Genuine points of uncertainty

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jdc
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Re: Genuine points of uncertainty

Post by jdc » Mon Jul 26, 2021 6:37 pm

Herainestold wrote:
Mon Jul 26, 2021 5:33 pm
jdc wrote:
Mon Jul 26, 2021 4:46 pm
Yes, can everyone please expose themselves to a lethal cocktail of more than 4,000 irritants, toxins and cancer-causing substances in order to protect themselves from a virus that might not even be present.
Well, when discussing about aerosol spread, one of the analogies is the way tobacco smoke accumulates in a room. It is useful because we can all visualize it. If you are inside a room you can't see the ventilation, but you can see smoke. Except that nobody smokes inside anymore.So if it were allowed on a temporary basis for the duration of the pandemic, it would allow people to evaluate the risk inside. Tobacco smoke is very harmful but the harm comes from repeated exposure over many years, while even a ten second exposure to covid delta can result in an infection.
I don't know why I'm taking this seriously when you're surely joking but here goes:

The risk of something like lung cancer might come from repeated exposure over many years, but what about, say, triggering asthma attacks?

If you're making this temporary, just until coronavirus is eliminated, can you give me your estimate of when that will be? How temporary is temporary?

What made you choose cigarette smoking as a way to measure ventilation ahead of a CO2 monitor?

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Re: Genuine points of uncertainty

Post by Herainestold » Mon Jul 26, 2021 6:37 pm

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Re: Genuine points of uncertainty

Post by monkey » Mon Jul 26, 2021 7:11 pm

Herainestold wrote:
Mon Jul 26, 2021 5:33 pm
jdc wrote:
Mon Jul 26, 2021 4:46 pm
Yes, can everyone please expose themselves to a lethal cocktail of more than 4,000 irritants, toxins and cancer-causing substances in order to protect themselves from a virus that might not even be present.
Well, when discussing about aerosol spread, one of the analogies is the way tobacco smoke accumulates in a room. It is useful because we can all visualize it. If you are inside a room you can't see the ventilation, but you can see smoke. Except that nobody smokes inside anymore.So if it were allowed on a temporary basis for the duration of the pandemic, it would allow people to evaluate the risk inside. Tobacco smoke is very harmful but the harm comes from repeated exposure over many years, while even a ten second exposure to covid delta can result in an infection.
I thought you were joking too, but now I can't tell. I think it would make pubs and whatnot safer, because people would want to go back to the smokey days of yore, so the pub would be less busy.

If you're being serious, what makes you think cigarette smoke and Covid carrying aerosol behave in the same way? As far as I'm aware, the particle size is different, so you'd expect different behavior.

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Re: Genuine points of uncertainty

Post by Herainestold » Mon Jul 26, 2021 8:51 pm

monkey wrote:
Mon Jul 26, 2021 7:11 pm
Herainestold wrote:
Mon Jul 26, 2021 5:33 pm
jdc wrote:
Mon Jul 26, 2021 4:46 pm
Yes, can everyone please expose themselves to a lethal cocktail of more than 4,000 irritants, toxins and cancer-causing substances in order to protect themselves from a virus that might not even be present.
Well, when discussing about aerosol spread, one of the analogies is the way tobacco smoke accumulates in a room. It is useful because we can all visualize it. If you are inside a room you can't see the ventilation, but you can see smoke. Except that nobody smokes inside anymore.So if it were allowed on a temporary basis for the duration of the pandemic, it would allow people to evaluate the risk inside. Tobacco smoke is very harmful but the harm comes from repeated exposure over many years, while even a ten second exposure to covid delta can result in an infection.
I thought you were joking too, but now I can't tell. I think it would make pubs and whatnot safer, because people would want to go back to the smokey days of yore, so the pub would be less busy.

If you're being serious, what makes you think cigarette smoke and Covid carrying aerosol behave in the same way? As far as I'm aware, the particle size is different, so you'd expect different behavior.
You guys. I'm not serious, but it is an analogy I have read and I was doing a thought experiment.
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Re: Genuine points of uncertainty

Post by WFJ » Tue Jul 27, 2021 1:43 pm

So if both the carrier and receiver are double masked (cloth over surgical), it reduces aerosol exposure to about 25% of that were they both singly masked with a surgical mask. What does that amount to in the real world? A few minutes more before infection if you are in an exposed environment?

I think if you compare this to an FFP2 or FFP3 masks, it would be an orders of magnitude difference. Everyone should wear at least a surgical mask when out in public, to help slow the spread, but if someone is specifically concerned about preventing their own infection, they should really wear an FFP2 or FFP3 mask.

From a public health point of view, I think one of the problems with suggesting double masking is that is suggests to people that cloth masks have some purpose. Ever since initial shortages of surgical and FFP2 masks ended, the messaging to the public should have been that cloth masks are useless.

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Re: Genuine points of uncertainty

Post by Herainestold » Tue Jul 27, 2021 1:49 pm

WFJ wrote:
Tue Jul 27, 2021 1:43 pm
So if both the carrier and receiver are double masked (cloth over surgical), it reduces aerosol exposure to about 25% of that were they both singly masked with a surgical mask. What does that amount to in the real world? A few minutes more before infection if you are in an exposed environment?

