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 20 Apr 2025: Laos 65.7 µg/m³, India 40.6 µg/m³ and Thailand 32.7 µg/m³.
- 1Laos3 cities65.7
- 2India188 cities40.6
- 3Thailand85 cities32.7
- 4Chile46 cities25.1
- 5South Korea140 cities21.3
- 6Serbia39 cities21.2
- 7Hong Kong13 cities21.1
- 8Mexico46 cities, was 1219.6
- 9Taiwan44 cities18.9
- 10Peru6 cities18.0
- 11Poland72 cities16.0
- 12Malta5 cities13.3
- 13Latvia4 cities12.8
- 14Czechia5 cities, was 1712.7
- 15Romania10 cities12.7
- 16Hungary3 cities, was 1112.6
- 17Belgium44 cities12.5
- 18Bosnia and Herzegovina3 cities12.4
- 19Slovakia42 cities12.4
- 20Japan544 cities11.9
+ 25 more countries, the next at 11.2 µg/m³
- 40United States850 cities6.3
Not counted on this day, too few cities measured: Kosovo since 19 Apr 2025, Ireland since 13 Apr 2025, China since 14 Mar 2025 and 2 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, Turkey and Iran, which publish only on their own websites. We are building the reader for China's network. The networks of Turkey and Iran don't answer requests from outside their countries, so we can't read them. Most cities there are missing from this board, not clean. Why.