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 Apr 2024: Laos 66.6 µg/m³, India 46.3 µg/m³ and China 40.1 µg/m³.
- 1Laos3 cities66.6
- 2India5 cities46.3
- 3China4 cities40.1
- 4Pakistan3 cities31.8
- 5Thailand82 cities31.4
- 6Chile44 cities25.0
- 7Peru6 cities21.1
- 8South Korea141 cities21.0
- 9Taiwan43 cities19.6
- 10Mexico11 cities17.4
- 11Hong Kong12 cities, was 1315.6
- 12Greece6 cities14.8
- 13Malta5 cities14.6
- 14Serbia24 cities14.6
- 15Poland75 cities13.4
- 16Bosnia and Herzegovina5 cities13.0
- 17North Macedonia9 cities12.6
- 18Japan520 cities11.8
- 19Singapore5 cities11.2
- 20Czechia38 cities10.8
+ 26 more countries, 10.6 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.