Wildfire smoke pushes North American cities to worst air quality worldwide

Smoke from wildfires burning across Canada blackened skies over Toronto and spread across a wide stretch of the United States, from the Midwest through the Northeast, by Thursday. Government data showed 858 active fires burning across Canada as of Thursday morning, with 111 of them classified as out of control. Most of the fires burned in the central provinces of Manitoba, Saskatchewan and Ontario.

Readings from the air quality monitoring service IQAir showed that North American cities recorded some of the most hazardous air of any major cities in the world this week. Detroit posted the highest daily peak reading among the cities tracked, with levels surging at 11:00 p.m. local time on July 15. Chicago, New York City, Toronto and Minneapolis also registered very unhealthy or hazardous air quality during the same period.

Health experts note that wildfire smoke can linger in the atmosphere for weeks and tends to carry greater toxicity than typical air pollution. Multiple studies have linked exposure to wildfire smoke with higher rates of heart attacks, strokes, cancer, pregnancy complications and weakened immune function, raising concern for residents across the affected cities as the smoke continues to spread.

The hazardous air arrives just days before the FIFA World Cup final, scheduled to take place in New Jersey on Sunday in front of more than 80,000 fans. Forecasters expect rain to help clear the smoke from the region before Spain and Argentina take the field, though the timing has added an unexpected layer of concern to preparations for one of the year’s largest sporting events.

The scale of this week’s smoke event highlights a pattern that has become increasingly familiar across North America in recent years, as intensifying wildfire seasons in Canada send smoke drifting across international borders and disrupt daily life in cities far from the flames themselves. Public health officials in affected areas have urged residents, particularly those with respiratory conditions, children and the elderly, to limit outdoor activity until air quality improves, while transportation and event organizers continue monitoring conditions as the smoke moves through the region.