Polychlorinated phenoxyphenols

TCP), and pentachlorophenol (PCP), in order of abundance. Minor amounts of other trichlorophenols and dichlorophenols may also be present, as well as recalcitrant polychlorinated phenoxyphenols (PCPPs) and PCDD/Fs as impurities [75, 76]. In Finland, approximately 30,000 tons of CP products were used between 1934 and 1988, when they were banned because of their potential toxicity to humans and the environment [77, 78]. The careless manufacturing and application of wood preservatives together with the lack of suitable waste disposal caused massive contamination of river sediments and sawmill sites. For example, the river Kymijoki in southern Finland was identified as the largest source of dioxins accumulating in fish in the entire Baltic area. Similar products were used in other European countries, especially Nordic countries with a large forestry industry, such as Sweden [79]. 

List of abbreviations BOD, biological oxygen demand CA, chloroanisol CCA, copper-chromate-arsenate CP, chlorophenol 2,4-D, dichlorophenoxyacetic acid DCP, dichlorophenol CFSTR, continuous-flow stirred tank reactor FBBR, fluidized-bed biofilm reactor MCP, monochlorophenol NAPL, non-aqueous phase liquid PAH, polycyclic aromatic hydrocarbon PCPP, polychlorinated phenoxyphenol PCDF, polychlorinated dibenzofuran PCDD, polychlorinated dibenzodioxin PCR, polymerase chain reaction PCP, pentachlorophenol PCA, pentachloroanisole TeCP, tetrachlorophenol TeCA, tetrachloroanisole TCC, trichlorocatechol TCP, trichlorophenol TOC, total organic carbon 2,4,5-T, trichlorophenoxyacetic acid UASB, upflow anaerobic sludge blanket reactor VSS, volatile suspended solids. 

Technical CP formulations contain impurities such as polychlorinated phenoxyphenols (PCPPs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) (Humppi et al., 1984 Kitunen et al., 1985 Jackson Bisson, 1990). Therefore, PCPPs, PCDFs, and PCDDs are often found in CP-contaminated wood treatment sites (Kitunen et al., 1985, 1987 Jackson Bisson, 1990 Kitunen Salkinoja-Salonen, 1990 Trudell et al., 1994). PCPP concentrations up to 78 mg/kg, PCDF up to 3-8 mg/kg, and PCDDs at 13 mg/kg have been detected in CP-contaminated sites (Kitunen et al., 1987 Jackson Bisson, 1990). 

Humppi, T., Knuutinen, J. Paasivirta, J. (1984). Analysis of polychlorinated phenoxyphenols in technical chlorophenol formulations and in sawmill environment. Chemosphere, 11, 1235-41. 

Technical chlorophenol formulations are the major sources of PCDEs in the environment [4,40,45,46]. Hydroxy chlorodiphenyl ethers (OH-PCDE), also called polychlorinated phenoxyphenols (PCPP), are the main impurities of chlorophenols [39,47,48]. 2-OH-PCDEs are called predioxins, since they are phenolic precursors to polychlorinated dibenzo-p-dioxins (PCDD) [47]. The levels of 2-hydroxy-nonaCDEs have varied between 0.6 mg kg-1 and 1100 mg kg-1 in commercial pentachlorophenol preparations (sodium salts) [47]. 3,4,5,6-tetrachloro-2-(2,3,4,5,6-pentachlorophenoxy)phenol) is the main impurity of commercial pentachlorophenols [48]. 

As part of its operations between 1955 and 1977, a Finnish sawmill had been impregnating timber with a preservative to inhibit microbial degradation. This product, called Ky-5, contained a mixture of chlorophenols, namely, 2,4,6-trichlorophenol (7-15%), 2,3,4,6-tetrachlorophenol ( 80%) and pentachlorophenol (6-10%). Ky-5 also contained traces of polychlorinated phenoxyphenols and dibenzo-p-dioxins as impurities. Over the years this product had contaminated the soils around the sawmill. A cost-effective bioremediation strategy was needed that could be used at this site but also throughout Finland where 800 other sites of this type existed. 

Formation of dichlorobenzoquinone, trichlorobenzoquinone, tetrachloro-phenol and polychlorinated phenoxyphenols is also observed (Fig. 7). 

As discussed in the earlier survey (1), a biogenic source of polychlorinated dibenzo-p-dioxins and dibenzofurans is peroxidase-catalyzed transformation of chlorophenols as first reported by Oberg and Rappe (2041-2044). More recent studies confirm these observations (2045-2048). In addition to lactoperoxidase and horseradish peroxidase, human leukocyte myeloperoxidase catalyzes in vitro formation of dioxins and dibenzofurans from chlorophenols (2046, 2047). Formation rates are in the pmol/mol range (Scheme 3.6) demonstrating that a human biosynthesis of dioxins and furans is not only possible but also likely. These observations are reinforced by the reported in vivo (rats) conversion of the pre-dioxin nona-chloro-2-phenoxyphenol to octachlorodibenzo-p-dioxin (OCDD) (2049), and the production of hepta- and octachlorodibenzo-p-dioxin in the feces of cows fed pentachlorophenol-treated wood (Scheme 3.7) (2050, 2051). 

Kerkvliet NI, Brauner JA, Matlock JP. 1985. Humoral immunotoxicity of polychlorinated diphenyl ethers, phenoxyphenols, dioxins and furans present as contaminants of technical grade pentachlorophenol. Toxicology 36 307-324. 

In an intramolecular example of photodechlorination implying a phenolate anion, a triplet sensitizer and triethylamine, a cyclization of perchlorinated o-phenoxyphenol to octachlorodibenzodioxin is observed. An intramolecular electron transfer from the polychlorinated phenolate moiety to the perchloro-phenyl residue is considered together with an intermolecular electron transfer from external triethylamine followed by an intramolecular SrnI path for the ring closure [177]. 

At first sight, polychlorinated ge/n-dichlorocyclohexadienones seem to have thermal stability in the presence of trihalogenated phenols in 2.4.6 position. But detailed analysis of the reaction mass - now possible thanks to the development of the analytical method described above - shows that in all the cases a 3 to 15 % formation of polychloro phenoxyphenols occurs. After heating for 8 hours at 70°C the 2,4,4,6-tetrachlorocyclohexa-2,5-dien-l-one 2 (ImM) in 2,4,6-tetrachloro-phenol (10 mM), the following products 2,4-dichIoro 6-(2,4,6-tetrachlorophenoxy) phenol 8 and 2,6-dichloro 4-(2,4,6-trichlorophenoxy) phenol 2 (Fig. 9) are detected within the reaction mass. 

As soon as they reach 70°C, phenols with low chlorine content (phenol, monochlorophenols, dichlorophenols) produce polychloro phenoxyphenols in the presence of polychlorinated gem-dichlorocyclohexadienones. In this case there is some consumption of polychlorinated gem-dichlorocyclohexadienones. 

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