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Face masks effectively limit the probability of SARS-CoV-2 transmission

science.sciencemag.org

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Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#111

Post by DanBC »

mhb wrote: post #97
auxym wrote: post #86

Earlier quoted context omitted.

Last I checked in Canada, N95 masks are still about 3$ a pop for disposable, single use masks from industrial distributors. Pre pandemic, we bought 3M 8210s for about 15 cents in boxes of 160. I wouldn't call the current situation available and cheap. Oh, and if you thought surgical masks were mildly uncomfortable, N95s are an order of magnitude worst. They pretty much need a perfect seal with your face and the 3Ms u…

3M 8210s are US $26 for 20 now. $1.30 per mask seems pretty reasonable to me, but I've never bought them in industrial quantities so don't have that anchor. I've worn N95s for hours (actually P95s which have a nicer seal) and I agree that they're less comfortable than less effective alternatives. But it is a bit curious that people are concerned enough to be wearing their homemade mask alone in a car or walking outsi…

> a known effective mask.

...if you got a real one, and not one of the less effective fakes.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#112

Post by makomk »

toss1 wrote: post #91
omegaworks wrote: post #53

Earlier quoted context omitted.

Half the articles on your list are tangential (masks make it marginally harder to exercise, ok duh). The article posted helps us understand why the viral concentration in the environment also impacts efficacy, it helps explain why some of the articles you posted see inconclusive results.

And even the "masks make it marginally harder to exercise" is likely wrong. The winner of the 10,000m race at the 2019 USA Track & Field Championships wore a mask against his pollen allergies. [1] Worn properly, they just disappear. I wear N95s a work for many tasks, and they are mildly distracting for a few minutes, then I forget about them. Even more so now with wearing them for the pandemic. Yes, education about m…

According to that article, the winner of the 10,000m race wore a mask to protect against his allergies for the first 4,000m, by which point it was just too uncomfortable to continue wearing: "Rupp said Salazar told him to “wear it as long as you can. As soon as it starts to get real hot or uncomfortable, or starts to stick and get sweaty, throw it off.” The mask came flying off after 4,000 meters. But Rupp was content to bide his time until the 9,200-mark."

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#113

Post by function_seven »

rsj_hn wrote: post #75
tgsovlerkhgsel wrote: post #39

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model. Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respi…

> On the other hand, "observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of the coronavirus disease 2019 (COVID-19) (7–9)." So how to explain these contrasting results and apparent inconsistencies?

My hypothesis regarding surgical mask prevalence and how it correlates with better virus control:

People who wear masks--however effective they may be--also behave in other ways to limit the spread. They minimize time spent in public indoor spaces, they keep distance from other people, they're more likely to self-quarantine if a family member is sick, etc.

The mask-wearing prevalence is a proxy for how serious the wearer takes Covid as a threat.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#114

Post by ihsw »

slver wrote: post #71
sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

Bless your soul, but what I've learned from the way we handled the pandemic worldwide (and are still handling it) is that information that's readily available and should in theory reach everyone, flows ridiculously slowly, even among specialists and political figures, it's easily corrupted and distorted, and a loud ignorant minority counts as much in the public discourse, as the voices of millions of reasonable peopl…

I can't help but look at some peoples' rejection of public health guidance in the US as "not a bug/won't fix."

The relevant authorities (including traditional mainstream media) injected politics into the public discourse, which destroyed trust in what should be a normal public health process. Not only that but the relevant leaders of agencies decided to try manage the supply of masks through "steering" the public by downplaying the usefulness of masks.

Distrust of untrustworthy leaders is a feature, not a bug.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#115

Post by wrycoder »

rsj_hn wrote: post #75
tgsovlerkhgsel wrote: post #39

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model. Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

Indeed this is the money paragraph: "The effectiveness of masks, however, is still under debate. Compared to N95/FFP2 respirators which have very low particle penetration rates (around ~5%), surgical and similar masks exhibit higher and more variable penetration rates (around ~30-70%) (2, 3). Given the large number of particles emitted upon respiration and especially upon sneezing or coughing (4), the number of respi…

I suspect that in locations with a higher prevalence of masking the population is generally more vigilant: more hand washing, more social distance, stay at home when ill, avoid obviously ill people, and so on. May be a case of correlation, not causation.

It would be interesting to have a trial where everyone was wearing N95s, but we're not likely to see that.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#116

Post by simpleguitar »

slver wrote: post #71
sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

Bless your soul, but what I've learned from the way we handled the pandemic worldwide (and are still handling it) is that information that's readily available and should in theory reach everyone, flows ridiculously slowly, even among specialists and political figures, it's easily corrupted and distorted, and a loud ignorant minority counts as much in the public discourse, as the voices of millions of reasonable peopl…

Absolutely. Considering how long it took CDC and WHO to even acknowledge airborne transmission, even though the Chinese were very clear about it from very early on.

https://www.nytimes.com/2021/05/07/opinion/coronavirus-airbo...

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#117

Post by [deleted] »

mhb wrote: post #105
mulmen wrote: post #72

Earlier quoted context omitted.

If you tell me how something works and it fits within my mental model of the world then I will trust you. I will add this information to my mental model of the world. If you tell me something works but can't explain how I will consider if the claim is worth evaluating then attempt to understand it myself before accepting it. If you tell me to trust you with no explanation I will immediately distrust you.

That's reasonable and also what I would like. But what is the mental model of someone wearing their mask alone in the woods or in their car? So, yes, we should explain why an N95 is better than a handkerchief, but it seems like there are plenty of people who don't care about the details and just need to be told that one is more effective.

[deleted]

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#118

Post by nerdponx »

admissionsguy wrote: post #80
tgsovlerkhgsel wrote: post #39

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model. Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

Working down from the conclusion to find the necessary assumptions is the standard approach to COVID-related questions.

This is a valid way to do science.

"What assumptions are required to make this conclusion valid?"

If the assumptions turn out to be outlandish, then maybe we can't take the conclusion to be true.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#119

Post by orf »

Louis_Sarwal wrote: post #92
sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

We immediately face this issue: You should not act on information, or even knowledge. You should act on WISDOM. Wisdom is hard to gain, and yet it proves itself time after time to be better than the other forms of truth. Education is not the key; That would be wisdom. I do admit that most of what they teach is falsehood, and it would be better if it were truth.It would be better of there were no education at all than…

This comment is a pretty good argument for education reform, but likely not in the way you meant.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#120

Post by adrr »

bitcurious wrote: post #24
sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

I’m not sure there was any popular doubt over the efficacy of N95 masks. The problem was rather getting one - marketplaces like Amazon restricted access to masks if you weren’t affiliated with a hospital. So you were left with sketchy deals and weird vendor sites. I suspect Amazon killed quite a few people over the last year by restricting access - supply scaled pretty quickly.

This was an education issue. There were KN95 and KF94 masks available for purchase. I bought KN95 masks off Amazon sold by Amazon proper and later switched to KF94 when they became widely available. Both masks have similar performance to N95. Someone of the KF94 masks i bought showed 99% filtering effectiveness in government testing.
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