Directive 2008/50/EC
"This Directive lays down measures aimed at the following:
1.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;
2.assessing the ambient air quality in Member States on the basis of common methods and criteria;
3.obtaining information on ambient air quality in order to help combat air pollution and nuisance and to monitor long-term trends and improvements resulting from national and Community measures;
4.ensuring that such information on ambient air quality is made available to the public;
5.maintaining air quality where it is good and improving it in other cases;
6.promoting increased cooperation between the Member States in reducing air pollution." (http://eur-lex.europa.eu/legal-content/en/TXT/?uri=CELEX%3A32008L0050)
Pollution limits are provided in the directive annexes.