deonandan: wearing a mask is still helpful, but choose a good one

it seems so long ago now, but it was late in 2020 when ontario first made masks mandatory in all indoor public spaces. back then, most public health leaders believed that covid-19 was most commonly spread through large exhaled droplets that fall to the ground within a couple of metres. that’s why we had physical distancing, to keep people out of others’ droplet zones. a simple cloth mask would then serve as a kind of “wind break,” trapping those droplets just in front of the face and negating the need for distancing.

the assumption was that if enough people wore such masks, the overall effect on the population would substantially diminish disease transmission. sure enough, as evidence came trickling in , most of it pointed to measurable covid containment. indeed, when two symptomatic, infected hair stylists attended to 139 clients, none of them became infected, as the stylists were properly masked.

this explains why the simple cloth masks, while useful, aren’t as effective as some had expected in curtailing transmission. aerosols can leak through the open tops and sides of baggy cloth masks. but so-called respirator masks, such as the n95 or kn95 types, are fitted to the face for less leakage. clinicians have traditionally had their respirator masks “fit tested,” meaning that the seal around their faces has been tested to ensure a tight fit. this is not necessary for non-clinicians, as non-fit tested n95s are more than good enough for the rest of us.

an analysis by dr. lisa brosseau for the center for infectious disease research and policy showed that if two people near each other are wearing surgical masks and one of them is infected, it takes less than an hour for the other person to receive an infectious dose. but if they’re both wearing non-fit-tested n95s, it would take many hours to receive that same dose.