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 11 Apr 2025: Laos 66.6 µg/m³, India 41.6 µg/m³ and Thailand 36.0 µg/m³.
- 1Laos3 cities66.6
- 2India215 cities41.6
- 3Thailand87 cities36.0
- 4Serbia39 cities24.1
- 5South Korea140 cities23.1
- 6Chile45 cities22.6
- 7Mexico45 cities, was 1219.9
- 8Peru6 cities17.8
- 9Hong Kong13 cities17.6
- 10Poland71 cities17.6
- 11Taiwan44 cities17.6
- 12Bosnia and Herzegovina3 cities14.8
- 13Romania10 cities13.8
- 14United Kingdom5 cities13.6
- 15Slovakia42 cities13.0
- 16Ireland3 cities12.8
- 17Belgium44 cities12.6
- 18Latvia4 cities12.5
- 19Hungary5 cities12.4
- 20Greece9 cities12.2
+ 22 more countries, 12.0 µg/m³ and below
- 36United States850 cities6.1
Not counted on this day, too few cities measured: Luxembourg since 10 Apr 2025, China since 14 Mar 2025, Malta since 13 Mar 2025 and 3 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.