SmogRank / World / Canada / Ontario / September 2023
Most polluted cities in Ontario, Canada, September 2023
29 cities in Ontario, Canada ranked by their average PM2.5 over the 30 days. Worst: Cornwall at 10.5 µg/m³, #486 of 2,128 cities in the world. Cleanest: Brooklin at 6.9. 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%
- 2Cornwall 0%
- 3London 0%
- 3Oakville 0%
- 5Ottawa 0%
- 6Brantford 0%
- 6Windsor 0%
- 8Hamilton 0%
- 8Milton 0%
- 10Barrie 0%
- 10Kitchener 0%
- 12Toronto 0%
- 13Brampton 0%
- 13Greater Sudbury 0%
- 13Guelph 0%
- 13Newmarket 0%
- 17Waterdown 0%
- 18Sarnia 0%
- 19Mississauga 0%
- 20Kingston 0%
- 20St. Thomas 0%
- 22Parry Sound 0%
- 22St. Catharines 0%
- 24Peterborough 0%
- 25Chatham 0%
- 26North Bay 0%
- 27Belleville 0%
- 27Sault Ste. Marie 0%
- 29Brooklin 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, September 2023 · All cities in Canada, September 2023 · Ontario now
Use this board
SmogRank, most polluted cities in Ontario, Canada, PM2.5, September 2023, smogrank.com/ca/region/ontario/history/2023-09 (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.