The aim of this Directive is to define the basic principles of a common strategy in order to: (a) 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; (b) assess the ambient air quality in Member States on the basis of common methods and criteria; (c) obtain adequate information on ambient air quality and ensure that it is made available to the public; (d) maintain ambient air quality where it is good and improve it in other cases. For those pollutants listed in Annex I, the Commission shall submit to the Council proposals for the setting of limit values. In fixing the limit values account shall be taken of the factors laid down in Annex II. Once limit values and alert thresholds have been set, ambient air quality shall be assessed throughout the territory of the Member States, in accordance with the provisions laid down in article 6. Article 8 sets forth measures applicable in zones where levels are higher than the limit value. Article 11 concerns transmission of information and reports.