This research will continue our investigation of the effects of acid aerosol air pollution exposures on human health. Numerous site-years of ambient air acid aerosol, co-pollutant, and meteorological data have now become available for a variety of communities throughout North America as a result of the recent performance of the NYU and Harvard University air pollution exposure/health effects assessment studies. The overall objective of this continuing research will, therefore, be to employ the new knowledge we have gained regarding the nature and occurrence of acid aerosols in the environment in order to conduct a wider range of retrospective epidemiologic assessments of the impacts of acid aerosol exposures on human health. We propose to conduct this research in two phases: 1) the establishment of empirical methods for the retrospective estimation of population exposures to acid aerosols; and 2) the application of these exposure assessment methods to existing large scale epidemiologic data bases. We will use the newly available acid aerosol exposure data to establish generalizable methods and models for estimating past population acid aerosol exposures. This will then allow the merging of modeled acid aerosol exposures with already existing large, quality-assured health outcome data sets for a wide range of retrospective epidemiological investigations into the potential human health effects of acid aerosols. These data bases will include the nationwide cross-sectional records for spirometry from NHANES II, for morbidity from the HIS, and for mortality rates from the U.S. Census, as well as the 1974-1983 Ontario, Canada hospital admissions data compiled by Bates and Sizto. These statistical investigations into the various possible health effects of acid aerosols will address confounding environmental factors and potential contributions by and/or interactions with other air pollutants. Thus, in addition to expanding the methods available for retrospective human exposure assessment, this research will broaden the scope of both locations and health outcomes for which the effects of acid aerosols can be assessed.