It’s hard not to forget the 2023 Canadian wildfire season, when more than 16 million hectares of forest were lost, thousands were displaced and smoke suffocated cities across both Canada and the U.S.
And it turns out Canada experienced its worst air pollution levels that year since 1998, according to a new report released today by the University of Chicago’s Air Quality Life Index (AQLI). At the same time, the report found that pollution levels didn’t change much for the rest of the world in 2023.
If those levels continued for a person’s lifetime, the average Canadian would lose roughly two years of their life expectancy, according to the report.
Efforts have been made around the world, including in Canada, to curb harmful emissions of fine particulate matter with a diameter of less than 2.5 micrometres, also known as PM 2.5. But wildfires are reversing those advances — with serious health consequences.
“Air pollution is the greatest external threat to human well-being on the planet, and I don’t believe that that is widely recognized,” said Michael Greenstone, one of the report’s authors. “More years of life expectancy are lost for the average person on the planet due to air pollution than to maternal and child malnutrition, than due to alcohol, than due to tobacco.”
Canada’s national standard is 8.8 micrograms of PM 2.5 per square metre; the World Health Organization’s standard is five. In 2023, Canadians were exposed to 9.2 micrograms per square metre, or 1.5 times 2022 levels. And more than half of Canadians breathed air that surpassed that national standard.
Greenstone said that both Canada and the U.S. have made great strides over the past few decades to curb air pollution, particularly by mandating the installation of control devices to reduce pollution from the combustion of fossil fuels. But he says it’s frustrating to see it rise as it did in 2023.
“What’s really interesting about the reversals in Canada and the United States is they’re showing that air pollution is like the zombie that we thought we had killed, but it’s coming back to life.”
While 2023 may have been the worst year on record for wildfires, 2025 is the second worst, just behind 2024. And research has shown that as we continue to pump greenhouse gases into the atmosphere, wildfires will only increase.
This worries Dr. Courtney Howard, an emergency room physician in Yellowknife and the chair of the Global Climate and Health Alliance.
“I spend most of my time working for free on this issue, because climate change and its health impact is by far the biggest threat to health and health systems of our time,” she said.
But she noted that the AQLI report may have actually underestimated the health outcomes due to wildfire smoke air pollution.
Air-quality alerts across Canada due to wildfire smoke
Howard noted that a study released earlier this month noted that a given level of PM 2.5 from wildfire smoke has worse health outcomes than other forms of PM 2.5, such as those from gas-powered vehicles and industrial emissions.
By not separating the different sources, “you would underestimate the fire-related, PM 2.5-attributable mortality by 93 per cent,” Howard said. “So that means that if most of our PM 2.5 is due to wildfire smoke, probably the the health harms that this study identifies are actually an underestimation.”
And, she noted, the health effects are vast and serious, with particles being so small that they go down into the lungs and then enter the bloodstream, which can lead to lung illnesses such as asthma. This also has been associated with strokes, cardiovascular disease and chronic obstructive pulmonary disease.
Howard is frustrated to see the fossil fuel industry continue being subsidized by the government while people battle the consequences, such as wildfire smoke.
“We are subsidizing a sun-setting industry in Canada that actually is one of the biggest contributors to health harms for our children,” she said.
Greenstone has a unique analogy for what we’re seeing today: “I think of this return of air pollution through the wildfires as being the ghost of fossil fuels past.”
He says the recent report highlights the importance of knowing the air quality where you live. He said that government action across the world has increased. This includes China, which has seen a reduction of air pollution by 40 per cent since 2014.
“Air pollution is not just a number,” he said.
“It’s an indicator, so that people are able to lead healthier, fuller and longer lives.”
