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.

URL: http://books.nap.edu/catalog.php?record_id=10957#description