Smoke from Canadian wildfires can travel hundreds or even thousands of kilometres, turning a distant fire into a serious air-quality emergency. That danger was starkly illustrated when wildfire smoke from Ontario moved into the United States and contributed to exceptionally poor air quality across parts of the Midwest. In Michigan, the Air Quality Index reportedly reached an extraordinary 616, a level far beyond the EPA’s hazardous category. But the episode is part of a much larger concern. Scientists have increasingly linked worsening wildfire conditions with a warming climate, while new research shows that smoke-derived fine particulate pollution is already contributing substantially to premature deaths across the United States. A 2026 Science Advances study estimated that wildfire-smoke PM2.5 was responsible for approximately 24,100 deaths each year in the contiguous US between 2006 and 2020.
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