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 Apr 2025: Hong Kong 35.7 µg/m³, Laos 27.5 µg/m³ and Chile 25.0 µg/m³.
- 1Hong Kong13 cities35.7
- 2Laos3 cities27.5
- 3Chile48 cities25.0
- 4Peru6 cities22.5
- 5Taiwan44 cities22.4
- 6Mexico45 cities19.6
- 7Thailand84 cities17.4
- 8South Korea140 cities15.9
- 9Malta5 cities15.1
- 10Serbia39 cities14.8
- 11Lithuania4 cities14.4
- 12Poland73 cities13.7
- 13Latvia4 cities13.0
- 14Hungary3 cities, was 1211.9
- 15Greece3 cities, was 911.7
- 16Czechia22 cities, was 3510.8
- 17Japan506 cities10.6
- 18Bosnia and Herzegovina5 cities10.4
- 19Slovakia40 cities10.4
- 20Slovenia12 cities10.2
+ 23 more countries, 10.0 µg/m³ and below
- 34United States841 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.