Postapplication Formation of Pesticide Degradation Products in a Test House

Abstract

PP-29-060 Background/Aims: Human exposure to preexisting degradation products of pesticides is a concern when conducting dose reconstruction studies where metabolic products are used to estimate exposure. The purpose of this research was to determine whether there was significant formation and translocation of pesticide degradates in an unoccupied test house where pesticides had been recently applied. Methods: To conduct the study, propoxur, cis/trans permethrin, and cypermethrin were sprayed in a simulated crack and crevice application in 1 room of the test house. Fipronil was applied to the same surfaces via syringe. Floor surface samples (n = 47) were collected at 1, 2, 3, 7, 14, 21, 28, and 35 days postapplication using isopropanol wetted cotton wipes and a stainless steel template with a 929-cm2 wiping area. No samples were taken from surfaces that had received direct pesticide application. The wipes were analyzed to determine the concentrations of the parent pesticides and the following degradation products: 2-iso-propoxyphenol, cis/trans 3-(2,2-dichlorovinyl)-3-3-dimethyl-(1-cyclopropane) carboxylic acid (cis/trans DCCA), 3-phenoxybenzoic acid (3-PBA), fipronil sulfone, fipronil sulfide, and fipronil desulfinyl. Results: Excepting a single sample where fipronil was not found, the parent pesticides were present in all samples. In contrast, the propoxur metabolite 2-iso-propoxyphenol was not detected in any sample. Fipronil sulfide was present at low levels (5.5 ± 3.0 pg/cm2) in 44 samples, whereas fipronil sulfone and desulfinyl were not found. Trans-DCCA, cis-DCCA, and 3-PBA were present in low, but quantifiable amounts, in 42, 16, and 9 wipes, respectively. Although 2 of the degradates were present in most of the samples, their continuous low level occurrence throughout the study period did not indicate an association with the pesticide application performed in the study. Conclusion: The study results indicate that formation and translocation of these metabolites to other surfaces after a recent indoor pesticide application may not be a significant factor affecting dose reconstruction studies.