Biodegradation of coplanar polychlorinated biphenyls by anaerobic microorganisms from estuarine sediments.

In this study, we investigated the biodegradability of biphenyl and 5 congeners (one non-planar and four coplanar) of polychlorinated biphenyl (PCB). Biphenyl, the non-planar congener 2,3',4',5-tetrachlorobiphenyl (25-34 CB), and the four coplanar congeners 3,3',4,4'-tetrachlorobiphenyl (34-34 CB), 3,4,4',5-tetrachlorobiphenyl (345-4 CB), 3,3',4,4',5-pentachlorobiphenyl (345-34 CB), and 3,3',4,4',5,5'-hexachlorobiphenyl (345-345 CB) were amended at a concentration of 10 mg/L into anoxic sediment slurries collected from the estuaries of the Tansui River and the Erjen River. During 2 years' incubation under sulfidogenic conditions, biphenyl was persistent, while all other chlorinated congeners, except for 345-345 CB, were dechlorinated with or without a lag period in sediment slurries collected from both rivers. Dechlorination of coplanar and non-planar congeners began with para chlorine removal. All para chlorines from the mono-, di-, and trichlorobiphenyl groups could be removed by sediment slurries from both rivers. Microbial communities in sediment from the Erjen River additionally fostered meta-dechlorination activity, but only after removal of all the para chlorines. Addition of Tween 20 (0.05%, v/v) into sediment slurries from the Tansui River did not enhance dechlorination rates or extents, but the addition of toluene- or 3-chlorobenzoate-adapted sediments enhanced dechlorination of 34-34 CB and 345-4 CB.     

Microbial transformation and degradation of polychlorinated biphenyls

This paper reviews the potential of microorganisms to transform polychlorinated biphenyls (PCBs). In anaerobic environments, higher chlorinated biphenyls can undergo reductive dehalogenation. Meta- and para-chlorines in PCB congeners are more susceptible to dechlorination than ortho-chlorines. Anaerobes catalyzing PCB dechlorination have not been isolated in pure culture but there is strong evidence from enrichment cultures that some Dehalococcoides spp. and other microorganisms within the Chloroflexi phylum can grow by linking the oxidation of H(2) to the reductive dechlorination of PCBs. Lower chlorinated biphenyls can be co-metabolized aerobically. Some aerobes can also grow by utilizing PCB congeners containing only one or two chlorines as sole carbon/energy source. An example is the growth of Burkholderia cepacia by transformation of 4-chlorobiphenyl to chlorobenzoates. The latter compounds are susceptible to aerobic mineralization. Higher chlorinated biphenyls therefore are potentially fully biodegradable in a sequence of reductive dechlorination followed by aerobic mineralization of the lower chlorinated products.     

Isomer specific synthesis using the Suzuki-coupling. Polychlorinated terphenyls as standards for environmental analysis

Defined polychlorinated terphenyl (PCT) single congeners as reference standards are the prerequisite for the development of analytical methods for their determination and quantification in the environment. The selective synthesis of PCTs for environmental analytical purposes by application of the Suzuki-coupling reaction is described. Under easily modified standard reaction conditions of this coupling process the PCTs can be obtained by reaction of benzeneboronic acids with dibromobenzenes mostly in good yields, as described by the synthesis of following PCT congeners: p-PCT (3,3("),5,5(")-tetrachloro-, 2,2("),4,4(")-tetrachloro-, 2('),3,3("),5,5(")-pentachloro-); m-PCT (3,3("),5,5(")-tetrachloro-) and o-PCT (3,3("),5,5(")-tetrachloro-). The terphenyl congeners were characterized by NMR (1H, 13C)- and FT-IR-spectroscopy. Their purity was checked by GC/MS analysis. The experimental and quantum-chemically calculated FT-IR-spectra were compared and it was shown, that the determination of the chlorine substitution pattern in the terphenyl congeners by their typical absorption spectra is possible.     

