The general aim of this Directive is to define the basic principles of a common strategy to:
define and establish objectives for ambient air quality in the Community designed to avoid, prevent or reduce harmful effects on human health and the environment as a whole,
assess the ambient air quality in Member States on the basis of common methods and criteria,
obtain adequate information on ambient air quality and ensure that it is made available to the public, inter alia by means of alert thresholds,
maintain ambient air quality where it is good and improve it in other cases.