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 29 Apr 2025: Laos 44.8 µg/m³, India 39.0 µg/m³ and Chile 26.0 µg/m³.
- 1Laos3 cities44.8
- 2India173 cities39.0
- 3Chile47 cities26.0
- 4Thailand83 cities23.3
- 5Mexico48 cities, was 1220.4
- 6Hong Kong13 cities20.3
- 7Taiwan44 cities19.1
- 8Serbia32 cities18.4
- 9Peru5 cities18.0
- 10South Korea140 cities17.4
- 11Bosnia and Herzegovina4 cities12.8
- 12Poland72 cities11.4
- 13Hungary3 cities, was 1111.0
- 14Belgium44 cities10.9
- 15Latvia4 cities10.5
- 16Romania10 cities10.5
- 17Japan546 cities10.3
- 18Italy24 cities10.2
- 19Slovakia42 cities9.8
- 20United Kingdom68 cities, was 59.7
+ 22 more countries, 9.5 µg/m³ and below
- 35United States848 cities6.1
Not counted on this day, too few cities measured: Czechia since 28 Apr 2025, Greece since 26 Apr 2025, Kosovo since 19 Apr 2025 and 4 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.