Chronic Inhalation Toxicity of Unsymmetrical Dimethylhydrazine: Oncogenic Effects

Four animal species were exposed for 6-months to selected vapor concentrations of propellant grade unsymmetrical dimethylhydrazine to determine its oncogenic effects. The UDMH concentrations at or near the current threshold limit value were 0.05, 0.5, and 5 ppm. Animals were maintained for various time periods postexposure as long as: hamsters, 17 months; mice and rats, 19 months; and dogs, 54 months. The lung was a target organ in rats while the liver was the main target of 5 ppm UDMH induced neoplastic changes in rats and mice. Rats had an increased incidence of bronchiolar adenomas compared to controls. Mice exposed to 5 ppm UDMH developed a 4.7% incidence of liver hemangiosarcomas while controls had a 0.7% incidence. Kupffer cell sarcomas were also increased in UDHM exposed mice. Originator supplied