Application of compound-specific stable carbon isotope analysis for the biotransformation and trophic dynamics of PBDEs in a feeding study with fish

20 years of polybrominated diphenyl ethers on toxicity assessments

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants which continue to receive considerable attention because of their persistence, bioaccumulation, and potential toxicity. Although PBDEs have been restricted and phased out, large amounts of commercial products containing PBDEs are still in use and discarded annually. Consequently, PBDEs added to products can be released into our surrounding environments, particularly in aquatic systems, thus posing great risks to human health. Many studies and reviews have described the possible toxic effects of PBDEs, while few studies have comprehensively summarized and analyzed the global trends of their toxicity assessment. Therefore, this study utilizes bibliometrics to evaluate the worldwide scientific output of PBDE toxicity and analyze the hotspots and future trends of this field. Firstly, the basic information including the most contributing countries/institutions, journals, co-citations, influential authors, and keywords involved in PBDE toxicity assessment will be visualized. Subsequently, the potential toxicity of PBDE exposure to diverse systems, such as endocrine, reproductive, neural, and gastrointestinal tract systems, and related toxic mechanisms will be discussed. Finally, we conclude this review by outlining the current challenges and future perspectives in environmentally relevant PBDE exposure, potential carriers for PBDE transport, the fate of PBDEs in the environment and human bodies, advanced stem cell-derived organoid models for toxicity assessment, and promising omics technologies for obtaining toxic mechanisms. This review is expected to offer systematical insights into PBDE toxicity assessments and facilitate the development of PBDE-based research.

Additives of plastics: Entry into the environment and potential risks to human and ecological health

A steep rise in global plastic production and significant discharge of plastic waste are expected in the near future. Plastics pose a threat to the ecosystem and human health through the generation of particulate plastics that act as carriers for other emerging contaminants, and the release of toxic chemical additives. Since plastic additives are not covalently bound, they can freely leach into the environment. Due to their occurrence in various environmental settings, the additives exert significant ecotoxicity. However, only 25% of plastic additives have been characterized for their potential ecological concern. Despite global market statistics highlighting the substantial environmental burden caused by the unrestricted production and use of plastic additives, information on their ecotoxicity remains incomplete. By focusing on the ecological impacts of plastic additives, the present review aims to provide detailed insights into the following aspects: (i) diversity and occurrence in the environment, (ii) leaching from plastic materials, (iii) trophic transfer, (iv) human exposure, (v) risks to ecosystem and human health, and (vi) legal guidelines and mitigation strategies. These insights are of immense value in restricting the use of toxic additives, searching for eco-friendly alternatives, and establishing or revising guidelines on plastic additives by global health and environmental agencies.

Metabolic transformation of environmentally-relevant brominated flame retardants in Fauna: A review

Over the past few decades, production trends of the flame retardant (FR) industry, and specifically for brominated FRs (BFRs), is for the replacement of banned and regulated compounds with more highly brominated, higher molecular weight compounds including oligomeric and polymeric compounds. Chemical, biological, and environmental stability of BFRs has received some attention over the years but knowledge is currently lacking in the transformation potential and metabolism of replacement emerging or novel BFRs (E/NBFRs). For articles published since 2015, a systematic search strategy reviewed the existing literature on the direct (e.g., in vitro or in vivo) non-human BFR metabolism in fauna (animals). Of the 51 papers reviewed, and of the 75 known environmental BFRs, PBDEs were by far the most widely studied, followed by HBCDDs and TBBPA. Experimental protocols between studies showed large disparities in exposure or incubation times, age, sex, depuration periods, and of the absence of active controls used in in vitro experiments. Species selection emphasized non-standard test animals and/or field-collected animals making comparisons difficult. For in vitro studies, confounding variables were generally not taken into consideration (e.g., season and time of day of collection, pollution point-sources or human settlements). As of 2021 there remains essentially no information on the fate and metabolic pathways or kinetics for 30 of the 75 environmentally relevant E/BFRs. Regardless, there are clear species-specific and BFR-specific differences in metabolism and metabolite formation (e.g. BDE congeners and HBCDD isomers). Future in vitro and in vivo metabolism/biotransformation research on E/NBFRs is required to better understand their bioaccumulation and fate in exposed organisms. Also, studies should be conducted on well characterized lab (e.g., laboratory rodents, zebrafish) and commonly collected wildlife species used as captive models (crucian carp, Japanese quail, zebra finches and polar bears).

