Research Briefs

Tracking air pollution to and from the United States

Map of globe showing carbon monoxide transport.

This map shows the average carbon monoxide abundance in the free troposphere observed by NASA's MOPITT satellite instrument during an eight-day period in July 2004. Plumes of anthropogenic (human-made) carbon monoxide pollution are visible leaving Asia and crossing the Pacific Ocean, while plumes of pollution from forest fires in Alaska and Canada are shown drifting across North America and the Atlantic Ocean toward Europe. (Image courtesy David Edwards, NCAR.)

When it comes to global air pollution, what goes around comes around. Air pollution from factories, traffic, and power plants in Asia wafts over the Pacific Ocean to the United States, while pollutants produced in the United States wind up in Europe.

A report by the National Research Council of the National Academies released on September 29 takes a close look at how air pollution is transported to and from the United States, concluding that pollutants from foreign sources can significantly impact U.S. air quality and affect U.S. environmental goals. The work has implications for the Environmental Protection Agency's local air quality regulations.

"Pollution contributions from other continents affecting air quality in the United States are small but significant," says NCAR scientist David Edwards, a member of the NRC panel that issued the report. "As the EPA starts tightening regulations and lowering the pollution thresholds that urban areas must meet to comply with local air quality standards, foreign contributions will grow in importance."

The report, "Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants To and From the United States," is the first to examine four pollutant classes together: ozone, fine particulate matter, mercury, and persistent organic pollutants. It looks specifically at the impacts of long-range pollution transport on air quality, ground-level deposition and accumulation of pollutants, and the effects on radiative forcing (changes in the difference between the incoming and outgoing radiation energy) relevant to climate change.

The report recommends developing an "integrated pollutant attribution system" that would strengthen capabilities in emission inventories, atmospheric chemical and meteorological modeling, long-term ground-based observations, satellite remote sensing, and process-focused field studies.