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 7 days to 21 Jan 2023: Pakistan 106.6 µg/m³, Mexico 30.1 µg/m³ and Thailand 30.0 µg/m³.
- 1Pakistan4 cities106.6
- 2Mexico47 cities30.1
- 3Thailand59 cities30.0
- 4China3 cities26.9
- 5Peru4 cities23.3
- 6Hong Kong10 cities21.9
- 7Chile42 cities19.6
- 8South Africa9 cities18.6
- 9Poland70 cities18.4
- 10Greece10 cities15.7
- 11Italy14 cities13.2
- 12Romania7 cities13.2
- 13Hungary5 cities12.2
- 14Czechia27 cities12.0
- 15Bulgaria7 cities11.8
- 16Slovakia24 cities11.3
- 17Brazil13 cities10.0
- 18Ireland4 cities9.7
- 19The Netherlands29 cities9.4
- 20United Kingdom41 cities8.9
+ 9 more countries, 8.8 µg/m³ and below
- 23United States656 cities6.5
Not counted on this day, too few cities measured: Kosovo since 20 Jan 2023, Austria since 19 Jan 2023, Belgium since 19 Jan 2023 and 11 more countries. 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.