Azinphos‐methyl

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated azinphos‐methyl [86‐50‐0] considering all toxicological endpoints. Available publications and unpublished study reports are described in detail. In human studies, the critical effect of acetylcholinesterase (AChE) inhibition was not observed up to 0.25 or 0.29 mg/kg body weight and day in men after oral application up to 28 days. The NOAELs (no observed adverse effect levels) from studies with rodents or dogs are in the same range. Based on these valid data, the MAK value is increased to 1 mg/m3 for the inhalable fraction. Since a systemic effect is critical, Peak Limitation Category II is retained. As AChE inhibition is almost irreversible with a half‐life of 30 hours and a steady‐state is reached after 2 weeks, the excursion factor of 8 is confirmed. There is no adequate margin between the NOAELs for developmental and perinatal toxicity in rats and mice and the MAK value. Therefore, azinphos‐methyl is assigned to Pregnancy Risk Group B. Starting from the lowest calculated air concentration of 1.18 mg/m3 as the NAEC for perinatal toxicity and taking into account the absence of teratogenic effects in all studies, damage to the embryo or foetus is unlikely at concentrations of 0.1 mg/m3 and below. Exposure to this or lower concentrations would be the prerequisite for an assignment to Pregnancy Risk Group C. Azinphos‐methyl is neither genotoxic nor carcinogenic. Skin contact is expected to contribute significantly to systemic toxicity and azinphos‐methyl remains designated with “H”. Azinphos‐methyl has been shown to be skin sensitizing in the guinea pig. The substance is therefore labelled with “Sh”. Biomonitoring is recommended in addition to personal protective measures. A reduction of the erythrocytic AChE activity to 70% of the reference value (biological tolerance value for AChE inhibitors) must not be exceeded.