“My mask protects you and your mask protects me,” we are told.
But to what extent does a cloth mask also protect you from the novel coronavirus? The evidence is a lot less clear, experts tell Global News.
“Mostly, cloth masks are not great at protecting the wearer,” says the University of Toronto’s Colin Furness.
On the one hand, a mask easily traps the large droplets we exhale that might infect other people. On the other hand, what others exhale is a fine aerosol of smaller particles that can find their way through and around mask fabric that might infect us.
“You will keep your big droplets to yourself, but you will fairly readily inhale the smaller droplets of others,” Furness says.
Some masks are better than others, he says. Large masks that don’t leave gaps around the cheeks have less room for small particles to make their way around and inside the mask.
“What you want to do is minimize air leakage around the sides,” he says.
“Bigger is better. With a bit of a curve and some pleating in it, that will sort of help it hug the face. Definitely, definitely better.”
Some research showing that masks can also protect the wearer is from hospitals, which are a much more formal setting than the community, using masks designed for medical use, says McMaster University infectious disease expert Zain Chagla.
“It’s actually very hard to do real experimental studies in communities,” he says. “There are so many different factors — peoples’ adherence to things, their own personal risk in their households of getting infected. It’s much harder to generate the data.
“In a health care setting, it’s much more of a controlled system. People check in, you can monitor them relatively easily.”
One problem, Furness says, is that there’s a difficult design tradeoff with fabric masks: dense fabric in multiple layers works better, but makes it harder to breathe. Thin, loose fabric in a single layer is easy to breathe through, but doesn’t stop many small particles coming in.
“I don’t think there’s a particular harm to cloth masks, necessarily,” Chagla says. “Increasing the user’s risk of acquiring infection from others — it at least keeps it neutral, if not a little bit decreased, but a strong benefit of personal protection with a cloth mask is not there in the literature,” he explains.
“I’m not saying the story is closed on that. For now, there’s much more evidence in the protecting others domain than in the personal protection domain.”
Do some masks work better at protecting the wearer than others? And if so, why?
“I think there’s a lot of room for improvement based on doing some systematic testing of different fabrics and different designs,” Furness says.
“There’s still a lot we don’t know. We don’t have a perfect mask design yet.”
Federal public health officials recommend masks in enclosed spaces, like public transit and stores, where it’s hard to keep two metres apart from other people.
Wearing a non-medical mask in the community “has not been proven to protect the person wearing it,” federal chief public health officer Theresa Tam said in April.