© Esri, HERE, DeLorme, OpenStreetMap contributors
© Esri, HERE, DeLorme, MapmyIndia, OpenStreetMap contributors, and the GIS user community

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 may occur from long-term exposure to such pollutants.

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

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

Data can be filtered based on the “type of station”. The stations are classified in relation to the predominant emission sources: traffic stations, industrial stations and background stations (where the pollution level is not dominated by either traffic or industry). The present viewer allows filtering either the traffic stations and all types of stations (so also including industrial stations and background stations).

Please note that the air quality index is based on the up-to-date air quality reported by countries. These data are not formally verified by the countries.

The air quality index does not aim at compliance checking against air quality standards and can not be considered for this purpose.

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) (see ‘Missing data and gap filling’ below). Concentrations of up to five key pollutants determine the index level that describes the current air quality situation at each monitoring station. The index corresponds to the poorest level for any of five pollutants according to the following scheme.

Traffic stations

SO2 concentrations can be high only in much localized areas, and ozone concentrations are normally very low at traffic stations. Therefore, the index for these stations should be ideally calculated only with data (either measured or derived from CAMS models) for both NO2 and PM (i.e. either PM2.5 or PM10 or both).

All other locations

The index should be calculated for those stations with data (either measured or derived from CAMS models) for at least the three pollutants NO2, O3 and PM (i.e. either PM2.5 or PM10 or both).

Missing pollutant

To avoid leaving out a certain number of stations, the index is calculated for all monitoring stations with data for at least one pollutant, but those stations not fulfilling the minimum number of pollutants requirement are shown in transparent colour.

Averaging time

For NO2, O3 and SO2 , hourly concentrations of NO2, O3 and SO2 are used for the calculation of the index. For PM10 and PM2.5, the 24-hour running means, based on the last 24 hours, are considered for the calculation of the index.

Missing data and gap filling

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'.

Bands of concentrations and index levels

Pollutant Index level
(based on pollutant concentrations in µg/m3)
Good Fair Moderate Poor Very 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

Please, note that the air quality measurements that exceed the maximum value shown in the ‘Very poor’ category in the table are not taken into account for the index calculation, since these values are typically found to be erroneous.

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 the recent 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 measured at the air quality situation which may differ significantly (see Info).

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 index corresponds to the poorest level for any of five pollutants according to the following scheme.

Pollutant Index level
(based on pollutant concentrations in µg/m3)
Good Fair Moderate Poor Very 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

The colour scheme is provided to give information on the status of the air quality at each station. Colours are either full or semi transparent:

  1. Full colour (with a white border*): the minimum number of pollutants requirement needed to calculate the index are met (see Info for details).
  2. ii. Semi-transparent colour: the minimum number of polllutants requirements to calculate the index are not met – the colour indicates the air quality index as calculated for the available sub-set of pollutants only.

The grey dots indicate stations for which: no sufficient data or no data have been reported to allow the index to be calculated.

The graphs presented under “Show details” when clicking on a station on the map follows the same colour scheme. The concentrations indicated in the small table are:

An asterisk next to a value indicates that the value has been gap-filled (see details in Info).

The pie chart indicates the number of days for each Index level for the past 100 days (the highest hourly Index level in a day determines the daily Index level taken into account).

The XY graph presents the evolution of the index for the different pollutants over the last 10 days i.e. the concentrations normalised on the band values.

Details on the methodology to calculate the AQ Index can be found clicking on Info .