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A lady wears a protective face mask as she walks the seawall in English Bay in Vancouver, on May 4, 2020.JONATHAN HAYWARD/The Canadian Press

As the country gradually emerges from lockdown, Canadians may be wondering how and when to wear face masks.

Are face masks really necessary out in public? How protective are they? How do homemade masks compare with medical ones?

The Globe asked experts to weigh in:

Making sense of public health guidance

There’s debate about whether wearing face masks in public can reduce the spread of the new coronavirus, and health organizations differ on encouraging their use. For instance, the U.S. Centers for Disease Control and Prevention recommends that people wear cloth face coverings in public at places where it’s difficult to practice physical distancing, such as grocery stores and pharmacies, but the World Health Organization (WHO) does not.

In Canada, wearing non-medical masks and face coverings in public is optional, according to the Public Health Agency of Canada (PHAC). However, it says these masks and face coverings are required when people are travelling by air. It also encourages them for individuals travelling by ferry and other modes of marine transportation, and strongly encourages them for passengers of rail, bus and other land modes of transportation.

Mark Loeb, an infectious disease physician and a professor of pathology and molecular medicine at McMaster University, says the guidance likely differs at least partly because the evidence is uncertain for how effective masks are at reducing transmission of the virus within the general population.

However, he explained, the situation also matters. You’re safe if you take a walk outside and are not in close contact with others, he said. “But if you’re in a closed environment, like in a train or in an airplane, and you’re in a smaller space that clearly isn’t ventilated as well, your risk of transmission just generally is higher.”

Dr. Loeb adds that wearing a mask is likely of more value in an area with a high prevalence of infection, and situations where physical distancing can’t be maintained.

The messages from health organizations are consistent on a few points. Medical masks, including surgical masks and N95 respirator masks, should be reserved for health care workers and those looking after people who are infected. And masks alone are insufficient to protect against infection.

Weigh the benefits

Perhaps the strongest benefit of wearing a mask in the community is when you’re infected but don’t have enough symptoms to be aware of it and stay home, says Lynora Saxinger, infectious disease specialist at the University of Alberta.

A mask can reduce the spread of larger droplets from your nose and mouth, acting like a cover for coughs and sneezes, she says.

“So you’re not necessarily wearing it to protect you,” Dr. Saxinger says. “You’re kind of wearing it protect others. And if everyone does that, theoretically, there should be a community-based benefit to mask use.”

While the wearer may also get some protection, that’s not well studied, she says.

It’s important to note that wearing a mask could give people a false sense of security, she adds. For instance, with a mask, you may feel more confident and behave in ways that could put you at higher risk, such as getting closer to people than you otherwise would.

Pick the right mask

While N95 respirator masks can filter out 95 per cent of small particles, the filtration of medical masks can be highly variable, keeping out anywhere from 20 per cent to 90 per cent of small particles, Dr. Loeb says.

Most of the disposable masks you typically see are medical masks, Dr. Saxinger says, noting one of the main issues with them is the world’s manufacturers are scrambling to make enough. (“And let’s be honest, the number of disposable masks that the world is going to go through is actually kind of shocking too, and we should think about that,” she says.)

While cloth masks are suggested as an alternative, there’s very little data on their efficacy, which can vary depending on the type and weave of fabric, Dr. Saxinger says. She notes one study among health care workers found those who wore cloth masks during flu season had higher rates of infection, compared with those who wore disposable medical masks.

That suggests cloth masks may not be as good at protecting the wearer as medical masks, she says, but it’s unknown whether cloth masks are worse than none at all.

“There is that little question mark about could it actually be a problem to have moist cloth near your face,” she says, noting there is some suggestion that handling a damp mask after taking it off might increase a person’s risk of infection.

PHAC offers instructions online for how to make your own cloth mask at home, including options that do not require sewing. It says masks should be made of at least two layers of tightly woven fabric, such as cotton or linen, fit securely, and completely cover the nose and mouth without gaping.

Use your mask properly

Before putting on a mask, make sure it’s clean and dry, PHAC says. Wash your hands with soap and water for at least 20 seconds or use hand sanitizer before touching it.

Use a mask that you can take off without pulling it over your face or touching the front of it, Dr. Saxinger says.

Taking a break from it by pulling it down to your chin or up to your forehead or having it dangle on one ear is also “a terrible idea,” she says. The same goes for wearing it only over your mouth, with your nose exposed. “You’ve just basically … removed the reason for wearing it,” she says.

After taking it off, she recommends putting it in a plastic bag until you can deposit it directly into the laundry. Normal washing with soap and water is fine, she says.

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