Tris(3,5-xylenyl)phosphate

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.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 9.5X10+4(SRC), determined from a structure estimation method(2), indicates that tris(3,5-xylenyl)phosphate is expected to be immobile in soil(SRC). Volatilization of tris(3,5-xylenyl)phosphate from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 7.2X10-8 atm-cu m/mole(SRC), using a fragment constant estimation method(3). Tris(3,5-xylenyl)phosphate is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 2.1X10-8 mm Hg(SRC), determined from a fragment constant method(4). Tris(3,5-xylenyl)phosphate may be susceptible to hydrolysis in alkaline soils based on aquatic data for other triaryl phosphates(6). Biodegradation of aryl phosphates may occur slowly in the environment based on activated sludge tests showing 13 to 65% biodegradation of trixylenyl phosphate over 14 and 25 weeks, respectively(5).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 9.5X10+4(SRC), determined from a structure estimation method(2), indicates that tris(3,5-xylenyl)phosphate is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(3) based upon an estimated Henry's Law constant of 7.2X10-8 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Tris(3,5-xylenyl)phosphate may be stable to degradation in waters having slightly acidic and neutral pH values; however, decomposition of tris(3,5-xylenyl)phosphate may occur in alkaline waters(8). According to a classification scheme(5), an estimated BCF of 720(SRC), from a log Kow of 5.63(6), measured for Kronitex TXP, a commercial product containing tris(3,5-xylenyl)phosphate and other trixylenyl and triethylphenyl phosphate isomers, and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is high(SRC). Biodegradation of aryl phosphates may occur slowly in the environment based on activated sludge tests showing 13 to 65% biodegradation of trixylenyl phosphate over 14 and 25 weeks, respectively(6).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), tris(3,5-xylenyl)phosphate, which has an estimated vapor pressure of 2.1X10-8 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase tris(3,5-xylenyl)phosphate may be removed from the air by wet and dry deposition(SRC).

Using a structure estimation method based on molecular connectivity indices(1), the Koc for tris(3,5-xylenyl)phosphate can be estimated to be 9.5X10+4(SRC). According to a classification scheme(2), this estimated Koc value suggests that tris(3,5-xylenyl)phosphate is expected to be immobile in soil.

Acute oral toxicity was evaluated in rats (number, sex ratio and strain not reported) administered tri-3,5-xylenyl phosphate orally (dose levels, mortalities, clinical observations and gross necropsy not reported). The acute oral LD50 was reported to be >4640 mg/kg.

The inhibition of nonspecific esterase activity, and/or inhibition of aromatic amino acid esterase activity, and/or potential effects on specific cellular functions (phagocytosis, immunoglobin G synthesis, and inflammatory and immune mediator release) were evaluated with organic chemicals added to human peripheral blood monocytes. Trixylenyl phosphate inhibited monocyte alpha-naphthyl acetate esterase activity by 8% at a concentration of 1 mM and inhibited monocyte aromatic amino acid esterase activity by 10% at 250uM. Only inhibition values greater than 10% were considered to be statistically significant.

Specific use information for tris(3,5-xylenyl)phosphate was not located. However, trixylenyl phosphates are produced and used as flame retardants and plasticizers(1) and hydraulic fluids(2) and tris(3,5-xylenyl)phosphate may be released to the environment through various waste streams during such production and/or use(SRC).

No specific biodegradation data were located for tris(3,5-xylenyl)phosphate in either soil or aquatic systems. TXP (trixylenyl phosphate) added at 3 mg/L/day was biodegraded by 65% over 14 weeks in the SCAS test using activated sludge as an inoculum; at an initial concentration of 13 mg/L/day, using the same test method, only 13% biodegradation was reported over a 25-week period(1). Kronitex TXP is a commercial product primarily consisting of the 2,5-, 3,4-, 3,5- and/or the 2,4-isomers of trixylylphosphates along with mixes of xylenyl phosphates or xylenyl/ethylphenyl phosphates(2). The degradation of specific isomers within the mixture was not quantified(1). In general, the biodegradability of triaryl phosphates decreases with increasing number and size of substituent groups on the phenolic ring(1,3). Therefore, based on the evidence pertaining to TXP(1), tris(3,5-xylenyl)phosphate may be susceptible to biodegradation(1).

An estimated BCF value of 720 was calculated for tris(3,5-xylenyl)phosphate(SRC) using a log Kow of 5.63(2) measured for Kronitex TXP, a commercial product primarily consisting of the 2,5-, 3,4-, 3,5- and/or the 2,4-isomers of trixylylphosphates along with mixes of xylenyl phosphates or xylenyl/ethylphenyl phosphates(1), and a regression-derived equation(3). The actual BCF of tris(3,5-xylenyl)phosphate would be expected to be slightly higher, for a greater Kow value would be anticipated for tris(3,5-xylenyl)phosphate due to the presence of lower molecular weight constituents among the TXP mixture. This is in keeping with this class of chemicals as analogous tri-p-cresyl phosphate has measured BCFs of 1,420 and 928 in rainbow trout and fathead minnows, respectively(4). According to a classification scheme(5), this BCF value suggests the potential for bioconcentration of tris(3,5-xylenyl)phosphate in aquatic organisms is high(SRC).

