Tracing the Biotransformation of PCBs and PBDEs in Common Carp (<i>Cyprinus carpio</i>) Using Compound-Specific and Enantiomer-Specific Stable Carbon Isotope Analysis

Compound-specific and enantiomer-specific carbon isotope composition was investigated in terms of biotransformation of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) as well as atropisomers of chiral PCB congeners in fish by exposing common carp (<i>Cyprinus carpio</i>) to certain PCB and PBDE congeners. The calculated carbon isotope enrichment factors (ε_C) for PCB 8, 18, and 45 were −1.99, −1.84, and −1.70‰, respectively, providing evidence of the metabolism of these congeners in fish. The stable carbon isotopic compositions of PBDE congeners clearly reflect the debromination of PBDEs in carp. Significant isotopic fractionation was also observed during the debromination process of BDE 153 (ε_C = −0.86‰). Stereoselective elimination of chiral PCB congeners 45, 91, and 95 was observed, indicating a stereoselective biotransformation process. The similar ε_C values for E1-PCB 45 (−1.63‰) and E2-PCB 45 (−1.74‰) indicated that both atropisomers were metabolized by the same reaction mechanisms and stereoselection did not occur at carbon bond cleavage. However, the ε_C values of (+)-PCB 91 (−1.5‰) and (−)-PCB 95 (−0.77‰) were significantly different from those of (−)-PCB 91 and (+)-PCB 95, respectively. In the latter, no significant isotopic fractionations were observed, indicating that the stereoselective elimination of PCB 91 and 95 could be caused by a different reaction mechanism in the two atropisomers

Plant Uptake of Atmospheric Brominated Flame Retardants at an E-Waste Site in Southern China

Brominated flame retardants (BFRs) were measured in eucalyptus leaves and pine needles as well as the leaf surface particles (LSPs) of the two species at an e-waste site in southern China in 2007–2008. The monthly concentrations of total BFRs in the eucalyptus leaves and pine needles were in range of 30.6–154 and 15.1–236 ng/g dry weight, respectively, and relatively higher concentrations were observed in winter and spring. Correlation analysis of BFR concentrations and comparison of PBDE compositions between the plants and LSPs, air (gaseous and particle-bound phases), and ambient variables were conducted. The results revealed that BFRs in the plants, especially for less brominated BFRs, showed positive relationships with BFRs in the LSPs and negative relationships with the gaseous BFRs and ambient temperature. The PBDE profiles in the plants were similar to the gaseous profile for low brominated BDEs (di- through hexa-BDEs) and to the LSP profiles for highly brominated BDEs (hepta- through deca-BDEs). Applying McLachlan’s framework to our data suggests that the uptake of BFRs was controlled primarily by gaseous partitioning equilibrium for compounds with log octanol-air partition coefficients (<i>K</i>_OA) < 12 and by particle-bound deposition for compounds with log <i>K</i>_OA > 13. Different relationships between the plant/air partition coefficient (<i>K</i>_PA) and <i>K</i>_OA, which depend on the uptake mechanisms, were observed for polybrominated diphenyl ethers (PBDEs). This paper adds to the current knowledge of the factors and mechanisms governing plant uptake of semivolatile organic compounds with relatively high <i>K</i>_OA in the environment

Chiral Polychlorinated Biphenyls (PCBs) in Bioaccumulation, Maternal Transfer, and Embryo Development of Chicken

Polychlorinated biphenyls (PCBs) and enantiomer fractions (EFs) of PCB enantiomers (PCBs 95, 132, 135, and 149) were investigated in soil and chicken feed, chicken (Gallus domesticus) tissues, eggs on 0, 7, and 14 days after the onset of incubation, and newborn chick tissues. The EF values of PCBs 95, 132, and 149 changed significantly from soil to chicken tissues, and the values in the liver exhibited the highest deviation from the racemic ratio, indicating enantiomer-selective metabolism in hens. Congeners, which are highly resistant to degradation, such as PCBs 138, 153, and 180, exhibited the highest maternal transfer potentials when muscle and liver were used to assess the maternal transfer. However, uniform transfer ratios were observed for most of the PCB congeners when visceral fat was used. The EFs of chiral PCBs in eggs either did not match with muscle or with liver or were similar to those in visceral fat. These results indicate that hens mainly mobilized visceral fat for egg formation and PCBs were deposited in eggs by associating with these lipid materials. Further enantiomeric enrichment of PCBs 95, 132, and 149 occurred in the newborn chick tissues. However, an opposite enantioselectivity for PCB 135 in newborn chicks was observed. These results indicate that the potential toxicity of PCB enantiomers to newborn chicks may be different from that of adults

Elevated Levels of Polychlorinated Biphenyls in Plants, Air, and Soils at an E‑Waste Site in Southern China and Enantioselective Biotransformation of Chiral PCBs in Plants

