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 May 2025: Peru 37.6 µg/m³, Chile 34.8 µg/m³ and India 30.3 µg/m³.
- 1Peru4 cities37.6
- 2Chile47 cities34.8
- 3India212 cities30.3
- 4Laos3 cities26.0
- 5Mexico52 cities18.1
- 6South Korea140 cities14.9
- 7Thailand74 cities13.3
- 8Hong Kong13 cities12.8
- 9Taiwan45 cities10.5
- 10Malta5 cities10.0
- 11Ireland6 cities9.8
- 12Greece11 cities, was 99.4
- 13Czechia19 cities8.9
- 14Hungary12 cities, was 128.2
- 15Poland71 cities8.2
- 16Slovenia12 cities8.1
- 17Bosnia and Herzegovina5 cities7.8
- 18Switzerland11 cities7.8
- 19Romania11 cities7.8
- 20Slovakia42 cities7.5
+ 23 more countries, 7.4 µg/m³ and below
- 30United States830 cities5.7
Not counted on this day, too few cities measured: Martinique since 26 Apr 2025, Serbia since 25 Apr 2025, Luxembourg since 21 Apr 2025 and Croatia since 14 Mar 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.