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 28 Mar 2025: India 41.1 µg/m³, Laos 38.1 µg/m³ and Thailand 35.0 µg/m³.
- 1India231 cities, was 541.1
- 2Laos3 cities38.1
- 3Thailand73 cities35.0
- 4Serbia39 cities32.7
- 5Poland73 cities26.7
- 6Hungary5 cities24.8
- 7South Korea141 cities23.6
- 8Bosnia and Herzegovina4 cities21.5
- 9Romania10 cities21.4
- 10Chile44 cities20.3
- 11Mexico13 cities18.9
- 12Taiwan43 cities18.8
- 13United Kingdom7 cities18.2
- 14Belgium42 cities17.7
- 15Peru6 cities17.6
- 16Slovakia42 cities17.0
- 17Latvia4 cities16.9
- 18Bulgaria8 cities16.8
- 19Hong Kong13 cities16.4
- 20Germany233 cities16.3
+ 17 more countries, 15.9 µg/m³ and below
- 32United States840 cities6.1
Not counted on this day, too few cities measured: Martinique since 26 Mar 2025, Ireland since 25 Mar 2025, Portugal since 20 Mar 2025 and 7 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.