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 27 May 2025: Chile 38.2 µg/m³, Peru 36.6 µg/m³ and India 31.5 µg/m³.
- 1Chile46 cities38.2
- 2Peru3 cities36.6
- 3India200 cities31.5
- 4Mexico49 cities22.4
- 5South Korea140 cities14.7
- 6Hong Kong13 cities14.3
- 7New Zealand6 cities11.2
- 8Malta4 cities10.5
- 9Japan557 cities10.1
- 10Greece5 cities9.7
- 11Poland58 cities8.7
- 12Bosnia and Herzegovina5 cities8.1
- 13United Kingdom67 cities8.1
- 14Hungary9 cities, was 38.0
- 15Latvia4 cities8.0
- 16Slovakia41 cities8.0
- 17Slovenia12 cities7.7
- 18Belgium45 cities7.5
- 19Romania7 cities7.2
- 20The Netherlands34 cities7.1
+ 15 more countries, 7.0 µg/m³ and below
- 27United States836 cities5.5
Not counted on this day, too few cities measured: Lithuania since 25 May 2025, Estonia since 20 May 2025, Taiwan since 4 May 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.