Species-specific debromination of BDE99 in teleost fish: The relationship between debromination ability and bioaccumulation patterns of PBDEs

Polybrominated diphenyl ethers (PBDEs) are known to be broken down by debromination reactions in the natural environment, such as by photolysis, microbial and metabolic processes. Although species-specific debromination of PBDEs by fish has also been reported, it has only rarely been studied from the phylogenetic perspective. The objective of this study is to reveal the factors affecting species-specific debromination through validation between the bioaccumulation of PBDEs in muscle tissue and the ability to debrominate BDE99. As environmental observations, PBDE concentrations in muscle tissues were analyzed in 25 wild fish (Cyprinidae, Gobiidae and others). As in vitro experiments, debromination experiments were conducted using the hepatic microsomes of 21 fish species. Significant amounts of BDE99 were detected in almost none of the Cyprinidae. A relatively higher debromination ability was confirmed in the Cyprinidae in in vitro experiments. The Cyprinidae thus appears to be a family with high debromination ability. BDE99 has been detected in some goby species but not others. This pattern was also seen in in vitro experiments, suggesting that debromination ability is not consistent within the Gobiidae. In further quantitative comparisons, kinetic parameters such as K_m and v_max were determined for selected fish species. The common carp (Cyprinus carpio) and the Japanese crucian carp (Carassius cuvieri), both Cyprinidae, showed higher v_max values, whereas v_max values among three Gobiidae diverged widely. A comparison of field observations and in vitro experiments, revealed the bioaccumulation ratio of BDE99 to be affected by the BDE99 debromination ability of each fish species. This is the first report on classification of BDE99 accumulation ratio by debromination ability and a phylogenetic species comparison based on kinetic parameters for debromination reactions of PBDEs by fish.

Compound-specific carbon isotope analysis for mechanistic characterization of debromination of decabrominated diphenyl ether

RATIONALE

Decabrominated diphenyl ether (BDE-209) is a notorious persistent organic pollutant widely found in the environment. Developing a compound-specific isotope analysis (CSIA) method is much needed in order to trace its transport and degradation processes and to evaluate the effectiveness of the remediation of BDE-209 in the environment. However, the conventional CSIA method, i.e. gas chromatography (GC) combustion isotope ratio mass spectrometry, is not appropriate for BDE-209 because of its high thermal instability and incomplete combustion.

METHODS

We developed a high-performance liquid chromatography (HPLC) method for the separation and purification of BDE-209 that prevents its thermal reactivity as occurred in prior GC-based methods. The δ¹³ C value of the purified BDE-209 was determined using offline elemental analyzer isotope ratio mass spectrometry (EA/IRMS). This two-step method was applied to determine the δ¹³ C values of BDE-209 in two commercial samples and to characterize carbon isotope fractionation associated with the debromination of BDE-209 via nanoscale zero-valent iron.

RESULTS

The mean values of daily δ¹³ C analyses of six replicates of a BDE-209 standard varied from -27.66‰ to -27.92‰, with a standard deviation ranging from 0.07‰ to 0.16‰, indicating a good reproducibility of EA/IRMS. The EA/IRMS analysis of the purified BDE-209 standard indicated no obvious isotope fractionation during the sample purification. The impurity content in commercial BDE-209 samples may contribute additional variation of the δ¹³ C values of BDE-209. The δ¹³ C values of BDE-209 gradually changed from -27.47 ± 0.37‰ to -24.59 ± 0.19‰ when 74% of the BDE-209 standard was degraded within 36 h. The estimated carbon isotope enrichment factor was -1.72 ± 0.18‰.

CONCLUSIONS

The two-step method based on HPLC and EA/IRMS avoids the thermal instability of BDE-209 in the traditional CSIA method. It offers a novel approach for elucidating the degradation mechanisms of BDE-209 in the environment and for source identification in contaminated sites.

