Air pollution is a transboundary, multipollutant/multi-effect environmental problem. Although significant and welldirected efforts over more than two decades have led to a reduction in emissions, air pollution in Europe continues to pose risks and have adverse effects on human health and on natural and man-made environments.

There defines various important air pollution issues. These arise either from atmospheric deposition of pollutants or from direct exposure to ambient concentrations of pollutants i.e. from air quality.

Air pollution issues
Deposition of air pollutants
Ecosystem acidification and eutrophication: Emissions, atmospheric chemical reactions and subsequent deposition of nitrogen oxides (NOX) sulphur dioxide (SO2), and ammonia (NH3) are causing acidification of terrestrial and freshwater ecosystems. Eutrophication is a consequence of excess input of nitrogen nutrients (nitrogen oxides and ammonia), which disturbs the structure and function of ecosystems e.g. excessive algae blooming in surface waters.
Materials damage: Acidifying pollutants also cause deterioration of structures and monuments.

Air quality
Ground-level ozone is a strong photochemical oxidant which, in ambient air, can affect human health, and damage crops, vegetation and materials. Ozone is not emitted directly, but is formed in the lower atmosphere by reaction of volatile organic compounds and NOX in the presence of sunlight.

Exposure of particulate matter, measured as concentrations of PM10 or PM2.5 (particle diameter less than 10 and 2.5 μm respectively) in ambient air represents one of the largest human health risks from air pollution. Short-term inhalation of high concentrations may cause increased symptoms for asthmatics, respiratory symptoms, reduced lung capacity and even increased
death rates. Harmful compounds in particulate form can damage materials.
Airborne particles can be emitted directly to air (primary particles) or can be produced in the atmosphere from precursor gases (secondary particles) such as SO2, NOX and ammonia.

Sulphur dioxide (SO2) and nitrogen oxides (NOX - combinations of nitrogen monoxide, NO, and nitrogen dioxide, NO2) can have various adverse impacts on vegetation, human health, and materials.
Source: European environmental assessment report for 2003

Air emissions in cities of eastern Europe, the Caucasus and central Asia

Urban air quality in eastern Europe, the Caucasus and central Asia

Air Pollution in Russia