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 7 days to 9 Apr 2025: Laos 69.9 µg/m³, India 40.8 µg/m³ and Thailand 27.6 µg/m³.
- 1Laos3 cities69.9
- 2India209 cities40.8
- 3Thailand86 cities27.6
- 4Chile47 cities25.0
- 5Serbia38 cities22.4
- 6Taiwan44 cities21.9
- 7South Korea140 cities20.9
- 8Hong Kong13 cities19.8
- 9Peru5 cities17.5
- 10Mexico48 cities, was 1416.5
- 11Bosnia and Herzegovina3 cities14.3
- 12Ireland4 cities13.7
- 13Italy23 cities13.5
- 14United Kingdom68 cities, was 511.3
- 15Hungary12 cities11.0
- 16Czechia4 cities, was 3510.8
- 17Belgium44 cities10.7
- 18Slovenia12 cities10.3
- 19Slovakia42 cities10.2
- 20Romania10 cities10.1
+ 26 more countries, 9.6 µg/m³ and below
- 40United States843 cities5.2
Not counted on this day, too few cities measured: Croatia since 14 Mar 2025, China since 7 Mar 2025 and Pakistan since 6 Mar 2025.
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.