Persistency of highly toxic coplanar PCBs in aquatic ecosystems: uptake and release kinetics of coplanar PCBs in green-lipped mussels (Perna viridis Linnaeus)

The bioaccumulation potential of three highly toxic coplanar PCB isomers [3,3',4,4'-tetrachlorobiphenyl (T(4)CB); 3,3',4,4',5-pentachlorobiphenyl (P(5)CB); and 3,3',4,4',5,5'-hexachlorobiphenyl (H(6)CB)] was investigated using green-lipped mussels (Perna viridis Linnaeus) as a bioindicator, through a transplantation experiment at two locations in Hong Kong waters. By contrast to the relatively rapid uptake and release of many other PCB isomers, the non-ortho chlorine substituted coplanar PCB congeners exhibited slow uptake and clearance. The kinetic parameters of coplanar PCBs based on lipid weight-related data, and the degree of bioaccumulation based on the proportion of coplanar PCBs in total PCBs in mussels, clearly indicate that coplanar PCBs are highly bioaccumulative in lower organisms. On the assumption that mussels are unlikely to be particularly unusual with respect to their bioaccumulation of coplanar PCBs, it appears most likely that these highly toxic and persistent PCB congeners are concentrated by all aquatic organisms, and may reach higher consumers (including humans) in quantities of toxicological concern.     

Dehalogenation of 2,6-dibromobiphenyl and 2,3,4,5,6-pentachlorobiphenyl in contaminated estuarine sediment

Estuarine sediments from a USEPA Superfund site in coastal Georgia were extensively contaminated with Aroclor 1268, a mixture of highly chlorinated polychlorinated biphenyls used by a former chlor-alkali plant. Batch slurries of contaminated sediment were incubated for 1 yr with amendments of 2,6-dibromobiphenyl (26-BB) and 2,3,4,5,6-pentachlorobiphenyl (23456-CB) under anaerobic, sulfate-reducing conditions and different pH (5.5-7.5). Organic extracts of slurry sub-samples in a time series were analyzed by congener-specific GC-MS. Dechlorination of 23456-CB was pH dependent and occurred via two routes with the sequential loss of (1) meta and para chlorines and (2) para, ortho, and meta chlorines. Quantitative dehalogenation of 26-BB was observed at all pH. Supplementation of nonachlorobiphenyls (as primers) did not induce dechlorination of native Aroclor 1268 nor of the primers themselves. While contaminated estuarine sediments possess microbial consortia with diverse dehalogenating activities, lack of dechlorination of Aroclor 1268 and spiked nonachlorobiphenyl congeners suggests a bioavailability limitation or enzyme-substrate incompatibilities.     

Synthesis of [14C]biphenyl and of some chlorinated [14C]biphenyls containing 4-chloro-, 2,4-dichloro- and 2,3,6-trichlorophenyl nuclei from the corresponding labelled anilines

The preparation of ¹⁴C-labelled biphenyl, 2,5-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl, 2,2′,4,5′-tetrachlorobiphenyl, 2′,3,4,4′,5-pentachlorobiphenyl, 2,2′,3,4,4′-pentachlorobiphenyl, 2,3,3′,4′,6-pentachlorobiphenyl and 2,2′,3,3′,6-pentachlorobiphenyl is described [¹⁴C]Aniline hydrogen sulfate used as a starting material was acetylated, chlorinated and deacetylated followed by coupling to benzene or an appropriate chlorobenzene to give the biphenyls labelled in the phenyl nuclei having chlorine atoms at the 4-, 2,4- or 2,3,6-positions, respectively. The structures of the labelled compounds were established by comparison with authentic samples among which 2′,3,4,4′,5- and 2,2′,3,4,4′-pentachlorobiphenyl were not earlier described.A simple method for the preparation of 2,3,6-trichloroacetanilide, unlabelled and labelled, was worked out. 2,6-Dichloroacetanilide in concentrated hydrochloric acid gave the $\text{meta}$ substituted product when treated with chlorine.An improved thin layer chromatographic technique utilizing plates impregnated with certain tetraalkylammonium salts was used for separation of some of the labelled compounds prepared.     

