Isopropyl alcohol [MAK Value Documentation, 2018]

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) and the Pregnancy Risk Group of isopropyl alcohol [67‐63‐0]. In carcinogenicity studies no tumours were observed in rats and mice up to 5000 ml/m3. From the LOAEC in rats and mice of 2500 ml/m3 where narcotic effects were observed, a MAK value of 200 ml/m3 is derived also considering the increased respiratory volume at the workplace because the blood:air partition coefficient of isopropyl alcohol is > 5 (see List of MAK and BAT Values, Sections I b and I c). Therefore, the MAK value of 200 ml/m3 is confirmed. At this concentration, no irritation is expected in humans based on the limited data in humans and animals. Since a systemic effect is critical, Peak Limitation Category II is retained for isopropyl alcohol. Due to the half‐life of up to 2 hours in rats, the excursion factor of 2 is confirmed. In developmental toxicity studies, isopropyl alcohol does not result in teratogenicity but in fetotoxicity at maternally toxic doses in rats and rabbits. According to a PBPK model and considering the increased respiratory volume at the workplace, the NOAEL of 600 mg/kg body weight in rats is scaled to a concentration of 1000 ml/m3. There is no PBPK model for rabbits but due to the similar NOAEL for developmental toxicity in rabbits the same concentration is supposed. Because fetotoxicity was only observed at maternally toxic doses, the difference of the NOAEC for fetotoxicity and the MAK value is sufficient so that isopropyl alcohol remains assigned to Pregnancy Risk Group C