With wildfire smoke in the forecast for Toronto, is it time to bring back masks?

Smoke from wildfires raging in Quebec and northeastern Ontario is expected to blanket Toronto for much of the week, prompting a special air quality statement for the city and warnings of possible “high levels” of pollution.

With some Toronto residents already reporting the smell of smoke and conditions expected to worsen, experts say those in affected areas should consider wearing a mask and taking other precautions to reduce exposure.

“Every reduction in breathing this stuff provides a benefit to your health,” said Jeff Brook, an associate professor at the University of Toronto’s Dalla Lana School of Public Health and Department of Chemical Engineering and Applied Chemistry.

Those with a compromised respiratory or cardiovascular system may be most at risk of health complications from the smoke, said Brook, but added that masking can benefit everyone.

Toronto’s air quality health index was at a level 5 midday Tuesday, indicating a “moderate risk” to health. Environment Canada’s national wildfire smoke model forecasts air pollution to worsen in the region as the week progresses with significant amounts of smoke predicted for Thursday afternoon.

Environment Canada and the Province of Ontario had issued a special air quality statement for the region earlier in the day, warning of smoke from the forest fires throughout much of the week.

“High levels of air pollution are possible due to smoke from forest fires. Smoke plumes from forest fires in Quebec and northeastern Ontario may result in deteriorated air quality through most of this week,” the statement said.

Because the smoke contains fine particulate matter, Brook recommends wearing an N95 mask that fits snugly around the nose and mouth. “The standard advice would be a well-fit N95 does the trick,” he said.

However, Brook said a standard surgical mask could also work — though less effectively — if N95 masks are unavailable or if people find themselves taking off an N95 mask more often than they’re wearing it.

“If an N95 is uncomfortable and you’re taking it off more often than you’re wearing it, you’re kind of defeating the purpose,” added Brook.

In addition to masking, he recommends avoiding strenuous outdoor activities and closing all doors and windows. Investing in an air filter, such as a HEPA filter, can also help remove the fine pollutants that can still enter inside, even with windows and doors closed, he said.

“Most of this pollution is in the form of tiny particles that are like a fraction of the thickness of a human hair. They’re very small,” Brook explained.

Currently, Toronto is seeing northwesterly winds, bringing in smoke from fires burning in northeastern Ontario, explained David Phillips, a senior climatologist with Environment Canada.

“But likely tomorrow, we’re going to see the winds shift more to the east and that’s a concern because it’s going to take the smoke from the Quebec fires, which are much more prevalent right now, and move it through Eastern Ontario, and down through the GTA.”

Like Brook, Phillips said wearing a mask “might be wise,” especially for those at risk of experiencing more severe symptoms.

“It’s a day-to-day thing, so it’s not as if you’re going to be stuck with that mask for very long,” he added.

“People need to be their own kind of physician in that way.”

Clarification — June 7, 2023: This article was updated to be clear that the smoke affecting air quality in Toronto and the GTA is from wildfires raging in Quebec and northeastern Ontario, not just Quebec.

Joshua Chong is a Toronto-based staff reporter for the Star’s Express Desk. Follow him on Twitter: @joshualdwchong