Cwmafan vs London: PM2.5 compared
Over the last year, London's air was about 1.9× as polluted as Cwmafan's: PM2.5 averaged 9.7 µg/m³ against 5.2, on the 127 days both cities were measured. London had the dirtier air on 122 of those days, Cwmafan on 4. London was over the WHO's daily guideline of 15 µg/m³ on 14 of them, Cwmafan on 3.
Right now
The last year, day by day
Month by month
Year by year
| Year | Cwmafan | London | Days Cwmafan was worse |
|---|---|---|---|
| 2026 so far | 31 | 54 | 1 |
| 2025 | 30 | 49 | 14 |
| 2024 | 43 | 45 | 132 |
| 2023 | 48 | 48 | 115 |
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
Cwmafan
- 9 Mar 20267120.0 µg/m³
- 21 Mar 20266818.1 µg/m³
- 20 Mar 20266415.9 µg/m³
London
- 4 Mar 20269532.5 µg/m³
- 9 Mar 20269231.2 µg/m³
- 8 Mar 20268426.9 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
Cwmafan
Side by side with Swansea (the nearest), Gujranwala (the world's worst on 30 days).
London
Side by side with Borehamwood (the nearest), Birmingham (United Kingdom's 2nd worst on 30 days), Gujranwala (the world's worst on 30 days).
Use this page
SmogRank, PM2.5 daily means compared, Cwmafan and London, 8 Oct 2025 – 7 Oct 2026, smogrank.com/compare/gb-cwmafan/gb-london (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).