Geographic exposure modeling: A valuable extension of geographic information systems for use in environmental epidemiology

Geographic modeling of individual exposures using air pollution modeling te chniques can help in both the design of environmental epidemiologic studies and in the assignment of measures that delineate regions that receive the highest exposure in space and time. Geographic modeling can help in the int erpretation of environmental sampling data associated with airborne concent ration or deposition, and can act as a sophisticated interpolator for such data, allowing values to be assigned to locations between points where the data have actually been collected. Recent advances allow for quantification oi the uncertainty in a geographic model and the resulting impact on estim ates of association, variability, and study power. In this paper we present the terminology and methodology of geographic modeling, describe applicati ons to date in the field of epidemiology, and evaluate the potential of thi s relatively new tool.