Toronto has recorded the worst air quality of any major city worldwide as thick smoke from ongoing Canadian wildfires blankets the region.
The severe haze has pushed the city below other global hotspots, including New Delhi and Kinshasa, in real-time air quality monitoring data.
The deteriorating conditions are not confined to Canada.
Smoke plumes are drifting south, posing a threat to air quality in several major US cities.
The spread of the haze underscores the cross-border impact of the extreme weather event, complicating travel and health advisories for millions in North America.
This development follows a period of intense heat and fire risk across the continent.