SUBJECT: ESTIMATING PESTICIDE PRODUCT VOLATILE ORGANIC COMPOUND OZONE REACTIVITY. PART 1: SPECIATING TGA -BASED VOLATILE ORGANIC COMPUND EMISSIONS USING CONFIDENTIAL STATEMENTS

This memo describes a Confidential Statement of Formula (CSF)-based speciation/emission potential (EP) estimation procedure. EP refers the volatile fraction of a pesticide product under the conditions of the Department Pesticide Regulation’s (DPR’s) thermogravimetric analysis (TGA) method (Marty et al., 2010). EP is assumed to represent product volatilization under actual use conditions. Speciation refers to identification of the actual chemical species comprising the volatile fraction of a pesticide product. In this paper we document the EP estimation procedure and assess its accuracy by comparing product CSF estimated-EPs to measured-EPs. The volatile components of 134 nonfumigant products reported as used in the 1990 and/or 2007 San Joaquin Valley (SJV) ozone season pesticide volatile organic chemical (VOC) inventory were identified using product CSFs and an empirical vapor pressure (VP) cutoff. The total percentage of estimated volatiles in each product was then compared to TGA-measured EPs. The VP25C cutoff (vapor pressure at 25C) that yielded the best agreement between estimated and measured EPs was approximately 0.05 Pa. Components with VP25C > 0.05 Pa were classified as volatile, while those with VP25C < 0.05 were classified as nonvolatile. A paired t-test demonstrated a small but significant bias in estimated EPs relative to measured values. The mean difference between measured and estimated EPs (TGA-measured EP CSF-estimated EP) was +1.4% (p=0.003), the measured TGA EPs being greater. This difference was attributable to inadequate or inaccurate product composition information in most cases. For some products, composition data for the concentrated manufacturing use products (MUP) used to formulate end use products (EUP) was not available. The net effect was a low bias in CSF-estimated EPs because unidentified volatile components in the MUP