Variability in Ozone Metrics with Emission Reductions and Its Application in Health Impact Assessment

Abstract

With advancing evidence of long-term health risks of ozone exposure, cumulative exposures are of interest for air quality regulation. The current form of the ozone air quality standard in the United States pertains to an extreme value (the design value) of the ozone distribution. Using atmospheric chemical transport modeling, we examine how well attainment metrics correlate with average exposure levels. We use forward sensitivity analysis to contrast the responses of two types of ozone metrics to widespread emission reductions. One such metric is based on extreme values of the ozone distribution used for attainment designation, while the other is the seasonal average ozone concentration indicative of long-term exposure levels. We find that in locations that have high day-to-day variability in ozone concentrations, design values are more sensitive to emission reductions and are least indicative of changing exposure levels with emission reductions.