The Ambient Air Quality Directives require the assessment of the ambient air quality in Member States based on common methods and criteria for air quality monitoring and modelling. This comprehensive assessment is required throughout the whole territory of each country. The assessments should be done in a way so that they are representative of other locations. Find out more about spatial representativeness.
When air quality monitoring is being used for air quality assessment, it is extremely important to appropriately site sampling points. This ensures monitoring information can be used to obtain further information on:-
- Exposure
- Source apportionment that supports the development of air policy
- Air pollution management in the area
Key provisions
Amongst other key provisions, Directive 2008/50/EC (EU) 2024/2881:-
- Requires that air quality zones be classified according to an assessment regime, which will define which assessment methods are required.
- Establishes a minimum number of sampling points for regulated pollutants, ultrafine particles (UFPs) and for the additional pollutants of Annex VII.
- Establishes the location of these sampling points.
- Allows Member States to subtract the contribution of natural sources under certain conditions before comparing the ambient air pollutant concentrations to the limit values. See the Guidelines and an assessment study performed in 2022 for more information.
- Indicates that for designated zones or agglomerations within which limit values for PM10 are exceeded in ambient air, such exceedance is due to the re-suspension of particulates following winter sanding or salting of roads. See the Guidelines for more information.
Guidance
For the implementation of Directive 2008/50/EC, several guidance documents were prepared with the extensive support from national experts. These can still be consulted here, although some provisions may have changed with Directive (EU) 2024/2881:-
- Support document on setting up common measuring stations for PM2.5 under Directive 2008/50/EC on ambient air quality and cleaner air for Europe
- Guidance report on Preliminary Assessment under EC Air Quality Directives
- Guidance on Assessment under the EU Air Quality Directives
- Decision 2004/279/EC, guidance for implementing the ozone directive
- Guidance on assessment around point sources
Reference air quality measurement methods
For regulated pollutants, a reference measurement method has been prescribed, which can be found in Annex VI of the Ambient Air Quality Directive 2024/2881. The situation has evolved and the following reference measurement methods have been updated since the adoption:-
- Benzene part 1 EN 14662: 2023
- Ozone: EN14625:2024
The standards can be obtained through the national standardisation organisation here.
Non-reference measurement methods can also be used provided they respect provisions for equivalence set out in the Directives (Annex VI). A Commission Working Group on Equivalence has prepared a document describing principles and methodologies to be used to demonstrate the equivalence of alternative (non-reference) measurement methods to the reference methods described by the EN Standard methods:
The corresponding tool to facilitate the use of the guidance (in particular for checking the equivalence of non-reference methods for PM-monitoring) has been developed. The updated version is now available:
Air quality modelling
Air quality modelling applications are considered to provide supplemental information to air quality monitoring by enabling point data (from fixed measurements, for example) to be interpreted in terms of the geographical distribution of concentrations.
In addition to air quality assessments, modelling applications can provide more comprehensive information on public exposure, support the identification of sources, inform air quality plans and roadmaps, and perform future projections based on different measures scenarios.
A Forum for AIR quality Modelling (FAIRMODE) of modellers and users has been established. The aim of the Forum is to support the widespread and harmonised use of models through model validation and intercomparison exercises and through the management of the modelling network. The FAIRMODE webpage contains links to current activities.
Objective estimation of air quality
The Ambient Air Quality Directives also allow for objective estimation as an air quality assessment method for air quality zones with very good air quality. By identifying local pollution sources and information on regional air quality, an estimation of the concentration of a regulated pollutant is made.
Ensuring quality of air quality assessment information
Ensuring quality of assessment information either generated through monitoring, modelling or objective estimation is one of the paramount provisions of the Directive. Data quality objectives are prescribed which define maximum allowed uncertainty and data coverage (proportion of the calendar year for which there is valid data).
Member States are responsible for ensuring appropriate quality assurance of the assessment as well as the appropriate quality control of the information provided to the public and through the assessment reports. The Commission has set-up a community-wide process, managed by the Joint Research Centre (JRC).
AQUILA is a network of national reference laboratories that provides expert advice to the Commission. In its website you may find more information on its objectives, support documents and quality assurance procedures and programmes. It has prepared an extensive document that summarises the roles and responsibilities of the national reference laboratories and of the network itself, describes the quality assurance procedures and makes EU-wide comparisons.
The European Environment Agency (EEA) together with EIONET and its Topic Centre also supports quality assurance of the data and reporting of air quality assessment information.