4-Methylbenzenethiol

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

0.66 [mg/m3]

7.2 [mg/m3]

43 [mg/m3]

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 430(SRC), determined from a structure estimation method(2), indicates that 4-thiocresol is expected to have moderate mobility in soil(SRC). The pKa of 4-thiocresol is 6.82(3) indicating that the anionic form of 4-thiocresol will exist in slightly acidic to basic soils and anions are expected to have higher mobility than the neutral species(SRC). Volatilization of 4-thiocresol from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 3.6X10-4 atm-cu m/mole(SRC), using a fragment constant estimation method(4). However, 4-thiocresol in the anionic form will not volatilize. 4-Thiocresol is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.807 mm Hg(5).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 430(SRC), determined from an estimation method(2), indicates that 4-thiocresol is expected to slightly adsorb to suspended solids and sediment(SRC). Volatilization of the neutral species from water surfaces is expected(3) based upon an estimated Henry's Law constant of 3.6X10-4 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 3 hrs and 5.2 days, respectively(SRC). A pKa of 6.82(5) indicates that the anionic form of 4-thiocresol will exist in slightly acidic to basic waters and the anionic form will not volatilize from water(SRC). According to a classification scheme(6), an estimated BCF of 62(SRC), from an estimated log Kow of 3.2(7) and a regression-derived equation(8), suggests the potential for bioconcentration in aquatic organisms is moderate.

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 4-thiocresol, which has a vapor pressure of 0.807 mm Hg at 25 °C(2), is expected to exist solely in the vapor-phase in the ambient atmosphere. Vapor-phase 4-thiocresol 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 27 hrs(SRC), calculated from its rate constant of 1.4X10-11 cu cm/molecule-sec at 25 °C(SRC) determined using a structure estimation method(3). Although thiocresols may be susceptible to photolysis, sufficient experimental data are not available to predict the relative importance of their photolysis in the environment(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc for 4-thiocresol can be estimated to be 430(SRC). According to a classification scheme(2), this estimated Koc value suggests that 4-thiocresol is expected to have moderate mobility in soil. The pKa of 4-thiocresol is 6.82(3) indicating that the anionic form of 4-thiocresol will exist in slightly acidic to basic soils and anions are expected to have higher mobility than the neutral species(SRC). Volatilization from moist soil surfaces is not expected to be an important fate process for the anionic species.

An estimated BCF of 62 was calculated for 4-thiocresol(SRC), using an estimated log Kow of 3.2(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is moderate.

The Henry's Law constant for 4-thiocresol is estimated as 3.6X10-4 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that 4-thiocresol is expected to volatilize from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life of the neutral species from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 3 hrs(SRC). The volatilization half-life of the neutral species from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 5.2 days(SRC). A pKa of 6.82(3) for 4-thiocresol indicates that the anionic form of 4-thiocresol will exist in slightly acidic to basic waters and the anionic form is not expected to volatilize from water(SRC). 4-Thiocresol's Henry's Law constant(1) indicates that volatilization of the neutral species from moist soil surfaces may occur(SRC). However, 4-thiocresol in the anionic form is not expected to volatilize. 4-Thiocresol is not expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 0.807 mm Hg(4).

The rate constant for the vapor-phase reaction of 4-thiocresol with photochemically-produced hydroxyl radicals has been estimated as 1.4X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of approximately 27 hrs at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 4-Thiocresol is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2). Although thiocresols may be susceptible to photolysis, sufficient experimental data are not available to predict the relative importance of their photolysis in the environment(SRC).

4-Thiocresol's possible production as an antiseptic may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 0.807 mm Hg at 25 °C indicates 4-thiocresol will exist solely in the vapor phase in the ambient atmosphere. Vapor-phase 4-thiocresol 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 27 hrs. Although thiocresols may be susceptible to photolysis, sufficient experimental data are not available to predict the relative importance of their photolysis in the environment. If released to soil, 4-thiocresol is expected to have moderate mobility based upon an estimated Koc of 430. The pKa of 4-thiocresol is 6.82 indicating that the anionic form of 4-thiocresol will exist in slightly acidic to basic soils and these anions are expected to have higher mobility than the neutral species. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 3.6X10-4 atm-cu m/mole. However, volatilization of the anionic species from moist soil surfaces will not occur. 4-Thiocresol is not expected to volatilize from dry soil surfaces based upon its vapor pressure. If released into water, 4-thiocresol is expected to slightly adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization of the neutral species from water surfaces is expected to be an important fate process based upon this compound's estimated Henry's Law constant. However, based on the pKa, the anionic form of 4-thiocresol will exist in slightly acidic to basic waters and the anionic form will not volatilize from water. Estimated volatilization half-lives of the neutral species for a model river and model lake are 3 hrs and 5.2 days, respectively. An estimated BCF of 62 suggests the potential for bioconcentration in aquatic organisms is moderate. Hydrolysis is not expec