Application of an Urban-Scale Population Exposure Model (NEM/SAI) to Ozone Exposure Assessment

Abstract

Despite aggressive control efforts over several decades, more than 90 U.S. cities did not attain federal clean air standards for ozone in 1988, up from less than 70 several years ago. The widespread nature of ozone nonattainment and increased recognition of the health risks posed by ozone is causing substantial public health concern. An important aspect of the ozone nonattainment problem is the extent of population exposure. While outdoor ozone measurements are often used to characterize such exposure, people typically spend more than 80 percent of the time indoors where ozone levels are lower than outdoors, often substantially so. This paper discusses a modeling technique that has been employed to estimate ozone population exposure, taking into account indoor-outdoor differences as well as population activity patterns, mobility, and exercise level. The NEM/SAI urban-scale population exposure model, which has been used extensively in ozone exposure and health risk analyses, is described. Two examples are presented in which NEM/SAI is used for a large U.S. urban area to estimate (a) historical 1- and 8-hour ozone exposures and (b) projected future-year ozone exposures under alternative ozone nonattainment plans.