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 20 May 2025: Chile 37.6 µg/m³, Peru 36.1 µg/m³ and India 31.1 µg/m³.
- 1Chile46 cities37.6
- 2Peru6 cities36.1
- 3India213 cities31.1
- 4Mexico40 cities25.8
- 5South Korea139 cities14.6
- 6Thailand77 cities13.4
- 7Japan568 cities13.0
- 8New Zealand6 cities12.5
- 9Brazil43 cities11.4
- 10Malta4 cities11.2
- 11Serbia38 cities10.9
- 12Taiwan45 cities10.1
- 13United Kingdom69 cities9.4
- 14Belgium44 cities9.3
- 15Laos3 cities9.2
- 16Hong Kong13 cities8.1
- 17Italy8 cities, was 268.1
- 18Latvia4 cities8.0
- 19Poland72 cities7.8
- 20The Netherlands34 cities7.4
+ 18 more countries, the next at 7.1 µg/m³
- 30United States827 cities5.6
Not counted on this day, too few cities measured: France since 20 May 2025, Lithuania since 20 May 2025, Estonia since 19 May 2025 and 6 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.