The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated 3‐iodo‐2‐propynyl butylcarbamate (IPBC) to establish a maximum concentration at the workplace (MAK value), considering all toxicity endpoints. Available unpublished study reports and publications are described in detail.
IPBC is irritating to the eyes and respiratory tract and has a skin sensitizing potential. New data have substantiated the previous designation with “Sh”.
In a 5‐day aerosol inhalation study in rats, hyperplasia, squamous metaplasia and necrosis of the underlying cartilage of the larynx were observed at 1 mg/m3 and above. These effects were observed to an increased extent in the 13‐week study, in which the NOAEC was 0.23 mg/m3 and the LOAEC 0.3 mg/m3. Since the laryngeal irritation is the most sensitive endpoint, a MAK value of 0.1 mg/m3 (0.01 ml/m3) is established. IPBC has been attributed Peak Limitation Category I for local effects with an excursion factor of 2, since there was no direct sensory irritation but rather a tissue alteration and the NOAEC of the 5‐day study was 3 times the MAK value.
In rats IPBC caused no tumours in an oral 2‐year carcinogenicity study. Increased number of liver adenomas in male mice might have been caused by liver enzyme induction. Available studies in vitro and in vivo provided no evidence of a specific genotoxic effect. Therefore IPBC is not classified as carcinogen or germ cell mutagen.
In rats and mice, there was a sufficiently high difference between the oral NOAEL for developmental toxicity scaled to a concentration at the work place and the MAK value. Therefore IPBC is classified in Pregnancy Risk Group C.
Skin contact will not significantly contribute to the systemic toxicity of 3‐iodo‐2‐propynyl butylcarbamate.