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 19 Apr 2025: Laos 65.6 µg/m³, India 40.2 µg/m³ and Thailand 33.6 µg/m³.
- 1Laos3 cities65.6
- 2India189 cities40.2
- 3Thailand85 cities33.6
- 4Chile46 cities24.6
- 5Serbia39 cities22.3
- 6South Korea140 cities22.2
- 7Hong Kong13 cities21.6
- 8Mexico46 cities, was 1219.4
- 9Taiwan44 cities19.0
- 10Peru6 cities18.1
- 11Poland72 cities16.8
- 12Malta5 cities13.6
- 13Romania10 cities13.2
- 14Latvia4 cities13.0
- 15Slovakia42 cities12.9
- 16Bosnia and Herzegovina3 cities12.8
- 17Belgium44 cities12.6
- 18Czechia4 cities, was 1712.6
- 19Hungary3 cities, was 1112.6
- 20Japan544 cities12.0
+ 24 more countries, 11.4 µg/m³ and below
- 39United States850 cities6.2
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 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.