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 18 Mar 2025: India 42.6 µg/m³, Serbia 40.4 µg/m³ and Poland 32.0 µg/m³.
- 1India225 cities, was 542.6
- 2Serbia39 cities40.4
- 3Poland73 cities32.0
- 4Romania9 cities30.8
- 5Thailand85 cities25.1
- 6Bulgaria8 cities23.2
- 7Laos3 cities22.3
- 8Slovenia12 cities21.3
- 9Slovakia39 cities21.0
- 10Hungary9 cities20.9
- 11Latvia4 cities20.5
- 12Switzerland3 cities, was 1020.0
- 13Chile43 cities18.1
- 14Hong Kong13 cities18.0
- 15South Korea141 cities17.4
- 16Taiwan43 cities17.3
- 17Austria36 cities17.2
- 18Peru6 cities16.8
- 19Germany231 cities16.6
- 20Mexico10 cities16.4
+ 18 more countries, 16.1 µg/m³ and below
- 31United States834 cities6.6
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.