The Widespread and Alarming Spread of Canadian Wildfire Smoke and Its Impact on Health


Severe and unusual smoke from Canadian wildfires is spreading rapidly, posing significant health risks across eastern Canada and the United States. The uncontrolled wildfires in Quebec and other provinces have resulted in vast portions of these regions being covered in smoke and haze.

Air quality warnings have been issued in numerous cities and towns in Quebec, Ontario, and beyond, leading to hazy, apocalyptic skies and alerts in major metropolitan areas such as New York City and Washington, D.C.

According to Rebecca Saari, an air quality expert and associate professor at the University of Waterloo, the levels of air pollution observed are exceptionally severe and uncommon in Canada and parts of the United States. She emphasizes that people should be aware of the poor air quality conditions and take necessary precautions to protect themselves. Unfortunately, such occurrences are expected to become more frequent as climate change intensifies and prolongs the hot, dry conditions that fuel wildfires.


The fire risk for June is significantly above average in every province and territory, except for Newfoundland and Labrador, where it is considered average. The entire country is facing an exceptionally challenging wildfire season, with federal government officials warning of increased wildfire risks across most of Canada until August.

Presently, Quebec is grappling with over 150 forest fires, nearly 100 of which remain out of control. A storm system off the eastern coast of Nova Scotia has propelled the smoke from these fires towards Ontario and the United States, with forecasts predicting poor visibility as far south as North Carolina.

The extent of the haze is a matter of concern, and different countries employ different indexes to measure air quality. Canada employs the Air Quality Health Index (AQHI), while the United States uses the Air Quality Index (AQI). On Wednesday, the AQI exceeded a staggering 400 at times in Syracuse, New York City, and Pennsylvania’s Lehigh Valley. An AQI value below 50 is considered good, while anything above 300 is deemed “hazardous.”

Toronto, in particular, experienced some of the worst air quality globally, comparable to cities like Delhi, India, and Dhaka, Bangladesh, according to IQair, an online air quality monitoring service. Kingston and other areas in eastern Ontario fared even worse, exhibiting high levels of particulate matter known as PM2.5 levels.

These ultra-fine particles, approximately 30 times smaller than a human hair’s diameter, can penetrate the lungs and bloodstream, causing severe health consequences. Dr. Samir Gupta, a respirologist and associate professor at the University of Toronto, explains that the lungs are particularly susceptible to breathing symptoms, especially for individuals with pre-existing lung conditions like asthma.

A recent study from Stanford University likened the inhalation of PM2.5 levels to smoking cigarettes. It stated that an AQI measurement of 20 is equivalent to smoking one cigarette daily. Moreover, prolonged exposure to wildfire smoke with an AQI of 150, for instance, would be akin to smoking around seven cigarettes a day for someone continuously outside. Based on this calculation, residents of Kingston who spent eight hours outside during the peak of the haze unknowingly smoked the equivalent of nine cigarettes.

Environment Canada’s AQHI issued a “very high risk” warning for eastern Ontario cities, including Kingston, Ottawa, and Gatineau, Quebec. Montreal and Toronto were also classified as “high risk” areas. While most of Western Canada experienced a respite from the smoky air, parts of Vancouver and the Central Fraser Valley remained under “extreme risk.”

Environment Canada advises the general population in areas designated as “very high risk” to reduce or reschedule strenuous outdoor activities. At-risk populations, such as young children, seniors, and individuals with chronic conditions, are urged to avoid engaging in strenuous activities altogether.

Although air quality has improved in Montreal, with the smog warning lifted, immediate relief is not expected in parts of Ontario, where poor air quality conditions could persist through the weekend.

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