WASHINGTON -- Particulate matter research conducted by the U.S. Environmental Protection Agency and other scientists in recent years has led to a better understanding of the health effects caused by the tiny airborne particles, says a new report from the National Academies' National Research Council. However, the committee that wrote the report said that even as EPA implements strategies to control particulate matter in the near term, it should -- in concert with other agencies -- continue research in order to reduce uncertainties further and inform long-term decisions.
EPA should sponsor research to determine which chemical components and other characteristics of particulate matter are the most hazardous -- especially when mixed with other airborne pollutants -- and which population groups are the most susceptible, the report says. Research is also needed to better characterize and track particles from various emission sources. The government's continued support and enhancement of particulate matter research would "undoubtedly yield substantial benefits for years to come," the report concludes.
"Much has been learned in the last five years, and the evidence gained is already being used by decision-makers," said committee chair Jonathan Samet, professor and chair, department of epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore. "We need to continue to invest in developing an even greater understanding to take full advantage of the work already done, and to complete the foundation of evidence needed to protect public health. The emphasis now should shift from studying whether particulate matter causes adverse health effects to studying the dose at which those effects are likely to occur. We also need to know which aspects of particulate matter are most hazardous, and to learn how people are exposed to hazardous particles and how these particles trigger injury."
Particulate matter consists of diverse substances such as dust, smoke, soot, and other small particles emitted by cars and trucks, forest fires, electric power plants, and other sources. The report calls for a continued systematic approach to studying the large variety of possible relationships between particulate matter and health effects. A better understanding of the size and type of particulate matter being emitted by different sources is also needed, as are improved computer models to link pollution sources with concentrations of airborne particulate matter in specific areas. These improvements could lead to emission control strategies which target the particulate matter that presents the greatest threat to public health.
The report is the fourth and final one in a series requested by Congress to provide independent guidance to EPA's long-term particulate matter research program. Congress appropriated substantial funding for such research after EPA in 1997 tightened its standard for allowable concentrations of particulate matter. Under the Clean Air Act, EPA is required to review the scientific basis for the regulations every five years to determine if revisions are warranted. The agency's research effort has largely followed the first five years of a 13-year research agenda recommended by the committee in its first report.
By 1997, studies were already showing that inhaling particulate matter could exacerbate lung ailments, even causing premature death in some instances. New results confirm that outdoor measures of particulate matter are a good indicator for use in public health studies and that more particulate matter is deposited in the lungs of people with asthma or chronic obstructive pulmonary disease. Other findings show that a number of groups – such as seniors, and people with diabetes or heart disease -- may be particularly susceptible to the particles.
Researchers also should conduct a long-term study of the health effects of chronic exposure to particulate matter, the committee said. It also re-emphasized an earlier recommendation to include scientists from many disciplines in the overall research effort. In addition, the research program should move toward one that addresses multiple air pollutants, because real-world exposures involve complex mixtures of hundreds of air contaminants. EPA should continue to seek independent review of its particulate matter research program.
### The study was sponsored by EPA. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.
Copies of RESEARCH PRIORITIES FOR AIRBORNE PARTICULATE MATTER, IV: CONTINUING RESEARCH PROGRESS will be available later this spring from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at HTTP://WWW.NAP.EDU.
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