Chronic inhalation toxicity and carcinogenicity studies of 3-chloro-2-methylpropene in BDF1 mice

Chronic toxicity and carcinogenicity studies of 3-chloro-2-methylpropene (CMP), which has been widely used as an insecticide and chemical intermediate, were carried out in BDF1 mice. CMP was administered to mice in groups of 50 male and 50 female mice by the inhalation route 5 days per week for 104 weeks at doses of 0, 50, 100 or 200 ppm. Male and female mice in the CMP-exposed groups had decreased body weight but no noticeable clinical signs when compared with the control group. Dose-related increases in the incidences of gastric mucosal hyperplasia and squamous cell papilloma were observed in both sexes, and squamous cell carcinoma was observed in only one male mouse in the 100 ppm group. An increased incidence of Harderian gland adenoma in female mice was also recognized. In the nasal cavity, eosinophilic exudate associated with atrophy of olfactory epithelia, respiratory metaplasia of olfactory epithelia and olfactory gland, and eosinophilic changes in respiratory and olfactory epithelia were increased in both sexes.