against social distancing. That’s an argument for such social programs.

One might also argue that the health of the economy, and a higher standard of living, is a fundamental good that is worth the millions of humans lives that COVID-19 would cost. Or one might argue that the cost is worth it to preserve our freedom of movement—that the right of 300 million people to live their lives freely is more important than the right to life of the 4 million who would die as a result. A politician might even argue that since a poor economy might cost them the next election, and their election is in the best interests of the nation, the lives of 4 million Americans is just the price we have to pay.

I, however, do not think most Americans think a higher standard of living, the freedom to live life as usual for a few weeks or months, or the election of a political figure is worth 4 million American lives. So I doubt many would actually take these arguments seriously.

All in all, I think it is safe to conclude: No, the cure is not worse than the problem.

Copyright 2020, David Kyle Johnson

A Lethal Lack of Logic

How Lazy Logic is Making the Covid-19 Pandemic Worse

In the early days of the coming Coronavirus (Covid-19) crisis, I  saw a meme on Facebook that listed all the “end of the world crises” that the poster had survived. It looked something like the meme below: 

The implication of the person who posted this—let’s call him Bob—is that the current Coronavirus (Covid-19) is nothing to worry about. “It’s just the latest in an endless list of doomsday scenarios that amounted to nothing.” Bob is suggesting. “It’s all just media hype. There is no reason to cancel events, shut down the NBA, close schools, or even to wash your hands more often. We all need to calm down and stop overreacting.”

In a certain (very limited) way, I’m somewhat sympathetic to this kind of argument. Why?

Well, first, of all…I teach a course on “the end of the world” and one of the assignments I give is to read a list of all the failed “end of the world” predictions for the last 5000 years. Single spaced and 10 font, it’s 24 pages long! To the students, the lesson is clear: There is no reason to take any prophet’s prediction of the “end times” seriously; religious zealots have been saying “the end is near” for millennia. According to the Bible (Matthew 24), Jesus even said the end was near…and yet here we still are.

Second of all…Yes, the media sometimes blows things out of proportion. (Contrary to the crack reporting at the Globe, the world is not being “destroyed,” and they do not have a cure.) And we do need to stop overreacting. You don’t need to hoard toilet paper or bulk buy hand sanitizer (you are not going to be quarantined for months), and you don’t need to stock up on bottled water and batteries (Covid-19 is not going to affect our water or power supply).

Nevertheless, the logic of the above meme is fundamentally flawed. And the flaw it commits feeds a cognitive mistake that threatens to make the Covid-19 outbreak much, much worse.

What’s that mistake? It’s a false analogy, or a “false equivalence,” where you suggest that two things are alike, or equivalent, but they are actually different in very important ways. 

There is a huge difference, for example, between the Mayan 2012 “end of the world” prediction, and the Ebola outbreak of 2014. Yes, neither one of them killed Bob. But the Mayan 2012 calendar prediction was complete cockamamie nutbar pseudoscience from the beginning. But the Ebola outbreak of 2014 was a real thing—a real threat. Lots of people died, and it very well could have spread worldwide. But the reason Bob was never put in danger by Ebola in 2014 wasn’t because it was joke, or because it was over hyped. It was because the federal government took science-based actions to stop its spread at the source, overseas.

But we really have done nothing of the kind with Covid-19. Funding to the CDC’s overseas pandemic response team was cut, in 2018, in 39 of 49 counties, and never re-established. Given the nature of the disease, its spread to the US was thus inevitable. And so the fact that Bob didn’t get Ebola in 2014 (or SARS in 2004, or Swine Flu in 2010, etc.) is no reason to think that he won’t get Covid-19 in 2020. Not only were those viruses different (with different infection rates, etc.), but the US government actually took those seriously. Covid-19, it did not. 

It’s almost like all the pseudoscience/religious “end of the world” predictions were someone crying “wolf” when there was no wolf, and then all the previous disease outbreaks were someone crying wolf when there was a wolf–but since Bob didn’t have to go kill it, Bob convinced himself that there wasn’t one. But now Bob is in charge of the village’s wolf response. When someone called wolf again, he  didn’t go try to catch it–and now there’s a wolf lose in the village.

