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 10 Apr 2025: Laos 64.5 µg/m³, India 41.6 µg/m³ and Thailand 36.1 µg/m³.
- 1Laos3 cities64.5
- 2India219 cities41.6
- 3Thailand87 cities36.1
- 4Serbia39 cities24.7
- 5South Korea140 cities23.3
- 6Chile45 cities22.5
- 7Mexico48 cities, was 1220.6
- 8Poland71 cities18.9
- 9Peru6 cities17.7
- 10Taiwan44 cities17.7
- 11Hong Kong13 cities17.4
- 12Bosnia and Herzegovina3 cities14.4
- 13Romania10 cities14.1
- 14Lithuania4 cities13.8
- 15United Kingdom5 cities13.2
- 16Slovakia42 cities13.0
- 17Hungary6 cities12.9
- 18Latvia4 cities12.8
- 19Greece9 cities12.4
- 20Belgium44 cities12.2
+ 22 more countries, 12.2 µg/m³ and below
- 36United States848 cities6.0
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.