Wildfire smoke drifting south from Canada has triggered air quality alerts across more than 20 US states and Washington, D.C., with doctors warning that even healthy people can suffer effects from prolonged exposure to polluted air. Nearly 850 wildfires are currently burning across Canada, with more than 180 in Ontario alone, sending plumes into the Midwest and Northeast and creating some of the worst air quality the region has seen in years, according to reports cited in the article.

Medical experts, including a cardiothoracic surgeon at Mount Sinai, say the pollution poses particular risks to people with asthma, chronic obstructive pulmonary disease (COPD) and heart conditions, as well as to the elderly, children and pregnant women. The smoke has prompted widespread air quality warnings stretching from the Upper Midwest across affected states, with health professionals urging vulnerable groups to limit outdoor exposure and take precautions while the smoke persists.