Synthesis of polybrominated diphenyl ethers via symmetrical tetra- and hexabrominated diphenyliodonium salts

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants (BFRs) which have become widespread environmental pollutants due to their persistence and bioaccumulativeness. Pure authentic PBDE congeners are required for chemical analysis, assessments of their chemical/physical properties and toxicological studies. We here report an improved method for synthesis of authentic PBDE congeners applying bromophenols and symmetrical brominated diphenyliodonium salts as building blocks. Altogether, 13 PBDEs were synthesized of which seven are new. The improved coupling reaction between the bromophenol and the brominated diphenyliodonium salts resulted in enhanced yields for PBDEs substituted with more than six bromine atoms. Also, improvements in iodonium salt synthesis made it possible to synthesize symmetrical hexabromodiphenyliodonium salts for the first time, i.e. 2,2',3,3',4,4'-, 2,2',4,4',5,5'- and 2,2',4,4',6,6'-hexabromodiphenyliodonium salts and they made it possible to prepare octabrominated PBDEs via the actual coupling method. All synthesized compounds were characterized by (1)H NMR, (13)C NMR spectra and by their melting points. Also, all products except for the diphenyliodonium salts were characterized by mass spectra in electron ionization mode.     

Chlorination of bisphenol A in aqueous media: formation of chlorinated bisphenol A congeners and degradation to chlorinated phenolic compounds

The chlorination of bisphenol A (BPA) in aqueous media was investigated in order to describe the degradation profile of this compound and the formation of chlorinated products. Aqueous solutions of BPA (approx. 1 mg/l) were chlorinated by sodium hypochlorite solution at room temperature and under weakly alkaline conditions. Chlorinated compounds were extracted with dichloromethane and determined by gas chromatography/mass spectrometry (GC/MS). BPA was consumed completely within 5 min of chlorination, when the initial chlorine concentration was 10.24 mg/l (molar ratio to BPA, 58.7). On the other hand, when the initial chlorine concentration was 1.03 mg/l (molar ratio, 6.56), 9.3% of BPA still remained after 60 min chlorination. Five chlorinated BPA congeners, 2-chlorobisphenol A (MCBPA), 2,6-dichlorobisphenol A (2,6-D2CBPA), 2,2'-dichlorobisphenol A (2,2'-D2CBPA), 2,2',6-trichlorobisphenol A (T3CBPA) and 2,2', 6,6'-tetrachlorobisphenol A (T4CBPA) were formed in the earlier stages of chlorination. Several chlorinated phenolic compounds, 2,4,6-trichlorophenol (T3CP), 2,6-dichloro-1,4-benzoquinone (D2CBQ), 2,6-dichloro-1,4-hydroquinone (D2CHQ), C9H10Cl2O2, C9H8Cl2O and C10H12Cl2O2, were also formed by further chlorination.     

Synthesis and tentative identification of novel polybrominated diphenyl ether metabolites in human blood

Hydroxylated polybrominated diphenyl ethers (OH-PDBEs) are exogenous, bioactive compounds that originate, to a large extent, from anthropogenic activities, although they are also naturally produced in the environment. In the present study nine new authentic OH-PBDE reference standards and their corresponding methyl ether derivatives (MeO-PBDEs) were synthesised and characterised by NMR spectroscopy and mass spectrometry. Seven of the authentic reference standards prepared were thereafter tentatively identified in a pooled human blood sample. The tentatively identified OH-PBDEs were 3-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3'-hydroxy-2,2',4,4',6-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5-pentabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3'-hydroxy-2,2',4,4',5,6'-hexabromodiphenyl ether, 3-hydroxy-2,2',4,4',5,5'-hexabromodiphenyl ether and 4-hydroxy-2,2',3,4',5,5',6-heptabromodiphenyl ether. An additional seven OH-PBDEs were tentatively identified in the pooled human blood sample, of which one OH-PBDE, 4'-hydroxy-2,2',4,5,5'-pentabromodiphenyl ether, has not been identified in human blood before. The identification was performed using gas chromatography-mass spectrometry (GC-MS) recording the bromine ions m/z 79, 81. The tentative identification was supported by the peaks relative retention times (RRTs) compared to authentic references on two GC columns of different polarities for the hexa-, and heptabrominated OH-PBDEs, and three different GC columns for the pentabrominated OH-PBDEs. The OH-PBDE congeners most likely originate from human metabolism of a flame retardant, i.e. polybrominated diphenyl ethers (PBDEs), due to the relatively high concentrations of PBDEs in the same human blood sample and the fact that these PBDEs could form the tentatively identified OH-PBDEs via metabolic direct hydroxylation or via 1,2-shift.     

