Transboundary pollution from hazardous substances, acid rain and ground level ozone from the European continent still cause effects in Norway. One of these effectsis theacidification of water courses, which results in damage to fish and other aquatic species. At its worst, a third of Norway was affected by acidification.Transboundary pollution in the form of hazardous substances can be found in every lake in Norway, even those that are remote.

In Norway, between 500 and 2000 people die prematurely every year because of air pollution. Children and the old are most vulnerable. In the largest towns, current knowledge indicates that particulate matter and nitrogen dioxide pose the most serious risks to health, and result in a higher frequency of various types of respiratory problems. Particulate matter can also cause cardiovascular disease and death. Air pollution can also affect the health of animals and plants.

Road traffic is the dominant local source of air pollution in Norway, especially due to the widespread use of studded tires during the winter months. A car with studded tyres produces up to 100 times more particulate matter than a car with regular tyres.

Wood-burning also makes a substantial contribution to the concentration levels of particulate matter in the winter months. On cold days in areas where there are large numbers of wood-burning stoves, this can be the dominant source of particulate matter.

• Read more about Norway's goals and indicators on local air quality

Other important sources are industrial emissions and long-range transport of pollution from other European countries. As shown in the three figures below, long- range transboundary pollution is still a major pressure in the Norwegian environment as the domestic emissions only contributes to a smaller part of the deposition.

The Norwegian emissions of NMVOC and acidifying substances are on the decline, and emissions of NMVOC, SO2 and NH3 are now on target according to the UN Convention of Long Range Transboundary Air Pollution.

• Read more about Norway's goals and indicators on long-range air pollution

The national target for PM10, and to some extent the national target for NO2, will not be attained in 2010. Projections for 2020 show that the number of people exposed to exceedances of the national target for PM10 will be substantially reduced, primarily due to a decrease in the use of studded tyres and better technology, and increased introduction of clean burning wood-stoves.

Despite approved emissions reductions targets under several regulations such as the Convention on Long-Range Transboundary Air Pollution, acidification will continue to be a problem in large areas of South Norway, particularly in the southern and western parts. Even with a maximum feasible reduction scenario, the problems will persist until 2100 and beyond.

It is uncertain how the trend in ozone concentrations will change in the future. New methods for assessing ozone damage to vegetation (flux-based approach) indicate that even southern parts of Norway may experience more damage than previously assumed.

• Read more about ground-level ozone in Norway

Statutory limit values for particulate matter, nitrogen dioxide, sulphur dioxide, benzene, carbon monoxide and lead based on EUs directives on ambient air quality, are set out in the Norwegian Regulations relating to pollution control.

National targets for air quality have also been introduced for several pollutants. These are based on socio-economic considerations as well as considerations of public health, and are to be achieved by 2005 or 2010.

A regulation from 1997 introduced emission limits for PM10 for wood-burning stoves sold in Norway.

Measures to reduce emissions from road traffic are important responses and are divided into two categories: those designed to reduce the volume of traffic and those designed to reduce emissions.