Toluene

CAS RN:108-88-3

Environmental Fate

TERRESTRIAL FATE: Based on a classification scheme(1), Koc values of 37-178 measured in soil(2,3) indicate that toluene is expected to have high to moderate mobility in soil(SRC). Volatilization of toluene from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 6.64X10-3 atm-cu m/mole(4). Toluene is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 28.4 mm Hg at 25 deg C(5). Complete biodegradation of toluene was observed in lab microcosm tests during a 40 hour incubation period using soils previously exposed to toluene(6). The biodegradation half-life in various soils was reported as several hours to 71 days(7). These tests suggest that biodegradation is an important environmental fate process in soil(SRC).
AQUATIC FATE: Based on a classification scheme(1), a Koc value of 166 measured in lake sediment(2) indicates that toluene 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 6.64X10-3 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 1 hour and 4 days, respectively(SRC). According to a classification scheme(5), BCF values of 13(6) and 90(7) measured in fish suggest the potential for bioconcentration in aquatic organisms is low to moderate(SRC). The half-life of toluene in aerobic and anaerobic water was reported as 4 and 56 days(8), respectively, suggesting that biodegradation is an important environmental fate process in water(SRC).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), toluene, which has a vapor pressure of 28.4 mm Hg at 25 deg C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase toluene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals, nitrate radicals and ozone molecules(SRC). The half-life for the reaction with hydroxyl radicals is estimated to be 2 days(SRC), calculated from its rate constant of 5.93X10-12 cu cm/molecule-sec at 25 deg C(3). The half-life for the nighttime reaction with nitrate radicals is estimated as 491 days(SRC) calculated from its rate constant of 6.8X10-17 cu cm/molecule-sec at 25 deg C(4). The half-life for the reaction with ozone is estimated as 27,950 days(SRC) calculated from its rate constant of 4.1X10-22 cu cm/molecule-sec at 25 deg C(4). Toluene does not absorb light at wavelengths >290 nm(5) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).
Find more information on this substance at: Hazardous Substances Data Bank , TOXNET , PubMed