Dietary accumulation and metabolism of polybrominated diphenyl ethers by juvenile carp (Cyprinus carpio)

Polybrominated diphenyl ethers (PBDEs) are hydrophobic organic contaminants with properties and nomenclature similar to polychlorinated biphenyls (PCBs). While much information is available on the bioaccumulation and pharamcokinetics of PCBs, little information is available on PBDEs. In this study, juvenile carp were exposed to a diet spiked with a cocktail of four BDE congeners (2,4,4'-tribromoDE [BDE 28], 2,2',4,4'-tetrabromoDE [BDE 47], 2,2',4,4',5-pentabromoDE [BDE 99], and 2,2',4,4',5,5'hexabromoDE [BDE 153]) for 60 d followed by a 40-d depuration period. As a positive control, three PCB congeners with similar log K(ow), values (2,2',5,5'-tetrachlorobiphenyl [PCB 52], 2,2',4,4', 5,5'-hexachlorobiphenyl [PCB 153], and 2,2',3,4,4',5,5'-heptachlorobiphenyl [PCB 180]) were included in the cocktail to compare their assimilation and fate with the model BDE congeners. Concentrations of BDEs and PCBs were monitored in whole-fish tissues and liver tissues over the duration of the experiment. In addition, blood serum samples were taken and pooled among replicates to determine if any phenolic metabolites of BDE and PCBs were formed. Rapid assimilation of BDE 47 was observed relative to all other BDE and PCB congeners, whereas apparently no accumulation of BDE 99 occurred over the course of the experiment. Assimilation efficiencies for BDE 47 suggest that approximately 100% of the BDE 47 exposure was absorbed by carp tissues after 60 d. However, based on the time course of BDE 47 assimilation, it is improbable that all BDE 47 was assimilated; more likely, production of BDE 47 in carp tissues occurred as a result of debromination of higher-brominated compounds, possibly BDE 99. The net assimilation efficiencies of BDE 28 and BDE 153 were also apparently low (20 and 4%, respectively) relative to the three PCBs (40% assimilated) examined in this study. The low assimilation efficiency and high depuration rates for BDEs suggest a higher potential for biotransformation. While all three PCB compounds displayed very similar assimilation and depuration rates, three of the four BDE compounds displayed significantly different assimilation rates among BDE congeners and relative to the PCBs. This study suggests that BDEs have significantly different fate dynamics relative to PCBs in wild carp and likely other species of fish.     

Accumulation and distribution of polychlorinated dibenzo-p-dioxin, dibenzofuran, and polychlorinated biphenyl congeners in Atlantic salmon (Salmo salar)

Adult Atlantic salmon (Salmo salar) were fed on four diets containing polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) for 30 weeks. Lipid-normalized concentrations showed that all congeners were equally partitioned between whole-fish and fillet samples. Skinned fillet accumulated approximately 30% of the total PCDD/F and PCB content in fish. Accumulation efficiencies in whole fish were 43% for 2,3,7,8-chlorinated dibenzo-p-dioxins and dibenzofurans, 83% for dioxin-like PCBs, and 78% for other PCB congeners. Among PCDD/Fs, tetra- and pentachlorinated congeners were preferentially accumulated in salmon, whereas hepta- and octachlorinated dibenzo-p-dioxins were excreted in the feces. Substitution patterns that were associated with a preferential accumulation of PCBs in salmon included non-ortho substitution and tetrachlorination. Accumulation efficiencies and lipid-normalized biomagnification factors (BMFs) were not influenced by the PCDD/F and PCB concentrations of the diets. Biomagnification (BMF > 1) of tetra- and pentachlorinated dibenzo-p-dioxins and dibenzofurans and of all the PCBs was observed. Differences in the behavior of PCDD/F and PCB congeners resulted in a selective enrichment of the most toxic congeners in salmon.     