Dechlorination of hexachlorobiphenyl by using potassium-sodium alloy

2,2',4,4',5,5'-Hexachlorobiphenyl (HCB) was dechlorinated with potassium-sodium (K-Na) alloy under an inert gas atmosphere. Solvent effect was observed in the reaction. Dechlorination yields in benzene and cyclohexane were 99.9998%, and 99.99996%, respectively. The reaction was exothermic and proceeded at room temperature. In benzene, trace amounts of polychlorinated biphenyls (PCBs) as products by stepwise dechlorination and polychlorinated quarterphenyls as product of Wurtz-Fittig reaction were detected as reaction intermediate. Reaction products were biphenyl, cyclohexylbenzene, and dicyclohexyl. In cyclohexane, there were no products of Wurtz-Fittig reaction. Dechlorination at para-position preferred to that at ortho-position, judging from analysis of PCBs as intermediates of stepwise dechlorination.     

Biliary secretion,retention and excretion of five 14C-labelled polychlorinated biphenyls in the rat

Five ¹⁴C-labelled polychlorinated biphenyls: 2,4′,5-trichlorobiphenyl, 2,2′,4,5′-tetrachlorobiphenyl, 2,2′,4,5,5′-pentachlorobiphenyl, 2,2′,3,4,4′-pentachlorobiphenyl and 2,2′,4,4′,5,5′-hexachlorobiphenyl were administered orally to bile-cannulated rats. The activity secreted in the bile, excreted in the feces and the urine was determined. Residues of radioactivity in certain tissues and the carcass were also measured.The trichlorobiphenyl showed the highest absorption (93.8%±5.4) from the gastrointestinal tract and biliary secretion of radioactivity (87.6%±6.1 of the dose). The hexachlorobiphenyl showed the lowest absorption and biliary secretion, 28.2%±1.4 and 18.6%±1.3, respectively. The urinary excretion was low and the radioactive residues in the eviscerated carcasses increased with the chlorine content of the biphenyls.     

Brominated-chlorinated diphenyl ethers formed by thermolysis of polybrominated diphenyl ethers at low temperatures

Polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants (BFRs) used mainly as additives in different kinds of plastic material. Various PBDEs are found in all environmental compartments as well as in tissue and blood serum of animals and humans due to their persistence and tendency to bioaccumulate. Emission of PBDEs into the environment can occur during recycling of PBDE-containing plastic material or during their uncontrolled or insufficient combustion as e.g. in accidental fires or landfill fires. Under these circumstances, PBDEs can also function as precursor molecules for the formation of polybrominated dibenzodioxins (PBDDs) and dibenzofurans (PBDFs). In this study, we qualitatively investigated the reaction of two PBDE congeners, 2,2′,4,4′-tetrabromo diphenyl ether (BDE 47) and 2,2′,4,4′,5,5′-hexabromo diphenyl ether (BDE 153), as well as hexabromobenzene (HBB), a flame retardant used in the past, when exposed to temperatures between 250 °C and 500 °C. The formed reaction products were analysed by high resolution gas chromatography–low resolution mass spectrometry (HRGC-LRMS). Among others brominated–chlorinated diphenyl ethers were formed by chlorodebromination of the PBDEs. In addition, thermolysis of BDE 47 and BDE 153 in the presence of tetrachloromethane as model substance for an organic chlorine source was studied. Thermal treatment of HBB resulted in the formation of brominated–chlorinated benzenes.     

