67 Fipronil In Vitro Metabolism Revisited: Microsomal Incubations, Electrochemistry, and Their Relevance to Human Biomonitoring

Abstract

Abstract Fipronil is a phenylpyrazole insecticide widely used in indoor pest control and treatment of flea and tick infestations in household pets. Its applications may act as a source of exposure and cause negative health effects to humans and environment. Biomonitoring is a crucial tool for assessment of actual chemical exposure. However, this approach requires a biomarker which reflects exposure to parent compound and, preferably, can be detected in urine. Despite the fact a few studies on metabolism and biomonitoring of fipronil were published, there is no consensus on optimal biomarker of fipronil exposure in humans. In this work we attempt to address this issue by investigating the metabolism of fipronil and its selected biotransformation products using microsomal incubations and a purely instrumental approach utilizing thin-layer electrochemical cell equipped with a glassy carbon or boron-doped diamond working electrode. Liquid chromatography-tandem mass spectrometry experiments were conducted to elucidate the structure of generated metabolites. Moreover, samples from humans probably exposed to fipronil were analyzed as well. A comparison of products obtained using the two aforementioned in vitro approaches was drawn and relevance to in vivo results was discussed. The results presented here shed light on complexity of fipronil metabolism and highlight the possibilities associated with electrochemical studies. However, a large-scale human biomonitoring study is needed to confirm the results obtained in our work.