Impacts of intercontinental transport of aerosols on human mortality

Fine particulate matter (PM2.5) is associated with deleterious health impacts, including premature death from cardiopulmonary disease and lung cancer. Although the lifetime of tropospheric PM2.5 is roughly only a week, observations and modeling studies demonstrate that PM2.5 can be transported long distances, impacting air quality and health on regional or global scales. We estimate the mortality impacts of 20% primary PM and PM precursor emission reductions in four major world regions - North America, Europe, East Asia, and South Asia. We use surface concentrations simulated by an ensemble of global chemical transport models convened by the Task Force on Hemispheric Transport of Air Pollution and epidemiologically-derived concentration-response functions to calculate mortality impacts. We estimate that while >90% of avoided premature deaths resulting from these emission reductions occur within the source region, about 9,600 annual avoided deaths occur in other parts of the world. Reducing emissions in Europe avoids the most extra-regional premature deaths, due to large downwind populations in relatively close proximity. Compared with a previous study of 20% ozone precursor emission reductions, we find that the impacts of intercontinental ozone are greater than or equal to those of PM2.5 for most source-receptor pairs, due to the longer atmospheric lifetime and greater transport efficiency for ozone. However, impacts of intercontinental PM2.5 are greater for source-receptor pairs not separated by an ocean, due to the stronger relationship of PM2.5 with mortality. We examine the sensitivity of estimated premature deaths to the shape and magnitude of the concentration-response function, as well as the inter-model variation in simulated PM2.5 responses to emission reductions.