Spatial distribution of polybrominated diphenyl ethers and polybrominated biphenyls in lake trout from the Laurentian Great Lakes

Concentrations of two types of brominated flame-retardants (BFRs); polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) were determined in a single age class of lake trout (Salvelinus namaycush) collected from the Laurentian Great Lakes in 1997. Mean concentrations of total PBDE were highest in samples from Lake Ontario at 95+/-22 ng/g wet weight (ww) or 434+/-100 ng/g lipid weight (lw) while the lowest concentrations were observed in Lake Erie lake trout (27+/-8.6 ng/g ww, 117+/-37 ng/g lw). In all samples, the predominant PBDE congeners were 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), and 2,2',4,4', 6-pentabromodiphenyl ether (BDE-100), which are the primary components of the commonly used penta-BDE formulation flame retardant. Lake trout collected from Lake Huron had the highest concentrations of PBBs (3.1+/-1.7 ng/g ww, 15+/-8.5 ng/g lw), while the lowest levels were detected in fish from Lake Superior (0.25+/-0.13 ng/g ww, 1.7+/-0.89 ng/g lw). In all lake trout samples, 2,2',4,4',5,5'-hexabromobiphenyl (BB-153), a major constituent of the flame-retardant FireMaster BP-6, was the predominant PBB congener.     

Structure elucidation of four possible biogenic organohalogens using isotope exchange mass spectrometry

The molecular structures of four unknown bioaccumulating halogenated compounds, C10H6N2Br3Cl3, C10H6N2Br4Cl2, C10H6N2Br5Cl, and C10H6N2Br6 were characterized using isotope exchange positive chemical ionization (IE-PCI) mass spectrometry (MS) and identified by comparison to synthesized standards. NH3 and ND3 were used as reagent gases for the IE-PCI-MS experiment. The shift in mass of the quasimolecular ion between the NH3 and ND3 PCI obtained spectra indicated the number of exchangeable hydrogens attached to the two nitrogen atoms in C10H6N2Br4Cl2, and thus the type of amines present (primary, secondary, or tertiary). 19 compounds (13 amines of varying degree of substitution; six containing no nitrogen) were used as reference compounds and controls in the experiment to validate the IE-PCI technique. The results of the IE-PCI-MS indicated the presence of two tertiary amine functional groups. The molecular structures of the four hexahalogenated compounds were then proposed to be 1,1'-dimethyl-3,3',4,-tribromo-4',5,5'-trichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole, and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole and subsequently synthesized. Comparison of retention times and electron capture negative ionization (ECNI) full scans on various gas chromatography (GC) columns between the synthesized bipyrroles and the corresponding unknown compounds in biota indicated that three of the unknown compounds--possible marine natural products--were the proposed halogenated dimethyl bipyrroles. The placement of the halogen atoms on the fourth compound, C10H6N2Br3Cl3 could not be unequivocally determined since the synthesized standard could not be fully characterized.     

Examination of the bioaccumulation of halogenated dimethyl bipyrroles in an Arctic marine food web using stable nitrogen isotope analysis.

