| toxicity summary | IDENTIFICATION AND USE: 1,2-Dichloroethane is a colorless, oily liquid. It is used in production of vinyl chloride, trichloroethylene, vinylidene chloride, and trichloroethane. It is also used as lead scavenger in antiknock gasoline, paint, varnish, and finish removers, metal degreasing, soaps and scouring compounds, wetting and penetrating agents, ore flotation, and as a solvent. HUMAN STUDIES: Acute incidental exposure to 1,2-dichloroethane by inhalation or ingestion has resulted in a variety of effects in humans, including effects on the central nervous system, liver, kidney, lung and cardiovascular system. The respiratory effects exhibited by individuals who died following acute oral exposure to 1,2-dichloroethane included congestion, pulmonary edema and bronchitis. Ingestion of >/= 570 mg/kg/day of 1,2-dichloroethane resulted in severe hepatocellular damage and liver atrophy and necrosis. The potential carcinogenicity of 1,2-dichloroethane in exposed human populations has not been extensively investigated. It induced unscheduled DNA synthesis in primary cultures of human cells and gene mutation in several cell lines. Mutation frequency in human cell lines has been correlated with differences in glutathione-S-transferase activity. ANIMAL STUDIES: The acute toxicity of 1,2-dichloroethane is low in experimental animals. The results of short-term and subchronic studies in several species of experimental animals indicate that the liver and kidneys are the target organs. Morphological changes in the liver were observed in several species following subchronic exposure to airborne concentrations. Increases in the relative liver weight have been observed in rats following subchronic oral administration. The carcinogenicity of 1,2-dichloroethane has been investigated in a bioassays on experimental animals and significant increases were not reported in the incidence of any type of tumor in rats or mice exposed by by inhalation. There was a non-significant increase in the incidence of mammary gland adenomas and fibroadenomas in female rats exposed by inhalation. In contrast, there was convincing evidence of increases in tumor incidence in two species following ingestion. Significant increases in the incidence of tumors at several sites , hemangiosarcomas , fibromas of the subcutaneous tissue , adenocarcinomas and fibroadenomas of the mammary gland ) were observed in rats administered daily doses by gavage. Similar increases in the incidences of tumors at multiple sites , mammary gland adenocarcinomas and endometrial stromal polyp or endometrial stromal sarcoma combined and hepatocellular carcinomas ) occurred in mice administered daily doses by gavage. The incidence of lung tumors was significantly increased in female mice following repeated dermal application of 1,2-dichloroethane. Concomitant exposure to inhaled 1,2-dichloroethane and disulfiram in the diet resulted in an increased incidence of intrahepatic bile duct cholangiomas and cysts, subcutaneous fibromas, hepatic neoplastic nodules, interstitial cell tumors in the testes and mammary adenocarcinomas in rats, compared to rats administered either compound alone or untreated controls. No potential to initiate or promote tumor development was evident. In in vitro assays, 1,2-dichloroethane has been consistently positive in mutagenicity bioassays in Salmonella typhimurium. In cultured mammalian cells, 1,2-dichloroethane forms adducts with DNA. It also induces unscheduled DNA synthesis in primary cultures of rodent cells and gene mutation in several cell lines. There is no evidence that 1,2-dichloroethane is teratogenic in experimental animals. ECOTOXICITY STUDIES: In Chlorella pyrenoidosa the content of malondialdehyde increased with the increasing concentration of 1,2-dichloroethane. An increase in mutation frequency was reported in barley when kernels were treated for 24 hrs at 20 °C with 30.3 mM 1,2-dichloroethane.1,2-Dichloroethane is metabolized to 2-chloroacetaldehyde, S-glutathione by conjugation with glutathione, and to other putative reactive intermediates capable of binding covalently to cellular macromolecules in the liver, kidney, and other tissues. The conjugation of 1,2-dichloroethane with glutathione is catalyzed primarily by glutathione S-transferases. 1,2-Dichloroethane appears to be activated to mutagenic species to a lesser extent by the hepatic microsomal cytochrome P-450 enzyme system. Reactive metabolites of 1,2-dichloroethane produced by hepatic microsomal cytochrome P-450 can bind to cellular proteins and DNA. It has been suggested that 1,2-dichloroethane-induced toxicity occurs when the biotransformation processes are saturated, thereby allowing higher levels of 1,2-dichloroethane to circulate throughout the body and conjugate with glutathione instead of being detoxified and eliminated. |