Now, to be fair: There was a ban of travel from China (the original source of Covid-19), and it did likely buy us some extra time. But there was no way it was going to keep Covid-19 from ever reaching our shores.  (And given that it is already here, additional travel bans will do very little to help mitigate the spread of Covid-19. That would be like the revesre of closing the barn door after the horse has bolted…like building a levee during a flood.) If we had used the extra time to get testing kits and centers ready, we could have slowed the spread and made it manageable. But we didn’t. Indeed, the U.S. trails the developed world when it comes to the availability of Covid-19 testing kits.

Of course, there may fewer cases right now in the U.S. than the seasonal flu, but the trajectory of the spread of Covid-19 in the U.S. looks like it did early on in Italy and Iran. Hopefully our recent social distancing efforts (e.g., canceling large events, moving schools online) will help. But if things get out of hand in the U.S., like they did in Italy and Iran, and too many people get the virus all at once, hospitals could completely fill up. As a result, millions of people, even without Covid-19, will not be able to get the medical treatments they need, and die unnecessarily as a result.

And what has fueled this under-reaction is essentially the logical flaw in the meme. We’ve treated Covid as if it is analogous to the Mayan 2012 prediction—as a joke, a hoax—as something to not take seriously. I mean, it’s one thing for individual U.S. citizens to not have been worried in the early days of the outbreak, back in December; after all, our government has stepped up and taken care of such things in the past. But for the government to not take it seriously–well, that’s why were in the situation we are now.

It’s like the government was (and too many of us were) like Rudy Gobert, the NBA player who made fun of all the concern and precautions that the NBA was taking (like keeping reporters far away during player interviews) by making a point of wiping his bare hands on all the reporter’s mics and recording devices, before he left the room. Two days later, it was confirmed Gobert had Covid-19 and the NBA canceled its season. I hope no reporters in the room were infected as a result of Gobert’s reckless and irresponsible actions. But unfortunately, when it comes to our friends and the federal government not taking the COVID-19 threat seriously, we will likely not be so lucky.

Copyright 2020, David Kyle Johnson

Dear Loyal Readers of Christianity Today: It’s Time to Leave (Evangelical) Christianity, Today.

[Note: I’ve submitted the following to be published in Christianity Today.]

Christianity Today’s Mark Galli recently argued that “Trump Should Be Removed from Office” because “[n]one of his positives” outweigh his “grossly immoral character.” Galli is worried that, if evangelicals continue to support Trump, they’ll lose their moral authority.

Now, in all honestly, that ship has probably already sailed. As one of my former religious professors told me, if he wanted evangelicalism to preserve its moral credibility, he should have written an article calling evangelicals to abandon Trump after the “grab ‘em by the p*ssy” revelation. As a former evangelical myself, I can tell you: not many outside evangelicalism could still take its moral pronouncements seriously when it continued to support him after that.

Still, according to Christianity Today’s president Timothy Dalrymple, many evangelicals were encouraged by the letter because it made it seem as if they were not alone in their opposition to Trump. In reality, however, they practically are. Evangelical support for Trump hangs around 75%. And given the way that 75% has responded to Galli’s article, I believe it’s time for “the 25%” (those evangelicals who see Trump for what he is) to leave evangelical Christianity altogether—and to do so, today. Why?

I overviewed the logical mistakes of evangelical Trump supporters Franklin Graham and Eric Mataxas in my Psychology Today blog “A Logical Take,” but the mistake that should make the 25% ready to leave was theological. It occurred in an open letter response to Galli, signed by over 200 evangelical leaders, when the only thing it actually said in direct response to Galli’s concerns was this:

“We are proud to be numbered among those in history who, like Jesus, have been pretentiously accused of having too much grace for tax collectors and sinners…”

So, in response to Galli’s charge that Trump should be removed from office because he has committed impeachable offenses, and that evangelicalism is losing its moral credibility because it has aligned with and unquestionably excused away the behavior of a man who “is a near perfect example of a human being who is morally lost and confused,” the evangelical leaders of today have simply said “it’s all good, because Jesus associated with and forgave sinners.”

