That’s a whole different discussion that would be interesting. But it doesn’t answer my question.
if it makes coughing people wear masks, masks wore by people without a cough are useful.
And you don’t know when a person would start coughing.
Are you’re saying masks on people without coughs, sneezes or symptoms are purely a psychological aide for the small percentage of people who might be out in public with symptoms?
These epidemiological observations are among the evidence that Gandhi and colleagues cite in a paper in the Journal of General Internal Medicine , in which they propose that masks can lead to milder or asymptomatic infections by cutting down on the dose of virus people take in.
“Masks can prevent many infections altogether, as was seen in health care workers when we moved to universal masking. We’re also saying that masks, which filter out a majority of viral particles, can lead to a less severe infection if you do get one,” said Gandhi. “If you get infected, but have no symptoms – that’s the best way you can ever get a virus.”
imo, the most important thing on mask wearing is to make sure people who could spread the virus by coughing or sneezing wear masks.
Really need to get on with work, but a couple of points:
A cursory skimming of the first couple of pages of results gave the following:
- Link (2013): Both homemade and surgical masks significantly reduced number of expelled microorganisms (bacterial and viral aerosols). Surgical masks 3 times more effective.
- Link (2013): Influenza virus measurable from behind surgical mask, but the masks reduced exposure to aerosolized virus - reductions ranged from 1.1 to 55-fold (average: 6-fold) depending on mask design.
- Link (2006): Surgical masks reduced penetration of virions, but by variable amount depending on sample (penetration: 20.5% or 84.5%) and less effective in a certain size range (10-80 nm). Note the final sentence of the abstract, also: “It should be noted that the surgical masks are primarily designed to protect the environment from the wearer, whereas the respirators are supposed to protect the wearer from the environment.”
That isn’t a comprehensive list.
But, also, you’re asking here pretty much a loaded question: “Which of the articles show that face masks can prevent a pandemic?” Probably none, when you set the bar at absolute prevention. There seems to be a binary, black-and-white attitude with people who believe in this garbage, that masks either 100% work or 100% don’t work and there’s nothing in between, so if they don’t 100% work then they don’t work at all and blah blah blah my civil liberties. Do you really not see the issue here?
Of course masks aren’t 100% effective in preventing infection, but they don’t need to be 100% effective to reduce transmission below the point that it’s not self-sustaining. The goal is to reduce and/or delay transmission and risk, not to completely abolish it and if we can’t then everything’s pointless and we may all just as well drive our cars as fast as we can with our eyes closed.
Also, just to come back to this misleading analogy. Surgical masks are typically three-ply, where each layer is relatively thick (it seems about 10-50x thicker than the pore size of 0.3-10 μm) and there’s more material than holes. The better comparison would be if you had really thick tennis nets, made with really wide string, and tied three of them together to give you something, say, 0.5-1.0 meters wide. How many of the golf balls do you think will get through now?
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You deleted/ignored the first word I wrote there, and it’s an important one. Please try to be honest with your arguments. 
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Yes. The framing here of an all-or-nothing approach is, to put it mildly, unhelpful. It’s incremental actions, working together, that can help minimize risk.
Cheers,
Guy
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I did Andrew. Sorry about that. I also did it on purpose, because exhaled aerosols particles are significantly smaller than droplets produced by sneezing and coughing. (link)
However, most particles in exhaled breath are smaller than 4 μm, with a median between 0·7 and 1·0 μm.
Other previously quoted articles show that surgical face masks rarely stop particles smaller that 5 micormeters.
So wearing a mask offers very little protection against being infected by COVID-19?
I think I posted a link to the video.
I also thought afterwards that I should probably have written “expelled” rather than “exhaled”, as in exhaled, coughed, sneezed, and emitted during talking, whatever. And yes, the particle size varies with which one of those we’re referring to, no disagreement there. Again, though, I don’t think the main mechanism here is “filtering” so much as absorption and redirecting exhaled airflow around the wearer (I tried to explain what I mean here in a post back in March (March…)).
Someone else, I think @Brianjones, also posted this video recently, and it’s quite informative. I recommend watching it.
It’s also worth noticing the sentence immediately after this quote, conveniently omitted there:
Face masks rarely filter particles smaller than 5 micrometres in diameter and their filtering efficiency varies from 14% to 99%. Nevertheless, face masks do filter a great deal of debris.
I’m not sure debris means exhaled droplets or aerosols. It may be referring to dust or other particles.
That’s my understanding, yes. The infographics I saw suggest something along the lines of 20% reduction or something for the wearer (but don’t quote me on the exact value). But I’ve already said that several times, yeah? Protecting the wearer isn’t the main purpose.
Alternatively, if more people wear masks, everyone’s more protected, just not directly. So it’s an indirect effect, but one that isn’t acknowledged in sentences like the one you just wrote.
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Why are you so determined to believe that masks don’t do anything? Your emotional barrier to accepting logical statements/studies about the positive effects of mask use seems a lot higher than your barrier to accepting random videos from OAN or whatever saying that masks are useless.
I mean, what’s in it for you? Has Big Mask treated you badly in some way?
Conversely, what nefarious purpose do you believe others might have for claiming that masks work when they don’t? Do you think we’ve all got investments in the nonwoven fabric sector?
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I watched it. There’s a lot of unfounded assumptions about effectiveness especially with regard to equal two-way effectiveness which seems to contradict this.
And they’re clearly stated as assumptions in the video. The assumptions here are necessary for simplicity to highlight the overall point, and to make a video that the general public will watch and understand (without going into a 2-hour digression about statistics/probabilities/network dynamics/whatever, that many viewers wouldn’t have the education, interest, or patience to understand).
It’s this binary thing again - finding a fairly valid criticism (that the video contains some assumptions for demonstrative purposes) and deciding that that invalidates the entire thing.
Also, IIRC, the video assumes a filtration efficiency of 50% (again, as a representative value). The link you posted gives two values, 20.5% and 84.5%, the average of which would be 52.5%. This isn’t sufficient reason to consider the entire concept disregardable, I think.
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- I haven’t indicated whether I believe, or disbelieve anything
- I haven’t presented any emotions / emotional barrier
- There’s nothing in it for me
I don’t think there’s any nefarious purpose. This might surprise you, but I believe most people promoting masks actually have good intentions. I also wear a mask where required, and I don’t protest, or act like a Karen.
On the other hand I want to understand whether mask wearing is firmly based in science, or perhaps a misguided group-think movement based in politics and people’s perceptions or ‘common sense’.
50% reduction seems like a very arbitrary number. It would have only taken less than a minute to establish why 50% is a fair assumption. Put a link in the description if it’s too much for the general audience.
I believe the video links to a calculator where the user can input different values to simulate the effects - you could play around with that if you want to dwell too much on the precise value?
It’s necessarily arbitrary, because the real-world value will be more of a range, depending on numerous complex factors (off the top of my head: type(s) of expelled particle(s), particle size distribution, velocity, temperature, humidity, mask material, mask construction, how the mask is worn, face shape, etc.). I don’t know whether the real-world average value is 50% or 25% or 75% and I doubt the video authors do either, but that doesn’t mean the whole concept is invalid and we need to start sharing misleading OAN videos.
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