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 8 Apr 2025: Laos 71.5 µg/m³, India 41.4 µg/m³ and Thailand 30.0 µg/m³.
- 1Laos3 cities71.5
- 2India238 cities41.4
- 3Thailand86 cities30.0
- 4Chile47 cities23.2
- 5Serbia38 cities22.0
- 6South Korea140 cities20.7
- 7Taiwan44 cities20.0
- 8Hong Kong13 cities19.0
- 9Peru5 cities17.3
- 10Mexico48 cities, was 1417.0
- 11Bosnia and Herzegovina3 cities14.6
- 12Ireland3 cities13.5
- 13Czechia10 cities, was 3512.3
- 14Italy26 cities12.3
- 15Hungary12 cities11.2
- 16Slovakia42 cities11.0
- 17United Kingdom68 cities, was 510.7
- 18Romania10 cities10.2
- 19Slovenia12 cities10.2
- 20Belgium43 cities10.0
+ 26 more countries, 9.9 µg/m³ and below
- 41United States844 cities5.0
Not counted on this day, too few cities measured: Croatia since 14 Mar 2025, China since 7 Mar 2025 and Pakistan since 6 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.