1,1-Dichloroethylene

CAS RN:75-35-4

Exposure Summary

1,1-Dichloroethylene's production and use in polymers and organic synthesis and as an intermediate in the production of vinylidene polymer plastics, may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 600 mm Hg at 25 deg C indicates 1,1-dichloroethylene will exist solely as a vapor in the atmosphere. Vapor-phase 1,1-dichloroethylene will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl and nitrate radicals; the half-lives for these reactions in air are estimated to be 1.5 and 27 days, respectively. When adsorbed on silica gel, 1,1-dichloroethylene undergoes photolysis; approximately 72% of it degrades on exposure to 170 hours of sunlight. If released to soil, 1,1-dichloroethylene is expected to have high mobility based upon Koc values of 64-65. Volatilization from moist soil surfaces is expected based upon a Henry's Law constant of 0.0261 atm-cu m/mole. 1,1-Dichloroethylene may volatilize from dry soil surfaces based upon its vapor pressure. 1,1-Dichloroethylene had a biodegradation rate of 0.050 ug/g soil/hr in soil from Skellingsted landfill in Holback, Denmark, incubated with methane. Under simulated landfill anaerobic conditions, 1,1-dichloroethylene degraded in 1-3 weeks. If released into water, 1,1-dichloroethylene is not expected to adsorb to suspended solids and sediment based upon the Koc values. In anaerobic microcosms designed to simulate a groundwater environment, 50% of the 1,1-dichloroethylene disappeared in 5-6 months. However, 1,1-dichloroethylene had a biodegradation half-life of 1.25 years in ground water from a former manufacturing facility in New Jersey. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 3 hours and 4 days, respectively. BCFs of <13, measured in fish, suggest bioconcentration in aquatic organisms is low. A hydrolysis half-life of 6-9 months has been observed for 1,1-dichloroethylene at pH 4.5 to 8.5. Occupational exposure to 1,1-dichloroethylene may occur through inhalation and dermal contact with this compound at workplaces where 1,1-dichloroethylene is produced or used. Monitoring and use data indicate that the general population may be exposed to 1,1-dichloroethylene via inhalation of ambient air, ingestion of food and drinking water, and dermal contact with consumer products containing 1,1-dichloroethylene. (SRC)
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