Species-specific debromination of polybromodiphenyl ethers determined by deiodinase activity in fish

A combination of previous studies and the present study indicated species-specific debromination of polybromodiphenyl ethers (PBDEs) in teleost fish. Three situations of debromination were found, namely rapid debromination represented by debromination of BDE 99 to BDE 47 observed in common carp, tilapia, crucian carp, and oscar fish; slow debromination represented by debromination of BDE 99 to BDE 49 observed in the abovementioned fish and rainbow trout, salmon, and snakehead; and no or minor debromination observed in catfish. The results of experiments on cofactors, inhibitors, and substrate competitors indicated that activities of outer ring deiodinase of 3, 3', 5'-triiodothyronine (type I deiodinase), which cannot be inhibited by 6-propyl-2-thiouracil, were responsible for the rapid debromination, and the outer ring deiodinase of thyroxine (type II deiodinase) regulated the slow debromination. The debromination of BDE 99 to BDE 49 was more common, but occurred at a much lower rate (approximately 100 times lower) than the debromination of BDE 99 to BDE 47. This was because the activity of type II deiodinase was nearly two orders of magnitude lower than that of type I deiodinase in the fish species studied. Further studies on debromination of PBDEs and properties of deiodinase in more species are needed to confirm the hypothesis.

In Situ Microbial Degradation of PBDEs in Sediments from an E-Waste Site as Revealed by Positive Matrix Factorization and Compound-Specific Stable Carbon Isotope Analysis

In the present study, positive matrix factorization (PMF) and compound-specific isotope analysis were used to investigate the in situ biodegradation of polybrominated diphenyl ethers (PBDEs) in sediment cores collected from a pond at an e-waste recycling site in South China. The potential microorganisms relevant to the degradation of PBDEs were also assessed to aid in the understanding of in situ biodegradation. The PMF results suggested that reductive debromination took place in the sediments. The debromination signal (ratio of the concentration of factor 5 (PMF result) to the total PBDE content) was positively correlated with the relative abundance of Dehalococcoidetes at different core depths. The clear ¹³C enrichment of five PBDE congeners (BDE 28, 47, 49, 99, and 153) with increasing core depth indicated that a measurable change in isotope fractionation might have occurred during PBDE biodegradation. The in situ biodegradation was further validated by the widespread detection of mono-BDE congeners (BDE 2, BDE 3) and diphenyl ether in the sediments. This study provides new evidence to enhance our understanding of the in situ biodegradation of PBDEs and suggests that the extensive removal of bromine from PBDEs was mediated by indigenous microorganisms at the e-waste site.

Detecting the bioaccumulation patterns of chemicals through data-driven approaches

This work investigates the bioaccumulation patterns of 168 organic chemicals in fish, by comparing their bioconcentration factor (BCF), biomagnification factor (BMF) and octanol-water partitioning coefficient (K_OW). It aims to gain insights on the relationships between dietary and non-dietary bioaccumulation in aquatic environment, on the effectiveness of K_OW and BCF to detect compounds that bioaccumulate through diet, as well as to detect the presence of structure-related bioaccumulation patterns. A linear relationship between logBMF and logK_OW was observed (logBMF = 1.14·logBCF - 6.20) up to logK_OW ≈ 4, as well as between logBMF and logBCF (logBMF = 0.96·logBCF - 4.06) up to a logBCF ≈ 5. 10% of compounds do not satisfy the linear BCF-BMF relationship. The deviations from such linear relationships were further investigated with the aid of a self-organizing map and canonical correlation analysis, which allowed us to shed light on some structure-related patterns. Finally, the usage of K_OW- and BCF-based thresholds to detect compounds that accumulate through diet led to many false positives (47%-91% for K_OW), and a moderate number of false negatives (up to 5% for BCF). These results corroborate the need of using the experimental BMF for hazard assessment practices, as well as of developing computational tools for BMF prediction.

