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 13 May 2025: Chile 34.4 µg/m³, Peru 33.7 µg/m³ and India 31.3 µg/m³.
- 1Chile46 cities34.4
- 2Peru5 cities33.7
- 3India213 cities31.3
- 4Laos3 cities25.3
- 5Mexico51 cities18.8
- 6South Korea140 cities16.8
- 7Hong Kong13 cities14.3
- 8Thailand80 cities13.4
- 9Serbia28 cities12.7
- 10Taiwan45 cities11.8
- 11Ireland6 cities10.0
- 12Malta5 cities9.9
- 13Greece12 cities, was 99.0
- 14Czechia44 cities, was 128.9
- 15Slovenia12 cities8.9
- 16Japan556 cities8.6
- 17Poland74 cities8.5
- 18Bosnia and Herzegovina5 cities8.3
- 19Hungary12 cities, was 128.2
- 20Switzerland11 cities7.8
+ 25 more countries, 7.8 µg/m³ and below
- 33United States828 cities5.7
Not counted on this day, too few cities measured: Luxembourg since 21 Apr 2025.
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.