London vs Swansea: PM2.5 compared

London and Swansea were both measured on only 8 days over the last year, too few to compare them (it takes 30).

Right now

London#546on the 24-hour board of 738, at 18 US AQI (3.3 µg/m³)

Swansea#260on the 24-hour board of 738, at 38 US AQI (6.9 µg/m³)

Compare either city with another

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).

Swansea

Side by side with Cwmafan (the nearest), Gujranwala (the world's worst on 30 days).

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).