2,4,5-T

Cl CASRN: 93-76-5; DOT: 2765; DOT label: Poison; molecular formula: C8H5Cl3O3; FW: 255.48; RTECS: AJ8400000; Merck Index: 12, 9194 Physical state, color, odor, and taste: Colorless to pale brown, odorless crystals. Odor threshold from water is 2.92 mg/kg (quoted, Keith and Walters, 1992). Metallic taste. Melting point (°C): 154.8 (Plato and Glasgow, 1969) Density (g/cm3): 1.80 at 20/20 °C (Windholz et al., 1983) Diffusivity in water (x 10-5 cm2/sec): 0.54 at 20 °C using method of Hayduk and Laudie (1974) Dissociation constant, pKa: 2.80 and 2.83 at 25 °C (ionic strength <0.01 M, Jafvert et al., 1990) 2.88 (Nelson and Faust, 1969) Entropy of fusion (cal/mol⋅K): 19.5 (Plato and Glasgow, 1969) Heat of fusion (kcal/mol): 8.350 (DSC, Plato and Glasgow, 1969) Henry’s law constant (x 10-8 atm⋅m3/mol): 4.87 at 25 °C (approximate - calculated from water solubility and vapor pressure) Bioconcentration factor, log BCF: 1.36 (fish, microcosm) (Garten and Trabalka, 1983) Soil organic carbon/water partition coefficient, log Koc: 1.72 (Kenaga and Goring, 1980) 2.27 (Webster soil, Nkedi-Kizza et al., 1983)

ow 3.31, 3.38 (quoted – reported values involve divalent cations, Jafvert et al., 1990) 3.40 (Riederer, 1990) Solubility in organics (°C): Soluble in ethanol (548.2 mg/L), ether (243.2 mg/L), heptane (400 mg/L), xylenes (6.8 g/L), methanol (496 g/L), toluene (7.32 g/L) (quoted, Keith and Walters, 1992). Solubility in water: 278 ppm at 25 °C (quoted, Verschueren, 1983) 240 mg/L at 25 °C (Klöpffer et al., 1982) 220 mg/L at 20 °C (Riederer, 1990) 1.05 mM at 25 °C (Gunther et al., 1968) 150 g/L at 25 °C (Lewis, 1989) Vapor pressure (x 10-6 mmHg): 37.5 at 20 °C (Riederer, 1990) 6.46 at 25 °C (Lewis, 1989) Environmental fate: Biological. 2,4,5-T degraded in anaerobic sludge by reductive dechlorination to 2,4,5trichlorophenol, 3,4-dichlorophenol, and 4-chlorophenol (Mikesell and Boyd, 1985). An anaerobic methanogenic consortium, growing on 3-chlorobenzoate, metabolized 2,4,5-T to (2,5dichlorophenoxy)acetic acid at a rate of 1.02 x 10-7 M/h. The half-life was reported to be 2 d at 37 °C (Suflita et al., 1984). Under aerobic conditions, 2,4,5-T degraded to 2,4,5-trichlorophenol and 3,5-dichlorocatechol, which may degrade to 4-chlorocatechol or cis,cis-2,4-dichloromuconic acid, 2-chloro-4-(carboxymethylene)but-2-enolide, chlorosuccinic acid, and succinic acid (Byast and Hance, 1975). The cometabolic oxidation of 2,4,5-T by Brevibacterium sp. yielded a product tentatively identified as 3,5-dichlorocatechol (Horvath, 1970). The cometabolism of this compound by Achromobacter sp. gave 3,5-dichloro-2-hydroxymuconic semialdehyde (Horvath, 1970a). Rosenberg and Alexander (1980) reported that 2,4,5-trichlorophenol, the principal degradation product of 2,4,5-T by microbes, was metabolized to 3,5-dichlorocatechol, 4-chlorocatechol, succinate, cis,cis-2,4-dichloromuconate, 2-chloro-4-(carboxymethylene)but-2-enolide, and chlorosuccinate. Soil. 2,4,5-Trichlorophenol and 2,4,5-trichloroanisole were formed when 2,4,5-T was incubated in soil at 25 °C under aerobic conditions. The half-life under these conditions was 14 d (McCall et al., 1981). When 2,4,5-T (10 µg), in unsterilized tropical clay and silty clay soils, was incubated for 4 months, 5 to 35% degradation yields were observed (Rosenberg and Alexander, 1980). Hydrolyzes in soil to 2,4,5-trichlorophenol (Somasundaram et al., 1989, 1991) and 2,4,5-trichloroanisole (Somasundaram et al., 1989). The rate of 2,4,5-T degradation in soil remained unchanged in a soil pretreated with its hydrolysis metabolite (2,4,5-trichlorophenol) (Somasundaram et al., 1989). The half-lives of 2,4,5-T in soil incubated in the laboratory under aerobic conditions ranged from 14 to 64 d with an average of 33 d (Altom and Stritzke, 1973; Foster and McKercher, 1973; Yoshida and Castro, 1975). In field soils, the disappearance half-lives were lower and ranged from 8 to 54 d with an average of 16 d (Radosevich and Winterlin, 1977; Stewart and Gaul, 1977). Groundwater. According to the U.S. EPA (1986), 2,4,5-T has a high potential to leach to groundwater. Photolytic. When 2,4,5-T (100 µM), in oxygenated water containing titanium dioxide (2 g/L) suspension, was irradiated by sunlight (λ ≥340 nm), 2,4,5-trichlorophenol, 2,4,5-trichlorophenyl formate, and nine chlorinated aromatic hydrocarbons formed as major intermediates. Complete

