Wildfires in Ontario make Toronto air quality worst in world

Wildfires burning across Ontario have produced such intense smoke that Toronto's air quality has fallen to the worst level of any major city in the world, with the concentration of fine particulate matter reaching levels that public health officials describe as hazardous for everyone, regardless of age or health status.

The fires, which have been burning for more than a week and have consumed approximately 400,000 hectares of forest, are the latest in a series of severe wildfire seasons that have affected Canada with increasing frequency and intensity. The smoke plume has extended across much of eastern North America, affecting air quality in cities from Ottawa to New York.

In Toronto, the Air Quality Health Index reached 10+, the highest possible reading, and authorities advised residents to stay indoors, keep windows closed and avoid physical exertion. Schools suspended outdoor activities, several outdoor events were cancelled, and the city's public health department opened cooling centres for people without access to air-conditioned spaces.

The fires are being driven by a combination of factors that scientists have linked to climate change: an unusually dry winter and spring that left vegetation primed to burn, record-breaking early-summer temperatures, and a series of lightning storms that provided the ignition. Firefighting resources are stretched thin, with crews and equipment deployed across multiple provinces, and the Canadian military has been mobilised to assist in evacuation and firefighting efforts.

The air quality crisis in Toronto is a reminder that the effects of climate change are not confined to the places where the fires burn. Smoke travels, and the consequences of a warming planet are being felt by people who live thousands of kilometres from the front line.