SmogRank / World / Canada / Ontario / 2026
Most polluted cities in Ontario, Canada, 2026
29 cities in Ontario, Canada ranked by their average PM2.5 so far (278 of 365 days); 29 above the WHO annual guideline (5.0 µg/m³). Worst: Windsor at 10.8 µg/m³, #847 of 2,745 cities in the world. Cleanest: North Bay at 5.6. A city needs measurements on 70% of the days to be ranked.
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.
- 1Windsor 2%
- 2Waterdown 2%
- 3Sarnia 2%
- 4London 2%
- 5Hamilton 2%
- 6Toronto 2%
- 7Sault Ste. Marie 2%
- 8Alliston 2%
- 9Newmarket 1%
- 10Mississauga 1%
- 11Brantford 1%
- 12Guelph 1%
- 13Barrie 1%
- 14Nepeanlow-cost sensors 1%
- 15Kitchener 1%
- 16St. Thomas 1%
- 17Milton 1%
- 18Oakville 1%
- 19Brampton 1%
- 20St. Catharines 1%
- 21Greater Sudbury 1%
- 22Parry Sound 1%
- 23Belleville 1%
- 24North Bay 1%
- 25Chatham 1%
- 26Peterborough 1%
- 27Kingston 1%
- 28Cornwall 0%
- 29Ottawa 0%
Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.
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, 2026 · All cities in Canada, 2026 · Ontario now
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SmogRank, most polluted cities in Ontario, Canada, PM2.5, 2026 (so far), smogrank.com/ca/region/ontario/history/2026 (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.