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 10 May 2025: Chile 33.7 µg/m³, India 30.7 µg/m³ and Mexico 20.4 µg/m³.
- 1Chile47 cities33.7
- 2India208 cities30.7
- 3Mexico48 cities20.4
- 4Hong Kong13 cities12.9
- 5South Korea140 cities12.0
- 6Greece9 cities, was 910.3
- 7New Zealand4 cities9.8
- 8Malta4 cities8.8
- 9Switzerland10 cities8.6
- 10Hungary11 cities, was 128.5
- 11Poland55 cities8.1
- 12Slovenia12 cities8.0
- 13Austria37 cities7.8
- 14Slovakia39 cities7.8
- 15Japan554 cities7.6
- 16Romania8 cities7.5
- 17Bosnia and Herzegovina5 cities7.1
- 18Latvia4 cities7.0
- 19Italy20 cities6.9
- 20France44 cities6.8
+ 16 more countries, 6.4 µg/m³ and below
- 24United States833 cities5.4
Not counted on this day, too few cities measured: Portugal since 1 May 2025, Taiwan since 27 Apr 2025, Czechia since 26 Apr 2025 and 8 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.