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Air quality index

What is the source for air quality forecasts provided on Euronews?

The air quality forecasts presented here are provided by the Copernicus Atmosphere Monitoring Service (CAMS). As part of the European Union’s flagship programme Copernicus, CAMS delivers information about air quality and atmospheric composition in and outside Europe based on satellite and conventional Earth Observation measurements in combination with forecast models. Information and data are unrestricted and free of charge, with the aim to support policymakers, business and citizens with enhanced atmospheric environmental information. CAMS is implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF), with the support of over 30 entities distributed in Europe. Follow these links to have more information on Copernicus (copernicus.eu), CAMS (atmosphere.copermicus.eu) and ECMWF (ecmwf.int).

How is the European Air Quality index defined?

Air quality information is provided using the European Air Quality Index, which follows the definition of the European Environment Agency (EEA, eea.europa.eu). This index is computed for the five main pollutants regulated in the European legislation: O3 (ozone), NO2 (nitrogen dioxide), SO2 (sulfur dioxide), PM2.5 and PM10 (fine particulate matter with a diameter smaller than 2.5 micrometers and 10 micrometers respectively). or each pollutant, the value of the index ranges from 1 (good) to 5 (very poor). The European Air Quality index is computed for the different pollutants separately according to the concentrations (instantaneous or in average for the day, depending on the pollutant): the higher the concentrations, the higher the index. The European air quality index is given as an integer value, corresponding to 5 concentrations bands that are specific to each pollutant as defined in the table below.

PollutantIndex level
(based on polluant concentrations in µg/m3)
 
1
Very good
2
Good
3
Medium
4
Poor
5
Very Poor
Ozone (O3)0-8080-120120-180180-240240-600
Nitrogen dioxide (NO2)0-4040-100100-200200-400400-1000
Sulphur dioxide (So2)0-100100-200200-350350-500500-1250
Particules less than 10 µm (PM10)0-2020-3535-5050-100100-1200
Particules less than 2.5 µm (PM2.5)0-1010-2020-2525-5050-800
Note: PM10 and PM2.5 values are based on 24-hour running means

The overall hourly European Air Quality index is simply defined as the highest value of the 5 individual pollutants indexes computed for the same hour. For instance, if the indices relative to O3, NO2, SO2, PM2.5 and PM10 are 1,3,1,2,2 respectively, the overall index will be 3. The overall daily European Air Quality index is the highest value of the overall hourly European Air Quality index in the corresponding day. The overall daily European Air Quality index is used for the bulletins that are broadcast on Euronews, while this website also provides the hourly values as well as the indexes specific for each of the 5 pollutants considered.

What does this mean for me?

Information about the pollutants and their main effects on health can be found on EEA’s website (eea.europa.eu/themes/air/air-quality-standards). Legislation in Europe and in the different European countries aims at protecting populations, based on latest scientific information as compiled in particular by the World Health Organisation. In the case that the Air Quality index is “poor” (4) or “very poor” (5), please check with your national or local agency in charge of air quality about the situation and for advice about what you should do to limit your exposure (e.g. avoid exercising outside...) and to help mitigating the situation (e.g. take public transportations...).

Can I trust the information provided?

Information provided on this website are forecasts. Just like in the case for weather forecasts, this information is relying on advanced mathematical models that replicate the laws of physics in combination with past observations. As a result, there is a chance that a forecast is inaccurate. However, evaluation over the last six months of 2017 has indicated that forecasts were correct within 1 index value (perfect or over-/under-estimated by 1) in more than 98% of the time. You can find more information about how the CAMS air quality forecasts work here (in particular the FAQ section).

Forecast presented here are obtained on a computational grid with cells that are about 10km by 10km on the horizontal, which means that they cannot represent local effects (e.g. a road with heavy traffic within a few hundred meters...). Within large cities, the values provided by CAMS are representative of the “urban background” concentrations, corresponding to areas in the city that are not directly affected by local sources, such as car traffic (e.g. middle of a large park, quiet residential area). Areas affected by local sources are expected to have higher concentrations of NO2, PM2.5, PM10 and SO2 and lower concentrations of O3. For local information within cities and especially in case of the forecasts indicating “poor” (4) or “very poor” (5) air quality, please check with your national or local agency in charge of air quality. You can also check the latest observed values of the European Air Quality index on this website (airindex.eea.europa.eu), which is maintained by the EEA with the support of the national agencies in charge of air quality in each European country.

I have further questions about the air quality forecasts and how they are made?

Answers and dedicated support can be found here or at http://atmosphere.copernicus.eu/contact-us.