SmogRank / Countries / Canada / Ontario
Most polluted cities in Ontario, Canada
28 measured cities ranked by PM2.5, last 30 days. Worst: Hamilton at 5.8 µg/m³, #1391 in the world.
| # | City | µg/m³ | |
|---|---|---|---|
| 1 | Hamilton Ontario | 5.8 | |
| 2 | Windsor Ontario | 5.8 | |
| 3 | Brantford Ontario | 5.7 | |
| 4 | Barrie Ontario | 5.6 | |
| 5 | Cornwall Ontario | 5.5 | |
| 6 | Newmarket Ontario | 5.5 | |
| 7 | Toronto Ontario | 5.5 | |
| 8 | London Ontario | 5.4 | |
| 9 | Nepean low-cost sensorsOntario | 5.4 | |
| 10 | St. Thomas Ontario | 5.4 | |
| 11 | Guelph Ontario | 5.2 | |
| 12 | Oakville Ontario | 5.2 | |
| 13 | Kitchener Ontario | 5.1 | |
| 14 | Milton Ontario | 5.1 | |
| 15 | St. Catharines Ontario | 5.1 | |
| 16 | Sarnia Ontario | 5.0 | |
| 17 | Brampton Ontario | 4.9 | |
| 18 | Waterdown Ontario | 4.9 | |
| 19 | Greater Sudbury Ontario | 4.8 | |
| 20 | Chatham Ontario | 4.7 | |
| 21 | Belleville Ontario | 4.4 | |
| 22 | Mississauga Ontario | 4.4 | |
| 23 | Kingston Ontario | 4.3 | |
| 24 | Ottawa Ontario | 4.3 | |
| 25 | North Bay Ontario | 4.2 | |
| 26 | Alliston Ontario | 4.1 | |
| 27 | Peterborough Ontario | 3.6 | |
| 28 | Sault Ste. Marie Ontario | 3.6 |
Good 0–9.0Moderate 9.1+Unhealthy for sensitive groups 35.5+Unhealthy 55.5+Very unhealthy 125.5+Hazardous 225.5+No data
Estimated: cities without a monitor
Ontario cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.
| City | 7-day estimate |
|---|---|
| Etobicoke estimated | ≈ 6 µg/m³ |
| Markham estimated | ≈ 4 µg/m³ |
| Vaughan estimated | ≈ 5 µg/m³ |
| Richmond Hill estimated | ≈ 5 µg/m³ |
| Burlington estimated | ≈ 5 µg/m³ |
| Oshawa estimated | ≈ 5 µg/m³ |
| Gloucester estimated | ≈ 5 µg/m³ |
| Whitby estimated | ≈ 5 µg/m³ |
| Cambridge estimated | ≈ 5 µg/m³ |
| Orléans estimated | ≈ 4 µg/m³ |
| Ottawa South estimated | ≈ 5 µg/m³ |
| Ajax estimated | ≈ 5 µg/m³ |
| Thornhill estimated | ≈ 5 µg/m³ |
| Thunder Bay estimated | ≈ 5 µg/m³ |
| Waterloo estimated | ≈ 4 µg/m³ |
| Niagara Falls estimated | ≈ 6 µg/m³ |
| Pickering estimated | ≈ 5 µg/m³ |
| Kanata estimated | ≈ 4 µg/m³ |
| Willowdale estimated | ≈ 5 µg/m³ |
| Caledon estimated | ≈ 4 µg/m³ |
| Stoney Creek estimated | ≈ 5 µg/m³ |
| Halton Hills estimated | ≈ 5 µg/m³ |
| Norfolk County estimated | ≈ 5 µg/m³ |
| Aurora estimated | ≈ 5 µg/m³ |
| Welland estimated | ≈ 5 µg/m³ |
| Whitchurch-Stouffville estimated | ≈ 4 µg/m³ |
| Georgetown estimated | ≈ 5 µg/m³ |
| Quinte West estimated | ≈ 3 µg/m³ |
| Innisfil estimated | ≈ 4 µg/m³ |
| Timmins estimated | ≈ 5 µg/m³ |
| Stittsville estimated | ≈ 4 µg/m³ |
| Ancaster estimated | ≈ 5 µg/m³ |
| Woodstock estimated | ≈ 5 µg/m³ |
| Bowmanville estimated | ≈ 5 µg/m³ |
| Stouffville estimated | ≈ 4 µg/m³ |
| Leamington estimated | ≈ 3 µg/m³ |
| Brant estimated | ≈ 5 µg/m³ |
| LaSalle estimated | ≈ 6 µg/m³ |
| Stratford estimated | ≈ 5 µg/m³ |
| Orillia estimated | ≈ 3 µg/m³ |
Updated 2026-10-01 12:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.