Metabolites of polychlorinated biphenyls in human liver and adipose tissue

A method for analysis of hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs) was developed and adopted to the previously described method for determination of PCBs and methylsulfonyl-PCBs (MeSO2-PCBs) in human liver and adipose tissue. The concentrations of OH-PCBs (14 congeners), MeSO2-PCBs (24 congeners), and PCBs (17 congeners) in five paired samples of human liver and adipose tissue are reported. The sum of OH-PCB congeners was higher in liver (7-175 ng/g lipids) than in adipose tissue (0.3-9 ng/g lipids). In both liver and adipose tissue, 2,2',3,4,4',5'-hexachloro-3'-biphenylol (3'-OH-CB138) and 2,2',3,3',4,5'-hexachloro-4'-biphenylol (4'-OH-CB130) were the predominant hydroxylated PCB metabolites. The sum of OH-PCB congeners were of the same order of magnitude as those of methylsulfonyl metabolites of PCB in the same samples, 12 to 358 ng/g lipids and 2 to 9 ng/g lipids in liver and adipose tissue, respectively. The levels of PCBs were similar in liver and adipose tissue, 459 to 2,085 ng/g lipids and 561 to 2,343 ng/g lipids, respectively. The sum of OH-PCBs and the sum of MeSO2-PCBs correlated to the sum of PCBs. The determined PCB metabolites constituted 3 to 26% of total PCB concentration in the liver and 0.3 to 0.8% of total PCBs in the adipose tissue samples.     

Thyroid hormone status of newborns in relation to in utero exposure to PCBs and hydroxylated PCB metabolites

The associations between in utero exposure to polychlorinated biphenyls (PCBs) or hydroxylated PCB metabolites (OH-PCBs), and free thyroxin (fT4) or thyroid-stimulating hormone (TSH) status in the newborn were investigated as a pilot study of a large-scale epidemiologic study on in utero PCB or OH-PCB exposure and thyroid function of the newborns. Umbilical cord tissue was used as the media for the biological monitoring of PCBs/OH-PCBs exposure in utero. For the measurement of fT4 and TSH, a heel-prick blood sample spotted on filter paper, which is called Guthrie card, is collected from each neonate at day 4-6 postpartum for this study when the mass screening sampling was performed. We showed that the concentration of total OH-PCBs and one of the OH-PCB congeners (OH-PCB 187) was related significantly to higher fT4 level of newborns. On the other hand, the concentration of total PCBs and PCB congeners (PCB 118, 138, 153, and 180) showed no relationship with fT4 and TSH level of the newborns. The results obtained in this pilot study indicated the possibility that in utero OH-PCBs exposure affects thyroid hormone status of newborns.     

Enantiomeric fractions of chiral polychlorinated biphenyls provide insights on biotransformation capacity of arctic biota

Chiral polychlorinated biphenyls (PCBs) were measured in an arctic marine food web from the Northwater Polynya (NOW) in the Canadian Arctic to examine potential biotransformation of chiral PCB atropisomers. Organisms under investigation included pelagic zooplankton, Arctic cod (Boreogadus saida), seabirds, and ringed seals (Phoca hispida). Previous studies using achiral methods (e.g., biomagnification factors) have shown that chiral PCB congeners biomagnified in the NOW food web, but provided little information about biotransformation of PCBs except in extreme cases (i.e., high biotransformation). In this study, highly nonracemic enantiomeric fractions (EFs) were observed in several seabird species and ringed seals, but racemic EFs were found in prey (zooplankton and fish). This suggests stereoselective and species-specific biotransformation of individual PCB stereoisomers by birds and mammals. These results are consistent with previously reported biotransformation activity of chiral organochlorine pesticides, alpha-hexachlorocyclohexane, and chlordane within these organisms. This study demonstrates the utility of using chiral analysis of PCBs to investigate biotransformation within biota of arctic food webs.     

Polybrominated diphenyl ethers and polychlorinated biphenyls in freshwater fish from Taihu Lake, China: their levels and the factors that influence biomagnification

