1,4-Dibromobenzene

If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped or safely confined. Use water in flooding quantities as fog. Use "alcohol" foam, dry chemical or carbon dioxide. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Keep run-off water out of sewers and water sources. /Dibromobenzene/

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.

If material not on fire and not involved in fire: Keep sparks, flames, and other sources of ignition away. Keep material out of water sources and sewers. Build dikes to contain flow as necessary. Attempt to stop leak if without undue personnel hazard. /Dibromobenzene/

Personnel protection: Keep upwind. Avoid breathing vapors. ... /Dibromobenzene/

The halogenated benzenes, inducers of xenobiotic metabolism, were studied for their effects on the metabolism of malathion, malaoxon (lindane), and paraoxon and on the toxicity and lethality of these organophosphorus insecticides and parathion. One mmol/kg of 1,4-dichlorobenzene (p-dichlorobenzene), 1,2,4-trichlorobenzene, 1,4-dibromobenzene, 1,2,4-tribromobenzene, or hexabromobenzene or 0.1 mmol/kg hexachlorobenzene was administered po to male mice daily for 7 days. In general, the trihalogenated benzenes increased the LD50 of all 4 insecticides 2- to 6-fold. These increases were larger than those observed with the di- or hexahalogenated isomers. The bromide-substituted benzenes were usually more active than the chlorinated ones with the exception being hexabromobenzene. There was a good correlation between their effects on lethality and increases in in vitro carboxylesterase activity with either-malathion or malaoxon as the substrate. The trihalogenated benzenes decreased the inhibitory effect of malathion on cholinesterase activity in the brain and to a lesser degree in the red blood cells, but not in 1iver or plasma.

TERRESTRIAL FATE: Based on a recommended classification scheme(1), an estimated Koc value of 2,700(SRC), determined from an experimental log Kow(2,SRC) and a recommended regression-derived equation(3), indicates that p-dibromobenzene will have slight mobility in soil(SRC). Volatilization of p-dibromobenzene will be important from moist soil surfaces(SRC) given an estimated Henry's Law constant of 8.93X10-4 atm-cu m/mole(SRC), calculated using experimental vapor pressure(4) and water solubility(5). Volatilization from dry soil surfaces(SRC) should not be important based on an experimental vapor pressure of 0.0575 mm Hg(4,SRC). Based on limited screening data, p-dibromobenzene is resistant to biodegradation; after a period of two weeks, 0% biodegradation occurred(6).

AQUATIC FATE: Based on a recommended classification scheme(1), an estimated Koc value of 2700(SRC), determined from an experimental log Kow(2,SRC) and a recommended regression-derived equation(1), indicates that p-dibromobenzene may adsorb to suspended solids and sediment in water(SRC). p-Dibromobenzene will volatilize from water surfaces(1,SRC) based on an estimated Henry's Law constant of 8.33X10-4 atm-cu m/mole(SRC), calculated using experimental vapor pressure(3) and water solubility(4). Estimated half-lives for a model river and model lake are 6 and 157 hrs, respectively(1,SRC). According to a classification scheme(5), experimental BCF values ranging from 42.9 to 1,413(6,7,SRC) suggests that bioconcentration in aquatic organisms is moderate to very high(SRC). Based on limited screening data, this compound is resistant to biodegradation; 0 biodegradation occurred after a period of two weeks(6).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), p-dibromobenzene, which has an experimental vapor pressure of 0.0575 mm Hg at 25 °C(2,SRC), will exist solely as a vapor in the ambient atmosphere. Vapor-phase p-dibromobenzene 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 about 46 days(3,SRC). Particulate-phase p-dibromobenzene may be physically removed from the air by wet and dry deposition(SRC).

1,4-Dibromobenzene

Hepatic

1 x 10 ^-2 mg/kg-day

The Koc of p-dibromobenzene is estimated as approximately 2,700(SRC), using an experimental log Kow of 3.79(1,SRC) and a regression-derived equation(2,SRC). According to a recommended classification scheme(3), this estimated Koc value suggests that p-dibromobenzene has slight mobility in soil(SRC).

An experimental BCF value of 1,413 was determined for p-dibromobenzene(2,SRC) in the guppy (Poecilia reticulata). Studies also showed a depuration rate constant of 1.41 /d(2). When exposed to 10 ug/l p-dibromobenzene, the experimental BCF in carp ranged from 42.9 to 313. When exposed to 1 ug/l p-dibromobenzene, the experimental BCF ranged from 44.2 to 279(1). According to a classification scheme(3), these BCF values suggest that bioconcentration in aquatic organisms is moderate to very high(SRC).

The Henry's Law constant for p-dibromobenzene is estimated as 8.93X10-4 atm-cu m/mole(SRC) from its experimental values for vapor pressure, 0.0575 mm Hg(1), and water solubility, 20.0 mg/l(2). This value indicates that p-dibromobenzene will volatilize from water surfaces(3,SRC). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec) is estimated as approximately 5.9 hours(3,SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec) is estimated as approximately 157 days(3,SRC). p-Dibromobenzene's values for vapor pressure(1) and Henry's Law constant(1,2,SRC) indicate that volatilization from dry and moist soil surfaces may occur(SRC).

LIMITED EXPERIMENTS WITH ANIMALS SUGGEST MODERATE TOXICITY.

ADMIN ORALLY TO MALE RATS FOR 45 & 90 DAYS @ 10 & 20 MG/KG 1,4-DIBROMOBENZENE INCR LIVER TO BODY WT RATIOS, CYTOCHROME p450 CONTENT, EPN DETOXIFICATION & AZOREDUCTASE ACTIVITY.

1,4-Dibromobenzene was covalently bound to DNA from liver, kidney, lung, and stomach of mice after intraperitoneal administration. The covalent binding index value (23 in mouse liver) was typical of weak initiators. On the contrary, no interaction with DNA from rat organs was observed (covalent binding index detection limit: 1.3-2.6). The in vitro interaction of 1,4-dibromobenzene with calf thymus DNA was mediated mainly by microsomes, especially those from liver of both species and from mouse lung. Mouse subcellular fractions were more active then rat subcellular fractions. Both cytochrome p450 and glutathione-transferases are involved in 1,4-dibromobenzene bioactivation.

The rate constant for the vapor-phase reaction of p-dibromobenzene with photochemically produced hydroxyl radicals has been estimated as 0.35X10-12 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1,SRC). This corresponds to an atmospheric half-life of about 46 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1,SRC).