Index of air quality in the world's major cities: March 9

Daily air quality index of some of the world's major cities on March 9, using data from AirNow, CITEAIR, and the American Embassy in Beijing.

City		Average 08/03/2011	Average 09/03/2011
London (UK)
Madrid (Spain)			NA
Paris (France)
Brussels (Belgium)
Berlin (Germany )
Prague (Czech Republic)
Zurich (Switzerland)
Beijing (China)		NA
Beijing US embassy stats
Shanghai (China)		NA
Hong Kong (China)
Brunei (Brunei)
Seoul (South Korea)
New York (USA)
San Francisco (USA)
Mexico City (Mexico )
Montreal (Canada)
Toronto (Canada)
New Delhi (India)
Sydney (Australia)

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 8:00am GMT on March 9.
http://www.airqualitynow.eu
http://www.airnow.gov