A wildfire burns in the Chance Harbour, N.L., area on July 14, 2025.Dawn Gough/The Canadian Press
Even thousands of kilometres from the flames, Canadians were coughing, wheezing and red-eyed. As wildfires raged, smoke and haze spread last week across the country, sparking health warnings for millions of people. For a few hours, Toronto had the second worst air in the world. On a scale of 1 to 10, the city’s air quality was off the chart, officially clocked at 10+.
The smoke was a reminder that the threat of fires is bigger than the immediate danger posed to those nearby. As climate change causes hotter and drier conditions – which leads to more frequent and more fierce blazes – Canadians have to start taking seriously the toxic stew carried on the wind.
A century ago, professional cyclists believed that smoking cigarettes on the bike would “open up the lungs” during difficult races in the mountains. We now know that all smoke contains particulate matter that can damage the lungs, leading to cardiovascular problems, and even get into the bloodstream. The Canadian Lung Association warns bluntly that “there is no safe level of wildfire smoke.”
The risk is particularly bad for people with respiratory problems but everyone can be affected. Difficulty breathing, chest pain, heart palpitations and dizziness are among the symptoms. On a longer-term basis, a study published this month in the journal Radiology found that exposure to particulate matter in smoke can lead to the sort of scarring of the heart that can precede a heart attack.
There’s also a psychological impact. Canada has had several bad fire summers in the past few years. In some parts of the country, haze blocked out the sun for days or weeks, leaving a perpetually grey sky that dampened the mood. In extreme cases, skies turned an unnerving orange, reminiscent of an apocalyptic Hollywood film.
This new reality will force Canadians to change how they enjoy summer.
Urban parks in east Asia are packed early in the morning, as people stroll and work out before the heat becomes intolerable. In the same way, Canadians will have to learn to work around the smoke.
However, as was argued during debate over some of the more strict pandemic-era public health measures, this shift will have to be weighed against the value of activities curtailed. There is human benefit in exercise, in social contact, in variety. Staying inside is not always the best solution.
Still, some days won’t be suitable to go outside unless necessary. For those who must, public health officials recommend wearing a properly fitted N95 mask and limiting exposure as much as possible. And because a person can gulp 10 times as much air during strenuous exercise than while resting, officials urge a toned-down workout on days when smoke is present.
Without proper preparation, even staying inside offers only so much protection. Researchers say that most buildings keep out only about half of the air pollution present outside. Governments must ensure that air purifiers are more widely deployed in schools, seniors’ homes and medical facilities. For individual use, though, purifiers can be expensive, so creating a “clean room” can be more economical than filtering a whole home. Civic institutions such as libraries can also serve as refuges, if the air is kept properly clean.
Another tactic for keeping the air cleaner is, paradoxically, lighting fires. This space argued last week for a more pro-active approach to wildfire management, including more extensive use of prescribed burns. These are deliberately set fires that clear flammable material from an area in a controlled manner. It turns out these also have long-term benefits for air quality.
A pair of studies in the United States looked at the smoke emitted by prescribed burns and compared it to smoke from a similar area that burned in a wildfire. Although the results varied, the top-line is that the smoke from the prescribed burn was one-quarter to half as severe as the smoke from the wildfire. In effect, a smaller amount of smoke, created under controlled circumstances, replaces a larger amount of smoke that happens randomly down the road.
Some fire researchers say that we have entered the Pyrocene, an age in which human-caused fire activity is happening on a scale that is reshaping the planet. The bouts of wildfire smoke every summer are starting to look like evidence of this. Canadians will have to take them seriously, and unfortunately learn to live with it.