A surge of wildfires across Ontario, Canada, and parts of Minnesota in the United States has led to severe air quality deterioration across major cities in both countries. Residents in urban centres such as Toronto, New York, and Boston have been urged to limit strenuous outdoor activities due to dangerous levels of pollution carried by the smoke plumes.
The Canadian Interagency Forest Fire Centre reports a staggering 858 active wildfires currently burning across Canada, with almost 200 concentrated in Ontario. Additionally, 17 fires persist along Minnesota's northern edge, where emergency declarations are in place to bolster suppression efforts. In Ontario, the blazes are predominantly located north of Lake Superior, impacting remote areas, national parks, and several First Nation communities. Grand Council Chief Linda Debassige confirmed that the Namaygoosisagagun First Nation in northern Ontario suffered significant damage to homes and community buildings from a rapidly spreading fire.
While wildfires are a regular occurrence in Canada, their recent escalation is attributed to a 'heat dome' – a high-pressure system trapping warm air – which brought sustained hot weather and below-average rainfall to northern Ontario in late June. This combination has dried out vegetation, providing ample fuel for the fires. The unstable hot air can also generate strong winds, further aiding the spread of both the fires and their smoke.
Satellite imagery reveals that winds are primarily carrying the smoke southeast from Ontario, impacting Toronto, New York State, and reaching as far as Boston. Air quality tracking company IQAir has ranked Detroit, Toronto, and Minneapolis among the cities with the worst air quality globally. Wildfire smoke is particularly hazardous due to its content of fine particulate matter, known as PM2.5, and nitrogen dioxide. These microscopic particles can penetrate deep into the lungs, causing inflammation and exacerbating existing respiratory, heart, kidney, and eye conditions, as highlighted by the World Health Organisation.
Authorities are issuing air quality warnings, with 'orange alerts' advising individuals to avoid strenuous outdoor activities, remain indoors with windows closed, and consider wearing well-fitting N95 masks. These masks are designed to filter out 95% of the tiny particles, though vigilance is required against counterfeit products. Vulnerable groups, including those with chronic illnesses and children, are deemed most at risk. Many affected cities have activated emergency air quality protocols and are distributing certified masks at local centres.