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 9 Apr 2025: Laos 61.9 µg/m³, India 42.0 µg/m³ and Thailand 37.0 µg/m³.
- 1Laos3 cities61.9
- 2India225 cities, was 542.0
- 3Thailand87 cities37.0
- 4Serbia39 cities24.9
- 5South Korea140 cities23.5
- 6Chile45 cities22.4
- 7Mexico49 cities, was 1221.0
- 8Poland72 cities19.3
- 9Taiwan44 cities18.1
- 10Peru6 cities17.9
- 11Hong Kong13 cities17.5
- 12Romania10 cities14.8
- 13Bosnia and Herzegovina3 cities14.1
- 14Latvia4 cities13.5
- 15United Kingdom6 cities13.2
- 16Slovakia42 cities13.1
- 17Belgium44 cities12.8
- 18Hungary7 cities12.8
- 19Greece9 cities12.7
- 20Ireland3 cities12.0
+ 22 more countries, 11.4 µg/m³ and below
- 36United States849 cities6.0
Not counted on this day, too few cities measured: Lithuania since 8 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.