SmogRank / History / Country race
Countries, worst air first, day by day
Each country's typical measured city over the 30 days to every day since January 2023, worst first. Press Play to watch the order change, or drag the slider to any day.
The worst countries for PM2.5 over the 30 days to 30 Mar 2025: India 40.7 µg/m³, Laos 40.4 µg/m³ and Thailand 37.9 µg/m³.
- 1India231 cities, was 540.7
- 2Laos3 cities40.4
- 3Thailand73 cities37.9
- 4Serbia39 cities31.6
- 5Poland73 cities26.2
- 6Hungary5 cities23.1
- 7South Korea141 cities23.0
- 8Mexico24 cities21.0
- 9Romania10 cities20.7
- 10Bosnia and Herzegovina3 cities20.5
- 11Chile45 cities20.2
- 12United Kingdom7 cities18.1
- 13Belgium44 cities17.6
- 14Latvia4 cities17.3
- 15Peru6 cities17.3
- 16Slovakia42 cities16.9
- 17Taiwan43 cities16.9
- 18Germany234 cities16.0
- 19The Netherlands35 cities15.9
- 20Hong Kong13 cities15.8
+ 20 more countries, 14.7 µg/m³ and below
- 33United States840 cities6.2
Not counted on this day, too few cities measured: Martinique since 26 Mar 2025, China since 14 Mar 2025, Malta since 13 Mar 2025 and 5 more countries.
Countries counted each day
A country's number is its typical measured city: the median of its cities' means over the 30 days (a city needs 21 of them measured; 5 of 7 on the 7-day race), shown only with 3 such cities. A country whose monitors go quiet fades out where it stood rather than sliding down, so a gap never reads as cleaner air; "was" beside a city count marks a month after many cities joined or left. Some large countries are thin or missing because their monitors' licences don't allow reuse. How we rank.
Not covered: the government monitoring networks of China and Turkey, which publish only on their own websites; we are building the readers for them. Most cities there are missing from this board, not clean. Why.