Empirically Distinguishing Health Impacts of Transboundary and Domestic Air Pollution in Mixture

Particulate matter (PM) is a major, clinically important air pollutant. A large portion of emitted PM crosses borders, damaging health outside of its originating jurisdiction, but due in part to technical obstacles these pollutant flows remain unregulated. Proposed attribution approaches assume that units of PM originating in different jurisdictions cause the same harm, despite a widespread understanding that differing chemical and physical features of PM could generate distinct health effects. We use an atmospheric model to decompose the origins of PM individuals are exposed to at each location in South Korea, the nexus of one of the world's most contentious transboundary air pollution disputes, every day during 2005–2016. We then link these data to universal healthcare records in an econometric analysis that simultaneously measures and accounts for harms from seven types of PM, each from a distinct origin. We discover that the health harm of a unit of transboundary PM is approximately 5× (North Korea) and 2.6× (China) greater than a unit of PM originating within South Korea, and that health responses to PM from natural sources differs from those to anthropogenic sources. Because harms differ by origin, we compute that transboundary sources contribute only 43% of anthropogenic PM exposure in South Korea but generate over 70% of its associated respiratory health costs. Our results suggest that PM should be treated as a mixture of distinct pollutants, each with a unique measurable impact on human health.