The March 13, 2021 issue of Science News has an interesting article concerning the effectiveness of masks at preventing exposures to air borne microbes (including the covid-19 virus). One set of numbers when using medical masks was particularly enlightening to me. They performed a number of tests with two manikins (surrogates for people) spaced six feet apart. If the receiver alone wears a mask, it reduces the amount of inhaled droplets by 7.5%. If the source alone wears a mask, it reduces the receivers exposure by 41.3%. If both wear a mask, the reduction is 84.3%. Clearly, the most important player to reducing exposure is the source person (as we are being constantly told), but the real benefits come when both people wear masks.

If the masks are worn “properly” (knotting the ear loops close to the mask and tucking in the ends to eliminate side gaps), the single mask worn by the receiver reduced expose by 64.5% compared to when neither wears a mask. If both do this, then the reduction is 95.9%. Wearing double masks helps even more. When just the receiver wore a double mask, the protection increased to 83%. When both wore double masks, the protection increased to 96.4%.

While these numbers are interesting, and impressive, they still leave me scratching my head because I don’t know how to align the reductions in particles to reduction in risk. Obviously, if neither parties are infected the masks don’t do anything about reducing risks in that specific event. No infection means no risk, and it is as low as it can go. But what if the source is actually infected? What happens to the risk in that case? For example, if it takes 300 particles to cause infection (an ‘official’ estimate), and the source spews out 100,000 particles a minute (5 million in a sneeze), does reducing the exposure by 96.4% really help much? 300 particles is 0.3% of the initial 100,000 particles per minute. That means that the receiver still receives over 10 times as many particles as required to become infected each minute. Once again, it appears that the reduction in risk of infection is close to zero.

It sounds like wearing a mask is not necessarily “protective”, the only real protection is to avoid being in the vicinity of infected people. There are reports of what sound like valid investigations that found little evidence that mask wearing is particularly effective. Perhaps masks and distancing are helpful for necessary short term excursions into potentially infected areas (such as grocery stores and the like), but the real answer is to avoid infected people. I, for one, am willing to believe that masks worn by a source can prevent large globs of stuff from flying out of their mouth into my face, and that has GOT to be an improvement. I therefore do as we were told a year ago, I wear my mask to help protect others and sure wish they would do the same to help protect me.

By the way, while researching this piece I came upon a discussion about the back of the nose being the ideal “incubator” for the virus. Breathing viruses in through the mouth isn’t nearly as dangerous as breathing them into through the nose. Hence, all of those “nose breathers” that don’t put the mask over their noses are doing very little good for themselves. Perhaps it cuts down on the number of droplets being expelled when they talk or sneeze. I also found that the best science still points to vaccinated people being just as susceptible to infection, and just as contagious, as they were before being vaccinated. The only real difference is that they are protected from serious illness, and the creation of many more non-systematic people who think they are now “safe”. They may be safe in some sense, but those around them are not. Testing can help show that a person wasn’t infected when the took the test, but says nothing about what happened subsequently. Actually, since there is a delay of up to three days before tests show a positive response, the tests really only show that the person wasn’t infected three days before taking the test. A friend of mine that recently went to New Zealand said that prior to the flight all passengers tested negative, but by the time the landed in New Zealand, 6 tested positive. Those six were infected sometime between three days prior to their test and when they boarded the airplane. All were asymptomatic when they landed.