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 20 May 2025: India 33.8 µg/m³, Chile 33.0 µg/m³ and Mexico 22.5 µg/m³.
- 1India208 cities33.8
- 2Chile47 cities33.0
- 3Mexico48 cities22.5
- 4South Korea140 cities14.5
- 5Hong Kong13 cities13.9
- 6Brazil41 cities10.6
- 7Japan559 cities10.5
- 8Belgium25 cities10.2
- 9New Zealand6 cities9.5
- 10Hungary5 cities9.3
- 11Poland57 cities9.3
- 12Malta4 cities8.9
- 13United Kingdom67 cities8.8
- 14Slovenia12 cities8.2
- 15The Netherlands33 cities8.0
- 16Romania6 cities8.0
- 17Slovakia36 cities8.0
- 18Latvia3 cities7.2
- 19Spain39 cities6.9
- 20Austria32 cities6.8
+ 12 more countries, the next at 6.6 µg/m³
- 23United States842 cities5.9
Not counted on this day, too few cities measured: Bosnia and Herzegovina since 20 May 2025, Estonia since 20 May 2025, France since 20 May 2025 and 12 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, Turkey and Iran, which publish only on their own websites. We are building the reader for China's network. The networks of Turkey and Iran don't answer requests from outside their countries, so we can't read them. Most cities there are missing from this board, not clean. Why.