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 15 Apr 2025: Laos 35.3 µg/m³, Hong Kong 34.1 µg/m³ and Chile 24.3 µg/m³.
- 1Laos3 cities35.3
- 2Hong Kong13 cities34.1
- 3Chile44 cities24.3
- 4Taiwan44 cities22.0
- 5Thailand84 cities21.6
- 6Peru6 cities20.9
- 7Serbia39 cities18.8
- 8Mexico49 cities17.6
- 9South Korea140 cities17.1
- 10Poland72 cities12.9
- 11Belgium44 cities12.8
- 12Bosnia and Herzegovina5 cities12.5
- 13Italy26 cities12.5
- 14Czechia7 cities, was 3511.5
- 15United Kingdom68 cities, was 511.5
- 16Malta5 cities11.4
- 17Slovenia12 cities11.1
- 18The Netherlands34 cities11.0
- 19Japan509 cities10.7
- 20Latvia4 cities10.7
+ 22 more countries, 10.6 µg/m³ and below
- 35United States849 cities6.6
Not counted on this day, too few cities measured: Ireland since 12 Apr 2025, India since 11 Apr 2025, Estonia since 10 Apr 2025 and 4 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.