Air Quality in Canada

How air quality works in Canada: the index it uses, the pollutants that dominate, the seasonal pattern, the cities to watch, and the agencies that monitor it. Canada reports on the Air Quality Health Index (AQHI).

The big picture

Canada's baseline air quality is excellent. The country uses a distinctive index — the Air Quality Health Index (AQHI) — which reports the combined short-term health risk of ozone, NO₂, and PM2.5 on a 1–10+ scale, rather than the concentration of a single worst pollutant.

Dominant pollutants and where they come from

The overwhelming modern hazard is wildfire smoke (PM2.5), which has grown more frequent and severe. Beyond that: summer ozone and traffic NO₂ in the big metros (much reduced after Ontario's coal phase-out), industrial emissions in some regions, and winter wood-smoke in valley towns.

The seasonal pattern

Late spring through early autumn is wildfire season — smoke from fires in British Columbia, the Prairies, Ontario, and Quebec can blanket cities for days, sometimes giving Canadian metros some of the worst air on the continent. Winter adds localised wood-smoke in valleys. See Wildfire Smoke.

Who monitors it

Environment and Climate Change Canada publishes the AQHI jointly with the provinces and territories, which run the monitoring networks and issue smoke bulletins during fire season.

Cities in Canada

Primary sources: ECCC — Air Quality Health Index