1,1-Dimethylhydrazine: MAK Value Documentation, addendum - Translation of the German version from 2021

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) has re-evaluated the occupational exposure limit value (maximum concentration at the workplace, MAK value) of 1,1-dimethylhydrazine [57-14-7] considering all toxicological end points. Relevant studies were identified from a literature search. The acute toxicity of 1,1-dimethylhydrazine is caused by depletion of gamma-aminobutyric acid leading to the effects on the central nervous system. After chronic and subchronic exposure, target organs were blood, liver, nervous system, colon and spleen in dogs and liver and colon in rats. In mice, the substance caused lesions in the nose, lungs and gall bladder. In carcinogenicity studies, inhaled 1,1-dimethylhydrazine lead to tumours in the lungs, pituitary gland and pancreas in rats and to thyroid carcinomas, haemangiosarcomas and Kupffer cell sarcomas in mice. Ultra-pure 1,1-dimethylhydrazine induced tumours in the lungs, liver, blood vessels and the nasal mucosa of mice. Orally applied, it caused tumours in the liver and pituitary gland of rats, in the blood vessels, lungs and kidneys of mice and in the blood vessels and colon of hamsters. Therefore 1,1-dimethylhydrazine remains classified in Carcinogen Category 2. No MAK value can be derived. The substance is clastogenic and mutagenic in bacteria and soma cells in vitro and clastogenic in several organs after exposure in vivo. On the basis of these effects and its ability to inhibit DNA synthesis in mouse testes after oral application, 1,1-dimethylhydrazine has been classified in Germ Cell Category 3 A. 1,1-Dimethylhydrazine is irritating to the skin of dogs, guinea pigs and rabbits and to the eyes of rabbits. Due to the low LD₅₀ values determined in animals after dermal application and potential genotoxic effects after dermal application, the "H" designation (for substances which can be taken up through the skin in toxicologically relevant amounts) has been retained. Although no studies considering the sensitizing potential are available, the designation with "Sh" (for substances which cause sensitization of the skin) has been retained due to its structural similarity to the known contact allergen hydrazine.