Magnitude, trends, and impacts of ambient long-term ozone exposure in the United States from 2000 to 2015

Seltzer, Karl M.; Shindell, Drew T.; Kasibhatla, Prasad; Malley, Christopher S.

Long-term exposure to ambient ozone (inline-formulaO3) is associated with a variety of impacts, including adverse human-health effects and reduced yields in commercial crops. Ground-level inline-formulaO3 concentrations for assessments are typically predicted using chemical transport models; however such methods often feature biases that can influence impact estimates. Here, we develop and apply artificial neural networks to empirically model long-term inline-formulaO3 exposure over the continental United States from 2000 to 2015, and we generate a measurement-based assessment of impacts on human-health and crop yields. Notably, we found that two commonly used human-health averaging metrics, based on separate epidemiological studies, differ in their trends over the study period. The population-weighted, April–September average of the daily 1 h maximum concentration peaked in 2002 at 55.9 ppb and decreased by inline-formula0.43 [95 % CI: inline-formula0.28, inline-formula0.57] ppb yrinline-formula−1 between 2000 and 2015, yielding an inline-formula∼18 % decrease in normalized human-health impacts. In contrast, there was little change in the population-weighted, annual average of the maximum daily 8 h average concentration between 2000 and 2015, which resulted in a inline-formula∼5 % increase in normalized human-health impacts. In both cases, an aging population structure played a substantial role in modulating these trends. Trends of all agriculture-weighted crop-loss metrics indicated yield improvements, with reductions in the estimated national relative yield loss ranging from 1.7 % to 1.9 % for maize, 5.1 % to 7.1 % for soybeans, and 2.7 % for wheat. Overall, these results provide a measurement-based estimate of long-term inline-formulaO3 exposure over the United States, quantify the historical trends of such exposure, and illustrate how different conclusions regarding historical impacts can be made through the use of varying metrics.

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Seltzer, Karl M. / Shindell, Drew T. / Kasibhatla, Prasad / et al: Magnitude, trends, and impacts of ambient long-term ozone exposure in the United States from 2000 to 2015. 2020. Copernicus Publications.

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