Variations in long-term fine particulate matter air pollution associations with mortality by particle size, source, and composition

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SUMMARY Mortality associations with fine particulate matter (PM2.5) air pollution exposures have been well documented. However, the estimate as to how many deaths per unit mass are associated with PM2.5 exposure has varied widely across studies, adding to the uncertainty of generally applying these effect estimates to new situations for policy and health decision-making (e.g., to other cities or countries around the world). In this work, we will evaluate how these health impacts vary with PM2.5 mass source, size distribution, and composition in the large NIH-AARP “Diet and Health Study” cohort, comprising more than a half million older adults living in cities and states across the United States. Participants in this cohort have been well characterized by numerous individual characteristics (e.g., age, sex, race, presence or absence of diabetes, height, weight and smoking), as well as by residence census tract ecologic covariates (e.g., population and housing density, average income). The study participants have been followed since 1995-1996 for mortality, and cause of death has been ascertained. We will enhance the NIH-AARP cohort database by determining long-term participant PM2.5 mass source, composition, and size distribution (i.e., PM mass < 1.0 µm) exposures, and compare their respective associations with mortality. This will allow us to innovatively test the hypothesis that the PM2.5 mass –mortality effect estimates vary as a function of particle size, composition, and/or source characteristics, both overall and in potentially sensitive sub-populations, enabling a more informative assessment of excess mortality due to air pollution exposures. With this new insight, the PM2.5 health benefits can be optimized during mitigative public health and healthcare actions by considering PM2.5 source and composition, including to best protect the most vulnerable populations, and when evaluating the clean air health benefits of alternative energy source choices to address climate change.