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), two types of persistent organic pollutants that have been used widely, can be released into the environment and accumulate in organisms. To obtain a better understanding of the biomagnification of PBDEs and PCBs in fish, as well as the influences on biomagnification by fish size and physical properties of PBDEs and PCBs, a total of 200 samples of 24 fish species were collected and analyzed from Taihu Lake, the second largest freshwater lake in China. The concentrations of PBDEs and PCBs ranged from 8.59 to 74.28?ng/g lipid weight (lw) and from 10.30 to 165.20?ng/g lw, respectively. Trophic magnification factors (TMFs) were used to estimate the PBDE and PCB biomagnification potentials. The TMF values of PBDEs and PCBs ranged from 0.78 to 2.95 and from 0.92 to 2.60, respectively. Most of the TMFs were greater than 1, indicating that these contaminants were biomagnified in food chains. Fish size might influence the biomagnification evaluation, because different sized fish had different lipid content, leading to different lipid-based concentrations of PBDEs and PCBs. Parabolic relationships were observed between the TMFs and logK(OW) , as well as between the TMFs and the molecular volumes of PBDE and PCB congeners. The congeners with logK(OW) values of approximately 7 or molecular volumes of approximately 8?×?10?? nm3 had the greatest biomagnification potentials. Compared to molecular weight, molecular volume seems to be the better standard for analyzing the influence of molecular size on biomagnification.     

Predicting chemical contaminants in freshwater sediments through the use of historical biochemical endpoints in resident fish species

Previous studies in Bayou Bartholomew, Arkansas, USA, indicated significant relationships between the individual health of fish sampled from 13 sites and specific biochemical responses. Evaluation of several biochemical endpoints in 1994 indicated the bioavailable occurrence of either polychlorinated biphenyl (PCB) congeners or metals. To evaluate this possibility, in December 2000, sediments were collected at four sites on Bayou Bartholomew, where fish, collected in July 1994, had previously demonstrated the highest hepatic cytochrome P4501A (CYP1A) and heme oxygenase (HO) expression. Samples were analyzed for 89 PCB congeners, 18 organochlorine pesticides, and 25 metals. Total PCB concentrations ranged from 6.5 to 704 ng/g dry weight. Although several PCB congeners were observed, 81, 87, 99, 114, and 153 represented up to 33, 22, 29, 92, and 55% of the sum of PCBs from the four sites, respectively. Total organochlorine pesticide concentrations ranged from undetectable to 53.2 ng/g dry weight. Lindane, heptachlor, dachtal, dieldrin, hexachlorobenzene, dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyl ethane (DDE), and dichlorodiphenyl dichloroethane (DDD) isomers were detected in most samples. Detected organophosphate pesticides included malathion, chlorpyrifos, and dimethoate. Both p,p'-DDE and p,p'-DDD were the most predominant of the pesticides measured (0.5-14.1 and 0.7-58.5 ng/g dry wt). All metal concentrations analyzed were below sediment quality guideline values. Metals exceeding national average concentrations were cobalt (2 of 4 [2/4] sites), copper (1/4), molybdenum (4/4), antimony (3/4), selenium (4/4), tin (4/4), and zinc (1/4). These results were consistent with PCBs being causative agents for the biochemical and adverse individual responses observed in fish sampled from this waterway.     

Hydroxylated PCB metabolites and PCBs in serum from pregnant Faroese women

In the Faroe Islands in the North Atlantic, the traditional diet includes pilot whale meat and blubber and other marine food. Fatty fish and blubber of mammals may contain high concentrations of organohalogen substances (OHSs). Elevated levels of OHSs have been reported from the Faroe Islands, first documented in breast milk samples obtained in 1987. The aim of this study was to determine the concentrations of hydroxylated polychlorinated biphenyls (OH-PCBs) and polychlorinated biphenyls (PCBs) in serum samples from pregnant Faroese women known to differ in their dietary habits. High concentrations of OH-PCBs and PCBs were found in part of the human serum samples analyzed, and the relative OH-PCB and PCB congener distributions were similar to those observed elsewhere. There was a wide span between the lowest and highest OH-PCB and PCB concentrations in the serum samples analyzed, with ranges of 19-1,800 ng/g lipid weight (lw) and 150-22,000 ng/g lw, respectively. The ratio of sigmaOH-PCB/sigmaPCB averaged about 10% and varied little. 4-Hydroxy-2,2,3,4,5,5,6-heptachlorobiphenyl was the most abundant OH-PCB metabolite in all samples analyzed, with four other OH-PCB congeners as dominating metabolites in the serum. More than 25 additional OH-PCBs were indicated. This study confirms the presence of high concentrations of organohalogen substances in populations or areas far removed from their sources.     

