2,3,5,6-テトラクロロピリジン

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 1500(SRC), determined from a log Kow of 3.32(2) and a regression-derived equation(3), indicates that 2,3,5,6-tetrachloropyridine is expected to have low mobility in soil(SRC). Volatilization of 2,3,5,6-tetrachloropyridine from moist soil surfaces may be an important fate process(SRC) given an estimated Henry's Law constant of 8.5X10-3 atm-cu m/mole(SRC), using a fragment constant estimation method(4) although adsorption to soil surfaces may attenuate the rate of this process(SRC). 2,3,5,6-Tetrachloropyridine is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 6.1X10-3 mm Hg(SRC), determined from a fragment constant method(5). 2,3,5,6-Tetrachloropyridine is expected to be resistant to biodegradation under aerobic conditions in soil based on data from structurally-similar compounds(SRC). Only <0.1% and 3% of the available nitrogen was released over 64 days following the application of 2,3- and 2,6-dichloropyridine to soil(6). This compound may be susceptible to anaerobic biodegradation via dehalogenation(7).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 1500(SRC), determined from a log Kow of 3.32(2) and a regression-derived equation(3), indicates that 2,3,5,6-tetrachloropyridine may adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 8.5X10-3 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 4 hours and 6 days, respectively(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is 2.7 years if adsorption is considered(7). According to a classification scheme(5), an estimated BCF of 70(SRC), from its log Kow(2) and a regression-derived equation(6), suggests the potential for bioconcentration in aquatic organisms is moderate(SRC). 2,3,5,6-Tetrachloropyridine is expected to be resistant to biodegradation under aerobic conditions in water based on soil data from structurally-similar compounds(SRC). Only <0.1% and 3% of the available nitrogen was released over 64 days following the application of 2,3- and 2,6-dichloropyridine to soil(8). This compound may be susceptible to anaerobic biodegradation via dehalogenation(9).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 2,3,5,6-tetrachloropyridine, which has an estimated vapor pressure of 6.1X10-3 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase 2,3,5,6-tetrachloropyridine 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 nearly 3 years(SRC), calculated from its rate constant of 1.6X10-14 cu cm/molecule-sec at 25 °C(SRC) determined using a structure estimation method(3).

The Koc of 2,3,5,6-tetrachloropyridine is estimated as 1500(SRC), using a log Kow of 3.32(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that 2,3,5,6-tetrachloropyridine is expected to have low mobility in soil.

Information pertaining to the biodegradation of 2,3,5,6-tetrachloropyridine in soil and water was not located in the available literature. However, an aerobic biological screening study, which utilized a 10 mg/L yeast extract and an Aeric Ocharaqualf soil for inocula, indicates that chloropyridines are not readily biodegradable(1). At 24 °C and a pH of 7, less than 1% and 14% of the initial 2,3- and 2,6-dichlorpyridine were mineralized within 30 days as evidenced via the release of inorganic nitrogen(1). An aerobic soil grab sample study also demonstrated that dichlorpyridines are not readily biodegradable(2). 2,3- and 2,6-Dichloropyridine were added to fincastle silt loam (Aeric Ochraqualf) with a pH of 6.7 and incubated at 25 °C(2). Within 64 days, less than 0.1% and 3% of the available nitrogen were released to inorganic forms(2). Sterilized controls lost less than 5% of the starting material to volatilization and did not release inorganic nitrogen(2).

An estimated BCF of 70 was calculated for 2,3,5,6-tetrachloropyridine(SRC), using a log Kow of 3.32(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(SRC).

The Henry's Law constant for 2,3,5,6-tetrachloropyridine is estimated as 8.5X10-3 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This Henry's Law constant indicates that 2,3,5,6-tetrachloropyridine is expected to volatilize from water surfaces(2). 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)(2) is estimated as 4 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 6 days(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is 2.7 years if adsorption is considered(4). 2,3,5,6-Tetrachloropyridine's Henry's Law constant(1) indicates that volatilization from moist soil surfaces may occur(SRC). 2,3,5,6-Tetrachloropyridine is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 6.1X10-3 mm Hg(SRC), determined from a fragment constant method(3).

The rate constant for the vapor-phase reaction of 2,3,5,6-tetrachloropyridine with photochemically-produced hydroxyl radicals has been estimated as 1.6X10-14 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1). This corresponds to an atmospheric half-life of nearly 3 years at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). 2,3,5,6-Tetrachloropyridine is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(2). Pyridine has a weak absorption band that extends into the environmental UV spectrum(3), which suggests that direct photolysis is not likely to be an important fate process for 2,3,5,6-tetrachloropyridine (SRC).

The most probable human exposure to 2,3,5,6-tetrachloropyridine would be occupational exposure, which may occur through dermal contact or inhalation at places where it is produced or used. NIOSH (NOES Survey 1981-83) has estimated that 311 workers are potentially exposed to 2,3,5,6-tetrachloropyridine in the USA(1).

2,3,5,6-Tetrachloropyridine's production and use as a chemical intermediate in the production of pesticides such as chlorpyrifos and triclopyr may result in its release to the environment through various waste streams. If released to air, an estimated vapor pressure of 6.1X10-3 mm Hg at 25 °C indicates 2,3,5,6-tetrachloropyridine will exist solely as a vapor. Vapor-phase 2,3,5,6-tetrachloropyridine 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 3 years. If released to soil, 2,3,5,6-tetrachloropyridine is expected to have low mobility based upon an estimated Koc of 1500. Volatilization from moist soil surfaces is expected to be an important fate process based upon an estimated Henry's Law constant of 8.5X10-3 atm-cu m/mole. 2,3,5,6-Tetrachloropyridine is expected to be resistant to biodegradation under aerobic conditions in both soil and water based on soil data from structurally-similar compounds. Only <0.1% and 3% of the available nitrogen was released over 64 days following the application of 2,3- and 2,6-dichloropyridine to soil. 2,3,5,6-Tetrachloropyridine may be susceptible to anaerobic biodegradation via dehalogenation. If released into water, 2,3,5,6-tetrachloropyridine may adsorb to suspended solids and sediment 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 4 hours and 6 days, respectively. However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column; a half-life of 2.7 years is estimated if adsorption is considered in a model pond scenario. An estimated BCF of 70 suggests the potential for bioconcentration in aquatic organisms is moderate. Occupational exposure to 2,3,5,6-tetrachloropyridine may occur through inhalation and dermal contact with this compound at workplaces where 2,3,5,6-tetrachloropyridine is produced or used. (SRC)

/SRP:/ Basic treatment: Establish a patent airway. Suction if necessary. Watch for signs of respiratory insufficiency and assist ventilations if needed. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with normal saline during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool ... . Cover skin burns with dry sterile dressings after decontamination ... . /Poison A and B/

/SRP:/ Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in respiratory arrest. Positive pressure ventilation techniques with a bag valve mask device may be beneficial. Monitor cardiac rhythm and treat arrhythmias as necessary ... . Start an IV with D5W /SRP: "To keep open", minimal flow rate/. Use lactated Ringer's if signs of hypovolemia are present. Watch for signs of fluid overload. Consider drug therapy for pulmonary edema ... . For hypotension with signs of hypovolemia, administer fluid cautiously. Watch for signs of fluid overload ... . Treat seizures with diazepam (Valium) ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Poison A and B/