This is my very least favored topic. But I keep reporting on stuff relating to it because we keep hearing garbage that has nothing to do with science or data and everything to do with emotion and ideology. It couldn’t be more apparent on a population level that masks make exactly zero difference. Notwithstanding that, we have states doing dumb and dumber things like wear them all the time outside, wear them in your home; and we see stuff now like, well, they work but you aren’t wearing them right. Every kind of excuse for the fact that they simply don’t make any difference in community transmission as a transmitter or transmittee. And I have repeatedly tried to explain why, from just the statistical reality that even if effective in an individual encounter that doesn’t matter over a population level of encounters, to the physical reality that a mask worn over a long period of time is a pathogen collection device and after collecting them it is inevitable that those pathogens will get pulled or pushed into the body, or people will touch them or they don’t wear them right. And I am even more frustrated by the absence of meaningful research that would provide better guidance–do studies of what collects on a mask during long periods of wearing and what happens to what is collected. Do studies that are realistic, using mannequins or whatever, of long periods of breathing wearing a mask in the presence of pathogens and see what happens to them–are they collected on the mask and do they get pushed or pulled through. Show us, through contact tracing or other studies, that people who wear masks regularly are actually less likely to infect or be infected. Very little, if any, of that research is being done. And the reason it isn’t being done is because people are afraid the results won’t be consistent with the messages they want to deliver. So much for any real belief in science.
Here is a study on use of cloth and surgical masks by the public. (JAMA Article) It talks about filtration efficiency. The article starts with the assumption that masks work to reduce transmission from the wearer and to the wearer. There is no evidence to support that in regard to community transmission, and this study indicates why. They took masks frequently used by the public and studied them as is and with some suggested modifications designed to improve performance. (Wait, they might need improved performance?) The testing was the usual unrealistic put the masks in a chamber and see how they work. One funny note, typical of these rushed studies, is that they said the masks were tested at temperatures from 73.4 degrees F to 85.1 degrees C, which would be close to the boiling point of water. I think they meant both temperatures to be Fahrenheit. (See, I do read these studies carefully.) Humidity was 10% to 50%. This supposedly represents a range of indoor conditions. I don’t think many people keep their house at 73.4 degrees. Droplets with salt particles were used to test filtration efficiency, with a variety of sizes. Only one middle-aged man was used for the test. Total testing time per mask was 3 minutes. Yes, that certainly reflects realistic mask use. Particles behind the mask were measured. The best mask had a filtration efficiency, which is concentration of particles behind that mask compared to those in the chamber generally, of 79% (higher is better) and the worst, 26%. Just so you know, all those ear loop surgical masks you see people wearing have a filtration efficiency of less than 40%. An N95 mask, by comparison has one of over 98%. After modification, efficiency increased modestly for the masks. The results of this study explain exactly why I make that distinction between protection in a single encounter and protection across a large number of encounters. Only takes one exposure, potentially to small amount of virus, to create transmission.
And this study examined how to test the effectiveness of masks for stopping droplets going out. (Science Article) The authors here were using lasers to test for droplet emission from a person wearing a mask while speaking. 14 masks were tested, including an N95 one. The masks were tested ten times for about 30 seconds of speech and post-speech time, with each test. So again, a totally realistic setup for how people use masks in the community (suppressed laughter). The droplet transmission fraction was about one-tenth of a percent for an N95 mask, but was actually 110% for a neck gaiter. They noted that some masks just disperse larger particles into smaller ones. And it wasn’t clear from the discussion what the smallest size particle that could be detected was by this experimental setup. But again, the suggestion is that particles do get through in most masks used by public.