Geographies of risk in studies linking chronic air pollution exposure to health outcomes.

This article addresses the question of how to incorporate spatial processes into the assessment of chronic health effects from air pollution exposure. An analytic framework is developed around three related concepts: (1) the geography of susceptibility; (2) the geography of exposure; and (3) points of intersection between these two, termed the geography of risk. The article discusses how each concept encompasses many lower level issues such as meteorological dispersion of pollutants, time-space activity patterns, and population distributions of susceptible individuals in time and space. A key premise is that researchers should target studies with high degrees of overlap between geographies of exposure and susceptibility. Instances where the overlap remains incomplete, or systematically biased, usually produce attenuated or unreliable risk estimates, and some of this discordance may find expression in spatially autocorrelated residuals.