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Hydroxy-fipronil is a new urinary biomarker of exposure to fipronil
Citation:
Vasylieva, N., B. Bamych, D. Wan, E. El-Sheikh, H. Nguyen, H. Wulff, R. McMahen, M. Strynar, S. Gee, AND B. Hammock. Hydroxy-fipronil is a new urinary biomarker of exposure to fipronil. ENVIRONMENTAL INTERNATIONAL. Pergamon Press Ltd., New York, NY, 103:91-98, (2017).
Impact/Purpose:
Fipronil is a broad spectrum insecticide from the phenylpyrazole family. It is often used in four major domains: pest control in a wide variety of field crops, urban pest management, veterinary applications (especially in topical pet care products), and to control rice water weevil in crawfish rice ponds (2011; Simon-Delso et al. 2015; Watts 2012). Fipronil is a neurotoxic compound acting on invertebrate GABA-gated chloride channels in the central nervous system and thus has found a wide application mainly because the target insects have not developed resistance to the pesticide. Fipronil is also relatively persistent in the environment providing long-term protection, with half-life (t1/2) over 100 days in certain conditions (Gunasekara et al. 2007). A recent report by the U.S. Environmental Protection Agency (EPA) indicated a significant increase in the amount of fipronil used between 1998 and 2008 (Simon-Delso et al. 2015).
Description:
Occupational medical surveillance is highly desirable in manufacturing facilities where exposure to chemicals is significant. The insecticide fipronil is generally considered safe for humans but with increasing use, exposure to fipronil is of concern. Identification of urinary metabolites of fipronil may allow development of affordable, cheap and rapid procedures for human exposure evaluation. In this study we developed a fast and easy approach for synthesis of hydroxy-fipronil, a potential urinary metabolite of fipronil. This standard was used to develop a sensitive analytical LC-MS/MS method with a limit of quantification (LOQ) of 0.4 ng/mL. Fipronil sulfone, a known metabolite, and hydroxy-fipronil were quantified in urine samples from rats treated with a fipronil containing diet. Fipronil sulfone concentration centered around 20 ng/mL, while the concentration of hydroxy-fipronil was dose-dependent ranging in 10–10,000 ng/mL and thus being a more sensitive marker of fipronil exposure. A fipronil immunoassay with cross-reactivity to hydroxy-fipronil showed a good correlation in signal intensity with LC-MS data. It was also used to demonstrate the applicability of the method for sample screening in the evaluation of exposure levels.