Concentrations of four possibly naturally produced organohalogens--1,1'-dimethyl-3,3',4-tribromo-4,5,5'-trichloro-2,2'-bipyrrole (DBP-Br3Cl3), 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole (DBP-Br4Cl2), 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole (DBP-Br5Cl) and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole (DBP-Br6)--were quantitated and the extent of their magnification through an entire Arctic marine food web [measured as integrated trophic magnification factors (TMFs)] were calculated. The food web consisted of three zooplankton species (Calanus hyperboreus, Mysis oculata, and Sagitta sp.), one fish species [Arctic cod (Boreogadus saida)], four seabird species [dovekie (Alle alle), black guillemot (Cepphus grylle), black-legged kittiwake (Rissa tridactyla), and glaucous gull (Larus hyperboreus)], and one marine mammal species [ringed seal (Phoca hispida)]. Trophic levels in the food web were calculated from ratios of stable isotopes of nitrogen (15N/14N). All halogenated dimethyl bipyrrole (HDBP) congeners were found to significantly (P<0.02) biomagnify, or increase in concentration with trophic level in the invertebrate--fish--seabird food web. DBP-Br4Cl2 (TMF= 14.6) was found to biomagnify to a greater extent than DBP-Br3Cl3 (TMF = 5.2), DBP-Br5Cl (TMF = 6.9), or DBP-Br6 (TMF = 7.0), even though the Kow of DBP-Br4CI2 was predicted to be lower than those of DBP-Br5Cl and DBP-Br6. None of the four HDBP congeners in ringed seals followed the general trend of increasing concentration with trophic level, which was possibly due to an ability of the seals to metabolize HDBPs.     

Effect of coplanar PCB concentration on dechlorinating microbial communities and dechlorination in estuarine sediments

The effect of concentration of coplanar PCB on the dechlorinating microbial community and dechlorination were investigated in anoxic estuarine sediment collected from Er-Jen River and enriched with 10 and 50 mg L⁻¹ of 3,4,4′,5-tetrachlorobiphenyl, 3,3′,4,4′,5-pentachlorobiphenyl, and 3,3′,4,4′,5,5′-hexachlorobipheny. Dechlorination rates were similar in the cultures enriched with 10 and 50 mg L⁻¹ of 3,4,4′,5-tetrachlorobiphenyl, whereas significantly higher dechlorination rates were observed in cultures enriched with 10 mg L⁻¹ of 3,3′,4,4′,5-pentachlorobiphenyl. No dechlorination was observed in sediment slurries enriched with 3,3′,4,4′,5,5′-hexachlorobipheny. Para dechlorination occurred prior to meta dechlorination during reductive dechlorination of 3,4,4′,5-tetrachlorobiphenyl and 3,3′,4,4′,5-pentachlorobiphenyl. GC-MS and denaturing gradient gel electrophoresis (DGGE) were used to detect dechlorination products and dechlorinating microorganisms in the enriched sediment cultures during the process of degradation. Two Chloroflexi phylotypes observed in DGGE were responsible for para and meta dechlorination respectively. Phylotype Cp-1 has 98% similarity to uncultured bacterium N5-12. Phylotype Cm-1 has 99% similarity to uncultured dechlorinating bacterium m1 or SF1 belonging to the ο-17/DF-1 group of PCB-dechlorinating bacteria.     

Congener-specific analysis of non-dioxin-like polychlorinated biphenyls in blood collected from 127 elderly residents in Nakagawa Town, Fukuoka Prefecture, Japan

