Scientific basis for the VOC reactivity issues raised by Section 183(e) of the Clean Air Act Amendments of 1990

This article deals with reactivity and photochemical modeling methods needed to develop emission control strategies for ambient ozone reduction, and with the uncertainties associated with relevant data and methods. Specifically, the article identifies and describes existing reactivity data for volatile organic compound (VOC) emissions from consumer and commercial products (CCP), and methods for developing control strategies for such emissions that take into account emissions reactivities. Existing reactivity data consist of Incremental Reactivity data and K-OH-reactivity data. Both types of data are subject to uncertainties associated with lack of experimental evidence, which is particularly severe for CCP emissions species; theoretical derivation and/or experimental measure ment of reactivity; and variation of VOC reactivity with ambient conditions. Methods are described for using the reactivity concept to estimate the contribution of CCP emissions to ambient ozone. Also, to comply with one of the requirements of Section 183(e) of the 1990 Clean Air Act Amendments and with current U.S. Environmental Protection Agency policy on reactivity, existing reactivity data were used to classify VOCs into three reactivity classes: ''negligibly reactive'', ''reactive'', and ''highly reactive''.