Determination of polychlorinated biphenyl and polycyclic aromatic hydrocarbon elimination rates in adult green and leopard frogs

The purpose of the present study was to quantify elimination kinetics of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in adult green frogs (Rana clamitans) and leopard frogs (Rana pipiens). Three experiments were conducted: PCB elimination rate constants were determined for both frog species, and PAH elimination rate constants were determined for leopard frogs only. In green frogs, significant PCB elimination rate constants ranged from 0.013 to 0.04 d(-1) (time for frogs to achieve 90% steady state with water [t90] = 57.8-178.2 d). In leopard frogs, significant PCB elimination rate constants ranged from 0.004 to 0.047 d(-1) (t90 = 48.8-657.9 d). Polycyclic aromatic hydrocarbon elimination in leopard frogs was faster than PCB elimination in either frog species: Significant PAH rate constants ranged from 0.069 to 0.188 d(-1) (t90 = 12.2-33.5 d). In both species, and for both PCBs and PAHs, a significant inverse relationship was found between the chemical elimination rate constant and Kow. These results show that adult anurans have relatively low elimination rates of PCBs but exhibit a small capacity for metabolic biotransformation of PAHs that is comparable to that of invertebrates but lower than that of fish. These findings suggest that adult amphibians have the potential to be used as biomonitors for persistent organic chemicals.     

Fetal exposure to PCBs and their hydroxylated metabolites in a Dutch cohort

Polychlorinated biphenyls (PCBs) are still the most abundant pollutants in wildlife and humans. Hydroxylated PCB metabolites (OH-PCBs) are known to be formed in humans and wildlife. Studies in animals show that these metabolites cause endocrine-related toxicity. The health effects in humans have not yet been evaluated, especially the effect on the fetus and newborn. The aim of this study is to measure the levels of PCBs and OH-PCBs in maternal and cord blood samples in a population with background levels of PCBs. We analyzed 51 maternal and corresponding cord blood samples in the northern part of the Netherlands. The PCB concentrations in maternal plasma ranged from 2 to 293 ng/g lipid, and OH-PCB concentrations from nondetectable (ND) to 0.62 ng/g fresh weight. In cord plasma, PCB concentrations were 1-277 ng/g lipid, and OH-PCB concentrations, ND to 0.47 ng/g fresh weight. The cord versus maternal blood calculated ratio was 1.28 +/- 0.56 for PCBs and 2.11 +/- 1.33 for OH-PCBs, expressed per gram of lipid. When expressed per gram fresh weight, the ratios are 0.32 +/- 0.15 and 0.53 +/- 0.23 for PCBs and OH-PCBs, respectively. A significant correlation between the respective maternal and cord levels for both PCBs and OH-PCBs was found. Our results indicate that OH-PCBs and PCBs are transferred across the placenta to the fetus in concentrations resulting in levels of approximately 50 and 30%, respectively, of those in maternal plasma. More research in humans is needed to evaluate potential negative effects of these endocrine disruptors on the fetus.     

河北省动物源性食品中指示性多氯联苯的暴露水平研究

目的 调查河北省动物源性食品中6种指示性多氯联苯(polychlorinated biphenyls,PCBs)的污染水平.方法2019年在河北省共采集了96份食物样品(包括带鱼、黑鱼、鸡蛋、猪肝、猪肉和牛肉),利用同位素稀释-高分辨气相-高分辨磁质谱法(HRGC-HRMS)测定样品中6种指示性PCBs(PCB 28、...     

Influence of lake characteristics on the biomagnification of persistent organic pollutants in lake trout food webs

