Valifenalate, a fungicide widely used in Europe, is currently under review for regulatory renewal by the EU. Recent studies on Beagle dogs and Wistar rats have observed mild thyroid effects, raising questions about its safety.
RSA in collaboration with KalyCell and ToxConsult contributed to this year’s Society of Toxicology (SOT) Annual Meeting (10-14 March 2024 in Salt Lake City, USA) with a poster about the mode of action of the pesticide active substance Valifenalate inducing mild thyroid effects in rats and dogs in vivo. Comparative in vitro assays in rat, dog and human hepatocytes showed marked species differences in the induction of liver enzymes, T4-UGT activity and T4 disappearance. These results, alongside with assays negative for inhibition of TPO, DIO and NIS activities, demonstrate that the mild thyroid effects observed for Valifenalate in rats and dogs in vivo occur via an indirect liver enzyme mediated mode of action which is not relevant to humans. This is another example amongst the majority of pesticides with thyroid effects that do not act directly on the thyroid but indirectly via liver enzyme induction.
View the Scientific Research Poster for this study.