Geneva, 26 June 2001 

"Contrary to received opinion, peaks of summertime smog are not caused by local polluters alone," says Kaj Bärlund, Environment Director at the United Nations Economic Commission for Europe (UNECE). "Whether air pollution levels in your area comply with air-quality standards or breach them may actually depend on how much pollution it receives from across the ocean."

Leading European and North American scientists have agreed that there is strong evidence for intercontinental movements of fine particles and ozone across the northern hemisphere between North America, Europe and Asia. They presented their findings at a recent conference on air pollution across the Atlantic and the Arctic, hosted by the United States Environmental Protection Agency (EPA) and Environment Canada within the framework of the UNECE Convention on Long-range Transboundary Air Pollution.

The new findings show that fine particles and ozone travel not only across borders but also across oceans. This implies that it may not be enough to take local measures such as clamping down on car use during pollution peaks to meet air-quality standards, since some of the pollution is emitted overseas.

Fine particles are emitted by many sources, including motor vehicles, particularly those that run on diesel, industry and other combustion sources. Some particles are small enough to penetrate the lungs. They are blamed for several health problems, such as increased risk of heart and lung disease. They can also carry carcinogenic substances and have been associated with premature deaths. Ground-level ozone, also known as summer smog and not to be confused with stratospheric ozone that forms the ozone layer, is a secondary pollutant caused by industrial and motor vehicle emissions and the use of certain products such as solvents and paints. It irritates the eyes and is known to damage lung function, particularly in children and asthmatics. It also causes leaf injury in plants, including crops and trees, and causes mainly organic materials like paint or rubber to disintegrate.

Movements of air pollutants within continents are already well understood. In Europe, work under the Convention has relied on so-called blame matrices, based on actual pollution-monitoring data and computer models, to quantify the movement of air pollutants from one country to another and to design cost-effective pollution-reduction strategies.

Modelling intercontinental flows of fine particles or ground-level ozone will be much more difficult. Yet, this is one of the challenges that scientists will have to take up, because quantifying the impact of intercontinental air pollution is a prerequisite for effective cooperation to curb it.

For more information, please contact:

Henning Wuester
UNECE Environment and Human Settlements Division
Palais des Nations, office 323
CH - 1211 Geneva 10, Switzerland

Phone: (+41 22) 917 23 63
Fax:    (+41 22) 907 06 21
E-mail: [email protected]

Ref:  ECE/ENV/01/03