SmogRank / World / United Kingdom / Wales / September 2025

Most polluted cities in Wales, United Kingdom, September 2025

4 cities in Wales, United Kingdom ranked by their average PM2.5 over the 30 days. Worst: Chepstow at 6.2 µg/m³, #1,961 of 3,052 cities in the world. Cleanest: Cwmafan at 3.2. A city needs measurements on 70% of the days to be ranked.

← Chepstow 6.2 µg/m³ 20 µg/m³0
Every city in Wales, United Kingdom ranked for September 2025, one column each, worst on the left and cleanest on the right; height is PM2.5 in µg/m³. Point at it to read a city; tap to open it.
  1. 1Chepstow
    34
  2. 2Cardiff
    32
  3. 3Newport
    26
  4. 4Cwmafan
    18
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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, September 2025 · All cities in United Kingdom, September 2025 · Wales now

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SmogRank, most polluted cities in Wales, United Kingdom, PM2.5, September 2025, smogrank.com/gb/region/wales/history/2025-09 (accessed 8 Oct 2026). Some readings from 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.

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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.