I think if you compare this to an FFP2 or FFP3 masks, it would be an orders of magnitude difference. Everyone should wear at least a surgical mask when out in public, to help slow the spread, but if someone is specifically concerned about preventing their own infection, they should really wear an FFP2 or FFP3 mask.

From a public health point of view, I think one of the problems with suggesting double masking is that is suggests to people that cloth masks have some purpose. Ever since initial shortages of surgical and FFP2 masks ended, the messaging to the public should have been that cloth masks are useless.
I would like to see a study comparing double masking to FFP2 masks before making any judgements. You may well be correct.
I don't think cloth masks are totally useless, but again, studies.
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Re: Genuine points of uncertainty

Post by Chris Preston » Tue Jul 27, 2021 11:46 pm

WFJ wrote:
Tue Jul 27, 2021 1:43 pm
So if both the carrier and receiver are double masked (cloth over surgical), it reduces aerosol exposure to about 25% of that were they both singly masked with a surgical mask. What does that amount to in the real world? A few minutes more before infection if you are in an exposed environment?

I think if you compare this to an FFP2 or FFP3 masks, it would be an orders of magnitude difference. Everyone should wear at least a surgical mask when out in public, to help slow the spread, but if someone is specifically concerned about preventing their own infection, they should really wear an FFP2 or FFP3 mask.

From a public health point of view, I think one of the problems with suggesting double masking is that is suggests to people that cloth masks have some purpose. Ever since initial shortages of surgical and FFP2 masks ended, the messaging to the public should have been that cloth masks are useless.
The whole point of everyone wearing masks is to reduce the size and number of aerosols being emitted, and hence the volume of potential infective particles in the air, not to provide protection of individuals against exposure. For the purpose intended, cloth masks work adequately. The advantage of cloth masks is they are reusable.

For protection against exposure, you are going to need a properly fitted N95 mask that you change on a regular basis.

The incremental benefit of having everyone double mask is so small to be of limited value. It is probably more of a choice for people who might be particularly susceptible to COVID-19 infection to reduce their risks in certain situations.

Virtually all of the transmission is occurring in situations where people are not wearing masks at all and are inside in situations with poor ventilation. Even where they are occurring in larger areas, they are usually occurring where ventilation is poor and/or people are close together.
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Re: Genuine points of uncertainty

Post by shpalman » Tue Aug 03, 2021 6:22 pm

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Re: Genuine points of uncertainty

Post by bolo » Tue Aug 03, 2021 6:47 pm

I have previously linked to the DHS Master Question List for COVID. It is updated monthly. The July 13 update includes a full page about mask effectiveness, with references for each sentence. The document as a whole has 865 references, which should be enough to keep you lot busy.

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Re: Genuine points of uncertainty

Post by Herainestold » Tue Aug 03, 2021 7:37 pm

bolo wrote:
Tue Aug 03, 2021 6:47 pm
I have previously linked to the DHS Master Question List for COVID. It is updated monthly. The July 13 update includes a full page about mask effectiveness, with references for each sentence. The document as a whole has 865 references, which should be enough to keep you lot busy.
Thanks. A good resource.
Wearing a cloth mask over a medical procedure mask (i.e. “double masking”) significantly improved filtration efficiency.694
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Re: Genuine points of uncertainty

Post by Millennie Al » Wed Aug 04, 2021 1:19 am

shpalman wrote:
Tue Aug 03, 2021 6:22 pm
Face masks effectively limit the probability of SARS-CoV-2 transmission, apparently this "is still under debate".
Well, that paper is just about theoretical modelling, so doesn't really add much. And to take one point from it:
Moreover, randomized clinical trials have shown inconsistent or inconclusive results, with some studies reporting only a marginal benefit or no effect of mask use (5, 6). Thus, surgical and similar masks are often considered to be ineffective. On the other hand, observational data show that regions or facilities with a higher percentage of the population wearing masks have better control of COVID-19 (7–9). So how are we to explain these contrasting results and apparent inconsistencies?
It should be immediately obvious that one possible explanation is that masks are ineffective but their use is stronglky correlated with something which is effective. This is highly plausible as people who take the disease seriously and want to prevent its spread will do several different things to achieve this, one of which is highly likely to be mask wearing as it is cheap and easy.

To test the effectiveness of masks, we need randomised controlled trials. For example, where a significant number of volunteers are given masks and told to use them, but half are given dummy masks which have very poor filtration and half are given effective masks.

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Re: Genuine points of uncertainty

Post by Millennie Al » Wed Aug 04, 2021 1:25 am

Herainestold wrote:
Tue Aug 03, 2021 7:37 pm
bolo wrote:
Tue Aug 03, 2021 6:47 pm
I have previously linked to the DHS Master Question List for COVID. It is updated monthly. The July 13 update includes a full page about mask effectiveness, with references for each sentence. The document as a whole has 865 references, which should be enough to keep you lot busy.
Thanks. A good resource.
Wearing a cloth mask over a medical procedure mask (i.e. “double masking”) significantly improved filtration efficiency.694
Following up that reference shows that it is a study on three people in a test environment. Back in the real world, people use masks to justify risky behaviour (e.g. going to a pub), thinking that a mask makes a big difference.

