Ambient Air Quality and Cleaner Air for Europe
Directive 2008/50/EC on ambient air quality and cleaner air for Europe, which is based on the previous article corresponding to the current Article 192 TFEU, aims at defining and establishing objectives for ambient air quality designed to avoid, prevent, or reduce harmful effects on human health and the environment as a whole. Among its further objectives are counted assessing the ambient air quality in Member States on the basis of common methods and criteria; monitoring long-term trends and improvements resulting from national and EU measures; ensuring that information on ambient air quality is made available to the public; maintaining air quality where it is good and improving it in other cases; and promoting increased cooperation between the Member States in reducing air pollution. (Art 1.)
The fundamental obligation incumbent on the Member States is to establish zones throughout their territory for the purpose of air quality assessment and management. A zone that is a conurbation with a population in excess of 250,000 inhabitants or which has a certain population density, to be established by the Member States, is referred to as an ‘agglomeration’. Air quality assessment and air quality management shall be carried out in all zones and agglomerations. (Arts 2 and 4.)
Chapter II of the Directive (Arts 5—11) sets out rules regarding the assessment of ambient air quality in relation to sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter, lead, benzene, and carbon monoxide. Each zone and agglomeration shall be classified in relation to specific assessment thresholds set out in Annex II. The classification shall be reviewed at least every five years. Ambient air quality is to be assessed with respect to the above listed pollutants in all zones and agglomerations. How this is to be done in a specific zone or agglomeration varies depending on whether the level of pollutants is above or below the pertinent assessment threshold. The chapter also contains specific assessment criteria for ozone.
Chapter III of the Directive (Arts 12—22) deals with the management of ambient air quality. A number of limit values, target values, and thresholds are set out in Annexes XI to XIV of the Directive. More specifically, these are limit values for the protection of human health, information and alert thresholds, critical levels for the protection of vegetation, national exposure reduction target, and target value and limit value for PM2.5.
In zones and agglomerations where the levels of sulphur dioxide, nitrogen dioxide, PM10, PM2.5, lead, benzene, and carbon monoxide in ambient air are below the respective limit values, the Member States shall maintain the levels of those pollutants below the limit values and shall endeavour to preserve the best ambient air quality compatible with sustainable development (Art 12).
As regards limit values, the levels of sulphur dioxide, PM10, lead, and carbon monoxide in ambient air must not exceed the limit values in any zone or agglomeration. All necessary measures not entailing disproportionate costs are also to be taken to reduce exposure to PM2.5 with a view to attaining the national exposure reduction target laid down in Section B of Annex XIV. (Arts 13—16.)
An ‘alert threshold’ is a level beyond which there is a risk to human health from brief exposure for the population as a whole and at which immediate steps are to be taken by the Member States, whereas an ‘information threshold’ is a level beyond which there is a risk to human health from brief exposure for particularly sensitive sections of the population and for which immediate and appropriate information is necessary. If the specified information threshold or any of the alert thresholds are exceeded, the Member State concerned must take the necessary steps to inform the public by means of radio, television, newspapers, or the Internet. (Arts 2 and 19.)
Where an exceedance of a limit value for a given pollutant is attributable to natural sources it shall not be considered as an exceedance for the purposes of the Directive, provided that the Member State has provided the Commission with evidence demonstrating that the exceedance is attributable to natural sources (Art 20).
All necessary measures not entailing disproportionate costs are to be taken to ensure that the target values and long-term objectives for ozone are attained. In zones and agglomerations in which ozone levels meet the long-term objectives, Member States shall, in so far as factors including the transboundary nature of ozone pollution and meteorological conditions permit, maintain those levels below the long-term objectives. The best ambient air quality compatible with sustainable development and a high level of environmental and human health protection shall be preserved through proportionate measures. (Arts 17 and 18.)
The Directive does provide, under certain circumstances, for the postponement of attainment deadlines as well as for exemption from the obligation to apply certain limit values, but these provisions were mainly relevant during the first few years after the entry into force of the Directive (Art 22).
Where, in given zones or agglomerations, the levels of pollutants in ambient air exceed any limit value or target value, plus any relevant margin of tolerance in each case, Member States shall ensure that air quality plans are established for those zones and agglomerations in order to achieve the related limit value or target value. Those plans shall be communicated to the Commission without delay. (Art 23.)
Where, in a given zone or agglomeration, there is a risk that the levels of pollutants will exceed one or more of the alert thresholds specified in Annex XII, Member States shall draw up action plans indicating the measures to be taken in the short term in order to reduce the risk or duration of such an exceedance. Where this risk applies to limit values or target values, such short-term action plans may be drawn up where appropriate. Specific rules apply to ozone. The short-term action plans may, depending on the individual case, provide for effective measures to control and, where necessary, suspend activities which contribute to the risk of the respective limit values or target values or alert threshold being exceeded. (Art 24.)
The public, as well as appropriate organisations, such as environmental organisations, shall be informed, adequately and in good time, of ambient concentrations of the pollutants covered by the Directive and of air quality plans and programmes (Art 26).
Where any alert threshold, limit value, or target value plus any relevant margin of tolerance or long-term objective is exceeded due to significant transboundary transport of air pollutants or their precursors, the Member States concerned shall cooperate and, where appropriate, draw up joint activities, such as the preparation of joint or coordinated air quality plans (Art 25).
Directive 2004/107/EC relating to arsenic, cadmium, mercury, nickel, and polycyclic aromatic hydrocarbons in ambient air still remains as an independent directive but may in future be incorporated into Directive 2008/50/EC.10 It contains inter alia target values and rules on assessment of ambient air concentrations and deposition rates for the substances covered.
 OJ L 23/3.
In a number of cases the Court of Justice has established that the persons concerned must be in a position to rely on the mandatory rules included in the directives relating to air quality, designed as they are to protect public health, whenever the failure to observe the measures required by those directives could endanger human health.      In Janecek the Court found that where there is a risk that limit values or alert thresholds may be exceeded, persons directly concerned must be in a position to require the competent national authorities to draw up an action plan. This applies even if those persons have other courses of action available to them for requiring the authorities to take measures to combat atmospheric pollu- tion.12 Member States are not obliged to take measures to ensure that those limit values and/or alert thresholds are never exceeded. They are only obliged to take such measures—in the context of an action plan and in the short term—as are capable of reducing to a minimum the risk that the limit values or alert thresholds may be exceeded and of ensuring a gradual return to a level below those values or thresholds. In doing so they shall take account of the factual circumstances and all opposing interests.13
Although Janecek concerned interpretation of Directive 96/62, its continued relevance, mutatis mutandis, in relation to Article 23 of Directive 2008/50/EC has been confirmed by subsequent case lawd4
-  PM2.5 and PMj0 are defined in Art 2.
-  Case C-237/07 Janecek ECLI:EU:C:2008:447, para 38 and the case law cited there.
-  Ibid, para 42. 13 Ibid, paras 44—47.
-  14 Case C-404/13 ClientEarth ECLI:EU:C:2014:2382, para 57.
-  15 Ground- i evel ozone should not be confused with the stratospheric ozone layer. Ground- i evel
-  ozone is formed through chemical reactions involving oxides of NOx, CO, and VOC (ie ‘ozone precursors’) and sunlight.
-  COM(2005) 446 final (n 8) 5.