11 ms·

The effectiveness of cloth masks has been misrepresented

39 points by martingoodson 6y ago

blakesterz 6y ago
So IF I read this correctly, cloth masks still do a pretty good job? The post ends with... "I have reanalysed the Korean data using the suggested replacement value of half the LOD and the results don’t change very much, suggesting a reduction of 70% of virus particles when using cloth masks." And it starts with... "His key claim is that “cotton masks reduce virus emitted duringcoughing by 96%”, citing a recent South Korean study." So 70% isn't as good as 96%, but it seems like that's still a decent number. Or am I reading this wrong?
- shamino 6y ago
  When giving out numbers scientifically, it's important to be precise, or have the uncertainty known. In that case, 96% is widely different than 70%. As Andy Slavitt says in his April 22 podcast, when someone claims to know something too precisely in regards to this pandemic, and they don't say "we don't know" enough, run the other direction.
  - shamino 6y ago
    You also want to have someone doing a scientific study to be as unbiased as possible. As I understand it, (most of?) his family is immunocompromised. This doesn't mean he shouldn't do it, nor that what he's doing is not saving millions of lives, but it's a little easier to question the "salesmanship" aspect of it when he hasn't spent a lot of time in the field.
- gerry_shaw 6y ago
  "Cloth masks reduces virus from coughing by 96%" vs "Cloth masks tested on 4 people reduces virus from coughing by 70%" If that is the only study being citied to go against public health officers I'm be skeptical. If cloth masks work it should be feasible to do a larger study and prove it with a high degree of confidence.
- bambax 6y ago
  The study that finds 70% effectiveness was based on just 4 people, one of whom couldn't produce virus particles even without a mask. Another most serious study based on over 1500 hospital workers found that cloth masks let through over 95% of particles. That more serious study was done in 2015 but there's no reason to think it would not still be correct.
- bcoates 6y ago
  No, 70% isn't nearly enough. A single contamination event (like a cough) is in the neighborhood of a million virus particles to stop. Think about hand sanitizers: some advertise 99.9% reduction, which is "millions become thousands", bare-minimum levels of actually reducing risk of infection from an exposure. 70% is like "millions become fewer millions"
  - marcosdumay 6y ago
    70% is "a 2m safety distance becomes some X, that isn't very easy to calculate". There's very likely an exponential fall of virus with distance, so it's probably something visibly smaller than 2m, but not by a lot. Besides, that's hardly the only variable at play. The virus doesn't spread on the atmosphere only by dispersion, so the particles energy is relevant. It doesn't spread in only in dry particles, so that ratio is relevant, as is the efficiency in blocking the larger wet particles. And it doesn't spread only by coughing, so the efficiency on normal breathing and speaking is important too. Also, we don't need completely effective barriers for people at the street, this is not ebola. We just need to reduce the virus spread by ~60%. The one thing we know is that the countries where people use masks are having an easier time fighting the virus. We don't really know if it's because of the masks, but it's a good bet.
Loughla 6y ago
I get the importance of following science in weird times like these. But, if the author of articles agrees people should still wear masks, what is the end game of this article? The people who want to open back up economies using masks instead of appropriate other precautions, will not read this. The people who will read this and understand it will not change their views. The people who will read this and misunderstand it will just add to the negativity and confusion by claiming that no one should wear masks. Maybe I'm just going into a depression spiral, but what's the point?
- sct202 6y ago
  This is how I feel at work sometimes; like someone will say something kind of wrong but mostly right or their rationale for something is a little bit off. Is it really worth derailing a meeting over?
  - marcosdumay 6y ago
    This is the worst. If you correct them you'll derail the meeting for a short time and look bad. If you don't correct them, there is a risk somebody will follow their premises into some conclusion that leads to very bad actions, and you won't be able to explain why, derailing much more than a meeting.
- SpicyLemonZest 6y ago
  If it were discovered that people systematically refuse to correct false claims about the efficacy of masks, that would hurt confidence in mask recommendations much more than any individual article could. I agree that a headline like "Cloth masks are effective, but Masks4All is doing bad science" would have been better.
- bcoates 6y ago
