2022/12/18 by Hartwig, Andrea, MAK Commission
#1 #2 #2-Tetrachlorethan #2-Tetrachloroethane #Acetylene tetrachloride #Acetylentetrachlorid #Gefahrstoff #Hautresorption #Kanzerogenität #Leber #Luft #MAK value #MAK-Wert #Toxizität #Wirkungsmechanismus #air #carcinogenicity #hazardous substance #liver #maximale Arbeitsplatzkonzentration #maximum workplace concentration #mode of action #skin absorption #toxicity
paper · doi:10.34865/mb7934e7_4ad
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 carcinogenicity classification of 1,1,2,2-tetrachloroethane [79-34‑5]. Available publications and unpublished study reports are described in detail. The critical effect is liver toxicity in humans, rats and mice. Valid inhalation studies are not available. After oral application, 1,1,2,2-tetrachloroethane is a liver tumour promoter and induces neoplastic nodules and carcinomas in rats and mice. The NOAEL for carcinogenic effects in rats is 43 mg/kg body weight. 1,1,2,2-Tetrachloroethane is not genotoxic. The mechanism responsible for tumour development in the liver is most likely the formation of reactive metabolites, e.g. dichloroacetic acid and free radicals. As the primary mode of action is non-genotoxic, 1,1,2,2-tetrachloroethane is classified in Carcinogen Category 4. After 14-week oral application, the NOAELs for liver effects are 20 and 80 mg/kg body weight for rats and male mice, respectively. Based on the NOAEL of 20 mg/kg body weight, a MAK value of 2 ml/m3 is derived. Irritation is not expected to occur at this concentration because 10-minute exposure of volunteers to 13 ml/m3 did not induce local effects. As the critical effect of 1,1,2,2-tetrachloroethane is systemic and its half-life is not known, the assignment to Peak Limitation Category II and the excursion factor of 2 are retained. 1,1,2,2-Tetrachloroethane remains classified in Pregnancy Risk Group D because sufficient data for developmental toxicity are not available. 1,1,2,2-Tetrachloroethane can be absorbed via the skin in toxicologically relevant amounts and remains designated with “H”. A sensitizing potential is not expected from the data available.