Particulate matter, which is federally regulated, has raised concern recently because of numerous studies linking it to serious health problems. Fine particulate matter (called PM 2.5 because it is less than 2.5 microns in diameter or 30 times smaller than the diameter of a human hair) includes soot, dust, aerosols, metals and sulfates primarily emitted by vehicles and industrial sources. It contributes to the smog so common in American cities.

In the first of two "SuperSite" studies initiated by the U.S. Environmental Protection Agency (EPA), about 60 scientists from the Georgia Institute of Technology and other institutions have converged at an Atlanta air quality research facility owned by Georgia Power. They began measuring PM 2.5 around the clock at 7 a.m. Aug. 3 and will continue through 7 a.m. Sept. 1.

"We are trying to determine how to measure the concentration and composition of fine particulate matter in the atmosphere and the types of instruments best suited to do that," said Dr. William Chameides, a professor in the Georgia Tech School of Earth and Atmospheric Sciences and head of the SuperSite study. "We need to do this to understand the health effects and the sources, and to monitor compliance with EPA standards." Specifically, the research team expects to:

* evaluate emerging and/or state-of-the-science PM measurements. * compare and contrast similar and dissimilar PM measurements.

* evaluate the precision, accuracy and completeness of information that can be gained from the planned EPA network of Super Sites. * evaluate the scientific information gained by combining various independent and complementary PM measurements.

* address various scientific issues and their ozone- and PM-related policy implications with the database they are developing.

Chameides hopes to discover whether the production of ground-level ozone and PM 2.5 are chemically related. Both are secondary pollutants, meaning they are not directly emitted into the atmosphere, but are instead generated in the atmosphere by chemical reactions. "It's possible that controlling one pollutant without controlling the other might make one worse," Chameides said. "The trick is to fully understand how they interact so you can come up with a strategy to deal with both of them."

Chameides is spearheading the SuperSite study under the auspices of the ongoing Southern Oxidants Study (SOS), which involves about 20 universities and agencies. EPA is providing the primary funding for the Atlanta SuperSite study. Other funds are coming from the U.S. Department of Energy, Tennessee Valley Authority, and the National Oceanic and Atmospheric Administration.

Georgia Power and its parent, Southern Company, are providing the research facility and some equipment. The facility was already in use for other SOS-affiliated studies funded in part by utility companies and other industry partners. They include research by the Southeastern Aerosol Research Characterization / Aerosol Research Inhalation Epidemiology Study (SEARCH/ARIES) and the Southern Center for the Integrated Study of Secondary Aerosols (SCISSAP).

In addition to Georgia Tech, other universities participating in the SuperSite study include: Harvard University, the University of Miami, the University of Delaware, the University of Minnesota, Texas Technological University, the University of California-Riverside, Rutgers University, Brigham Young University and the University of Alabama at Huntsville.

Researchers expect to gather again next March to analyze their data in preparation for a preliminary report to the EPA in June 2000. This report may recommend further study to investigate the link between PM and human health.

Then researchers expect to present results of the SuperSite study at the annual meeting of the American Geophysical Union in December 2000. A final report to the EPA will follow in February 2001.

Meanwhile, EPA's 1997 revised standard for PM 2.5 is being challenged in federal court by trucking associations and other industry groups. The new standard calls for an annual PM 2.5 average set at 15 micrograms per cubic meter and a 24-hour PM2.5 average of 65 micrograms per cubic meter.

The new standard was prompted by recent studies that associated both short- and long-term exposure to fine particles with serious health problems, particularly in children and the elderly. Health effects included premature death, and increased hospital admissions and emergency room visits; increased respiratory symptoms and disease; decreased lung function; and alterations in lung tissue and structure and in respiratory tract defense mechanisms.

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