1,4-Dioxane

CAS RN: 123-91-1

Exposure Summary

1,4-Dioxane's production and use as a solvent for cellulose acetate, ethyl cellulose, benzyl cellulose, resins, oils, waxes, spirit-soluble dyes, as well as for many other organic and some inorganic compounds; and its use as a stabilizer in chlorinated solvents may result in its release to the environment through various waste streams. If released to the atmosphere, a vapor pressure of 38.1 mm Hg at 25 deg C indicates that 1,4-dioxane will exist solely in the vapor phase. Vapor-phase 1,4-dioxane is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 33 hours. 1,4-Dioxane is a very weak absorber of UV light though results of aqueous photolysis studies suggest that direct photolysis is not an important environmental fate process. If released to soil, 1,4-dioxane is expected to have very high mobility based upon measured Koc values of 17 and 29. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 4.8X10-6 atm-cu m/mole. 1,4-Dioxane may volatilize from dry soil surfaces based upon its vapor pressure. Screening tests have found 1,4-dioxane resistant to biodegradation and slow to biodegrade. Using soil microcosms 1,4-dioxane was not biodegraded within 120 days and, therefore, considered recalcitrant. Acclimated soils have been shown to degrade 1,4-dioxane within 33 days. If released into water, 1,4-dioxane is not expected to adsorb to suspended solids and sediment based upon the Koc values. 1,4-Dioxane is considered non-biodegradable under conventional bio-treatment technologies based on results of wastewater treatment monitoring data. 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 7.3 and 56 days, respectively. Measured BCF values in the range of 0.2-0.7 suggest bioconcentration in aquatic organisms is low. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions. Occupational exposure to 1,4-dioxane may occur through inhalation and dermal contact with this compound at workplaces where 1,4-dioxane is produced or used. Monitoring data indicate that the general population may be exposed to 1,4-dioxane via inhalation of ambient air, ingestion of food and drinking water, and dermal contact with consumer products containing 1,4-dioxane. (SRC)
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