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Abstract
Three groups of 100 Wistar rats and Syrian golden hamsters of each sex were exposed by inhalation to 0, 10, or 50 ppm (v/ v)-chloroprene for 6 h/day, 5 days a week for up to 24 and 18 mo, respectively. To maintain the chemical Integrity of this highly reactive material in the exposure chambers,-chloroprene vapor was generated from freshly distilled chloroprene (99.6% -chloroprene; 0.3% -chloroprene and <50 ppm chloroprene dimers) by passing nitrogen through liquid-chloroprene at 0 C. This mixture was then conducted through Teflon and stainless steel transport tubes into the main airflow for the chambers. After 72 wk on test a technical fault in chamber operation procedures resulted in the accidental death of 87 male and 73 female rats at 10 ppm unrelated tochloroprene. Otherwise, survival of the remaining 10 ppm rats and the rats exposed at 50 ppm was unaffected by exposure. Survival among both groups of hamsters exposed to-chloroprene was higher than the controls. All treated rats exhibited slight restlessness during exposure, but only during the first few weeks on test. At 50 ppm, rats also showed an increased incidence of alopecia, slight growth retardation, and an increased incidence of foci of altered liver cells, a change frequently seen in aged rats. Hamsters showed only a slight growth retardation and a slight reduction in amyloidosis at 50 ppm. No serious adverse effects were seen in either species at 10 ppm. Overall, there was no evidence of carcinogenicity related to-chloroprene exposure in either rats or hamsters at vapor concentrations as high as 50 ppm.