Ulf Troeng, who told me about the map, clarifies that:
“Data is not available from all countries, it is mostly collected from the developed part of the world. But anyway, the map gives you a pretty good picture of where the air is clean and where it is dirty. In that way it also says something about where sources of pollution are located.”
The numbers refer to the Air Quality Index (AQI) which uses the following scale:
- 0 – 50: Good, Air quality is considered satisfactory, and air pollution poses little or no risk
- 51 -100: Moderate, Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
- 101-150: Unhealthy for Sensitive Groups, Members of sensitive groups may experience health effects. The general public is not likely to be affected.
- 151-200: Unhealthy, Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects
- 201-300: Very Unhealthy, Health warnings of emergency conditions. The entire population is more likely to be affected.
- 300+: Hazardous, Health alert: everyone may experience more serious health effects
The Data sources used for the Air Quality, Air Pollution, PM2.5 (fine particulate matter), PM10 (respirable particulate matter), NO2 (nitrogen dioxide), SO2 (sulfur dioxide), CO (carbon monoxide), O3 (ozone)
As you can see in the map above, 3 cities in Western China (Korla, Aksu & Kashi) all had the worst possible score of 999, when the data was checked, with many others falling into the Unhealthy or Very Unhealthy category.
So any of the three could be considered as having the world’s worst air pollution problem. Contrast them with Japanese cities next door or ones in North America, Europe and Australia below:
While a long way from perfect, air pollution levels are noticeably lower in all regions compared to China. Want to learn more about air pollution in China and around the world? Be sure to visit http://aqicn.org and have a look at:
- The River Runs Black: The Environmental Challenge to China’s Future, Second Edition
- Clearer Skies Over China: Reconciling Air Quality, Climate, and Economic Goals
- This Changes Everything: Capitalism vs. the Climate
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