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 28 Mar 2023: China 42.3 µg/m³, Pakistan 37.1 µg/m³ and Thailand 31.5 µg/m³.
- 1China3 cities42.3
- 2Pakistan4 cities37.1
- 3Thailand66 cities31.5
- 4Chile43 cities25.1
- 5Mexico51 cities22.7
- 6South Africa7 cities15.8
- 7Peru5 cities15.1
- 8Romania7 cities14.1
- 9Brazil13 cities13.8
- 10Greece7 cities13.6
- 11Bulgaria5 cities13.0
- 12Poland64 cities12.3
- 13Slovakia25 cities12.1
- 14Italy19 cities11.8
- 15Czechia23 cities11.1
- 16Hong Kong8 cities10.6
- 17Hungary7 cities8.8
- 18Spain85 cities7.8
- 19United States662 cities7.2
- 20Ireland4 cities7.1
+ 14 more countries, 6.9 µg/m³ and below
Not counted on this day, too few cities measured: Kosovo since 28 Mar 2023, Luxembourg since 26 Mar 2023, Bosnia and Herzegovina since 22 Mar 2023 and 8 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.