SmogRank / World / Canada / Ontario / January 2025
Most polluted cities in Ontario, Canada, January 2025
27 cities in Ontario, Canada ranked by their average PM2.5 over the 31 days. Worst: Windsor at 8.5 µg/m³, #1,271 of 2,426 cities in the world. Cleanest: Sault Ste. Marie at 3.6. 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 0%
- 2Toronto 0%
- 3Hamilton 0%
- 4Waterdown 0%
- 5Brantford 0%
- 6Milton 0%
- 6Sarnia 0%
- 8London 0%
- 9St. Thomas 0%
- 10Barrie 0%
- 10Kitchener 0%
- 10Newmarket 0%
- 13Oakville 0%
- 14Chatham 0%
- 15Mississauga 0%
- 16Guelph 0%
- 17St. Catharines 0%
- 18Brampton 0%
- 19Peterborough 0%
- 20Ottawa 0%
- 21Belleville 0%
- 22Alliston 0%
- 23Kingston 0%
- 24Greater Sudbury 0%
- 25North Bay 0%
- 26Parry Sound 0%
- 27Sault Ste. Marie 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
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SmogRank, most polluted cities in Ontario, Canada, PM2.5, January 2025, smogrank.com/ca/region/ontario/history/2025-01 (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.