THE APPLICATION OF EXPOSURE-BASED CRITERIA IN DEVELOPING ALTERNATIVE PRIMARY AMBIENT OZONE STANDARDS

The form of the primary National Ambient Air Quality Standard (NAAQS) for ozone has been a matter of some concern in recent years. The Envir onmental Protection Agency is reviewing the ozone NAAQS and has propos ed a set of alternative standards that address some deficiencies. Howe ver, the proposed alternatives are all based upon the ozone concentrat ions occurring at the peak monitor, which may riot be representative o f the air quality and population exposure throughout a nonattainment a rea. Representativeness could be improved by converting the form of th e standard from an exceedance-based metric (with x allowable exceedanc es per year, on average) to one based upon exposure. Three approaches to defining an exposure-based standard are developed here. Data from t he San Francisco Bay area are used to illustrate the proposed standard s.