ASSESSING THE HEALTH BENEFITS OF REDUCING PARTICULATE MATTER AIR-POLLUTION IN THE UNITED-STATES

Most Americans are exposed daily to airborne particulate matter (PM), a pollutant regulated by the U.S. Environmental Protection Agency, Cur rent national standards are set for PM10 (particles less than 10 mu m in diameter) and new standards have been promulgated for PM2.5 (partic les less than 2.5 mu m in diameter), Both particle sizes have been ass ociated with mortality and morbidity in studies in the United States a nd elsewhere and an unambiguously safe level of ambient PM has been di fficult to identify, PM10 concentrations have been reduced significant ly in U.S. cities over the past two decades and relatively few locatio ns continue to exceed national PM10 standards, However, the new PM2.5 standards will require further reductions in PM concentrations and add itional expenditures for emission controls, Information about the heal th and economic benefits of achieving lower PM concentrations is impor tant because: (1) expected costs of further PM reductions rise after t he least-cost options are exhausted, and (2) there is uncertainty abou t the existence of a threshold safe level for PM, This paper develops and applies a methodology for quantifying the health benefits of poten tial reductions in ambient PM, Although uncertainties exist about seve ral components of the methodology, the results indicate that the annua l nationwide health benefits of achieving the new standards for PM2.5 relative to 1994-1996 ambient concentrations are likely to be between $14 billion and $55 billion annually, with a mean estimate of $32 bill ion. (C) 1998 Academic Press.