Is this what it’s come to? We now have to explain why Jesus’ concern for poor social outcasts doesn’t entail that Donald Trump should be president? Jesus showed concern for people like Mary Magdalene (a prostitute) because they were given a poor lot in life and treated unfairly. He forgave their sins because they were repentant. Trump is literally, by his own admission, none of these things. Not only was he born into privilege and wealth, but he famously says he is never wrong, sorry, or responsible for anything. He is not repentant; he has not “changed his ways.” He doesn’t even go to church. And even if he had, Jesus showing “grace” to sinners did not include recommending them for high office.

Using Jesus’ ministry to the poor and sinners as an excuse to ignore Trump’s impeachable offenses, to excuse away his “immoral actions in business and his relationship with women, about which he remains proud… [his] habitual string[s] of mischaracterizations, lies, and slanders” is a perversion of the gospel so repugnant and offensive, condemnation of its should be universal. If evangelicals opposed to Trump were in the majority, I would say they were morally obligated to kick those who embrace this idea out. But since they are in the minority, they are morally obligated to leave evangelicalism—and to be vocal to their friends and family about why.

I know it won’t be easy. I did it myself long ago when I saw the early warning signs of Trumpism coming. But for the good of their souls, the gospel, and even the good of the nation, it must be done. Maybe, just maybe, a mass exodus of Christians of good conscious from the evangelical churches of the nation, all saying that they are leaving because evangelicalism has made Trump a golden idol, could break the spell Trump has on it.

About That Open Letter to *Christianity Today*

Since I wrote my article about Franklin Graham’s response to Mark Galli’s Christianity Today article, which called for the president to be removed from office, the response from the evangelical community has skyrocketed.  Sunday, over 200 evangelical leaders signed an open letter condemning Galli’s article and sent it to Timothy Dalrymple, the president of Christianity Today. And this, it turns out, provides yet another perfect opportunity for identifying and addressing logical fallacies.

To see them, it will be useful to look at what one of the signatories, conservative radio host Eric Metaxas, tweeted before signing the letter.

“What makes the @CTmagazine editorial odd (if not preposterous) is that it implies those like Biden or Pelosi, who use the power of their offices to promote the murder of the unborn & the demonization of a biblical sexual ethic, less “morally troubling” than Trump & his tweets.”

The main mistake here is a strawman fallacy; Metaxas is recasting Galli’s argument, suggesting it says something it doesn’t say, to make it easier to attack. How so? 

First, Galli doesn’t imply anything about the democratic candidates; he doesn’t mention them at all and says nothing about their moral standing. He’s just saying that, given his impeachable offenses and “grossly immoral character,” evangelicals shouldn’t support Trump anymore. Notice that, if Trump was removed from office now, Mike Pence would replace him as president and evangelicals could support him in 2020 instead. In a way, Metaxes strawmans Galli by presenting another fallacy: a false dichotomy (saying there are only two options when there are more). “It’s either Trump or the Democrats.” Clearly there are other options.

The second way Metaxas strawmans Galli’s argument is by minimalizing Galli’s concerns about Trump and exaggerating (what he sees as) the moral offenses of democrats. Thinking that abortion should be legal is not equivalent to “promot[ing[ the murder of the unborn.” Whether abortion is murder is a matter of philosophic debate (which cannot be settled scientifically) scientifically), and many religious groups advocate against choosing abortion while still maintaining that it should be legal. (Some even argue that keeping it legal is part of the most effective way to reduce its frequency.) Something similar could be said about the democrats’ position on homosexual marriage; it is not demonizing “biblical sexual ethics.” (Note that most biblical marriages do not involve just one man and one woman.) Further, Galli is not just concerned about “Trump & his tweets.” Galli mentions Trump’s impeachable offenses, the fact that he hires criminals (many of which are now in jail), his immoral action in business (e.g., Trump stole money from a children’s cancer charity), and the fact that he brags about his sexual misconduct.

