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 27 Apr 2025: Laos 46.3 µg/m³, India 39.8 µg/m³ and Chile 25.3 µg/m³.
- 1Laos3 cities46.3
- 2India183 cities39.8
- 3Chile47 cities25.3
- 4Thailand83 cities24.6
- 5Hong Kong13 cities20.4
- 6Mexico44 cities, was 1219.8
- 7Serbia35 cities18.8
- 8Taiwan44 cities18.3
- 9Peru5 cities17.6
- 10South Korea140 cities16.9
- 11Czechia5 cities, was 1713.2
- 12Poland72 cities12.3
- 13Bosnia and Herzegovina3 cities12.0
- 14Latvia4 cities11.4
- 15Hungary3 cities, was 1111.2
- 16Belgium44 cities10.7
- 17Romania10 cities10.7
- 18Slovakia42 cities10.2
- 19Italy23 cities10.1
- 20Lithuania4 cities10.1
+ 22 more countries, 10.0 µg/m³ and below
- 36United States846 cities6.3
Not counted on this day, too few cities measured: Greece since 26 Apr 2025, Luxembourg since 21 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.