"The air must be clean enough not to represent a risk to human health or to animals, plants or cultural assets."
Inhaling air pollutants adversely affects health. For many people, pollution in the air around them can also reduce life expectancy. The pollutants that are most harmful to health are inhalable particles, groundlevel ozone and certain hydrocarbons.
Air pollution also causes corrosion, speeding the breakdown of materials such as metals, plastics and limestone. This can result in damage, for example, to buildings and cultural heritage. In addition, groundlevel ozone harms forest trees and farm crops.
High concentrations of air pollutants thus represent a large cost to society, in terms for instance of health care, reduced harvests and repairs.
Local emissions, from factories, vehicles, woodfired domestic heating and other sources, affect the air in the immediate vicinity. Certain pollutants however, such as sulphur dioxide and ground-level ozone, can be transported long distances across national borders.
What are the challenges?
A major source of air pollution, especially in urban areas, is road traffic. Vehicle exhausts contain particles, nitrogen dioxide and organic compounds, and promote the formation of ground-level ozone. Traffic also causes emissions of abrasion particles, loosened from road surfaces by studded tyres. Positive trends include increasingly efficient engines and new, environmentally less damaging fuels, but these developments are partly offset by constant growth in traffic. In many towns, air quality is also impaired by emissions of particles and organic compounds from the burning of wood.
To reduce emissions of pollutants that are carried long distances by winds, international cooperation is under way within both the EU and the UN. There is often uncertainty about what impact legislation and other policy instruments have in practice, which means that it may be several years before we can assess whether and how air quality has been affected.