1,2,4-Tribromo-3,5,6-trichlorobenzene

The Koc of 1,2,4-tribromo-3,5,6-trichlorobenzene is estimated as approximately 9.3X10+4(SRC), using an estimated log Kow of 6.6(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that 1,2,4-tribromo-3,5,6-trichlorobenzene is expected to be immobile in soil.

An estimated BCF of 6.1X10+4 was calculated for 1,2,4-tribromo-3,5,6-trichlorobenzene(SRC), using an estimated log Kow of 6.6(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is very high.

The Henry's Law constant for 1,2,4-tribromo-3,5,6-trichlorobenzene is estimated as 2.39X10-4 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that 1,2,4-tribromo-3,5,6-trichlorobenzene is expected to volatilize from water surfaces(2,SRC). Based on this Henry's Law constant, the estimated volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec) is approximately 13 hours(2,SRC). The estimated volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec) is approximately 10 days(2,SRC). The volatilization half-life from a model pond 2 m deep is estimated to be about 6.3 days ignoring adsorption(3); when considering maximum adsorption the volatilization half-life increases to 95 years(3). 1,2,4-Tribromo-3,5,6-trichlorobenzene's estimated Henry's Law constant(1) indicates that volatilization from moist soil surfaces may be an important fate process(SRC). 1,2,4-Tribromo-3,5,6-trichlorobenzene is not expected to volatilize from dry soil surfaces based on an estimated vapor pressure of 3.4X10-5 mm Hg(SRC), determined from a fragment constant method(4).

Halogenated benzenes in varying states of substitution were tested against phenobarbital and 3-methylcholanthrene as positive controls for the induction of cytochrome p450. Rats were given po injections of chemical daily for 14 days, microsomal fractions were prepared, and NADPH-cytochrome c reductase activity and cytochrome p450 content was determined. 1,2,4-Trichlorobenzene, 1,2,4-tribromobenzene and hexachlorobenzene resulted in increases in enzyme activity and cytochrome p450 content, and hexabromobenzene was without effect. The evidence suggested that the chlorinated and brominated benzenes are inducers of the phenobarbital type. /Halogenated benzenes/

1,2,4-Trichlorobenzene, 1,3,5-trichlorobenzene, hexachlorobenzene, 1,2,4-tribromobenzene, 1,3,5-tribromobenzene and hexabromobenzene were compared for their abilities to induce acetanilide esterase, acetanilide hydroxylase and procaine esterase. Except for hexabromobenzene all induced acetanilide esterase whereas the hydroxylation of acetanilide was seen only with the fully halogenated benzenes and with 1,3,5-tribromobenzene. Hepatic procaine esterase activity was increased by the 3 chlorinated benzenes and 1,2,4-tribromobenzene. /Chlorinated benzenes/

The rate constant for the vapor-phase reaction of 1,2,4-tribromo-3,5,6-trichlorobenzene with photochemically-produced hydroxyl radicals has been estimated as 1.5X10-14 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of about 3.0 years at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 1,2,4-Tribromo-3,5,6-trichlorobenzene is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2).

No evidence was found that 1,2,4-tribromo-3,5,6-trichlorobenzene is produced commercially. If released to air, an estimated vapor pressure of 3.4X10-5 mm Hg at 25 °C indicates 1,2,4-tribromo-3,5,6-trichlorobenzene will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase 1,2,4-tribromo-3,5,6-trichlorobenzene will be degraded slowly in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 3.0 years. Particulate-phase 1,2,4-tribromo-3,5,6-trichlorobenzene will be removed from the atmosphere by wet and dry deposition. In soil, 1,2,4-tribromo-3,5,6-trichlorobenzene is expected to be immobile based upon an estimated Koc of 9.3X10+4. Volatilization from moist soil surfaces may be an important fate process based upon an estimated Henry's Law constant of 2.4X10-4 atm-cu m/mole. However, adsorption is expected to attenuate this process. If released into water, 1,2,4-tribromo-3,5,6-trichlorobenzene is expected to adsorb to suspended solids and sediment in water based upon the estimated Koc. Volatilization from water surfaces may be an important fate process based upon this compound's estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 13 hours and 10 days, respectively. However, adsorption to suspended solids and sediment in the water column is expected to attenuate volatilization. An estimated BCF of 6.1X10+4 suggests the potential for bioconcentration in aquatic organisms is very high. Biodegradation of 1,2,4-tribromo-3,5,6-trichlorobenzene in soil and water is expected to be slow because of the high degree of halogenation. 1,2,4-Tribromo-3,5,6-trichlorobenzene is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups. (SRC)