||Efficacy of Ozone Exposure Indices in the Standard Setting Process.
Lee, E. H. ;
Hogsett, W. E. ;
Tingey., D. T. ;
||NSI Technology Services Corp., Corvallis, OR.;Corvallis Environmental Research Lab., OR.
Air pollution ;
Farm crops ;
Periodic variations ;
Air pollution effects(Plants) ;
Ozone exposure index ;
National Crop Loss Assessment Network program
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Determining the appropriate ozone exposure index for a secondary ambient air quality standard requires a consideration of the underlying biological basis for the response and a method of describing the temporal fluctuations in pollutant concentrations. An exposure index that adequately relates chronic pollutant exposure and the reduction in agricultural crop yield using a set of data for a specific year and site should give comparable proportional yield loss estimates for experiments replicated in time and/or space under similar environmental and edaphic conditions. This perspective is used to evaluate the adequacy of several indices of O3 exposure for use in describing the exposure-response relationships for the major agricultural crops studies by the U.S. Environmental Protection Agency's National Crop Loss Assessment Network (NCLAN) program and Pennsylvania State University (PSU). Although results indicate that no single exposure index is 'best' for all species, several general trends are indicated from studies replicated in time under similar environmental conditions but with varying exposure durations. Year-to-year differences in the magnitude of response were minimized by exposure indices that are cumulative and weight peak concentrations more than low concentrations. Because these indices may have potential for use in a standard setting process, the authors recommend that efforts to validate the results from the NCLAN and PSU studies focus on understanding the biological basis for the response through additional data sets and future field experiments on crops.