The biomagnification of polychlorinated biphenyls (PCBs) and major organochlorine pesticides (OCPs) was studied using lake trout (Salvelinus namaycush) and other food web organisms collected from 17 lakes in Canada and the northeastern United States between 1998 and 2001. Whole lake trout (n = 357) concentrations of the sum (Sigma) of 57 PCB congeners ranged between 1.67 and 2,890 ng/g wet weight (median 61.5 ng/g wet wt). Slimy sculpin had the highest mean concentrations of SigmaPCB of all forage fish (32-73 ng/g wet wt). Positive relationships between log (lipid wt) concentrations of PCB congener 153, PCB congener 52, p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, cis-chlordane, trans-nonachlor, or dieldrin and trophic level (determined using stable nitrogen isotope ratios) were found for most of the 17 food webs, indicating biomagnification of these PCBs and OCPs. The p,p'-dichlorodiphenyldichloroethylene had the highest trophic magnification factors (TMFs) of the 14 individual compounds studied, averaging 4.0 +/- 1.8 across the 17 lakes, followed by trans-nonachlor (3.6 +/- 1.5) and PCB congener 153 (3.4 +/- 1.2). Average TMFs for 14 individual PCBs or OCPs were significantly correlated with log octanol-water partition coefficient, implying that the rate of accumulation along the food web is dependent on hydrophobicity and recalcitrance. Significant correlations (p < 0.05) were found between TMFs of SigmaPCBs, hexachlorobenzene, alpha-hexachlorocyclohexane, and lindane and lake area, latitude, and longitude, but not for 11 other PCBs or OCPs. Overall, the results of the present study show that biomagnification of PCBs and most OCPs, as measured by TMFs, is only weakly influenced by such factors as latitude and longitude. Exceptions are hexachlorocyclohexane isomers and hexachlorobenzene, which had generally greater TMFs in northern lakes, possibly due to lower rates of elimination and biotransformation in the food web.     

Availability of polychlorinated biphenyls in field-contaminated sediment

Two chemical approaches, Tenax extraction and matrix solid phase microextraction (matrix-SPME), were evaluated as surrogates to estimate bioavailability of polychlorinated biphenyls (PCBs) from field-contaminated sediment. Aroclor 1254 was the primary contaminant found in sediment from Crab Orchard Lake in Marion, Illinois, USA, and a total of 18 PCB congeners were selected for study. Bioaccumulation was determined by exposing the freshwater oligochaete, Lumbriculus variegatus, to the sediment for 28 d. Differences in the rapidly desorbing fraction of PCBs and fraction desorbed within 6 h, defined by Tenax extraction, accounted for 39 and 31% of the differences among biota-sediment accumulation factor values, respectively. A better relationship (r2 = 0.95) was found between the oligochaete PCB body residues and the concentration of PCBs in the rapidly desorbing fraction of sediment. The degree of chlorination and planarity of the PCB congeners affected both desorption and bioaccumulation. The higher chlorine substituted and planar PCBs showed less chemical and biological availability, due to their stronger sorption to sediment, compared to the lower chlorinated and nonplanar PCBs. Accumulation of PCBs by L. variegatus correlated well (r2 = 0.88) with matrix-SPME fiber concentrations. The ratio of measured body residue to estimated body residue from the pore water concentration measured by matrix-SPME ranged from 0.4 to 1.3 with an average of 0.9. Overall, both Tenax and matrix-SPME approaches were useful surrogates of bioaccumulation for a field-contaminated sediment.     

Depuration of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in breast milk from California first-time mothers (primiparae)

BACKGROUND: Little is known about the rates of loss (depuration) of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) from mothers during lactation. Depuration rates affect infant exposure to chemicals during breast-feeding, and fetal and lactational transfers during subsequent pregnancies. OBJECTIVE: Our objective in this study was to estimate depuration rates of PBDEs and PCBs using serial samples of breast milk. METHOD: Nine first-time mothers (primiparae) each collected samples at 4, 6, 8, 12, 16, 20, and 24 weeks after birth. Nine additional primiparae each collected two samples at varying time intervals (18 to > 85 weeks after birth). Analytical precision was assessed to evaluate the accuracy of measured monthly percentage declines in PBDEs and PCBs. RESULTS: The four major PBDE congeners decreased 2 or 3% +/- 1% per month over the 6-month period. These decreases were consistent over a 50-fold range (21-1,330 ng/g lipid weight) of initial PBDE concentrations in breast milk. The change in PCB-153 ranged from + 0.3% to -0.6% per month, with heterogeneous slopes and greater intraindividual variability. PBDE and PCB concentrations declined 1% per month over longer periods (up to 136 weeks). CONCLUSIONS: Our data indicate that PBDEs and PCBs are not substantially (4-18%) reduced in primiparae after 6 months of breast-feeding. Consequently, the fetal and lactational exposures for a second child may not be markedly lower than those for the first. Participants were volunteers from a larger study population (n = 82), and were typical in their PBDE/PCB levels and in many demographic and lifestyle factors. These similarities suggest that our results may have broader applicability.     

