SmogRank / World / Canada / Ontario / July 2023
Most polluted cities in Ontario, Canada, July 2023
20 cities in Ontario, Canada ranked by their average PM2.5 over the 31 days. Worst: Barrie at 13.5 µg/m³, #216 of 1,375 cities in the world. Cleanest: Sault Ste. Marie at 8.3. A city needs measurements on 70% of the days to be ranked.
OpenAQ's archive, where our readings come from, has almost none for one of these days. Cities in the United States and Europe have it from the EPA's and the European Environment Agency's own records of the same monitors; elsewhere a city's average is over its other days. Why.
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.
- 1Parry Sound 7%
- 2Barrie 7%
- 3Kingston 4%
- 4St. Catharines 4%
- 5Cornwall 3%
- 6Peterborough 3%
- 7Windsor 3%
- 8Belleville 3%
- 9St. Thomas 3%
- 10North Bay 3%
- 11Ottawa 3%
- 12Hamilton 0%
- 13London 0%
- 14Kitchener 0%
- 14Sarnia 0%
- 16Brantford 0%
- 17Toronto 0%
- 18Chatham 0%
- 18Greater Sudbury 0%
- 20Sault 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
All cities in the world, July 2023 · All cities in Canada, July 2023 · Ontario now
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SmogRank, most polluted cities in Ontario, Canada, PM2.5, July 2023, smogrank.com/ca/region/ontario/history/2023-07 (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.