Supplemental Reports to Accomplishments of the Particulate Matter

This EPA Website document summarizes the progress made by the EPA PM Centers in identifying and understanding the health effects of PM air pollution since the mid-course report prepared in 2002 (Lippmann et al., 2003). When the PM Centers were designated in 1999, the primary body of evidence for health effects of PM consisted of epidemiologic studies of associations of short-term PM concentrations with daily mortality and long-term average PM with long-term mortality. In the first six years of the PM Centers program there was substantial work to understand and assess potential flaws and weaknesses in this body of evidence, and to develop an understanding of the mechanisms underlying these associations. In the more recent work, the PM Centers research has substantially expanded the range of clinical and preclinical health effects indicators associated with PM exposures. With respect to toxicological studies, both in experimental animals and in vitro, increasing efforts were devoted to using real-world particles and exposures (e.g., use of ambient PM concentrators) and mimicking human conditions of compromised organ functions in animals for evaluating PM effects. While interest has continued in measuring the respiratory effects of PM, much of the recent research has focused on identifying and understanding the cardiovascular health effects of PM 2.5 exposures. MORTALITY The Harvard Six Cities and the American Cancer Society Cancer Prevention II (ACS) prospective cohort studies provided some of the most important evidence to support the 1997 and 2006 PM 2.5 annual average NAAQS. Extended mortality follow-up of the ACS cohort for nine more years more than doubled the number of deaths observed. The extended ACS cohort follow-up verified that cardiopulmonary mortality was significantly associated with PM 2.5 , that excess annual mortality was not associated with larger particles, and that there was a significant association of PM 2.5 with lung cancer (Pope et al., 2002). The extended follow-up of the Harvard Six-Cities cohort for eight more years approximately doubled the number of deaths observed (Laden et al., 2006). PM 2.5 concentrations for the extended follow-up years were estimated from PM 10 and visibility measures. PM 2.5-mortality associations were observed for all-cause mortality equivalent to those found in the original analysis. However, PM 2.5 concentrations were substantially lower in the extended follow-up period than in the original analysis, especially for two of the most polluted cities. Reductions in PM 2.5 concentrations were associated with reduced mortality risk, and were largest in …