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 23 Apr 2024: Laos 66.6 µg/m³, India 44.8 µg/m³ and China 41.8 µg/m³.
- 1Laos3 cities66.6
- 2India5 cities44.8
- 3China4 cities41.8
- 4Thailand82 cities32.5
- 5Pakistan3 cities31.8
- 6Chile44 cities24.1
- 7South Korea138 cities20.5
- 8Taiwan43 cities20.5
- 9Malta4 cities18.9
- 10Peru6 cities18.9
- 11Mexico11 cities17.0
- 12Hong Kong12 cities, was 1316.1
- 13Greece5 cities15.0
- 14Serbia24 cities14.2
- 15North Macedonia9 cities13.6
- 16Bosnia and Herzegovina5 cities13.0
- 17Poland77 cities12.8
- 18Japan512 cities11.6
- 19Singapore5 cities11.2
- 20Czechia37 cities10.9
+ 26 more countries, 10.7 µg/m³ and below
- 37United 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 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.