Asthma-related ER visits rose in Ontario following 2023 wildfire smoke exposure.
Emergency room visits for asthma went up across Ontario in the summer of 2023 after thick wildfire smoke drifted into the province. That summer marked one of Canada’s worst wildfire seasons, with flames burning through forests in multiple regions. One fire in Quebec alone stretched over a million acres, sending dense smoke across provincial lines and into neighboring communities, including heavily populated areas of Ontario.
Researchers tracked emergency department records from nearly the entire province, covering areas where 95 percent of Ontarians live. They focused on a stretch of time beginning eight weeks before the first major wildfire smoke event in early June and ending four weeks after a second wave of smoke hit in July. What they found was a clear rise in asthma-related visits to hospitals after the first smoke event. In the days following that episode, the number of people seeking help for asthma symptoms rose by as much as 24 percent, and the increase lasted for nearly a week after the smoke had cleared. The timing matched the days when the air quality had dropped significantly due to the smoke drifting in from Quebec.
Surprisingly, the second wave of smoke in July did not have the same effect. This led researchers to wonder why one event led to a spike in asthma problems and the other did not. One thought is that people may have been more prepared the second time. For example, those with asthma may have already been prescribed or were already taking medications after the first event, making them less likely to have serious issues the second time. Another idea is that people may have listened more closely to air quality warnings. Maybe they stayed indoors, used air filters, or kept their children inside to lower the risk of breathing problems.
While the study focused on asthma, experts say wildfire smoke can affect other areas of health too. The short-term effects on breathing are well known, but some are looking into whether smoke from fires may also impact brain function, blood sugar, and even mental health. These links aren’t as well understood yet, but some researchers believe it’s worth paying more attention to how wildfire smoke affects the body as a whole, not just the lungs.
One doctor from British Columbia pointed out that while poor air quality from fires has become common in western Canada, it’s now spreading more often to other parts of the country. She says Canada should have a more consistent plan to help people limit their exposure to wildfire smoke both indoors and outside. That could mean better public guidance, cleaner indoor air systems, or more access to protective tools like air purifiers and masks.
As wildfire seasons grow longer and more intense, the impact on health is becoming harder to ignore. Communities far from where the fires start can still feel the effects when the wind carries smoke hundreds of miles away. Emergency rooms are likely to keep seeing the fallout unless more steps are taken to help people protect themselves when the skies turn hazy. This study adds to a growing pile of evidence that smoke from wildfires is more than just a nuisance. For people with breathing conditions like asthma, it can quickly become a medical emergency. The way people responded to the second wave of smoke may offer some hope—if people have the right tools and information, it is possible to reduce the harm.
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Asthma-related emergency visits increase during wildfire smoke events in Ontario
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