The Henry's Law constant for tris(3,5-xylenyl)phosphate is estimated as 7.2X10-8 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that tris(3,5-xylenyl)phosphate is expected to be essentially nonvolatile from water surfaces(2). Tris(3,5-xylenyl)phosphate's Henry's Law constant(1) indicates that volatilization from moist soil surfaces is not expected to occur(SRC). Tris(3,5-xylenyl)phosphate is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 2.1X10-8 mm Hg(SRC), determined from a fragment constant method(3).

NO NEUROPARALYTIC EFFECTS WERE FOUND IN ROOSTERS GIVEN TRI-3,5-XYLENYL PHOSPHATE ORALLY. WHEN ADMIN AT 1 G/KG/DAY FOR 40 DAYS ORALLY TRI-3,5-XYLENYL PHOSPHATE SHOWED LOW TOXICITY.

OMTI, A FIREPROOF AEROSOL LUBRICANT FOR TURBINES BASED ON TRI-3,5-XYLENYL PHOSPHATE, INHALED BY MICE, RATS, AND GUINEA PIGS AT 1-10 MG/CU M 4 HR DAILY FOR 16 WK SHOWED RELATIVELY LOW TOXICITY TO THE LUNG, SKIN, & PERIPHERAL NERVES.

Triaryl phosphates are generally stable to hydrolysis at neutral pH values and undergo moderate hydrolysis in acidic solutions(1). Triaryl phosphates will degrade at appreciable rates in natural waters under alkaline conditions to apparently stable, water soluble, anionic diesters such as diaryl phosphates(1). No persistence data specific to tris(3,5-xylenyl)phosphate were available; however, based on data pertaining to triphenyl and tricresyl phosphates(1), tris(3,5-xylenyl)phosphate is expected to hydrolyze in natural alkaline waters. Tris(3,5-xylenyl)phosphate is not expected to directly photolyze due to the lack of absorption in the environmental UV spectrum (>290 nm)(SRC).

Specific use information pertaining to tris(3,5-xylenyl)phosphate was not available, although triaryl phosphates are generally employed as flame-retardants and plasticizers(1) and in hydraulic fluids(2). Occupational exposure to tris(3,5-xylenyl)phosphate may occur through inhalation of dust particles and dermal contact with this compound at workplaces where tris(3,5-xylenyl)phosphate is produced or used(SRC).

Tris(3,5-xylenyl)phosphate's production and use as a flame-retardant, plasticizer, or hydraulic fluid may result in its release to the environment through various waste streams. If released to air, an estimated vapor pressure of 2.1X10-8 mm Hg at 25 °C indicates tris(3,5-xylenyl)phosphate will exist solely in the particulate phase in the ambient atmosphere. Particulate-phase tris(3,5-xylenyl)phosphate will be removed from the atmosphere by wet and dry deposition. If released to soil, tris(3,5-xylenyl)phosphate is expected to be immobile based upon an estimated Koc of 9.5X10+4. Volatilization from moist soil surfaces is not expected to be an important fate process based upon an estimated Henry's Law constant of 7.2X10-8 atm-cu m/mole. Tris(3,5-xylenyl)phosphate is not expected to volatilize from dry soil surfaces based upon its vapor pressure. Biodegradation of aryl phosphates may occur slowly in the environment based on activated sludge tests showing 13 to 65% biodegradation of trixylenyl phosphate over 14 and 25 weeks, respectively. Under alkaline conditions in soil and water environments, appreciable abiotic degradation may occur via hydrolysis. If released into water, tris(3,5-xylenyl)phosphate is expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is not expected to be an important fate process based upon this compound's estimated Henry's Law constant. An estimated BCF of 720 suggests the potential for bioconcentration in aquatic organisms is high. Occupational exposure to tris(3,5-xylenyl)phosphate may occur through inhalation of dust particles and dermal contact with this compound at workplaces where tris(3,5-xylenyl)phosphate is produced or used.(SRC)

Used as a flame retardant; [HSDB]

Used in flame retardants compositions

Non-flammable hydraulic fluid (steel works, furnaces, mines); polyvinyl chloride plasticizer /Trixylyl phosphate/

(1981) 90,401 million pounds /Trixylyl phosphate/

(1983) 9,921 million pounds /Trixylyl phosphate/