Scientific Basis for the VOC Reactivity Issues Raised by Section 183(e) of the Clean Air Act Amendments of 1990

Abstract

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 (CCF), and methods for developing control strategies for such emissions that take into account emissions reactivities. Existing reactivity data consist of Incremental Reactivity data and KOH-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 measurement 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".

An Alternative Approach to Photochemical Ozone Creation Potentials Applied under European Conditions

“…Even though this rate is of great importance, since it opens the VOC for further reactions in the atmosphere, it does not solely determine the amount of O 3 being produced from a certain VOC. 15,16 Lifetimes calculated from k OH are shown in Table A1 for the 83 VOCs under study in this article.…”

Reactivity-Based VOC Control for Solvent Products: More Efficient Ozone Reduction Strategies

“…The products of that initial reaction are available to react again, and those secondary reaction products react yet again, and so forth, until nonreactive products are produced, terminating the reaction series. Thus, while k OH may be useful to obtain an estimate of the relative reactivity of a compound, a more robust method is needed to determine the overall effect of a VOC on atmospheric ozone, which depends, as we saw in the previous section, on many variables including atmospheric conditions and the presence of other reactants (18).…”

“…At this writing, the EPA has promulgated national regulations for three categories: Architectural and Industrial Maintenance Coatings, Consumer Products, and Automobile Refinish Coatings (28). Interested readers are referred to an excellent discussion by Dimitriades of the scientific issues surrounding this seemingly straightforward mandate (18).…”

“…Compounds may be added to the exempt list in 40CFR51.100(s) if it can be demonstrated that their reactivity is equal to or less than that of ethane (18,27). There are several significant problems inherent in this system.…”

The Ozone Formation Potential of 1-Bromo-Propane

“…The EPA definition of reactivity is based on an "ethane k OH bright line" criterion, where an individual VOC can be declared nonreactive if it can be shown to have an ozone-forming potential equal to or less than that of ethane. 6 All other VOCs are considered to be reactive and are, for regulatory control purposes, treated equally. In practice, the ozone-forming comparison to ethane has typically been based on the reaction rate constant (k OH ) for the OH radical reaction with the candidate VOC compared with the k OH for ethane.…”