SmogRank / World / Canada / Ontario / 2024
Most polluted cities in Ontario, Canada, 2024
28 cities in Ontario, Canada ranked by their average PM2.5 over the 366 days; 25 above the WHO annual guideline (5.0 µg/m³). Worst: Windsor at 8.5 µg/m³, #890 of 2,052 cities in the world. Cleanest: North Bay at 4.6. A city needs measurements on 70% of the days to be ranked.
OpenAQ's archive, where our readings come from, has almost none for one of these days. Cities in the United States and Europe have it from the EPA's and the European Environment Agency's own records of the same monitors; elsewhere a city's average is over its other days. Why.
OpenAQ's archive, where our readings come from, has almost none from Canada for March 20, 2024: cities in Canada are averaged over their other days. Why.
Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.
- 1Thunder Bay 0%
- 2Windsor 0%
- 3Hamilton 0%
- 4Brantford 0%
- 5London 0%
- 5Milton 0%
- 5Toronto 0%
- 8Barrie 0%
- 9Kitchener 0%
- 10Oakville 0%
- 11Sarnia 0%
- 11St. Thomas 0%
- 13Waterdown 0%
- 14Guelph 0%
- 15Brampton 0%
- 15Chatham 0%
- 15Newmarket 0%
- 15St. Catharines 0%
- 19Brooklin 0%
- 20Mississauga 0%
- 21Ottawa 0%
- 22Peterborough 0%
- 23Greater Sudbury 0%
- 23Kingston 0%
- 25Belleville 0%
- 26Parry Sound 0%
- 27Sault Ste. Marie 0%
- 28North Bay 0%
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
All cities in the world, 2024 · All cities in Canada, 2024 · Ontario now
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SmogRank, most polluted cities in Ontario, Canada, PM2.5, 2024, smogrank.com/ca/region/ontario/history/2024 (accessed 6 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.