We conducted congener-specific analysis of non-dioxin-like polychlorinated biphenyls (non-dioxin-like PCBs) in blood collected in February 2004 from 127 elderly residents living in Nakagawa Town, Fukuoka Prefecture, Japan. The present study is one of the few studies in which 56 non-dioxin-like PCBs congeners were measured in human blood. Of the 127 elderly residents, 51 were men (mean: 68.1 years) and 76 were women (mean: 68.1 years). Among 197 non-dioxin-like PCB congeners, 56 were identified in the blood of elderly residents. The arithmetic mean total concentrations of 56 non-dioxin-like PCBs congeners in the blood of elderly men and women in Nakagawa Town were 419 (median: 378) and 363 (median: 323)ngg(-1)lipid, respectively, and the concentrations were in the range of 172-1102 and 119-1226ngg(-1)lipid, respectively, indicating that the total concentrations in elderly men are significantly higher than those in elderly women. The contamination of non-dioxin-like PCBs in the blood of elderly men and women in Fukuoka Prefecture was found to have decreased compared to past levels. The ratios of hexachlorinated biphenyls (hexaCBs) to the total concentrations of 56 non-dioxin-like PCBs congeners in the blood of elderly men and women were 44.6% and 45.6%, respectively, which was particularly high compared with those of other congeners. 2,2',4,4',5,5'-HexaCB (#153) among hexaCBs congeners, the most abundant congener in the blood of elderly men and women, contributed approximately 23.0% and 23.5% to the total concentrations of 56 non-dioxin-like PCBs congeners, respectively. Furthermore, 2,2',3,4,4',5'-hexaCB (#138), 2,3,3',4',5,6-hexaCB (#163)/2,3,3',4',5',6-hexaCB (#164), 2,2',3,4,4',5,5'-heptaCB (#180), and 2,2',3,4,4',5,6'-heptaCB (#182)/2,2',3,4',5,5',6-heptaCB (#187) also showed high ratios to the total concentrations of 56 non-dioxin-like PCBs congeners detected in the blood of elderly men and women. A statistical examination of the relationship between the total concentrations of 56 non-dioxin-like PCBs congeners in blood and the age of elderly residents who were over 60 years indicated statistically significant correlations between the total concentrations of these PCBs congeners and the age of elderly women. However, similar correlations were not observed in elderly men. The results of the present study have indicated the current levels of non-dioxin-like PCBs in the blood of elderly men and women in Fukuoka Prefecture, Japan and can be used as baseline data for those over age 60.     

Highly toxic coplanar PCBs: occurrence, source, persistency and toxic implications to wildlife and humans

Isomer-specific determinations of PCB congeners in a wide variety of animal species such as fish, marine mammals (whale, dolphin and porpoise) and terrestrial mammals (dog, cat and human) revealed the environmental occurrence of highly toxic coplanar 3,3',4,4'-tetrachlorobiphenyl (T(4)CB), 3,3',4,4',5-pentachlorobiphenyl (P(5)CB) and 3,3',4,4',5,5'-hexachlorobiphenyl (H(6)CB) within a range of few pg g(-1) to several ten ng g(-1) in fat tissues (except fish) on a wet weight basis. Detection of these toxic residues in wild specimens collected from remote areas such as the North Pacific suggests the already widespread distribution of coplanar PCBs as in the case of general PCB pollution. The clear positive correlations between concentrations of total PCBs and each of the three coplanar PCBs obtained in all mammals analysed suggest that the sources of coplanar PCB contamination to the environment are mainly commercial PCB preparations. Comparison of the composition of three toxic coplanar PCBs in commercial PCB mixtures and in the various animals indicates the relative metabolisability of these congeners as follows: 3,3',4,4'-T4CB>3,3',4,4',5-P5CB>3,3',4,4',5,5'-H6CB. Moreover, marine mammals seem to have lower potency to metabolise the coplanar PCBs in comparison with terrestrial mammals. In human adipose tissues, the concentrations of coplanar PCBs were found to be much higher than 2,3,7,8-tetrachlorodibenzo-p-dioxin (T(4)CDD), 2,3,4,7,8-pentachlorodibenzofuran (P(5)CDF) and other toxic congeners. 'T(4)CDD-equivalent' analysis based on the enzyme induction potencies and the residues of these toxic chemicals indicates that 3,3',4,4',5-P(5)CB may impose a greater toxic threat than dioxins and furans to the humans and probably to wildlife also.     

Patterns of contamination by organochlorines and mercury in the eggs of two river passerines in Britain and Ireland with reference to individual PCB congeners

