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 30 days to 17 Apr 2025: Laos 65.8 µg/m³, India 41.7 µg/m³ and Thailand 34.9 µg/m³.
- 1Laos3 cities65.8
- 2India186 cities41.7
- 3Thailand85 cities34.9
- 4Serbia39 cities24.5
- 5Chile46 cities23.8
- 6South Korea140 cities23.2
- 7Hong Kong13 cities22.3
- 8Mexico47 cities, was 1219.5
- 9Taiwan44 cities19.1
- 10Peru6 cities18.5
- 11Poland72 cities17.7
- 12Czechia3 cities, was 1714.8
- 13Malta5 cities14.3
- 14United Kingdom5 cities14.2
- 15Bosnia and Herzegovina3 cities14.0
- 16Romania10 cities14.0
- 17Slovakia42 cities13.6
- 18Hungary3 cities, was 1113.3
- 19Belgium44 cities12.6
- 20Latvia4 cities12.6
+ 23 more countries, 11.9 µg/m³ and below
- 38United States851 cities5.9
Not counted on this day, too few cities measured: Luxembourg since 17 Apr 2025, Ireland since 13 Apr 2025, China since 14 Mar 2025 and 2 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.