But Metaxes also commits a version of the confusingly named “tu quoque” fallacy. The phrase essentially translates as “you also” or “you too.” In class, I call it the “two wrongs don’t make a right” fallacy. Usually people use it to excuse away their own failings by pointing to some failing of their accuser. For example, if your doctor says you need to quit smoking, then you probably do—even if your doctor smokes himself. The fact that you need to quit smoking is determined by facts about your health, not someone else’s habits. Your doctor might be a hypocrite, but that doesn’t change the fact that you need to stop smoking. So if you say “I don’t need to quit smoking beacuse you smoke too,” you commit the “you too” fallacy.

But one also commits this fallacy when one tries to excuse away another person’s moral failings by pointing to the moral failings of someone else. And this is essentially what Metaxes is doing by pointing to the moral failings of democrats. Even if (as Metaxes assumes) the democrats are morally worse than Trump, it wouldn’t follow that Trump is morally upstanding enough to deserve evangelical support. It wouldn’t alleviate Galli’s worry that evangelicals are losing their moral credibility by making excuses for Trump’s behavior. If your friend belongs to a cult that worships Charlie Manson, you can’t morally defend them by saying “Well, at least they don’t worship Jim Jones or David Koresh.”

I chose to bring all this up because all of Metaxes’ mistakes can be found in the open letter signed by evangelical leaders that I mentioned at the opening of this article. In fact, it essentially does all three in one line:

As one of our signatories said to the press, “I hope Christianity Today will now tell us who they will support for president among the 2020 Democrat field?”

This strawmans Galli argument (suggesting he is saying evangelicals should support a democrat), presents a false dichotomy (other republicans, independents, and political neutrality are still an option), and even implies that the sins of democrats excuse away Trump’s moral failings.

But the letter also commits other mistakes. For one, as we used to say in debate, it “drops” Galli’s argument; it doesn’t engage with it. In defense of their support of Trump, the letter states that its signatories “are simply grateful” that Trump has “advanced policies” that they agree with (on issues from abortion to Israel). But Galli acknowledges this specifically.

“Trump’s evangelical supporters have pointed to his Supreme Court nominees, his defense of religious liberty, and his stewardship of the economy, among other things, as achievements that justify their support of the president.  …[but]… None of the president’s positives can balance the moral and political danger we face under a leader of such grossly immoral character.”

Galli knows this is why they support him. He is arguing it is not a good enough reason. The letter doesn’t address this argument at all. They just say, “Yep, that’s why we support him.” In debate, this kind of mistake would be enough to make you lose the round.

But perhaps most egregiously, the open letter commits a false analogy. It doesn’t defend Trump’s behavior or character, essentially admitting that Galli is right about that. Instead, it defends its signatories’ embrace of Trump by citing the way that Jesus embraced tax collectors and sinners.

“We are proud to be numbered among those in history who, like Jesus, have been pretentiously accused of having too much grace for tax collectors and sinners, and we take deeply our personal responsibility to render unto Caesar what is Caesar’s — our public service.”

Alexander Andreyevich Ivanov/wikimedia commons

Christ’s Appearance to Mary Magdalene after the Resurrection

Source: Alexander Andreyevich Ivanov/wikimedia commons

While I am no biblical scholar, I have had my share of theology and bible courses…and I know that Jesus would not have recommended putting Mary Magdalene (a prostitute with whom he associated) in charge of the Roman government. Jesus ministered to social outcacts because he cared about the them; he granted sinners “grace” because they were repentant. Trump, by his own admission, is neither. The example of the Biblical Jesus does call evangelicals to minster to sinners, to not cast them aside like socieity has, to forgive them if they are repentant. It does not, however, call evangelicals to put unrepentent sinners in charge of the government, or to ignore or make excuses for their sinful behavior. The analogy simply does not hold.

None of this, of course, will heal the divie that is now happening within the evangelical movement. But it should help us all identify these kinds of logical fallacies when we see them.