Potential developmental neurotoxicity of deltamethrin

Following a request from the Commission, the Panel on Plant Protection Products and their Residues (PPR) was asked to deliver a scientific opinion on the possible developmental neurotoxicity of deltamethrin. The potential developmental neurotoxicity of deltamethrin was addressed by the notifier in guideline-compliant reproductive and developmental toxicity studies in different animal species including a multi-generation study in rats and a separate developmental neurotoxicity (DNT) study in the rat, in accordance with the new OECD guideline TG426. The data available from the open literature include experimental studies carried out in rodents involving exposure during prenatal life and/or during neonatal life. These studies had several limitations and did not provide any clear evidence for a developmental neurotoxic effect of deltamethrin. The PPR Panel concluded that deltamethrin has been adequately tested for developmental neurotoxicity and that the available data do not indicate that deltamethrin is a developmental neurotoxic agent. The existing health-based guidance values for deltamethrin are based on neurological signs, as the most relevant critical effects observed in adult animals from different species. The lowest NOAEL of 1 mg/kg bw/day, used for risk assessment, was obtained in the 90-day and 1-year dog studies for which a 100-fold default safety factor (SF) was considered appropriate. No developmental neurotoxicity was observed at the highest dose tested of about 7 mg/kg bw/day in the DNT study complying with the new OECD guideline. This study provides a state-of-the-science evaluation of developmental neurotoxicity. The results of this study provide a margin of safety of more than 600. The PPR Panel concludes that the existing health-based guidance values provide adequate protection against any potential developmental neurotoxicity of deltamethrin that would, anyhow, occur only at doses causing severe systemic toxicity.