  The author of the article did not say that "people should still wear masks", he said "I’m not claiming that people shouldn’t wear masks". If you want something more actionable, "behave as if nobody was wearing a mask" which is absolutely not the position the #Masks4All guy is taking; he is promoting people in physical proximity but wearing masks as appropriate.
toomim 6y ago
I'm part of a mask-providing charity. [1] This article is misleading in three ways: 1) It acts as if a single person speaks for #Masks4All. But #Masks4All is a hashtag, not a person. 2) It says that #Masks4All claims cloth masks are 96% effective. I've never heard that. We always claim cloth masks are 30% effective, surgical masks are 60-80%, and N95 masks are 95% effective. 3) It says that cloth masks are 70% effective, and then exaggerates this to say that cloth masks are "not effective." Who in their right mind would say that "70% effective" means "not effective?" [1] https://maskedprotectors.org/ https://maskedprotectors.org/
- kerkeslager 6y ago
  > 1) It acts as if a single person speaks for #Masks4All. But #Masks4All is a hashtag, not a person. This is always a big indicator that someone has no idea what's going on on the internet. A similar trend goes for almost anyone who talks about "anonymous".
- jawns 6y ago
  There are a bunch of variables here that we need to know to be able to say whether any type of mask reduces the likelihood of infecting others, and the percentage of viral particles filtered by the mask is just one of them. Another key factor is the rate at which the risk of infection changes depending on the percentage of particles filtered. For instance, it's conceivable that you can be equally likely to be infected whether 5% or 95% of particles are filtered, depending on the "potency" of the particles that are not filtered. If contact with just N particles increases a person's likelihood of infection by some percentage, and the average cough transmits 100N particles, then even if you filter out 95% of those, you're still at 5N. But we know that in most cases, increasing the percentage of filtered particles maps in some way (though maybe not linearly) with reducing the number of infections. All that is to say: I think we need to be careful about using this one variable -- percentage of particles filtered -- when talking about effectiveness of masks. Effectiveness is more of a holistic calculation, taking into account viral potency, the distance unfiltered viral particles travel through the mask, the degree to which they linger in the air, etc.
  - 6y ago
generalpass 6y ago
I wonder if the author of this article is aware that evolutionary biologist Bret Weinstein uses and promotes using a bandana as being far more effective than nothing for those who are unable to get an N95 mask.
haltingproblem 6y ago
This is pure clickbait and here is why. In the debate over masks, the anti-mask side always forgets that this epidemic is multiplicative i.e. it each person spreads it to multiple people (R0 > 1). Even a marginally effective mask that cuts infection by 30% will greatly bend the curve. How? A 30% effective mask (where 100% is full hazmat outfit) does not mean 30% fewer cases. It could mean greater than 30% or even 90% fewer cases. The same non-linearities (read: exponential) that work for virus spread also help in the other direction. [1] Social distancing is expensive and we need it. Social distancing requires the shutdown of large parts of our economy and changing the way we live. Masks are a relatively minor inconvenience and one whose effectiveness, no matter how marginal, we can not afford to ignore. Do science all you want, and that blog post is hardly science, but do it with an ethical and moral responsibility to not turn people away from masks. Turning people away from masks is akin to telling them the virus is not contagious or fatal. References: [1] https://twitter.com/nntaleb/status/1249296844712218624 https://twitter.com/nntaleb/status/1249296844712218624
- jatone 6y ago
  the point of the article wasn't to say don't wear a mask. the point was that it is dangerous to tell people a mask is 90% effective when its not. lying about the effectiveness WILL cause people will take risks they shouldn't making the situation worse. being honest about the masks effectiveness and explain why it still helps is the best thing we can do.
salmonellaeater 6y ago
> The researchers found that 97% of particles penetrated through cotton masks. Why would a ‘review of the evidence’ neglect this key finding? This statement in the article is completely disingenuous. The study in question[1] was looking at whether wearing a mask protects the wearer from getting infected. The primary purpose of wearing the mask is to prevent the wearer from infecting others. These are unrelated! [1] Text of the study: https://bmjopen.bmj.com/content/5/4/e006577.full https://bmjopen.bmj.com/content/5/4/e006577.full
maa5444 6y ago
but they pollute you as you are forced to breath in some CO2 from exhaled #smartfox

