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 25 Apr 2024: Laos 65.5 µg/m³, India 45.5 µg/m³ and China 40.6 µg/m³.
- 1Laos3 cities65.5
- 2India5 cities45.5
- 3China4 cities40.6
- 4Thailand82 cities32.0
- 5Pakistan3 cities31.8
- 6Chile44 cities24.5
- 7South Korea140 cities20.6
- 8Taiwan43 cities20.0
- 9Peru6 cities19.4
- 10Malta4 cities18.9
- 11Mexico11 cities17.3
- 12Hong Kong12 cities, was 1316.0
- 13Greece6 cities15.6
- 14Serbia24 cities14.2
- 15North Macedonia9 cities13.6
- 16Poland75 cities13.1
- 17Bosnia and Herzegovina5 cities12.9
- 18Brazil21 cities12.6
- 19Japan519 cities11.4
- 20Singapore6 cities11.1
+ 27 more countries, the next at 10.7 µg/m³
- 39United States793 cities5.5
Not counted on this day, too few cities measured: Montenegro since 26 Mar 2024, Switzerland since 20 Mar 2024, Slovakia since 19 Mar 2024 and 2 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.