A CRITICAL-REVIEW OF PM(10)-MORTALITY TIME-SERIES STUDIES

While the mortality effects of particulate matter (PM) have been obvio us during extreme historical pollution episodes (e.g., the London Fog of 1952), evaluating effects at more routine pollution levels has requ ired the use of complex statistical modeling approaches. This paper cr itically reviews available time-series studies on PM(10) mortality to provide a common basis for an evaluation of the PM(10)-mortality assoc iation. These PM(10) studies confirm that an acute pollution-mortality association can occur at routine ambient levels, and suggest that suc h effects extend below the present United States air quality standards , especially for susceptible subpopulations. Furthermore, these new PM (10) studies are consistent with the hypothesis noted in past studies that PM is a causal agent in the mortality impacts of air pollution. T he relative risks (RRs)for PM(10) mortality, however, were found to va ry across studies. Variation probably was caused by differences in PM( 10) composition and in the PM(10) averaging period employed in the ana lysis, as well as differences in whether other pollutants were conside red simultaneously in the mortality-PM(10) model. Overall, the RR esti mates derived from available PM(10)-total mortality studies suggest a 24-h average, 100 mu g/m(3) PM(10) acute exposure effect on the order of RR approximate to 1.05-1.10 in the general population. Higher PM(10 ) RRs were indicated for the elderly and for those with preexisting re spiratory conditions, both of which represent subpopulations who appea r to be especially at risk for the mortality implications of acute exp osures to air pollution. A key research question remaining involves a determination of the component or components of PM(10) (e.g., fine par ticles, sulfates, acid aerosols, or ultrafine particles) that are most important to the noted acute PM-mortality associations.