Cornwall vs Ottawa: PM2.5 compared
Over the last year, Cornwall's air was 5% more polluted than Ottawa's: PM2.5 averaged 6.1 µg/m³ against 5.8, on the 347 days both cities were measured. Cornwall had the dirtier air on 201 of those days, Ottawa on 133. Cornwall was over the WHO's daily guideline of 15 µg/m³ on 11 of them, Ottawa on 13.
Right now
The last year, day by day
Month by month
Year by year
| Year | Cornwall | Ottawa | Days Cornwall was worse |
|---|---|---|---|
| 2026 so far | 36 | 34 | 176 |
| 2025 | 41 | 40 | 143 |
| 2024 | 34 | 34 | 100 |
| 2023 | 52 | 54 | 147 |
Means in US AQI over the days both cities were measured that year; a year shows once they share 30 such days.
Each city's worst days
Cornwall
- 17 Feb 202610235.9 µg/m³
- 18 Jul 20268024.9 µg/m³
- 12 Jul 20267723.1 µg/m³
Ottawa
- 12 Jul 20268426.8 µg/m³
- 17 Feb 20268326.3 µg/m³
- 3 Feb 20267723.0 µg/m³
Daily means in US AQI, with µg/m³ beside them, since the index stops at its top value, over the days both cities were measured in the last year. Each date opens that day's world board.
Compare either city with another
Cornwall
Side by side with Castlegar (Canada's worst on 30 days), Gujranwala (the world's worst on 30 days).
Ottawa
Side by side with Castlegar (Canada's worst on 30 days), Gujranwala (the world's worst on 30 days).
Use this page
SmogRank, PM2.5 daily means compared, Cornwall and Ottawa, 8 Oct 2025 – 7 Oct 2026, smogrank.com/compare/ca-cornwall/ca-ottawa (accessed 8 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.
The same rules as every SmogRank figure: reference monitors first, and a day counts with 18 measured hours. How we measure.
Updated 2026-10-08 20:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index. Some readings: Uzhydromet (Uzbekistan's Hydrometeorological Service); Department of Environment, Nepal; Vietnam's government monitors; Aurassure; Umhverfisstofnun (Environment Agency of Iceland); Love My Air (City and County of Denver), no reuse terms published (why we use them).