39 points by martingoodson 6y ago

So IF I read this correctly, cloth masks still do a pretty good job? The post ends with... "I have reanalysed the Korean data using the suggested replacement value of half the LOD and the results don’t change very much, suggesting a reduction of 70% of virus particles when using cloth masks." And it starts with... "His key claim is that “cotton masks reduce virus emitted duringcoughing by 96%”, citing a recent South Korean study." So 70% isn't as good as 96%, but it seems like that's still a decent number. Or am I reading this wrong?

shamino 6y ago
When giving out numbers scientifically, it's important to be precise, or have the uncertainty known. In that case, 96% is widely different than 70%. As Andy Slavitt says in his April 22 podcast, when someone claims to know something too precisely in regards to this pandemic, and they don't say "we don't know" enough, run the other direction.
- shamino 6y ago
  You also want to have someone doing a scientific study to be as unbiased as possible. As I understand it, (most of?) his family is immunocompromised. This doesn't mean he shouldn't do it, nor that what he's doing is not saving millions of lives, but it's a little easier to question the "salesmanship" aspect of it when he hasn't spent a lot of time in the field.
gerry_shaw 6y ago
"Cloth masks reduces virus from coughing by 96%" vs "Cloth masks tested on 4 people reduces virus from coughing by 70%" If that is the only study being citied to go against public health officers I'm be skeptical. If cloth masks work it should be feasible to do a larger study and prove it with a high degree of confidence.
bambax 6y ago
The study that finds 70% effectiveness was based on just 4 people, one of whom couldn't produce virus particles even without a mask. Another most serious study based on over 1500 hospital workers found that cloth masks let through over 95% of particles. That more serious study was done in 2015 but there's no reason to think it would not still be correct.
bcoates 6y ago
No, 70% isn't nearly enough. A single contamination event (like a cough) is in the neighborhood of a million virus particles to stop. Think about hand sanitizers: some advertise 99.9% reduction, which is "millions become thousands", bare-minimum levels of actually reducing risk of infection from an exposure. 70% is like "millions become fewer millions"
- marcosdumay 6y ago
  70% is "a 2m safety distance becomes some X, that isn't very easy to calculate". There's very likely an exponential fall of virus with distance, so it's probably something visibly smaller than 2m, but not by a lot. Besides, that's hardly the only variable at play. The virus doesn't spread on the atmosphere only by dispersion, so the particles energy is relevant. It doesn't spread in only in dry particles, so that ratio is relevant, as is the efficiency in blocking the larger wet particles. And it doesn't spread only by coughing, so the efficiency on normal breathing and speaking is important too. Also, we don't need completely effective barriers for people at the street, this is not ebola. We just need to reduce the virus spread by ~60%. The one thing we know is that the countries where people use masks are having an easier time fighting the virus. We don't really know if it's because of the masks, but it's a good bet.

Loughla 6y ago

I get the importance of following science in weird times like these. But, if the author of articles agrees people should still wear masks, what is the end game of this article? The people who want to open back up economies using masks instead of appropriate other precautions, will not read this. The people who will read this and understand it will not change their views. The people who will read this and misunderstand it will just add to the negativity and confusion by claiming that no one should wear masks. Maybe I'm just going into a depression spiral, but what's the point?

sct202 6y ago
This is how I feel at work sometimes; like someone will say something kind of wrong but mostly right or their rationale for something is a little bit off. Is it really worth derailing a meeting over?
- marcosdumay 6y ago
  This is the worst. If you correct them you'll derail the meeting for a short time and look bad. If you don't correct them, there is a risk somebody will follow their premises into some conclusion that leads to very bad actions, and you won't be able to explain why, derailing much more than a meeting.
SpicyLemonZest 6y ago
If it were discovered that people systematically refuse to correct false claims about the efficacy of masks, that would hurt confidence in mask recommendations much more than any individual article could. I agree that a headline like "Cloth masks are effective, but Masks4All is doing bad science" would have been better.
bcoates 6y ago
The author of the article did not say that "people should still wear masks", he said "I’m not claiming that people shouldn’t wear masks". If you want something more actionable, "behave as if nobody was wearing a mask" which is absolutely not the position the #Masks4All guy is taking; he is promoting people in physical proximity but wearing masks as appropriate.

