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 27 May 2025: Chile 40.8 µg/m³, Peru 32.4 µg/m³ and India 26.2 µg/m³.
- 1Chile45 cities40.8
- 2Peru3 cities32.4
- 3India181 cities26.2
- 4Mexico47 cities21.3
- 5New Zealand6 cities15.2
- 6South Korea140 cities14.9
- 7Hong Kong13 cities14.3
- 8Thailand78 cities11.6
- 9Taiwan45 cities10.8
- 10Greece8 cities10.5
- 11Malta4 cities10.4
- 12Serbia38 cities9.9
- 13Laos3 cities9.6
- 14Latvia4 cities8.8
- 15Poland74 cities8.8
- 16Japan560 cities8.6
- 17Italy19 cities, was 267.9
- 18Slovakia42 cities7.8
- 19Czechia27 cities, was 127.7
- 20Hungary11 cities7.3
+ 23 more countries, 7.2 µg/m³ and below
- 35United States825 cities4.5
Not counted on this day, too few cities measured: Lithuania since 20 May 2025, Martinique since 16 May 2025 and Luxembourg since 21 Apr 2025.
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.