Characterizing the Influence of Metabolism on the Halogenated Organic Contaminant Biomagnification in Two Artificial Food Chains Using Compound- and Enantiomer-Specific Stable Carbon Isotope Analysis

Two artificial food chains, food tiger barb-oscar fish and food tiger barb-redtail catfish, were established in the laboratory. The species-specific biotransformation of ortho, para'-dichlorodiphenyltrichloroethane, 12 polychlorinated biphenyl, and five polybrominated diphenyl ether congeners were characterized by measuring the compound- and enantiomer-specific stable carbon isotope composition (δ¹³C), enantiomeric fraction of the chiral chemicals, and metabolites in the fish. Compound- and enantiomer-specific biotransformations were revealed by the alteration of δ¹³C and EF in both predator fish species. Significant correlations between the carbon stable isotope signatures and the depuration rates and biomagnification factors (BMF) were observed. Chemicals that exhibited changes in δ¹³C during the experiment have higher k_d and lower BMF values than those with unchanged δ¹³C. Specifically, the difference between the predicted BMF based on the log K_ow and the measured BMF, ΔBMF, was significantly positively and linearly correlated to the change in the δ¹³C (expressed by Δδ¹³C/δ¹³C_initial, the percentage of Δδ¹³C: δ¹³C_ending-δ¹³C_initial to the initial δ¹³C_initial) in both food chains. These results indicated that the impact of metabolism on the bioaccumulation potential of organic contaminants can be predicted by the stable carbon isotope fractionation of chemicals in the fish.

Body size-dependent bioaccumulation, tissue distribution, and trophic and maternal transfer of phenolic endocrine-disrupting contaminants in a freshwater ecosystem

Parabens, bisphenol A (BPA), triclosan, and triclocarban are recognized endocrine-disrupting contaminants (EDCs); and their occurrence in the environment has attracted increasing concern. Body size-dependent bioaccumulation, tissue distribution, trophic magnification, and maternal transfer of methyl-, ethyl-, propyl-, and butylparabens; 2-phenylphenol (PHP); BPA; triclosan; and triclocarban were investigated in freshwater fish of the Pearl River catchment, China. Most of the EDCs were detected in more than half of the biota samples, ranging from not detected to 6750 ng g^-1 lipid weight, with median concentrations of 5 to 72 ng g^-1 lipid weight. Livers generally contained the highest EDC levels (1609 ± 1860 ng g^-1 lipid wt, mean ± standard deviation), followed in decreasing order by eggs (842 ± 1317 ng g^-1 lipid wt), belly fats (488 ± 465 ng g^-1 lipid wt), and dorsal muscles (240 ± 239 ng g^-1 lipid wt) of the wildlife. Body size-dependent bioaccumulation of the EDCs was observed in the freshwater fish, which varied according to species, tissue, and compound. The concentrations of triclosan, PHP, and BPA usually showed decreasing trends, whereas parabens mostly demonstrated increasing tendency with increasing fish weights, indicating effects of growth dilution and bioaccumulation, respectively. Potential biomagnification was shown by triclosan with trophic magnification factors of 3.0, 4.3, and 4.0 in liver, belly fat, and dorsal muscle, respectively. In addition, the potential of maternal transfer in the fish was primarily revealed for methyl- and propylparabens, PHP, triclosan, and BPA. Presence of the EDCs in the freshwater organisms of the Pearl River catchment warrants more attention considering the potential of trophic magnification and maternal transfer. Environ Toxicol Chem 2018;37:1811-1823. © 2018 SETAC.

Compound-specific isotopic and congener-specific analyses of polychlorinated biphenyl in the heat medium and rice oil of the Yusho incident