toomim 6y ago

I'm part of a mask-providing charity. [1] This article is misleading in three ways: 1) It acts as if a single person speaks for #Masks4All. But #Masks4All is a hashtag, not a person. 2) It says that #Masks4All claims cloth masks are 96% effective. I've never heard that. We always claim cloth masks are 30% effective, surgical masks are 60-80%, and N95 masks are 95% effective. 3) It says that cloth masks are 70% effective, and then exaggerates this to say that cloth masks are "not effective." Who in their right mind would say that "70% effective" means "not effective?" [1] https://maskedprotectors.org/ https://maskedprotectors.org/

kerkeslager 6y ago
> 1) It acts as if a single person speaks for #Masks4All. But #Masks4All is a hashtag, not a person. This is always a big indicator that someone has no idea what's going on on the internet. A similar trend goes for almost anyone who talks about "anonymous".
jawns 6y ago
There are a bunch of variables here that we need to know to be able to say whether any type of mask reduces the likelihood of infecting others, and the percentage of viral particles filtered by the mask is just one of them. Another key factor is the rate at which the risk of infection changes depending on the percentage of particles filtered. For instance, it's conceivable that you can be equally likely to be infected whether 5% or 95% of particles are filtered, depending on the "potency" of the particles that are not filtered. If contact with just N particles increases a person's likelihood of infection by some percentage, and the average cough transmits 100N particles, then even if you filter out 95% of those, you're still at 5N. But we know that in most cases, increasing the percentage of filtered particles maps in some way (though maybe not linearly) with reducing the number of infections. All that is to say: I think we need to be careful about using this one variable -- percentage of particles filtered -- when talking about effectiveness of masks. Effectiveness is more of a holistic calculation, taking into account viral potency, the distance unfiltered viral particles travel through the mask, the degree to which they linger in the air, etc.
- 6y ago

generalpass 6y ago

I wonder if the author of this article is aware that evolutionary biologist Bret Weinstein uses and promotes using a bandana as being far more effective than nothing for those who are unable to get an N95 mask.

haltingproblem 6y ago

This is pure clickbait and here is why. In the debate over masks, the anti-mask side always forgets that this epidemic is multiplicative i.e. it each person spreads it to multiple people (R0 > 1). Even a marginally effective mask that cuts infection by 30% will greatly bend the curve. How? A 30% effective mask (where 100% is full hazmat outfit) does not mean 30% fewer cases. It could mean greater than 30% or even 90% fewer cases. The same non-linearities (read: exponential) that work for virus spread also help in the other direction. [1] Social distancing is expensive and we need it. Social distancing requires the shutdown of large parts of our economy and changing the way we live. Masks are a relatively minor inconvenience and one whose effectiveness, no matter how marginal, we can not afford to ignore. Do science all you want, and that blog post is hardly science, but do it with an ethical and moral responsibility to not turn people away from masks. Turning people away from masks is akin to telling them the virus is not contagious or fatal. References: [1] https://twitter.com/nntaleb/status/1249296844712218624 https://twitter.com/nntaleb/status/1249296844712218624

jatone 6y ago
the point of the article wasn't to say don't wear a mask. the point was that it is dangerous to tell people a mask is 90% effective when its not. lying about the effectiveness WILL cause people will take risks they shouldn't making the situation worse. being honest about the masks effectiveness and explain why it still helps is the best thing we can do.

salmonellaeater 6y ago

> The researchers found that 97% of particles penetrated through cotton masks. Why would a ‘review of the evidence’ neglect this key finding? This statement in the article is completely disingenuous. The study in question[1] was looking at whether wearing a mask protects the wearer from getting infected. The primary purpose of wearing the mask is to prevent the wearer from infecting others. These are unrelated! [1] Text of the study: https://bmjopen.bmj.com/content/5/4/e006577.full https://bmjopen.bmj.com/content/5/4/e006577.full

maa5444 6y ago

but they pollute you as you are forced to breath in some CO2 from exhaled #smartfox