UCLA

Limited research has been conducted on the contributions of local and nonlocal emission sources to ambient fine particulate matter (PM_2.5) and ozone (O₃) and their associated mortality. In this study, we estimated the total mortality resulting from long-term PM_2.5 and O₃ exposures in California in 2012 using multiple concentration response functions (CRFs) and attributed the estimated mortality to different emission groups. The point estimates of PM_2.5-associated mortality in California ranged from 12,700 to 26,700, of which 53% were attributable to in-state anthropogenic emissions. Based on new epidemiological evidence, we estimated that O₃ could be associated with up to 13,700 deaths from diseases of both the respiratory and cardiovascular systems in California. In addition, 75% of the ambient O₃ in California was due to distant emissions outside the western United States, leading to 92% of the O₃-associated mortality. Overall, distant emissions lead to greater mortality burdens of air pollution in California than local anthropogenic emissions.