Crosby and Wong (1973) studied the photolysis of 2,4,5-T in aqueous solutions (100 mg/L) under alkaline conditions (pH 8) using both outdoor sunlight and indoor irradiation (λ = 300-450 nm). 2,4,5-Trichlorophenol and 2-hydroxy-4,5-dichlorophenoxyacetic acid formed as major products. Minor photodecomposition products included 4,6-dichlororesorcinol, 4-chlororesorcinol, 2,5-dichlorophenol, and a dark polymeric substance. The rate of photolysis increased 11-fold in the presence of sensitizers (acetone or riboflavin) (Crosby and Wong, 1973). The rate of photolysis of 2,4,5-T was also higher in natural waters containing fulvic acids when compared to distilled water. The major photoproduct found in the humic acid-induced reaction was 2,4,5trichlorophenol. In addition, the presence of ferric ions and/or hydrogen peroxides may contribute to the sunlight-induced photolysis of 2,4,5-T in acidic, weakly absorbing natural waters (Skurlatov et al., 1983). Chemical/Physical. Carbon dioxide, chloride, dichloromaleic, oxalic and glycolic acids, were reported as ozonation products of 2,4,5-T in water at pH 8 (Struif et al., 1978). Reacts with alkali metals and amines forming water-soluble salts (Worthing and Hance, 1991). When 2,4,5-T was heated at 900 °C, carbon monoxide, carbon dioxide, chlorine, HCl, and oxygen were produced (Kennedy et al., 1972, 1972a). Pignatello (1992) investigated the reaction of 2,4,5-T (0.1 mM) with Fenton’s reagent in an airsaturated acidic solution at 21 °C. When the concentrations of Fe2+ and hydrogen peroxide concentrations were both >1mM, the reaction time for complete transformation was <1 min. The transformation of 2,4,5-T to the major product, 2,4,5-trichlorophenol, decreased with increasing the initial pH. In the presence of Fe3+ and excess hydrogen perioxide, the mineralization of 2,4,5-T to carbon dioxide and chloride ions is nearly complete. The rate of reaction is sensitive to pH, the optimum pH at approximately 2.75. The reaction with Fe3+ and hydrogen perioxide is accelerated in the presence of UV light (λ >300 nm). 2,3,5-T will not hydrolyze to any reasonable extent (Kollig, 1993). Exposure limits (mg/m3): NIOSH REL: TWA 10, IDLH 250; OSHA PEL: TWA 10; ACGIH TLV: TWA 10 (adopted). Symptoms of exposure: Skin irritation. May also cause eye, nose, and throat irritation (NIOSH, 1987). An acceptable daily intake reported for humans is 0.03 mg/kg body weight provided the product contains ≤0.01 mg TCDD/kg 2,4,5-T (Worthing and Hance, 1991). Toxicity: EC50 (5-min) for Photobacterium phosphoreum 51.7 mg/L (Somasundaram et al., 1990). LC50 (96-h) for rainbow trout 350 mg/L and carp 355 mg/L (Hartley and Kidd, 1987). Acute oral LD50 for chickens 310 mg/kg, dogs 100 mg/kg, guinea pigs 381 mg/kg, hamsters 425 mg/kg, mice 389 mg/kg, rats 300 mg/kg (quoted, RTECS, 1985). Acute oral LD50 for rats >5,000 mg/kg (Worthing and Hance, 1991). A NOEL of 30 mg/kg diet was observed for rats during 2-yr feeding trials (Worthing and Hance, 1991). Drinking water standard: No MCLGs or MCLs have been proposed although 2,4,5-T has been listed for regulation (U.S. EPA, 1996). A DWEL of 400 µg/L was recommended (U.S. EPA, 2000). Uses: Plant hormone; defoliant. Formerly used as a herbicide. Banned by the U.S. EPA.