European Union – Environment. Articles 13(1) and 23(1) of Directive (EC) 2008/50 should be interpreted as meaning that, in order to establish whether a limit value with an averaging period of one calendar year, as laid down in Annex XI to that directive, had been exceeded, it was sufficient that a pollution level higher than that value be measured at a single sampling point. The Court of Justice of the European Union so held, among other things, in a preliminary ruling in proceedings regarding the obligation to develop an air quality plan for the Brussels zone (Belgium) and to install the sampling points legally required to monitor air quality.