/leftypol/ - Leftist Politically Incorrect

>These also only were 70% effective because they lack a proper air-seal for the skin-contact areas.
They were 0% effective because there is no evidence that masks reduce the spread of airborne respiratory diseases.

>If 80% of the population could be convinced to willingly wear those during flu-season, it might be possible to diminish the common-flue enough that most people wouldn't suffer any symptoms.
It would not be possible, because there is no evidence that masks reduce the spread of airborne respiratory diseases.

https://doi.org/10.1002/14651858.CD006207.pub6/14651858.CD006207.pub6/full
<Wearing masks in the community probably makes little or no difference to the outcome of influenza‐like illness (ILI)/COVID‐19 like illness compared to not wearing masks (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.84 to 1.09; 9 trials, 276,917 participants; moderate‐certainty evidence. Wearing masks in the community probably makes little or no difference to the outcome of laboratory‐confirmed influenza/SARS‐CoV‐2 compared to not wearing masks (RR 1.01, 95% CI 0.72 to 1.42; 6 trials, 13,919 participants; moderate‐certainty evidence).
<There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection.

The fundamental problem with face-mask theory is an incorrect assumption about how respiratory illnesses spread that ultimately stems from Tuberculosis research from the early 20th century. For about 80 years it was received wisdom that respiratory diseases spread through water droplets and aerosols were unimportant, despite the fact that this hypothesis never had good evidence supporting it. Were this not to be the case–and the evidence is quite abundant now that it is not–then nothing short of an enclosed system with an oxygen supply and CO2 storage would be capable of stopping the spread of airborne respiratory diseases. Even industrial respirators are designed to protect humans from foreign particles on the outside by filtering inhalation. By design they do nothing to filter exhalation. You can read about the history of this incorrect assumption here:
https://doi.org/10.1098/rsfs.2021.0049

>>474091
<These also only were 70% effective because they lack a proper air-seal for the skin-contact areas.
>They were 0% effective because there is no evidence that masks reduce the spread of airborne respiratory diseases.
No i meant 70% of the air-flow goes through the filter material and 30% of the airflow creeps in through the sides because they don't seal very good.

Sorry for the ambiguous phrasing.

>>474091
So i have now read https://doi.org/10.1098/rsfs.2021.0049 , which was very interesting. Thanks for linking. I found analysis about the historical roots of confused definitions of aerosols vs droplets interesting, but i don't really understand why this should render filters ineffective

When i researched face-filters, i did not look at medical research. I just looked at the sizes of viruses and compared them to the particle-sizes that commercially available filter material were claiming to filter out in their spec sheets. Based on particle size they should be able to handle viruses.

>Were this not to be the case–and the evidence is quite abundant now that it is not–then nothing short of an enclosed system with an oxygen supply and CO2 storage would be capable of stopping the spread of airborne respiratory diseases.
I get that's what the research results say, but i don't understand why.

>Even industrial respirators by design do nothing to filter exhalation.
That ought to be a fixable flaw.

>>474095
>That ought to be a fixable flaw.
Well yeah, here's your fix.

>>474097
A modified re-breather loop is actually not a bad idea.
You would not need CO2 scrubber material or an oxygen supply. You only need to make the loop out of a suitable gas-permeable materiel, that will equalize CO2 and oxygen concentrations with the outside air, via molecular exchange through the gas-permeable barrier. It's basically a filter that needs zero air-flow, because it can exploit Dalton’s Law.

<The Pressure of a Mixture of Gases: Dalton’s Law
<Unless they chemically react with each other, the individual gases in a mixture of gases do not affect each other’s pressure. Each individual gas in a mixture exerts the same pressure that it would exert if it was present alone in the container. The pressure exerted by each individual gas in a mixture is called its partial pressure .

Basically the air you breath out into the re-breather-loop only has around 16% oxygen left in it. The partial pressure for oxygen inside the re-breather-loop would be much lower than the outside air. Pressure equalization would draw in lots of oxygen-gas through the gas-permeable material. The same would happen for CO2 but in the other direction. Gas-permeability only needs holes large enough for molecules to fit through, viruses are huge compared to molecules.

>>474091

As a non-science guy, why should I trust that instead of this?

https://www.pnas.org/doi/10.1073/pnas.2119266119
>We resolve conflicting results regarding mask wearing against COVID-19. Most previous work focused on mask mandates; we study the effect of mask wearing directly. We find that population mask wearing notably reduced SARS-CoV-2 transmission (mean mask-wearing levels corresponding to a 19% decrease in R). We use the largest wearing survey (n = 20 million) and obtain our estimates from regions across six continents. >We account for nonpharmaceutical interventions and time spent in public, and quantify our uncertainty. Factors additional to mask mandates influenced the worldwide early uptake of mask wearing. Our analysis goes further than past work in the quality of wearing data–100 times the size with random sampling–geographical scope, a semimechanistic infection model, and the validation of our results.

>>474105
Because the Cochraine review is a meta study of multiple randomized controlled trials, while that PNAS paper is an observational study based on self-reported data without any experimental design. Carefully controlled experimental design is more reliable at removing confounding variables than observational data.

>>474106
I'm reading an article rn in which a guy claims that the Cochrane review included studies in which N95s were used "intermittently."
https://www.news.com.au/lifestyle/health/expert-slams-gold-standard-cochrane-review-mask-verdict/news-story/af7f698fefb0d4ea3e742a2fba3e06b3
>“The Conchrane review combined studies that were dissimilar — they were in different settings (healthcare and community) and measuring different outcomes (continuous use ofN95 vs intermittent),” she said.

If it was broad enough that mask use wasn't even required to be consistent, that seems like it might be too broad.

It also looks like Cochrane themselves have acknowledged the limits of their review:
https://www.cochrane.org/news/statement-physical-interventions-interrupt-or-reduce-spread-respiratory-viruses-review
>The review authors are clear on the limitations in the abstract: 'The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions.' Adherence in this context refers to the number of people who actually wore the provided masks when encouraged to do so as part of the intervention. For example, in the most heavily-weighted trial of interventions to promote community mask wearing, 42.3% of people in the intervention arm wore masks compared to 13.3% of those in the control arm.

This seems in line with the flaws the Australian critic pointed to…