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 16 Apr 2025: Hong Kong 35.2 µg/m³, Laos 32.9 µg/m³ and Chile 23.7 µg/m³.
- 1Hong Kong13 cities35.2
- 2Laos3 cities32.9
- 3Chile44 cities23.7
- 4Taiwan44 cities22.3
- 5Peru6 cities22.2
- 6Thailand84 cities20.5
- 7Mexico47 cities17.9
- 8Serbia39 cities17.4
- 9South Korea140 cities16.5
- 10Malta5 cities15.6
- 11Poland72 cities13.3
- 12Italy27 cities12.7
- 13Bosnia and Herzegovina5 cities12.4
- 14Belgium44 cities11.5
- 15Hungary3 cities, was 1211.5
- 16Latvia4 cities11.3
- 17Slovenia12 cities11.2
- 18Czechia14 cities, was 3511.1
- 19United Kingdom68 cities, was 510.8
- 20The Netherlands34 cities10.6
+ 23 more countries, 10.4 µg/m³ and below
- 35United States847 cities6.7
Not counted on this day, too few cities measured: Ireland since 12 Apr 2025, India since 11 Apr 2025, Kosovo since 10 Apr 2025 and 3 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.