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 12 Apr 2025: Laos 49.2 µg/m³, Thailand 25.3 µg/m³ and Chile 24.9 µg/m³.
- 1Laos3 cities49.2
- 2Thailand85 cities25.3
- 3Chile47 cities24.9
- 4South Korea140 cities21.0
- 5Taiwan44 cities20.7
- 6Hong Kong13 cities19.3
- 7Serbia38 cities19.1
- 8Peru5 cities17.0
- 9Mexico47 cities, was 1416.4
- 10Italy25 cities13.6
- 11Belgium44 cities11.9
- 12Bosnia and Herzegovina3 cities11.7
- 13Japan548 cities11.5
- 14United Kingdom68 cities, was 511.1
- 15Slovenia12 cities10.9
- 16Poland71 cities10.2
- 17Hungary10 cities9.6
- 18France96 cities9.4
- 19Romania11 cities9.2
- 20Slovakia41 cities9.0
+ 21 more countries, 8.9 µg/m³ and below
- 33United States849 cities5.9
Not counted on this day, too few cities measured: Ireland since 12 Apr 2025, Czechia since 11 Apr 2025, India since 11 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.