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 19 Mar 2025: India 42.5 µg/m³, Serbia 40.6 µg/m³ and Poland 31.4 µg/m³.
- 1India228 cities, was 542.5
- 2Serbia39 cities40.6
- 3Poland73 cities31.4
- 4Romania9 cities30.8
- 5Hungary8 cities26.7
- 6Thailand85 cities24.7
- 7Bulgaria8 cities23.0
- 8Laos3 cities21.9
- 9Slovenia12 cities21.0
- 10Slovakia40 cities20.9
- 11Latvia4 cities20.5
- 12Switzerland3 cities, was 1019.6
- 13Chile43 cities18.2
- 14South Korea141 cities17.9
- 15Hong Kong13 cities17.7
- 16Peru6 cities16.8
- 17Taiwan43 cities16.8
- 18Austria36 cities16.7
- 19Mexico10 cities16.5
- 20Germany231 cities16.4
+ 18 more countries, 16.2 µg/m³ and below
- 31United States832 cities6.7
Not counted on this day, too few cities measured: Bosnia and Herzegovina since 18 Mar 2025, China since 14 Mar 2025, Malta since 13 Mar 2025 and 6 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.