Unhatched eggs were collected in 1988 and 1990 from nests of the Eurasian Dipper Cinclus cinclus and the Grey Wagtail Motacilla cinerea in Wales, eastern Scotland and south-western Ireland. Mercury concentrations in Dipper eggs (geometric means 0.45-0.91 ppm (microg g(-1)) dry mass) were significantly lower in eastern Scotland than in either south-western Ireland or Wales, where the incidence of detectable residues increased markedly between 1988 (2% of eggs) and 1990 (69%). By contrast, DDE (geometric means 0.63-3.54 ppm in lipid), TDE (<0.01-1.80 ppm), DDT (<0.01-0.65 ppm), total PCBs (3.99-10.47 ppm), HEOD (0.39-0.61 ppm) and HCB (0.02-0.13 ppm) were all significantly higher in Scottish eggs than others. Around 33-46% of the total PCB burden in Dipper and Grey Wagtail eggs could be accounted for by six congeners (IUPAC numbers 118, 180, 101, 153, 138 and 170). Amongst these attributable PCBs, Dipper eggs from eastern Scotland were dominated by congener 153 (2,2',4,4',5,5'-hexachlorobiphenyl), whilst Welsh and Irish eggs were dominated by congener 118 (2,3',4,4',5-pentachlorobiphenyl). With the latter exception, all the individual congeners were found at significantly higher concentrations in Scottish eggs than others. Grey Wagtail eggs were dominated by congeners 118 and 101 (2,2,4,5,5'-pentachlorobiphenyl). In general, these congeners are common, widespread, and dominant components in the eggs of other wild birds for which data are available. Consistent with the low to medium levels of contaminants found in Dipper eggs, there was only slight evidence of any toxic effects. These included moderate shell thinning in relation to increasing DDE, and some evidence that contaminants had contributed to egg failure.     

Stable chlorine intramolecular kinetic isotope effects from the abiotic dehydrochlorination of DDT

INTENTION, GOAL, SCOPE, BACKGROUND: Identifying different sources and following reaction pathways of chlorinated organic contaminants in the environment can be challenging, especially when only their concentrations are available. Compound-specific stable chlorine measurements of some contaminants have recently been shown to provide additional information and an increased understanding of their biogeochemistry. These studies, however, have been generally limited to volatile molecules. OBJECTIVE: Here, the stable chlorine isotope ratios of the semi-volatile pesticide, 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) were investigated. Specifically, the intramolecular stable chlorine isotopic compositions of DDT and the kinetic isotope effect (KIE) for the abiotic dehydrochlorination of DDT to 2,2-bis(p-chlorophenyl)-1,1-dichloroethene (DDE) were determined. METHODS: Selective chemical oxidation of DDT to dichlorobenzophenone (DCBP) and analysis of each compound was used to calculate the stable chlorine isotope ratios of the alkyl and aromatic chlorines in DDT. To determine the KIE for dehydrochlorination, DDT was reacted in a basic solution to yield DDE at 52 degrees C, 60 degrees C, and 72 degrees C for 3, 5, and 5 days, respectively. RESULTS AND DISCUSSION: Significant intramolecular stable chlorine isotopic differences were observed in one sample of DDT where the alkyl and aromatic delta 37Cl values were -5.76 +/- 0.45 and -2.21 +/- 0.24%@1000, respectively. Dehydrochlorination of DDT to DDE in basic solutions at 52, 60, and 70 degrees C resulted in a substantial intramolecular KIE where the alkyl chlorines of DDE shifted by approximately 3%@1000 relative to the alkyl chlorines in DDT. However, no temperature dependence was observed. The KIE, calculated by an iterative program, was 1.009. CONCLUSIONS: Intramolecular differences in the stable chlorine isotope ratios were observed in DDT and this is the first such finding. Dehydrochlorination of DDT yields a measurable and distinct intramolecular stable chlorine KIE. RECOMMENDATION AND OUTLOOK: The results of this study demonstrate the existence of significant intramolecular differences in chlorinated organic compounds. Many other chlorinated semi-volatile and volatile organic contaminants are synthesized from multiple sources of chlorine, and we recommend that similar studies be performed on many such molecules in order to attain a clear understanding of their intramolecular chlorine isotopic differences. The existence of a measurable KIE for the dehydrochlorination of DDT to DDE shows the potential strength of using isotopic measurements to investigate the biogeochemistry of these important compounds. For example, the isotopically depleted aqueous chloride produced by dehydrochlorination of DDT to DDE may be a useful tracer of these reactions in freshwater environments.