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 6 Aug 2023: Chile 41.1 µg/m³, Pakistan 33.6 µg/m³ and China 22.3 µg/m³.
- 1Chile44 cities41.1
- 2Pakistan4 cities33.6
- 3China3 cities22.3
- 4Malta4 cities18.1
- 5Mexico32 cities14.7
- 6India5 cities14.5
- 7Greece8 cities13.9
- 8Thailand11 cities13.3
- 9Martinique3 cities12.6
- 10Singapore5 cities11.4
- 11Serbia3 cities11.2
- 12Romania7 cities11.0
- 13North Macedonia7 cities10.9
- 14Canada113 cities10.4
- 15United States750 cities10.1
- 16Bulgaria6 cities9.9
- 17Slovakia27 cities9.9
- 18Hungary7 cities9.1
- 19Hong Kong11 cities9.0
- 20Czechia29 cities8.8
+ 13 more countries, 7.7 µg/m³ and below
Not counted on this day, too few cities measured: Italy since 29 Jul 2023, Lithuania since 27 Jul 2023 and Luxembourg since 27 Jul 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.