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 14 May 2025: Peru 35.0 µg/m³, Chile 33.8 µg/m³ and India 32.0 µg/m³.
- 1Peru5 cities35.0
- 2Chile47 cities33.8
- 3India208 cities32.0
- 4Laos3 cities23.4
- 5Mexico51 cities18.4
- 6South Korea140 cities18.2
- 7Hong Kong13 cities14.8
- 8Thailand82 cities13.6
- 9Serbia32 cities13.0
- 10Taiwan45 cities12.0
- 11Ireland6 cities10.3
- 12Malta5 cities10.1
- 13Japan556 cities10.0
- 14Czechia44 cities, was 128.9
- 15Poland75 cities8.8
- 16Slovenia12 cities8.7
- 17Greece13 cities, was 98.3
- 18Hungary12 cities, was 128.3
- 19Bosnia and Herzegovina5 cities8.2
- 20New Zealand6 cities8.1
+ 25 more countries, 8.0 µg/m³ and below
- 35United States824 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.