I'll quote the entire results section (FFE = fitted filtration efficiency):
As shown in the Table, procedure masks worn singly by study volunteers showed a range of mean (SD) FFE between 43% (2%) and 62% (11%). On average, across all masks and volunteers, adding a second procedure mask improved mean (SD) FFE from 55% (11%) when single masking to 66% (12%) when double masking. Single cloth masks performed less efficiently (mean [SD] FFE range, 41% [12%] to 44% [12%]) than the procedure masks. Doubling a cotton mask improved FFE but could reduce breathability.

Although adding a procedure mask (mean [SD] FFE, 61% [13%]) over the cloth masks provided modest increases in their FFE (mean [SD] range, 55% [10%] to 60% [14%]), the overall performance was no different than wearing the procedure mask by itself. In contrast, wearing a procedure mask under the cloth face covering produced marked improvements in overall FFE (mean [SD] range, 66% [5%] to 81% [6%]).
So even in ideal conditions masks make quite a modest difference.

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Re: Genuine points of uncertainty

Post by shpalman » Wed Aug 04, 2021 7:00 am

Millennie Al wrote:
Wed Aug 04, 2021 1:25 am
Herainestold wrote:
Tue Aug 03, 2021 7:37 pm
bolo wrote:
Tue Aug 03, 2021 6:47 pm
I have previously linked to the DHS Master Question List for COVID. It is updated monthly. The July 13 update includes a full page about mask effectiveness, with references for each sentence. The document as a whole has 865 references, which should be enough to keep you lot busy.
Thanks. A good resource.
Wearing a cloth mask over a medical procedure mask (i.e. “double masking”) significantly improved filtration efficiency.694
Following up that reference shows that it is a study on three people in a test environment. Back in the real world, people use masks to justify risky behaviour (e.g. going to a pub), thinking that a mask makes a big difference...
Unfounded concerns about risk compensation threaten public health when they delay the introduction of protective measures such as wearing of face coverings

If people spend 11–24 fewer minutes at home on average and increase visits to some commercial locations—most notably restaurants or pubs where obviously you spend most of the time with the mask off anyway, I'm not going to blame the mask mandate for making people feel safer I'm going to blame whoever let restaurants and pubs open.

The outbreak linked to clubs in Lincoln isn't because everyone felt safe there because they had masks on, it's because of clubs opening with no distancing or masking requirement.
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Re: Genuine points of uncertainty

Post by Herainestold » Wed Aug 04, 2021 2:06 pm

Double masking helped India ameliorate its Delta surge, however I think lockdowns, distancing and changes in behaviour were more important.
That information on risk compensation was good, thanks.
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Re: Genuine points of uncertainty

Post by Millennie Al » Thu Aug 05, 2021 12:08 am

shpalman wrote:
Wed Aug 04, 2021 7:00 am
Millennie Al wrote:
Wed Aug 04, 2021 1:25 am
Back in the real world, people use masks to justify risky behaviour (e.g. going to a pub), thinking that a mask makes a big difference...
Unfounded concerns about risk compensation threaten public health when they delay the introduction of protective measures such as wearing of face coverings
That's actually titled "Is risk compensation threatening public health in the covid-19 pandemic?", presumably intending to take advantage of Betteridge's law. The introduction is "Unfounded concerns about risk compensation threaten public health when they delay the introduction of protective measures such as wearing of face coverings, argue Theresa Marteau and colleagues". They "argue" rather than "show" or "prove". Very unconvincingly, in my opinion, as there is very litle addressing confounding factors.
If people spend 11–24 fewer minutes at home on average and increase visits to some commercial locations—most notably restaurants or pubs where obviously you spend most of the time with the mask off anyway, I'm not going to blame the mask mandate for making people feel safer I'm going to blame whoever let restaurants and pubs open.
This argues in the opposite direction - that there is a risk compensation effect. However, it's just observational and seems to assume that mask mandates are introduced at random, so confounding factors can be ignored. Despite this paper saying the opposite of the previous one, I don't believe it either.
The outbreak linked to clubs in Lincoln isn't because everyone felt safe there because they had masks on, it's because of clubs opening with no distancing or masking requirement.
And here you show risk compensation yourself. It's not because of clubs opening with no distancing or masking requirement. It's simply because of clubs opening. There are some situations where it is so important that you get close enough to someone else that you risk disease transmission. In those cases, you want every possible advantage. Such situations occur, for example, involving medics interacting with patients. Otherwise, you just avoid the situation.

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Re: Genuine points of uncertainty

Post by Millennie Al » Thu Aug 05, 2021 12:09 am

Herainestold wrote:
Wed Aug 04, 2021 2:06 pm
Double masking helped India ameliorate its Delta surge
How do you know?

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Re: Genuine points of uncertainty

Post by shpalman » Wed Sep 08, 2021 3:01 pm

having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Genuine points of uncertainty

Post by shpalman » Tue Aug 23, 2022 10:22 am

having that swing is a necessary but not sufficient condition for it meaning a thing
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