National authorities are competent to control the choice of the location of air quality monitoring stations and to take any measures deemed necessary with regard to the national authority concerned, confirmed the Court of Justice of the European Union in a judgment delivered on Wednesday 26 June (Case C-723/17).
In this case, following a complaint lodged by residents of the Brussels-Capital Region and the association ClientEarth against the Brussels-Capital Region, the Dutch-speaking court of first instance in Brussels asks the Court to interpret the Air Quality Directive (2008/50/EC as amended by Directive 2015/1480). It wished to know: first, to what extent national courts could control the location of sampling points (measuring stations) and whether it was possible to establish an average value from the results of different measuring stations to assess compliance with the limit values.
Relying on the reasoning of the Advocate General (see EUROPE 12204/29), the Court notes that the Directive provides for detailed rules on the use and location of sampling points to measure air quality on the territory of each Member State. These rules introduce clear, precise and unconditional obligations that can be invoked by individuals against the State, such as the obligation to install a minimum number of sampling points, particularly at the most polluted locations.
Thus, according to the Court, in order to ensure compliance with the objective of the Directive, it is for the competent national authorities to choose the location of sampling points in order to minimise the risk that exceeding the limit values will go unnoticed. These authorities must base their decisions on sound scientific data and establish comprehensive documentation to support the location of all monitoring sites, the Court considers.
In the final analysis, the European judge considers that it is for the national courts to verify compliance with these obligations within the limits of the margin of discretion permitted by the Directive. And these courts are competent to take any necessary measures, such as an injunction, to ensure that air quality sampling points are placed in accordance with EU rules.
As regards the question of the possibility of establishing an average value, the Court replies that the determination of the average of the values measured in a geographical area or agglomeration does not provide a useful indication of the population's exposure to polluting substances. According to it, the level of pollution measured at each individual measuring station is decisive. In order to establish that a limit value has been exceeded for the average calculated per calendar year, it is therefore sufficient for a pollution level higher than this value to be measured at an isolated sampling point.
See the ruling: http://bit.ly/2N9k70n (Original version in French by Mathieu Bion)