DESTINATIONS

City	Quality
Amsterdam	Good [31]
Berlin	Good [41]
Brussels	Good [41]
Krakow	Moderate [68]
Oslo	N/A
Prague	Good [45]
London	Good [30]
Madrid	Moderate [51]
Paris	Poor [80]
Stockholm	Very good [18]
Zurich	Very good [20]

Legend

Air Quality
Very low 'Very good'	0/25
Low 'Good'	25/50
Medium 'Moderate'	50/75
High 'Poor'	75/100
Very high 'Very poor'	>100
N/A	N/A

Data: 

The above data was collected from http://www.airqualitynow.eu, an interactive webservice designed to display and compare air quality and developed as part of the European Union's ‘Common Information To European Air' (CITEAIR) project.

The data is taken from the ‘general background air quality index' and represents the minimum level of air quality experienced by a citizen in each of the above cities, the data represents an hourly index and is subject to change throughout  the day.

The indices have five levels from ‘Very low' to ‘Very high' and are based upon the quantity of three major pollutants PM10, NO2, O3 and where data is available, will also take into account pollutants CO, PM2.5 and SO2. These pollutants are of major concern throughout Europe due to their various detrimental effects on health.

Particulate Matter (PM10) particles are small enough to penetrate deep into a person's lungs and as such pose a significant health risk, these particles are most commonly attributed to road traffic emissions and in particular diesel vehicles.  NO2 refers to nitrogen dioxide and is detrimental to the bronchial system. Ground level Ozone (03) is, unlike other pollutants listed above, not emitted directly into the atmosphere but rather is a secondary pollutant formed by reaction between Nitrogen Dioxide (NO2), hydrocarbons and sunlight.