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 29 Mar 2023: China 40.7 µg/m³, Pakistan 34.2 µg/m³ and Thailand 27.8 µg/m³.
- 1China3 cities40.7
- 2Pakistan4 cities34.2
- 3Thailand70 cities27.8
- 4Chile41 cities24.1
- 5Mexico52 cities22.8
- 6Peru5 cities15.2
- 7South Africa8 cities14.1
- 8Brazil13 cities13.9
- 9Greece7 cities12.9
- 10Romania7 cities12.6
- 11Hong Kong7 cities12.3
- 12Poland64 cities10.9
- 13Slovakia25 cities10.6
- 14Italy18 cities9.9
- 15Bulgaria5 cities9.7
- 16Czechia23 cities9.4
- 17Hungary7 cities8.2
- 18Spain85 cities7.7
- 19Ireland4 cities7.6
- 20United States682 cities6.8
+ 13 more countries, 6.3 µg/m³ and below
Not counted on this day, too few cities measured: Sweden since 29 Mar 2023, Kosovo since 28 Mar 2023, Luxembourg since 26 Mar 2023 and 9 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.