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 24 Apr 2023: China 54.9 µg/m³, India 50.5 µg/m³ and Thailand 35.8 µg/m³.
- 1China3 cities54.9
- 2India3 cities50.5
- 3Thailand50 cities35.8
- 4Pakistan4 cities35.6
- 5South Africa3 cities34.7
- 6Chile45 cities25.7
- 7Mexico41 cities22.0
- 8Hong Kong9 cities14.5
- 9Poland63 cities13.3
- 10Czechia29 cities12.6
- 11Greece8 cities11.7
- 12Romania7 cities11.5
- 13Slovakia25 cities11.3
- 14Hungary8 cities11.2
- 15Bulgaria6 cities10.4
- 16Belgium37 cities10.0
- 17Italy15 cities9.0
- 18The Netherlands31 cities8.7
- 19United Kingdom53 cities8.5
- 20Spain88 cities8.2
+ 14 more countries, 7.9 µg/m³ and below
- 26United States683 cities7.0
Not counted on this day, too few cities measured: Peru since 24 Apr 2023, Kosovo since 2 Apr 2023, Bosnia and Herzegovina since 30 Mar 2023 and 5 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.