© Esri, HERE, DeLorme, OpenStreetMap contributors
© Esri, HERE, DeLorme, MapmyIndia, OpenStreetMap contributors, and the GIS user community
Legend
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The European Air Quality Index

The European Air Quality Index allows users to understand more about 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.

The Index is based on concentration values for up to five key pollutants, including:

It reflects the potential impact of air quality on health, driven by the pollutant for which concentrations are poorest due to associated health impacts.

The index is calculated hourly for more than two thousand air quality monitoring stations across Europe, using up-to-date data reported by EEA member countries. These data are not formally verified by the countries.

By default, the air quality index depicts the situation 3 hours ago. Users can then select any hour in the preceding 48 hours and view forecast values for the following 24 hours.

The user can filter the selection by country and by station type. Stations are classified in relation to the predominant emission sources, including traffic, industry and background where the pollution level is dominated neither by traffic nor by industry. The user can view all stations, traffic stations only or non-traffic stations only (i.e. industrial, urban or regional background stations).

European Union legislation sets air quality standards for both short-term (hourly or daily) and long-term (annual) air quality levels. Standards for long-term levels are stricter than for short-term levels, since serious health effects may occur from long-term exposure to 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 air quality index is not a tool for checking compliance with air quality standards and cannot be used for this purpose.

Methodology

The Index uses ‘up-to-date’ air quality data officially reported every hour by EEA member countries, complemented where necessary by modelled air quality data from the European Union’s Copernicus Atmosphere Monitoring Service (CAMS).

Concentrations values for up to five key pollutants determine the index level that reflects air quality at each monitoring station. The index corresponds to the poorest level for any of five pollutants, according to the table shown below.

Circles on the map represent the locations of air quality monitoring stations. The colours reflect air quality at the given hour at that station.

Calculating the index for traffic stations

When calculating the index for traffic stations we only use data for NO2 and PM (either PM2.5, PM10 or both). This is because SO2 concentrations can be high in localized areas and distort the picture of local air quality, while ozone levels are normally very low at traffic stations.

Calculating the index for industrial and background stations

At industrial and background stations, the index is calculated for those stations with data (either measured or modelled) for at least the three pollutants NO2, O3 and PM (either PM2.5, PM10 or both).

Stations missing data for certain pollutants

To avoid leaving out stations that do not report data for all pollutants or for which missing data cannot be gap-filled, the index is calculated for all monitoring stations with data for at least one pollutant. Those stations that do not report data or for which data cannot be gap-filled for the minimum pollutants for that station type are depicted as transparent dots, indicating that the index is not calculated with the minimum range of pollutants.

Averaging time for pollutants

For NO2, O3 and SO2, hourly concentrations are fed into the calculation of the index.

For PM10 and PM2.5, the 24-hour running means for the past 24 hours are fed into the calculation of the index.

Missing data and gap filling

When data is not reported for a given hour, values are approximated, or 'gap-filled' using CAMS modelled air quality data. In such cases, it is marked as 'modelled data' (see below).

The method used for gap-filling depends on the pollutant.

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 are no measured values for the same hour over three of the four previous days, the value for the given pollutant is not calculated and is reported as 'no data'

Forecast index

Forecast values are shown as transparent dots. To calculate the forecast values for the following 24 hours, CAMS modelled air quality data are used and corrected using the gap-filling methods described above. No forecast values are provided for SO2.

Bands of concentrations and index levels

The bands are based on the relative risks associated to short-term exposure to PM2.5, O3 and NO2, as defined by the World Health Organization in its report on the Health Risks of Air Pollution in Europe project (HRAPIE project report).

The relative risk of exposure to PM2.5 is taken as basis for driving the index, specifically the increase in the risk of mortality per 10 µg/m3 increase in the daily mean concentration of PM2.5.

Assuming linearity across the relative risks functions for O3 and NO2, we calculate the concentrations of these pollutants that pose an equivalent relative risk to a 10 µg/m3 increase in the daily mean of PM2.5.

For PM10 concentrations, a constant ratio between PM10 and PM2.5 of 1:2 is assumed, in line with the World Health Organization´s air quality guidelines for Europe.

For SO2, the bands reflect the limit values set under the EU Air Quality Directive.

Pollutant Index level
(based on pollutant concentrations in µg/m3)
Good Fair Moderate Poor Very poor Extremely poor
Particles less than 2.5 µm (PM2.5) 0-10 10-20 20-25 25-50 50-75 75-800
Particles less than 10 µm (PM10) 0-20 20-40 40-50 50-100 100-150 150-1200
Nitrogen dioxide (NO2) 0-40 40-90 90-120 120-230 230-340 340-1000
Ozone (O3) 0-50 50-100 100-130 130-240 240-380 380-800
Sulphur dioxide (SO2) 0-100 100-200 200-350 350-500 500-750 750-1250

Air quality measurements that exceed the maximum values in the ‘extremely poor’ category are not taken into account for the index calculation, since these values are typically found to be erroneous.

Health messages

The index bands are complemented by health related messages that provide recommendations for both the general population and sensitive populations. The latter includes both adults and children with respiratory problems and adults with heart conditions.

AQ index General population Sensitive populations
Good The air quality is good. Enjoy your usual outdoor activities. The air quality is good. Enjoy your usual outdoor activities.
Fair Enjoy your usual outdoor activities Enjoy your usual outdoor activities
Moderate Enjoy your usual outdoor activities Consider reducing intense outdoor activities, if you experience symptoms.
Poor Consider reducing intense activities outdoors, if you experience symptoms such as sore eyes, a cough or sore throat Consider reducing physical activities, particularly outdoors, especially if you experience symptoms.
Very poor Consider reducing intense activities outdoors, if you experience symptoms such as sore eyes, a cough or sore throat Reduce physical activities, particularly outdoors, especially if you experience symptoms.
Extremely poor Reduce physical activities outdoors. Avoid physical activities outdoors.

Additional information

When clicking on a station on the map, a pop-up window appears with the following additional information:

1. The name of the station and the air quality index at that station and hour.

2. A “View station” option, that provides the location of the station using © Google Maps.

3. A “Show details” option, with a summary of the station information; the air quality index and the associated health advice for the general population and sensitive populations; and two graphs.

The values indicated when hovering over the horizontal bars to the right show the hourly concentrations for each pollutant measured at the station or gap-filled over the last 4 days. By hovering over the bars, the concentration values are given. An asterisk next to a value indicates that the value has been gap-filled

The pie chart indicates the number of days that feel under each Index band over the past 365 days. The highest hourly Index level in a day determines the daily Index level taken into account.

4. Links to information on air pollution for the country where the station is located and to the webpage of the administration in charge of reporting the concentrations for that station.

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.

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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 Extremely poor
Particles less than 2.5 µm (PM2.5) 0-10 10-20 20-25 25-50 50-75 75-800
Particles less than 10 µm (PM10) 0-20 20-40 40-50 50-100 100-150 150-1200
Nitrogen dioxide (NO2) 0-40 40-90 90-120 120-230 230-340 340-1000
Ozone (O3) 0-50 50-100 100-130 130-240 240-380 380-800
Sulphur dioxide (SO2) 0-100 100-200 200-350 350-500 500-750 750-1250

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 365 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 .