The EPA supported Particulate Matter (PM) Health Effects Research Center was established in 1999 as one of five new U.S. academic programs focused on the characterization of the biological basis for the effects of ambient air PM on excess mortality and morbidity. The NYU Center has the particular focus of identifying the specific PM components that have a disproportionate influence on health. The research in the NYU PM Center includes characterization of: 1) the components of ambient air PM; 2) the association between specific components and/or source-related mixtures and effects in human populations through panel and cohort studies and through epidemiological studies involving large data bases on daily mortality and hospital admissions and community air quality parameters; and 3) controlled exposure studies of groups of normal and "susceptible" laboratory animals to either concentrated ambient PM (CAPs) or specific PM components that may account for health effects.