Ethanthiol

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) of ethanethiol [75‐08‐1]. No new studies are available for ethanethiol itself. Therefore, the MAK value is derived by read‐across with the structurally similar methyl mercaptan for which the MAK value of 0.5 ml/m3 is based on slight behavioural changes at 2 ml/m3 in a 90‐day inhalation study in rats. The MAK value of 0.5 ml/m3 for ethanethiol is supported by a limited inhalation study with 3 volunteers, showing irritation and other symptoms after repeated exposure to ethanethiol in a concentration of 3.9 ml/m3, but not after 0.39 ml/m3. The behavioural changes in rats exposed to methyl mercaptan are presumably not neurotoxic effects but a result of the odour nuisance or the local irritation. Therefore, ethanethiol is classified in Peak Limitation Category I with an excursion factor of 1 by analogy with methyl mercaptan. There are no developmental toxicity studies and ethanethiol remains assigned to Pregnancy Risk Group D. According to skin absorption models, percutaneous absorption is expected to contribute significantly to systemic toxicity. Therefore, ethanethiol is designated with an “H”. There are no data on sensitization.