2,2′-Thiobis(4-methyl-6-tert-butylphenol)
MAK Value Documentation – Translation of the German version from 2022
Andrea Hartwig1 (Chair of the Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Deutsche Forschungsgemeinschaft)MAK Commission2
1 Institute of Applied Biosciences, Department of Food Chemistry and Toxicology, Karlsruhe Institute of Technology (KIT), Adenauerring 20a, Building 50.41, 76131 Karlsruhe, Germany
2 Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, Deutsche Forschungsgemeinschaft, Kennedyallee 40, 53175 Bonn, Germany
Abstract
The German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) summarized and evaluated the data for 2,2′-thiobis(4-methyl-6-tert-butylphenol) [90-66-4] to derive an occupational exposure limit value (maximum concentration at the workplace, MAK value), considering all toxicological end points. 2,2′-Thiobis(4-methyl-6-tert-butylphenol) is neither irritating to the human skin in vitro nor irritating to the eyes of rabbits. In a gavage study carried out according to OECD Test Guideline 422, the incidence and severity (minimal to slight) of follicular hypertrophy in the thyroid glands of male rats were increased at 150 mg/kg body weight and day and above. Additionally, slight changes in the colloid were observed at 500 mg/kg body weight and day. The Commission determined a NOAEL of 50 mg/kg body weight and day for this study. This dose has been scaled to a concentration of 10 mg/m3 I (inhalable fraction), a level of exposure protective against systemic effects. As 2,2′-thiobis(4-methyl-6-tert-butylphenol) is used diluted in metal-working fluids, the technically based limit value of 10 mg/m3 prevents toxicity if the dissolved solid is inhaled during this application. To prevent the induction of unspecific effects in the respiratory tract by the poorly soluble substance (< 8 μg/l water), the MAK value has been set at the level of the general dust limit value of 4 mg/m3 I. Peak limitation is regulated in accordance with Section V f) and g) of the List of MAK and BAT Values. A study with the substance was carried out according to OECD Test Guideline 422. As this study does not include a complete investigation of teratogenicity, 2,2′-thiobis(4-methyl-6-tert-butylphenol) has been assigned to Pregnancy Risk Group D. The substance is not genotoxic in vitro and there are no in vivo data. No carcinogenicity study has been performed. Skin contact is expected to make a relatively minor contribution to systemic toxicity. The available data show no evidence of sensitization.
