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 21 Jul 2023: Chile 38.1 µg/m³, Pakistan 36.1 µg/m³ and China 23.6 µg/m³.
- 1Chile46 cities38.1
- 2Pakistan4 cities36.1
- 3China3 cities23.6
- 4Malta4 cities15.4
- 5India5 cities15.3
- 6Mexico12 cities13.9
- 7Thailand11 cities13.3
- 8Greece8 cities13.1
- 9Canada101 cities13.0
- 10Italy14 cities12.3
- 11Slovakia26 cities11.9
- 12Serbia3 cities11.2
- 13United States749 cities10.8
- 14Czechia35 cities10.7
- 15Hungary8 cities10.5
- 16Romania6 cities10.4
- 17Bulgaria6 cities10.2
- 18Singapore5 cities9.5
- 19Luxembourg3 cities9.3
- 20Spain89 cities9.0
+ 13 more countries, 8.8 µg/m³ and below
Not counted on this day, too few cities measured: Martinique since 11 Jul 2023, Poland since 29 May 2023 and The Netherlands since 23 May 2023. Days missing from the source archive fall in this window, so fewer countries are counted.
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.