Reproduction success of American kestrels exposed to dietary polychlorinated biphenyls

While reproduction of wild birds is adversely affected by multiple environmental contaminants, we determined that polychlorinated biphenyls (PCBs) alone alter reproduction. Captive American kestrels (Falco sparverius), fed PCB-spiked (Aroclor 1248:1254:1260) food (7 mg/kg body weight/d) prior to and during the first breeding season only (100 d) laid eggs with environmentally relevant levels of total PCBs (34.0 microg/g whole egg wet wt vs 0 microg/g for controls). Reproduction changed during, not after, PCB exposure in this two-year study. The PCB-exposed pairs laid smaller clutches later in the season and laid more totally infertile clutches. Hatching success was reduced in PCB-exposed pairs, and 50% of PCB nestlings died within 3 d of hatching. Nearly 60% of PCB-exposed pairs with hatchlings failed to produce fledglings. Higher levels of total PCB residues and congeners were associated with later clutch initiation and fewer fertile eggs, hatchlings, and fledglings. We suggest that nonpersistent PCB congeners have a greater influence on reproduction than do persistent congeners.     

Trophic transfer and biotransformation of polychlorinated biphenyls in zebra mussel, round goby, and smallmouth bass in Lake Erie, USA

Trophic transfer of polychlorinated biphenyl (PCB) congeners in zebra mussels (Dreissena polymorpha), round gobies (Neogobius melanstomus), and smallmouth bass (Micropterus dolomieu) were assessed in four sites along the south shore of the west and central basin of Lake Erie (all sites were in OH, USA). Total PCB levels in smallmouth bass (1,091-1,520 ng/g wet weight) and round gobies (118-256 ng/g wet weight) were similar among sites despite a west-to-east decrease in total PCB concentrations in zebra mussels (29-97 ng/g wet weight). At all sites, PCB body burden increased three- to fivefold at each successive trophic level, suggesting biomagnification in this nonnative food chain. Whereas fish species were dominated by the hexachlorine homologue, zebra mussels were dominated by penta- and hexachlorine homologues; the average degree of chlorination of PCBs was 56.1% for zebra mussels, 60.4% for round goby, and 59.9% for smallmouth bass bodies. Predictive structure-activity relationships based on chemical characteristics, such as the octanol-water partition coefficient (log K(ow)), had little predictive power on bioaccumulation and biotransformation of PCB congeners because of nonlinearity, threshold relationships, and species-specific differences. Calculated trophic transfer for the smallmouth bass-round goby linkage was higher than for the round goby-zebra mussel linkage. Only when PCB congeners were grouped by chemical structure first (vicinal [adjacent] H-atom position in the phenyl ring) were linear relationships achieved. It appeared that the chemical group to which each congener belonged influenced biotransformation more than species-specific (round gobies vs smallmouth bass) differences. Biotic changes at midtrophic levels, such as exotic species invasions, may have an increasingly important role in determining pollutant cycling and hence pollutant residues in top predators.     

Enantiomeric composition of chiral polychlorinated biphenyl atropisomers in dated sediment cores

Enantiomer fractions (EFs) of seven chiral polychlorinated biphenyls (PCBs) were measured in dated sediment cores of Lake Hartwell (SC, USA) and Lake Ontario (USA) to detect, quantify, and gain insight regarding microbial reductive dechlorination of PCBs in lake sediments with high and low concentrations, respectively. Lake Hartwell sediments had high total PCBs (5-60 microg/g), with significantly nonracemic EFs that generally were consistent with those from previous laboratory microcosm reductive dechlorination experiments using sediments from these sites. Thus, stereoselective reductive dechlorination had occurred in situ, including at total PCB concentrations of less than the threshold of approximately 30 to 80 microg/g suggested as being necessary for reductive dechlorination. Enantiomer fractions of PCBs 91, 95, 132, and 136 in Lake Hartwell cores were significantly correlated both with concentrations of those individual congeners and with total PCB concentration for some sites. This result indicates that enantioselective microbial dechlorination activity increases with higher concentrations within sediments for these congeners. Enantiomer composition reversed with depth for PCBs 91, 132, and 176, suggesting that multiple microbial populations may be present within the same core that are enantioselectively dechlorinating PCBs. Such observations indicate that concentration and time are not the only factors affecting biotransformation, complicating prediction of enantioselectivity. Comparison of EFs with dates suggested biotransformation half-lives of approximately 30 years, which is on the same time scale as sequestration by burial. In contrast, Lake Ontario sediments (maximum total PCBs, 400 ng/g) had racemic or near-racemic amounts of most congeners throughout the core profile, which is consistent with achiral indicators suggesting no microbial biotransformation within Lake Ontario sediments. Thresholds for reductive dechlorination may exist, but they would be at concentrations of less than 30 to 80 microg/g.     

