Dimethyl Sulfoxide

CAS RN:67-68-5

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that dimethyl sulfoxide is expected to have very high mobility in soil(SRC). Volatilization of dimethyl sulfoxide from moist soil surfaces is not expected to be an important fate process(SRC) given a Henry's Law constant of 1.03X10-8 atm-cu m/mole(3). Dimethyl sulfoxide is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure 0.60 mm Hg(4). The available biodegradation screening tests have conflicting results(5), but based on available data and weight-of-evidence approach, dimethyl sulfoxide is expected to be inherently biodegradable(6). For example, a 3.1% of theoretical BOD using activated sludge in a 2-week Japanese MITI test suggests that dimethyl sulfoxide is not readily biodegradable(7) while 90-99% biodegradation in other screening tests suggest that it is readily biodegradable(5,6).
AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 2(SRC), determined from a structure estimation method(2), indicates that dimethyl sulfoxide is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon a Henry's Law constant of 1.03X10-8 atm-cu m/mole(4). According to a classification scheme(5), BCF values of <4 measured in fish (Cyprinus carpio)(6) suggest the potential for bioconcentration in aquatic organisms is low. Dimethyl sulfoxide is stable to hydrolysis in water(7). The available biodegradation screening tests have conflicting results(8), but based on available data and weight-of-evidence approach, dimethyl sulfoxide is expected to be inherently biodegradable(7). For example, a 3.1% of theoretical BOD using activated sludge in a 2-week Japanese MITI test suggests that dimethyl sulfoxide is not readily biodegradable(6) while 90-99% biodegradation in other screening tests suggest that it is readily biodegradable(7,8).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), dimethyl sulfoxide, which has a vapor pressure of 0.60 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the atmosphere. Vapor-phase dimethyl sulfoxide is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 4.3 hours(SRC), calculated from its rate constant of 9.0X10-11 cu cm/molecule-sec at 25 deg C(3). Vapor-phase dimethyl sulfoxide is also degraded in the atmosphere by reaction with nitrate radicals which occur predominantly in night-time air(SRC); the half-life for this reaction in air is estimated to be 1.4 hours(SRC), calculated from its rate constant of 5.0X10-13 cu cm/molecule-sec at 25 deg C(3). Dimethyl sulfoxide does not absorb light at wavelengths >290 nm(4) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC). Dimethyl sulfoxide has been detected in rainwater(5) indicating that it may be removed from the air by wet deposition(SRC).
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