The Geographic Distribution of Future Ozone-Related Asthma Exacerbation Emergency Department Visits in the Us in a Warming Climate

Abstract

IntroductionAsthma affects >24 million children and adults in the United States (US). Daily fluctuations in ground level ozone are associated with higher rates of emergency department (ED) visits for asthma exacerbations. For a given level of anthropogenic emissions of ozone precursors, ozone levels are expected to increase by mid-century due to climate change, with a greater increase under a higher versus a lower climate change scenario. We aimed to quantify the magnitude and spatial distribution of asthma ED visits potentially averted mid-century under a mitigation (RCP4.5) versus a business as usual (RCP8.5) greenhouse gas emissions scenario. MethodsWe projected daily 8-hr maximum ozone levels across the contiguous US for 2036-2055 under two Representative Concentration Pathways (RCP4.5 and RCP8.5) using a 2040 emissions inventory and regional climate and chemical transport models. We then used BenMAP to estimate mid-century ozone-related asthma ED visits for all ages under each RCP, assuming constant population and no adaptation compared to the present. ResultsOzone levels are projected to be an average of 1.3 ppb lower across the US under RCP4.5 versus RCP8.5, with the largest differences projected for the Northern Plains, Midwest, and Northeast. Nationally, 2,809 fewer ozone-related ED visits per year mid-century (out of 91,431 total ozone-related ED visits under RCP8.5) are projected under RCP4.5 versus RCP8.5, all other factors held constant. The largest differences (greatest potential benefits under RCP4.5) in asthma-related ED visits are projected for the Northeast and Midwest regions, including Chicago, New York City, Cleveland, Detroit, and Philadelphia. ConclusionsThese results suggest that adhering to the lower greenhouse gas emissions described by RCP4.5 would lead to lower daily ozone levels and substantially fewer ED visits for asthma across the US, with potential health benefits considerably larger for some communities and individuals than others.