1,1-Dichloroethane

Abstract

The presence of 1,1-dichloroethane in the environment is mainly related to its production, storage, consumption, transport, and disposal when it is used as a chemical intermediate, solvent, finish remover, and degreaser. 1,1-Dichloroethane is a colorless, oily liquid with a chloroform-like odor and flammable properties. Its odor threshold in air is 486 or 810mg/m3. 1-1-DCE is a hazardous waste site chemical; therefore (in USEPA's National Priorities List), and the greatest source of exposure is via inhalation of the compound through contaminated air, especially closer to source areas (production areas in occupational setting). Other sources of exposure are from eating contaminated food, skin contact, or drinking contaminated water. 1-1-DCE affects the function of the central nervous system (CNS) and was used as an anesthetic in the past but is currently used as an intermediate in chemical synthesis. Acute inhalation exposure to high levels forms ethylidene dichloride in humans which results in CNS depression and a cardio-stimulation resulting in arrhythmias. Animal studies have shown its nephrotoxic effects, and metabolites excreted via exhalation or in the urine. 1-1-DCE reaches the environment when 1,1,1-trichloroethane is biodegraded or when it is vaporized from surface waters and soils. A few animal studies have examined the toxicity and carcinogenicity of 1-1-DCE but have failed to conclusively identify the critical targets of toxicity. Effects of 1-1-DCE are limited to renal toxicity in cats, maternal and fetal toxicity in rats, and alterations in body weight gain. A positive dose-related trend was observed for the incidence of hemangiosarcomas and mammary adenocarcinomas in female rats, hepatocellular carcinomas in male mice, and endometrial stromal polyps in female mice. Two states (California and New Jersey) have set standards for drinking water: 5 and 50μgl−1, respectively. 1,1-DCE is classified as a possible human carcinogen (Category C) based on no human data and limited evidence of carcinogenicity in two animal species (rats and mice).