ATTAINMENT AND EFFECTS ISSUES REGARDING ALTERNATIVE SECONDARY OZONE AIR-QUALITY STANDARDS

The present secondary National Ambient Air Quality Standard (NAAQS) for O-3, established in 1979, is based on limited information from a few field studies on vegetation and may not be protective of crop damage due to O-3, alone or in combination with other pollutants. Considerable information from field studies conducted in the past decade indicate that there is poor functional correspondence between agricultural production and the air quality index of the current secondary NAAQS for O-3. Because the current O-3 NAAQS is based on data for extreme values of air quality, the index (or form) of the NAAQS ignores key features of hourly exposure data that are desirable and important to minimizing the risk of crop damage. Previous analyses of existing vegetation effects data indicate that exposure indices that cumulated the hourly O-3 concentrations over the season, as well as preferentially weighted the higher concentrations appear to have major advantages over the mean and peak indices on the basis of statistical fits to the data. The peak-weighted, cumulative indicators whose form and level are determined from crop studies were found useful in achieving a target production level that is higher than that of the current O-3 NAAQS indicator with fewer violations. These alternative air quality indicators compare favorably with the current O-3 NAAQS in terms of protection against adverse welfare effects and air quality properties to better identify areas having adequate air quality.