Index of air quality in the world's major cities: December 22

(AFP PHOTO / NASA EARTH OBSERVATORY)

Daily air quality index of some of the world's major cities on December 22, using data from AirNow, CITEAIR, and the American Embassy in Beijing.

City	Average 22/12/2010
London (UK)	Good
Madrid (Spain)	NA
Paris (France)	Good
Brussels (Belgium)	Moderate
Berlin (Germany )	Moderate
Prague (Czech Republic)	Moderate
Zurich (Switzerland)	Good
Beijing (China)	NA
Beijing - US embassy stats	Moderate
Shanghai (China)	Unhealthy for sensitive groups
Hong Kong (China)	Moderate
Brunei (Brunei)	Good
New York (USA)	Good
San Francisco (USA)	Good
Mexico City (Mexico )	Unhealthy for sensitive groups
Montreal (Canada)	Good
Toronto (Canada)	Good
New Delhi (India)	Unhealthy
Sydney (Australia)	NA

The Air Quality Index (AQI) or Air Pollution Index (API) measures the parts of pollutant in a specified volume of air. The lower the AQI the fewer particles of pollution are in the air. For a more detailed explanation see http://www.airnow.gov/index.cfm?action=aqibasics.aqi.

All results are color-coded following the American AQI standard shown below. For all countries outside of Europe, the US and Canada, that region's definition of AQI terms has been accepted.

Legend 

Air Quality
Good
Moderate
Unhealthy for sensitive groups
Unhealthy
Very Unhealthy
Hazardous

Data: Data relating to Europe, the US and Canada is taken from CITEAIR - Common Information to European Air ( http://www.airnow.gov / http://www.airqualitynow.eu); data concerning China is taken from both official Chinese government sources and the US Embassy's automated air index Twitter account. For all countries the data displayed falls within either that country's definition of the level of air quality or the international AQI index. Data for all European, US and Canadian cities refers to background, not roadside, levels of air quality.

All data was collected at 1:00pm GMT on December 22.

http://www.airqualitynow.eu
http://www.airnow.gov