The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the work place (MAK value) and the Pregnancy Risk Group of naled [300‐76‐5].
Naled is a cholinesterase inhibitor. In an 13‐week study in rats at 1 mg/m3 there was a 18% inhibition of the cholinesterase activity in erythrocytes. The calculated lower 95% confidence limit of the benchmark dose (BMDL) for a 30% inhibition, which is regarded as not adverse, was 2 mg/m3. A MAK value of 1 mg/m3 was established for the inhalable fraction. It is now lowered to 0.5 mg/m3 taking into account the increased respiratory volume at the workplace (see List of MAK and BAT Values, Sections I b and I c). Since a systemic effect is the critical effect, Peak Limitation Category II is retained and the default excursion factor of 2 confirmed.
For rats, the NOAEL for developmental toxicity was 8 mg/kg body weight and day. Naled was assigned to Pregnancy Risk Group C because the difference between the MAK value and the NOAEL scaled to a concentration in the workplace air was sufficient. There are no new data on developmental toxicity. This classification is retained since now the difference to the MAK value is twice as high.