E-waste that contains polychlorinated biphenyls (PCBs) is moved across national boundaries, often from industrialized countries in the northern hemisphere, where the items were formerly used, to subtropical and tropical regions in southeastern Asia and Africa. As a result, there is a high likelihood that PCBs will be released into the environment from a primary source due to the elevated temperatures encountered in these low-latitude regions. In the present study, PCBs and enantiomer fractions (EFs) of chiral PCBs (PCB 84, 95, 132, 136, 149, and 183) were analyzed in air, eucalyptus leaves, pine needles, and soil at an e-waste site and a rural site in southern China. The concentrations of PCBs at the e-waste site ranged from 7825 to 76330 pg/m³, 27.5 to 1993 ng/g, and 24.2 to 12045 ng/g in the air (gas plus particle), plant leaves, and soils, respectively. The atmospheric PCB composition profiles in the present study indicated relatively high abundances of penta- and hexa-PCBs, which were different from those previously observed in the air across China. The Clausius–Clapeyron regression analysis indicated that evaporation from local contaminated surfaces constitutes a primary emission source of PCBs in the air at the e-waste site. The chiral signatures of PCBs in the air at the e-waste site were essentially racemic (mean EFs = (0.484 ± 0.022)–(0.499 ± 0.004) in the gaseous phase) except for PCB 84 (0.420 ± 0.050), indicating that racemic sources dominate the PCB emission in the air. PCB chiral signatures in the soils ((0.422 ± 0.038)–(0.515 ± 0.016)) were similar to those in the air except for PCB 95. However, the chiral PCBs in the plants (especially the eucalyptus leaves) had significantly nonracemic residues ((0.368 ± 0.075)–(0.561 ± 0.045)) compared to those in the air and soil. This finding suggests that enantioselective biotransformation of these atropisomeric PCBs was very likely to occur in the plant leaves, possibly due to metabolism by cytochrome P-450 enzymes in leaves. To our knowledge, this is the first report on the enantioselective metabolism of chiral PCBs in plants under field conditions

Bioaccumulation of Persistent Halogenated Organic Pollutants in Insects: Common Alterations to the Pollutant Pattern for Different Insects during Metamorphosis

Few studies have examined the accumulation and fate of persistent halogenated organic pollutants (HOPs) in insects. We measured HOPs, including dichlorodiphenyltrichloroethanes (DDTs), polychlorinated biphenyls, and halogenated flame retardants, in insects from four taxonomic groups collected from an e-waste site. Dragonfly larvae collected from a pond contained the highest concentrations of all chemicals except DDTs, while the litchi stinkbugs contained the lowest. Different insect taxa exhibited different contaminant patterns which could be attributed to their habitats and feeding strategies. Bioaccumulation factors for dragonfly larvae and biomagnification factors for moth and grasshopper larvae were significantly positively correlated with the octanol–water partition coefficient of the chemicals (log <i>K</i>_OW < 8). Common nonlinear correlations between the ratio of larval to adult concentrations and log <i>K</i>_OW were observed for all taxa studied. The ratio of concentrations decreased with increasing values of log <i>K</i>_OW (log <i>K</i>_OW < 6–6.5), then increased (6 < log <i>K</i>_OW < 8) and decreased again (log <i>K</i>_OW > 8). This result implies that the mechanism that regulates organic pollutants in insects during metamorphosis is common to all the taxa studied

Using Compound-Specific Stable Carbon Isotope Analysis to Trace Metabolism and Trophic Transfer of PCBs and PBDEs in Fish from an e‑Waste Site, South China

Two fish species (mud carp and northern snakehead) forming a predator/prey relationship and sediment samples were collected from a pond contaminated by e-waste. The concentrations and stable carbon isotope ratios (δ¹³C) of individual polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) congeners were measured to determine if compound-specific carbon isotope analysis (CSIA) could be used to provide insight into the metabolism and trophic dynamics of PCBs and PBDEs. Significant correlations were found in the isotopic data of PCB congeners between the sediment and the fish species and between the two fish indicating identical origin of PCBs in sediment and fish. Most PCB congeners in the fish species were enriched in ¹³C compared with the PCB congeners in the sediments as a result of isotopic fractionation during the metabolism of PCBs in fish. The isotopic data of several PCB congeners showing isotopic agreement or isotopic depletion could be used for source apportionment or to trace the reductive dechlorination process of PCBs in the environment. The PCB isotopic data covaried more in the northern snakehead than in the mud carp when compared to the sediment, implying that a similar isotopic fractionation occurs from the prey to the predator fish for a PCB congener possibly due to similar metabolic pathways. The PBDE congener patterns differed in the three sample types with a high abundance of BDE209, 183, 99, and 47 in the sediment, BDE47, 153, and 49 in the mud carp and BDE47, 100, and 154 in the northern snakehead. The isotopic change of BDE congeners, such as BDE47 and BDE49, in two fish species, provides evidence for biotransformation of PBDEs in biota. The results of this study suggest that CSIA is a promising tool for deciphering the fate of PCBs and PBDEs in the environment

Polychlorinated Biphenyls (PCBs) in Human Hair and Serum from E‑Waste Recycling Workers in Southern China: Concentrations, Chiral Signatures, Correlations, and Source Identification

Hair is increasingly used as a biomarker for human exposure to persistent organic pollutants (POPs). However, the internal and external sources of hair POPs remain a controversial issue. This study analyzed polychlorinated biphenyls (PCBs) in human hair and serum from electronic waste recycling workers. The median concentrations were 894 ng/g and 2868 ng/g lipid in hair and serum, respectively. The PCB concentrations in male and female serum were similar, while concentrations in male hair were significantly lower than in female hair. Significant correlations between the hair and serum PCB levels and congener profiles suggest that air is the predominant PCB source in hair and that hair and blood PCB levels are largely dependent on recent accumulation. The PCB95, 132, and 183 chiral signatures in serum were significantly nonracemic, with mean enantiomer fractions (EFs) of 0.440–0.693. Nevertheless, the hair EFs were essentially racemic (mean EFs = 0.495–0.503). Source apportionment using the Chemical Mass Balance model also indicated primary external PCB sources in human hair from the study area. Air, blood, and indoor dust are responsible for, on average, 64.2%, 27.2%, and 8.79% of the hair PCBs, respectively. This study evidenced that hair is a reliable matrix for monitoring human POP exposure