Air quality

The European Air Quality Index

The European Air Quality Index allows users to understand more about current air quality where they live, work or travel. Displaying up-to-date information for Europe, users can gain insights into the air quality in individual countries, regions and cities.

European Union legislation sets air quality standards both for the short-term (hourly/daily) and long-term (annual) air quality levels: standards for long-term levels are necessarily stricter than for short-term levels, because serious health effects occur from long-term exposure to such pollutants.

About the Index

The Index indicates the short-term air quality situation at more than two thousand air quality monitoring stations across Europe, using up-to-date data reported by EEA’s member countries. It does not reflect the long-term (annual) air quality situation, which may differ significantly.

Measurements of up to five key pollutants supported by modelled data determine the index level that describes the current air quality situation at each monitoring station. The single index level corresponds to the poorest index level for any of five pollutants according to the following scheme.

Pollutant Index level
(based on pollutant concentrations in µg/m3)
GoodFairModeratePoorVery poor
Particles less than 2.5 µm (PM2.5) 0-10 10-20 20-25 25-50 50-800
Particles less than 10 µm (PM10) 0-20 20-35 35-50 50-100 100-1200
Nitrogen dioxide (NO2) 0-40 40-100 100-200 200-400 400-1000
Ozone (O3) 0-80 80-120 120-180 180-240 240-600
Sulphur dioxide (SO2) 0-100 100-200 200-350 350-500 500-1250
Notes:
  1. Given the small number of pollutants often measured at traffic air quality monitoring stations, the index is calculated only for those traffic stations which measure both NO2 and PM (i.e. either PM2.5 or PM10 or both).
  2. For air quality monitoring stations at all other locations, the index is calculated for those stations which measure at least the three pollutants NO2, O3 and PM (i.e. either PM2.5 or PM10 or both).
  3. The index is not calculated for air quality measurements that exceed the maximum value shown in the ‘Very poor’ category. Reported up-to-date measurements higher than these values are typically found to be erroneous, and in such instances are flagged for further analysis and marked as 'no data'.
  4. PM10 and PM2.5 values are based on 24-hour running means

Index methodology

The Index uses ‘up-to-date’ air quality data officially reported every hour by the EEA’s member countries, and complemented – as necessary – by modelled air quality data from the European Union’s Copernicus Atmospheric Monitoring Service (CAMS). Note that the up-to-date air quality reported by countries is not formally verified and therefore is not considered for compliance against air quality standards.

By default, the air quality index depicts the situation 6 hours ago – however users can select any specific hour in the preceding 48 hours.

When data from countries has not been reported for a given hour, values are approximated ('gap-filled') using CAMS modelled air quality data. In such cases, it is clearly marked within the Index as ‘modelled data’.

The gap-filling method used depends on the pollutant, i.e.

When data from countries has not been reported for a given hour, values are approximated ('gap-filled') using CAMS modelled air quality data. In such cases, it is clearly marked within the Index as being 'modelled data'.

The gap-filling method used depends on the pollutant, i.e.

Difference method: the value is approximated by taking the CAMS modelled value, and adding or subtracting a correction difference. This correction is the average difference between previously measured values and the CAMS modelled value for the same hour for at least three of the four previous days.

Multiplicative method: the value is approximated by taking the CAMS modelled value, and applying a correction factor. This correction is the average ratio between the previously measured values and the CAMS modelled values for the same hour for at least three of the four previous days.

In cases where there no measured values for the same hour over three of the four previous days, the index value for the given pollutant is not calculated and is reported as 'no data'.

Further information

The European Environment Agency publishes a range of information on air quality:

The European Air Quality Index was developed jointly by the European Commission’s Directorate General for Environment and the European Environment Agency to inform citizens and public authorities about air quality status across Europe.

Legend explained

Circles on the map represent the locations of air quality monitoring stations. The colour corresponds to the air quality index at the given hour at that station. Note that it does not reflect the annual average air quality situation which may differ significantly (see Info).

Three colour schemes are provided to give information on the status of the data at each station:

  1. Full colour: the minimum data requirement needed to calculate the index are met (see Info for details).
  2. Semi-transparent colour: the minimum data requirements to calculate the index are not met – the colour indicates the air quality index as calculated for the available pollutants only.
  3. Grey: not sufficient data to allow the index to be calculated.

Measurements of up to five key pollutants supported by modelled data determine the index level that describes the current air quality situation at each monitoring station. The single index level corresponds to the poorest index level for any of five pollutants according to the following scheme.

Pollutant Index level
(based on pollutant concentrations in µg/m3)
GoodFairModeratePoorVery poor
Particles less than 2.5 µm (PM2.5) 0-10 10-20 20-25 25-50 50-800
Particles less than 10 µm (PM10) 0-20 20-35 35-50 50-100 100-1200
Nitrogen dioxide (NO2) 0-40 40-100 100-200 200-400 400-1000
Ozone (O3) 0-80 80-120 120-180 180-240 240-600
Sulphur dioxide (SO2) 0-100 100-200 200-350 350-500 500-1250
Notes:
  1. Given the small number of pollutants often measured at traffic air quality monitoring stations, the index is calculated only for those traffic stations which measure both NO2 and PM (i.e. either PM2.5 or PM10 or both).
  2. For air quality monitoring stations at all other locations, the index is calculated for those stations which measure at least the three pollutants NO2, O3 and PM (i.e. either PM2.5 or PM10 or both).
  3. The index is not calculated for air quality measurements that exceed the maximum value shown in the ‘Very poor’ category. Reported up-to-date measurements higher than these values are typically found to be erroneous, and in such instances are flagged for further analysis and marked as 'no data'.
  4. PM10 and PM2.5 values are based on 24-hour running means