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 17 May 2025: Peru 37.4 µg/m³, Chile 35.3 µg/m³ and India 32.4 µg/m³.
- 1Peru5 cities37.4
- 2Chile48 cities35.3
- 3India212 cities32.4
- 4Mexico43 cities21.9
- 5South Korea140 cities18.2
- 6Laos3 cities13.6
- 7Thailand77 cities13.6
- 8New Zealand6 cities12.8
- 9Serbia36 cities11.9
- 10Taiwan45 cities11.8
- 11Japan558 cities11.7
- 12Hong Kong13 cities11.5
- 13Malta5 cities11.5
- 14Ireland3 cities10.8
- 15United Kingdom69 cities8.9
- 16Latvia4 cities8.3
- 17Italy8 cities, was 268.2
- 18Bosnia and Herzegovina5 cities8.1
- 19Slovenia12 cities7.7
- 20Hungary12 cities7.6
+ 23 more countries, 7.5 µg/m³ and below
- 29United States828 cities6.2
Not counted on this day, too few cities measured: Czechia since 17 May 2025, Martinique since 16 May 2025 and 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.