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 18 May 2025: Chile 36.4 µg/m³, Peru 34.2 µg/m³ and India 31.6 µg/m³.
- 1Chile47 cities36.4
- 2Peru6 cities34.2
- 3India214 cities31.6
- 4Mexico43 cities23.7
- 5South Korea139 cities17.2
- 6Thailand79 cities13.1
- 7Japan555 cities12.2
- 8New Zealand6 cities12.2
- 9Taiwan45 cities11.7
- 10Serbia36 cities11.3
- 11Malta5 cities10.9
- 12Hong Kong13 cities10.2
- 13Laos3 cities9.9
- 14United Kingdom68 cities9.1
- 15Belgium43 cities8.4
- 16Latvia4 cities8.2
- 17Bosnia and Herzegovina5 cities7.6
- 18Poland73 cities7.5
- 19France37 cities7.2
- 20Hungary12 cities7.1
+ 21 more countries, 7.0 µg/m³ and below
- 29United States825 cities5.9
Not counted on this day, too few cities measured: Greece since 18 May 2025, Ireland since 18 May 2025, Czechia since 17 May 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.