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 28 Sep 2023: Pakistan 41.0 µg/m³, Peru 26.4 µg/m³ and India 24.3 µg/m³.
- 1Pakistan4 cities41.0
- 2Peru4 cities26.4
- 3India5 cities24.3
- 4Chile43 cities23.8
- 5China3 cities23.4
- 6Singapore6 cities15.6
- 7Mexico42 cities14.9
- 8Brazil27 cities14.1
- 9Thailand11 cities14.0
- 10Greece7 cities13.9
- 11Malta4 cities13.7
- 12Serbia3 cities12.9
- 13Poland57 cities12.4
- 14Czechia36 cities11.5
- 15Italy30 cities10.7
- 16Hungary9 cities10.6
- 17Hong Kong11 cities9.6
- 18Slovakia27 cities9.5
- 19Bulgaria6 cities9.4
- 20Martinique3 cities8.9
+ 16 more countries, the next at 8.8 µg/m³
- 27United States771 cities7.6
Not counted on this day, too few cities measured: North Macedonia since 20 Sep 2023 and Reunion since 16 Aug 2023.
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, Turkey and Iran, which publish only on their own websites. We are building the reader for China's network. The networks of Turkey and Iran don't answer requests from outside their countries, so we can't read them. Most cities there are missing from this board, not clean. Why.