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 14 Apr 2025: Laos 39.9 µg/m³, Hong Kong 31.5 µg/m³ and Chile 25.5 µg/m³.
- 1Laos3 cities39.9
- 2Hong Kong13 cities31.5
- 3Chile45 cities25.5
- 4Taiwan44 cities22.3
- 5Thailand84 cities22.2
- 6Serbia39 cities20.8
- 7Peru6 cities19.3
- 8South Korea140 cities19.0
- 9Mexico49 cities17.6
- 10Bosnia and Herzegovina4 cities15.3
- 11Belgium44 cities13.2
- 12Italy27 cities12.7
- 13Poland70 cities12.2
- 14United Kingdom68 cities, was 511.7
- 15Slovenia12 cities11.5
- 16Japan515 cities11.4
- 17Romania10 cities10.7
- 18The Netherlands33 cities10.4
- 19Switzerland10 cities9.7
- 20Germany246 cities9.7
+ 21 more countries, 9.7 µg/m³ and below
- 33United States849 cities6.6
Not counted on this day, too few cities measured: Ireland since 12 Apr 2025, Czechia since 11 Apr 2025, India since 11 Apr 2025 and 5 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.