cis-1,2-Dichloroethylene

IDENTIFICATION AND USE: cis-1,2-Dichloroethylene is a colorless liquid. The cis-isomer of 1,2-dichloroethylene has had only limited use as a solvent and chemical intermediate. It has not developed wide industrial usage in the US partly because of its flammability. HUMAN STUDIES: There are no data available. ANIMAL STUDIES: cis-1,2-Dichloroethylene at 16,000 ppm anesthetized rats in 8 minutes and killed them in 4 hours. The results of repeated exposures of cats and rabbits to vapor concentration of 0.16 to 0.19% in the air was reported. Animals exposed to cis-1,2-dichloroethylene at this concentration showed loss of appetite and some respiratory irritation but no histological changes. cis-1,2-Dichloroethylene was administered daily by gavage to male and female rats at the following dose levels: 1.0, 3.0, 10.0 and 22.0 mmol/kg/day for 14 days. Doses gavaged during the 90-day subchronic study were 0.33, 1.00, 3.00 and 9.00 mmol/kg/day. There were no compound-related deaths or histopathological changes demonstrated. Significant increases in relative liver weights were seen after 14- and 90-days of treatment in both sexes. This study demonstrates some indication of toxicity at subacute and subchronic exposure levels as low as 0.33 mmol/kg/day. Implications of liver abnormalities were demonstrated at an exposure level of 1 mmol/kg/day while kidney abnormalities (relative weights) were demonstrated at an exposure level of 0.33 mmol/kg/day. 1,2-dichloroethylene cis and trans were tested for their ability to induce point mutation, mitotic gene conversion and mitotic recombination in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in a suspension test with and without a mammalian microsomal activation system. In this test both cis and trans isomers were toxic but not genetically active even with metabolic activation. The clastogenic potential of cis-1,2-dichloroethylene was examined using Chinese hamster cells in culture and showed no significant increase in the incidence of chromosome aberrations when used with and without metabolic activation. cis-1,2-Dichloroethylene bound to the active site of hepatic microsomal cytochrome P450 with production of a type-I difference spectrum and stimulated co-inhibitable hepatic microsomal NADPH oxidation.