Washington, September 30 : A new study has determined that plumes of harmful air pollutants can be transported across oceans and continents and have a negative impact on air quality far from their original sources.

The study was done by researchers from the National Research Council, US.

Although degraded air quality is nearly always dominated by local emissions, the influence of non-domestic pollution sources may grow as emissions from developing countries increase and become relatively more important as a result of tightening environmental protection standards in industrialized countries.

“Air pollution does not recognize national borders; the atmosphere connects distant regions of our planet,” said Charles Kolb, chair of the committee that wrote the report and president and chief executive officer of Aerodyne Research Inc.

“Emissions within any one country can affect human and ecosystem health in countries far downwind. While it is difficult to quantify these influences, in some cases the impacts are significant from regulatory and public health perspectives,” he added.

The report examines four types of air pollutants: ozone; particulate matter such as dust, sulfates, or soot; mercury; and persistent organic pollutants such as DDT.

The committee found evidence, including satellite observations, that these four types of pollutants can be transported aloft across the Northern Hemisphere, delivering significant concentrations to downwind continents.

Ultimately, most pollutants’ impacts depend on how they filter down to the surface.

The health impacts of long-range transport vary by pollutant. For ozone and particulate matter -- which cause respiratory problems and other health effects -- the main concern is direct inhalation.

While the amount of ozone and particulate matter transported on international scales is generally quite small compared with domestic sources, neither of these pollutants has a known “threshold,” or concentration below which exposure poses no risk for health impacts.

Therefore, even small incremental increases in atmospheric concentrations can have negative impacts, according to the committee.

For instance, modeling studies have estimated that about 500 premature cardiopulmonary deaths could be avoided annually in North America by reducing ozone precursor emissions by 20 percent in the other major industrial regions of the Northern Hemisphere.

To enhance understanding of long-range transport of pollution and its impacts, the committee recommended a variety of research initiatives, such as advancing “fingerprinting” techniques to better identify source-specific pollutant characteristics, and examining how emissions from ships and aircraft affect atmospheric composition and complicate the detection of pollution from land-based sources. (ANI)