Coplanar PCBs in fish and mussels from marine and estuarine waters of New York State.

Thirty samples of striped bass from marine and estuarine waters of New York State, six samples of mussels from Long Island Sound, and one composite sample of freshwater mussels from Troy were analyzed by a recently developed method which combines sulfuric acid cleanup, carbon chromatography, and high-resolution gas chromatography for the determination of non-ortho- and mono-ortho-substituted polychlorinated biphenyls (PCBs), which are biologically active congeners of PCBs and approximate isostereomers of 2,3,7,8-tetrachlorodibenzo-P-dioxin of (2,3,7,8-TCDD). Non-ortho coplanar PCBs ranged from 0.2 to 37.1 ppb in fish. The highest concentrations of 37.1 ng/g of 3,3',4,4'-tetrachlorobiphenyl (77) and 7.5 ng/g of 3,3',4,4',5-pentachlorobiphenyl (126) were detected in a fish caught near Troy/Albany, New York. Mono-ortho-substituted PCBs ranged from 0.4 to 790 ppb in fish, with the major components identified as 2,3',4,4',5-penta-(118) and 2,3,3',4,4'-pentachlorobiphenyls (105). When concentrations were converted to 2,3,7,8-TCDD picogram equivalents, 99% of the equivalents were derived from three congeners (77, 105, and 126), 3,3',4,4',5-pentachlorobiphenyl (126) accounting for approximately 80% of the activity. At Troy pg/g TCDD equivalents derived from PCB were approximately 3000, whereas the actual 2,3,7,8-TCDD concentration was only 20 pg/g; hence, accurate coplanar PCB measurement is important.     

The Influence of Diet Properties and Feeding Rates on PCB Toxicokinetics in the Ring Dove

The influence of diet properties and feeding rate on the uptake and elimination of polychlorinated biphenyls (PCBs) was investigated in ring doves (Streptopelia rissoria). Elimination rates of PCBs were determined in birds dosed with an Aroclor mixture (1242:1248:1260, 1:1:1) and allowed to depurate on uncontaminated high-lipid or low-lipid/high-fiber diets for 105 days. Uptake rates for seven additional PCBs not found within the above Aroclor mixtures were studied in the same birds by feeding high- or low-lipid PCB-spiked diets for 15 days. The two diet treatments contributed to differences in feeding rates, fecal egestion rates, and total fat volume of the birds. Uptake rate constants of PCBs were higher for the low-lipid diet group, whereas PCB assimilation efficiencies were similar between the two groups. Whole-body elimination rates of Aroclor PCBs were most strongly influenced by the chlorine substitution pattern of the congeners, such that PCBs containing an open meta-para site on one of the phenyl rings were rapidly cleared from the animal. Whole-body elimination rates for persistent PCBs could only be determined for PCB 28; other congeners exhibited negligible elimination over the depuration period. For the latter compounds, fecal elimination rates were estimated using the excreta/carcass distribution coefficient and excreta production rates. For PCB 28, the fecal elimination rate was similar to the whole-body elimination rate, suggesting that fecal elimination of persistent PCBs dominates whole body elimination of these compounds. Diet treatment effects were less evident for PCB elimination rates compared to uptake rates. Steady-state biomagnification factors were estimated to range from 1.0 to 5.1 for rapidly cleared PCBs and from 27 to 97 for persistent congeners. Received: 11 October 2001/Accepted: 30 May 2002