Classification of monitoring stations and criteria to include them in EEA's assessments products

Briefly, depending on the predominant emission sources, stations are classified as follows:

• traffic stations: located in close proximity to a single major road;
• industrial stations: located in close proximity to an industrial area or an industrial source;
• background stations: where pollution levels are representative of the average exposure of the general population or vegetation.

Depending on the distribution/density of building, the area surrounding the station is classified as follows:

• urban: continuously built-up urban area;
• suburban: largely built-up urban area;
• rural: all other areas.

All stations officially reported to the EEA are included in the Europe’s air quality status briefing, independently of their designation for compliance checking, as far as they fulfil the data coverage criteria. For most of the pollutants, monitoring stations have to fulfil the criterion of reporting more than 75 % of valid data out of all the possible data in a year. The Ambient Air Quality Directives set, for compliance purposes, the objective of a minimum data capture of 90 % for monitoring stations, but, for assessment purposes, a coverage of 75 % allows more stations to be taken into account without a significant increase in monitoring uncertainties. For benzene, toxic metals As, Cd, Ni, Pb, and for BaP, it is 13 % (according to the air quality objectives for indicative measurements). The exception to the general rule is PM random fixed measurements, for which the required amount of valid data for the analysis is 13 %. Reporting stations not fulfilling the minimum data coverage can be found at the Annual AQ statistics table.

Measurement data are rounded following the general recommendations under Commission Implementing Decision 2011/850/EU. The number of considered decimals are indicated in the legend of the corresponding maps.

The assessments, in the cases of PM and SO₂, do not account for the fact that the Ambient Air Quality Directive 2008/50/EC provides Member States with the possibility of subtracting contributions to the measured concentrations from natural sources and winter road sanding/salting under specific circumstances.