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 22 Apr 2025: India 35.3 µg/m³, Chile 29.0 µg/m³ and Mexico 22.9 µg/m³.
- 1India214 cities35.3
- 2Chile47 cities29.0
- 3Mexico45 cities22.9
- 4Peru6 cities21.6
- 5Taiwan44 cities18.2
- 6Laos3 cities16.4
- 7Hong Kong13 cities15.9
- 8Thailand86 cities15.8
- 9South Korea140 cities15.7
- 10Lithuania4 cities15.6
- 11Latvia4 cities13.3
- 12Serbia38 cities13.0
- 13Japan542 cities12.6
- 14Malta5 cities11.3
- 15Poland71 cities11.3
- 16Romania10 cities9.7
- 17Belgium44 cities9.1
- 18Slovakia39 cities9.1
- 19Bosnia and Herzegovina5 cities8.7
- 20Czechia21 cities, was 358.4
+ 20 more countries, 8.4 µg/m³ and below
- 29United States846 cities6.7
Not counted on this day, too few cities measured: Luxembourg since 21 Apr 2025, Austria since 20 Apr 2025, Greece since 19 Apr 2025 and 6 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.