Is there anyplace where you can be assured that the air is clean?

Probably not.

Pollutants emitted from factories, traffic and cooking stoves half a world away could make the air you breathe in the United States more hazardous to your health, reports a committee of the National Academies.

For example, you might think that the air atop the towering Cascade Mountains in the Pacific Northwest was a sure bet to be unpolluted.  But scientists have a tracked a polluted air mass as it moved over eight days from East Asia to a mountaintop in central Oregon.

Plumes of harmful air pollutants containing ozone; dust, sulfates, soot or mercury  and persistent organic pollutants such as DDT. All can be transported across oceans and continents, according to the report issued today by National Research Council.

Pollutants –  tracked from Asia to the U.S. and from the U.S. to Europe — have a negative impact on air quality far from their original sources.

Charles Kolb, chair of the committee that wrote the report, said “Air pollution does not recognize national borders; the atmosphere connects distant regions of our planet.”

“Emissions within any one country can affect human and ecosystem health in countries far downwind,” he added.

While it is difficult to quantify these influences, in some cases the impacts are significant from regulatory and public health perspectives, the scientists reported.

Tracked with satellite observations, the researchers watched pollutants transported aloft across the Northern Hemisphere and deliver significant concentrations to downwind continents.

The health impacts vary by pollutant.

For ozone and particulate matter — which cause respiratory problems and other health effects — the main concern is direct inhalation.

Therefore, even small incremental increases in atmospheric concentrations of ozone and particulate matter can have negative impacts.

For mercury and persistent organic pollutants, the main health concern is their gradual accumulation on land and in watersheds, creating an increase in human exposure via the food chain.

The report was sponsored by the U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, NASA, and National Science Foundation and the National Academy of Sciences

Here is a link to a brief summary of the report.

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