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 11 May 2025: Peru 43.6 µg/m³, Chile 34.7 µg/m³ and India 31.1 µg/m³.
- 1Peru3 cities43.6
- 2Chile47 cities34.7
- 3India212 cities31.1
- 4Mexico52 cities19.6
- 5South Korea140 cities13.4
- 6Hong Kong13 cities12.5
- 7Malta5 cities9.9
- 8Greece10 cities, was 99.7
- 9Ireland6 cities9.7
- 10New Zealand6 cities9.3
- 11Switzerland11 cities8.4
- 12Hungary11 cities, was 128.4
- 13Poland58 cities8.2
- 14Slovenia12 cities8.0
- 15Romania10 cities7.6
- 16Bosnia and Herzegovina5 cities7.5
- 17Slovakia41 cities7.5
- 18Austria37 cities7.3
- 19Japan550 cities7.3
- 20Latvia4 cities7.1
+ 19 more countries, 7.0 µg/m³ and below
- 26United States829 cities5.5
Not counted on this day, too few cities measured: Taiwan since 27 Apr 2025, Czechia since 26 Apr 2025, Laos since 26 Apr 2025 and 5 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.