SmogRank / World / Canada / Ontario / May 2023
Most polluted cities in Ontario, Canada, May 2023
20 cities in Ontario, Canada ranked by their average PM2.5 over the 31 days. Worst: Hamilton at 11.7 µg/m³, #263 of 1,543 cities in the world. Cleanest: North Bay at 4.5. 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.
- 1Hamilton 0%
- 2Brantford 0%
- 3London 0%
- 4Windsor 0%
- 5Barrie 0%
- 6Chatham 0%
- 6Toronto 0%
- 8Kitchener 0%
- 9St. Thomas 0%
- 10Greater Sudbury 0%
- 10St. Catharines 0%
- 12Sarnia 0%
- 13Parry Sound 0%
- 14Belleville 0%
- 15Peterborough 0%
- 16Cornwall 0%
- 17Ottawa 0%
- 18Kingston 0%
- 19Sault Ste. Marie 0%
- 20North 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
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SmogRank, most polluted cities in Ontario, Canada, PM2.5, May 2023, smogrank.com/ca/region/ontario/history/2023-05 (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.