SmogRank / World / Canada / Ontario / May 2024
Most polluted cities in Ontario, Canada, May 2024
29 cities in Ontario, Canada ranked by their average PM2.5 over the 31 days. Worst: Hamilton at 8.4 µg/m³, #1,135 of 2,641 cities in the world. Cleanest: Sault Ste. Marie at 3.7. 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.
- 1Thunder Bay 3%
- 2Hamilton 0%
- 3Brantford 0%
- 4London 0%
- 5Windsor 0%
- 6Waterdown 0%
- 7Kitchener 0%
- 8Oakville 0%
- 9Milton 0%
- 9St. Thomas 0%
- 11Guelph 0%
- 12Toronto 0%
- 13Barrie 0%
- 13St. Catharines 0%
- 15Mississauga 0%
- 16Brooklin 0%
- 16Chatham 0%
- 16Newmarket 0%
- 19Sarnia 0%
- 20Brampton 0%
- 21Cornwall 0%
- 21Peterborough 0%
- 23Ottawa 0%
- 24Greater Sudbury 0%
- 25Belleville 0%
- 25Kingston 0%
- 27Parry Sound 0%
- 28North Bay 0%
- 29Sault 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, May 2024, smogrank.com/ca/region/ontario/history/2024-05 (accessed 7 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.