by guest contributor Andre Angelantoni
I’m pulling together the best I’ve been reading the last few weeks on masks. Below is the best study I’ve come across on viral/particle blockage by masks and I found it in this fabulous thread by McKernan: Masks Masquerading as Science
It appears that certain masks are making things worse. Certain homemade masks, which we’ve been told are just fine, appear to be turning the droplets into aerosols (<5µm):
“Our results clearly indicate that wearing surgical masks or unvented KN95 respirators reduce the outward particle emission rates by 90% and 74% on average during speaking and coughing, respectively, compared to wearing no mask. However, for the homemade cotton masks, the measured particle emission rate either remained unchanged (DL-T) or increased by as much as 492% (SL-T) compared to no mask for all of the expiratory activities.”
Efficacy of masks and face coverings in controlling outward aerosol particle emission from expiratory activities
https://www.nature.com/articles/s41598-020-72798-7
Their work did find some reduction in aerosol formation with surgical masks and, as expected, with N95s (note, however, that this was a lab study that measured brief controlled emissions; the study did not mimic conditions, such as while working long shifts, with repeated touching, adjusting, and removal, and so can’t be extrapolated to mean they reduce transmission in the real world). But we were told by those who wish us to wear masks that “anything is better than nothing.” That’s not true. The type of mask matters—and some masks are likely making far more aerosols than would be produced without them.
There are also the problems with mask particulate shedding: Masks, false safety and real dangers, Part 1: Friable mask particulate and lung vulnerability
And the bacteria growth! These cloth masks are showing many colonies growing of both bacteria and fungi in a short amount of time. These *should not* be re-inhaled into the lungs where they can cause lots of trouble that may not show up for months or even years. That’s explained here: Masks, false safety and real dangers, Part 2: Microbial challenges from masks.
We should remember that there are certain populations who we do want to protect so knowing when masks work and don’t work is important. Regarding the public, I personally am in the “let’s go for natural herd immunity” camp, using “focussed protection” (Gupta et al.) or “risk stratification” (Katz et al.) or whatever term describes distinguishing risk levels by population. Thus, even if masks work (and it could go either way; let’s see what the Danish study that’s having trouble getting published finds as well as the African RCT Aaby/Stabell-Benn are conducting), do we want to use them except when working with vulnerable populations? You can guess my answer to that question.
An excellent summary of mask effectiveness evidence (or non-evidence can be found here: Of masks and men: no clear evidence masks are effective in COVID-19
Before people start saying, “See? Masks work!” keep in mind that:• some masks are likely making it worse by creating more aerosols• The overall evidence is still crap…we don’t have any RCTs that would show us whether the net result is that masks are making things worse or better in real world situations. This single study just shows aerosol formation. There are a dozen other things that play a role, from good mask technique (the public is terrible with that and even medical people often make errors that cause contamination), to microbial colony formation, to fomite formation, to shedding, to lung re-inhalation, to ocular exposure (yes, the eyes are another hole in the head), particulate shedding (teflon, etc.), to nasal exposure to the brain and many more items. This is ONE STUDY. And it *still* doesn’t tell us if the current guidance is making things better or worse overall.
