Ethylene Oxide

CAS RN:75-21-8

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), a Koc value of 2.2(2), indicates that ethylene oxide is expected to have very high mobility in soil(SRC). Volatilization of ethylene oxide from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 1.48X10-4 atm-cu m/mole(3). Ethylene oxide is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 1.31X10+3 mm Hg(4). Since ethylene oxide hydrolyzes to ethylene glycol which is readily biodegraded, the importance of biodegradation of ethylene oxide in the environment is not able to be accurately assessed(3).
AQUATIC FATE: Based on a classification scheme(1), a Koc value of 2.2(2), indicates that ethylene oxide is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon a Henry's Law constant of 1.48X10-4 atm-cu m/mole(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 6 hours and 4 days, respectively(SRC). According to a classification scheme(5), an estimated BCF of 3(SRC), from its log Kow of -0.30(6) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Since ethylene oxide hydrolyzes to ethylene glycol which is readily biodegraded, the importance of biodegradation of ethylene oxide in the environment is not able to be accurately assessed(4).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), ethylene oxide, which has a vapor pressure of 1.13X10+3 mm Hg at 25 deg C(2), is expected to exist solely as a gas in the ambient atmosphere. Gas-phase ethylene oxide 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 57 days(SRC), calculated from its rate constant of 7.6X10-14 cu cm/molecule-sec at 25 deg C(3). Ethylene oxide does not contain chromophores that absorb at wavelengths >290 nm(4) and therefore is not expected to be susceptible to direct photolysis by sunlight(SRC). In a smog chamber experiment, 20% of the ethylene oxide degraded in 5.3 hr(5).
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