On the 11th June 2008, the European Commission published a directive 2008/50/EC of the European Parliment and of the Council from 21 May 2008 on ambient air quality and cleaner air for Europe. 'Ambient air' shall mean outdoor air in the troposphere, excluding workplaces.

The Sixth Community Environment Action Programme establishes the need to reduce pollution to levels which minimise harmful effects on human health, paying particular attention to sensitive populations, and the environment as a whole, to improve the monitoring and assessment of air quality including the deposition of pollutants and to provide information to the public.

In order to protect human health and the environment as a whole, it is particularly important to combat emissions of pollutants at source and to identify and implement the most effective emission reduction measures at local, national and Community level. Therefore, emissions of harmful air pollutants should be avoided, prevented or reduced and appropriate objectives set for ambient air quality taking into account relevant World Health Organisation standards, guidelines and programmes.

This Directive lays down measures aimed at the following:

• 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.
• Assessing the ambient air quality in Member States on the basis of common methods and criteria.
• 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.
• Ensuring that such information on ambient air quality is made available to the public.
• Maintaining air quality where it is good and improving it in other cases.
• Promoting increased cooperation between the Member States in reducing air pollution.

Assessment of ambient air quality criteria:

• Member States shall assess ambient air quality with respect to the pollutants.
• In all zones and agglomerations where the level of pollutants exceeds the upper assessment threshold established for those pollutants.
• In all zones and agglomerations where the level of pollutants is below the upper assessment threshold established for those pollutants, a combination of fixed measurements and modelling techniques will be used.
• Modelling techniques or objective-estimation techniques or both shall be sufficient for the assessment of the ambient air quality.

Anual average basis and shall be conducted using the following criteria:

• One sampling point shall be installed every 100,000 km2.
• Each Member State shall set up at least one measuring station or may covering the relevant neighbouring zones to achieve the necessary spatial resolution.
• Where appropriate, monitoring shall be coordinated with the monitoring strategy and measurement programme of the Cooperative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP).