Chlorobenzene [MAK value documentation, 2018]

Abstract The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated chlorobenzene [ 108‐90‐7 ] to derive a maximum concentration at the workplace (MAK value), considering all toxicity endpoints. Adverse effects are a depression of the central nervous system in humans and histological alterations in liver and kidney in rats. A 2 generation reproduction study with chlorobenzene vapour in Sprague‐Dawley rats resulted in a NOAEC of 50 ml/m 3 . Based on this NOAEC, a MAK value of 5 ml/m 3 is derived. This value is supported by a study with healthy volunteers at rest, who showed no neurotoxic or chemosensory effects at a NAEC of 5.9 ml/m 3 , which takes the increased respiratory volume at the work place into account. As systemic effects are critical, the substance remains assigned to Peak Limitation Category II and the excursion factor of 2 is confirmed. Chlorobenzene caused a statistically significantly increased incidence of neoplastic nodules in the liver of male F344 rats in a carcinogenicity study at the highest dose of 120 mg/kg body weight and day. As chlorobenzene is genotoxic only at high doses given intraperitoneally, and female rats and mice did not show any tumours in this study, it remains regarded neither as a carcinogen nor as a germ cell mutagen. From a synopsis of all data, the classification of chlorobenzene in Pregnancy Risk Group C is maintained. Chlorobenzene did not lead to contact sensitization in mice and guinea pigs.