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 28 Mar 2025: Thailand 58.5 µg/m³, India 41.6 µg/m³ and South Korea 32.3 µg/m³.
- 1Thailand73 cities58.5
- 2India232 cities41.6
- 3South Korea141 cities32.3
- 4Malta5 cities26.3
- 5Serbia36 cities, was 1225.0
- 6Chile39 cities24.6
- 7Poland72 cities24.6
- 8Mexico45 cities, was 1421.2
- 9Belgium44 cities20.8
- 10Taiwan44 cities19.9
- 11United Kingdom5 cities19.0
- 12Japan552 cities18.8
- 13Romania10 cities18.3
- 14Hong Kong13 cities18.0
- 15Slovakia42 cities18.0
- 16Germany250 cities17.7
- 17The Netherlands36 cities17.7
- 18Peru6 cities15.8
- 19Latvia4 cities14.9
- 20Greece9 cities14.0
+ 17 more countries, 11.7 µg/m³ and below
- 32United States823 cities5.9
Not counted on this day, too few cities measured: Laos since 28 Mar 2025, Lithuania since 28 Mar 2025, Luxembourg since 28 Mar 2025 and 8 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.