As a retired medical professional with a master’s degree in public health, I am responding to Val Mullen’s “scientific” view point on mask wearing for COVID-19 protection. (letter, Oct.7)

First, some explanation:

This teeny virus which scientist Mullen states is 125 nanometers is carried by bodily fluids varying in size from misty aerosol droplets to spit balls. As anyone who has worn a mask for 15 minutes can attest to, a lot of those droplets are caught in the mask. One also sees this moisture on a cold winter’s day when your breath freezes on exhalation. Cover it with a scarf and you get drenched, which is why masks are not to protect you but for the other guy.

Second, this teeny virus which Mullen states is 125 nanometers is very small compared to the weave of the cloth, however there are two layers in a tightly woven cotton mask where the weaves do not match up, giving the screen effect much more filter. A tight seal around the edges is also important.

Third, to be infected you have to have a large enough viral load to carry from aerosol to newly infected person with varying immune system responses. Catching the moisture in a mask decreases the viral load in the air; this is improved with social distancing.

Fourth, the 2018 influenza research cited by Mullen, found at the CDC website, was a literature review of 10 random controlled trials that also noted: “Most studies were underpowered because of limited sample size, and some studies also reported suboptimal adherence in the face mask group.”

Fifth, just because small sampled poorly controlled research, randomized or not, does not show benefits, is no proof. There just needs to be more thorough studies specifically for COVID-19.

Joan Cross

La Conner