CAS RN:75-34-3

Exposure Summary

1,1-Dichloroethane's production and primary use as a feedstock for the production of 1,1,1-trichloroethane and minor uses as a solvent or in extractions may result in its release to the environment through various waste streams. 1,1-Dichloroethane may occur in the environment as a biodegradation product of 1,1,1-trichloroethane or other chlorinated compounds. If released to air, a vapor pressure of 227 mm Hg at 25 deg C indicates 1,1-dichloroethane will exist solely as a vapor in the ambient atmosphere. Vapor-phase 1,1-dichloroethane will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 59 days. 1,1-Dichloroethane does not contain chromophores that absorb at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, 1,1-dichloroethane is expected to have very high mobility based upon Koc values of 30 and 9.2. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 5.62X10-3 atm-cu m/mole. 1,1-Dichloroethane is expected to volatilize from dry soil surfaces based upon its vapor pressure. The half-life of 1,1-dichloroethane under sulfate-reducing conditions was approximately 115 days using well monitoring data from a landfill with a contamination history, indicating that biodegradation is a slow environmental fate process in soil and water. The biodegradation half-life of 1,1-dichloroethane under anaerobic conditions has been reported to be >30-60 days. If released into water, 1,1-dichloroethane is not expected to adsorb to suspended solids and sediment based upon the Koc. 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 hrs and 4 days, respectively. An estimated BCF of 5 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis is not expected to be an important environmental fate process given a hydrolysis half-life of 61.3 years at 25 deg C and pH 7. Occupational exposure to 1,1-dichloroethane may occur through inhalation and dermal contact with this compound at workplaces where 1,1-dichloroethane is produced or used. Monitoring data indicate that the general population may be exposed to 1,1-dichloroethane via inhalation of ambient air, ingestion of contaminated drinking water, and dermal contact with consumer products containing 1,1-dichloroethane. (SRC)
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