Compound-specific isotope analysis (CSIA) can be used to examine the source and transformation processes of organic pollutants in the environment. We performed a carbon stable isotope analysis of polychlorinated biphenyl (PCB) congeners in the PCB heat-transfer medium (heat medium) and the original Kanechlor-400 (KC-400, a commercial brand of PCBs) involved in the Yusho incident. The main purpose is to investigate whether isotope fractionation occurred in the rice oil deodorization process that caused the incident. The carbon isotope ratios (δ¹³C values) of the targeted PCB congeners ranged from - 29.39 to - 27.00‰ in the heat medium and from - 28.77 to - 27.05‰ in the original KC-400. No significant differences were found in the δ¹³C values, suggesting carbon isotope fractionation did not occur for the targeted PCB congeners in the heat medium when deodorization of rice oil occurred at temperatures above 200 °C. Furthermore, we also conducted a congener-specific analysis of 64 PCB congeners found in the heat medium and rice oil contaminated by it. The total PCB congener concentrations were 503 mg/g in the heat medium and 81 μg/g in the rice oil. The concentrations of the highly chlorinated congeners were significantly lower in the heat medium than in the original KC-400, and the compositional ratios of the lowly chlorinated congeners were relatively lower in the rice oil than in the heat medium. These results suggest that the PCB congener patterns gradually changed from that of the original KC-400 in the deodorization process and subsequent contamination into the rice oil. Thus, a combination of CSIA and congener-specific analysis is a new approach for investigating the changing PCB congener profiles in samples from the Yusho incident.

Species-specific and structure-dependent debromination of polybrominated diphenyl ether in fish by in vitro hepatic metabolism

To explore the cause of species-specific differences and structure-activity relationships in the debromination of polybrominated diphenyl ethers (PBDEs) in fish, a series of in vitro measurements of hepatic metabolism of PBDE were made using crucian carp (Carassius carassius) and catfish (Silurus asotus) and the activity of deiodinase in liver microsomes was measured. Debromination was observed in the crucian carp but not in the catfish. No difference was found in total deiodinase activity despite the activity of type 1 deiodinase in crucian carp being twice that of catfish. It is difficult to determine whether the differences in deiodinase activity were responsible for the species-specific differences observed. In crucian carp, penta-brominated diphenyl ether congeners exhibited the highest debromination rates, and the transformation rate decreased with an increasing number of substituted bromines. Adjacent bromine substitution in the phenyl ring was a necessary, but insufficient, condition for debromination in crucian carp. Doubly flanked bromine was always preferentially removed, while single-flanked bromine, meta-substituted bromine, was debrominated the most, followed by para- and then ortho-bromine. No debromination was observed for single-flanked bromine when there was a symmetrical structure with (2, 4, 6) bromine substitutions in 1 phenyl ring, indicating that this structure can improve resistance to debromination metabolism. Environ Toxicol Chem 2017;36:2005-2011. © 2017 SETAC.

Tracing the Biotransformation of PCBs and PBDEs in Common Carp (Cyprinus carpio) 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 (Cyprinus carpio) 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.

Quantification of polybrominated diphenyl ethers (PBDEs) in food. A review

The polybrominated diphenyl ethers (PBDEs), a class of brominated flame retardants (BFRs), are food contaminants of animal origin. Interest in food matrices analysis is growing due to the toxicity of PBDEs and European Commission (EC) recommendation (118/2014/EU). Here we review papers concerning methods of PBDEs analysis while focusing on extraction, clean up, chromatographic separation and detection techniques. The emphasis is put on EC recommendation, the congeners and the efficiency of different detection systems. Some analytical problems caused by differences between low- and high-molecular-mass congener properties, especially the possible limitations of BDE-209 analysis, are discussed. Detection techniques and mass spectrometry (MS) ionization modes applied to PBDE level determination in food of animal origin are compared. The gas chromatography (GC) coupled to high-resolution MS is undoubtedly fit for that purpose, but ion trap MS could be used to PBDEs determination as well. ECD is the most sensitive technique; however, other halogen compounds present in sample may interfere with PBDEs congeners necessitating results confirmation. Moreover, the novel atmospheric pressure chemical ionization (APCI) method applied to GC in tandem with MS places this technique in the top category of the most sensitive techniques which may be used.

Tracing the biotransformation of polychlorinated biphenyls (PCBs) in common carp (Cryprinus carpio): Enantiomeric fraction and compound-specific stable carbon isotope analyses

Metabolites of polychlorinated biphenyls (PCBs) in fish are difficult to detect in vivo due to the complexity of biometabolism. In the present study, atropisomeric fraction analysis of chiral PCB congeners and compound-specific isotopic analysis (CSIA) were applied to trace the biotransformation of PCBs in fish by exposure of common carp (Cryprinus carpio) to the commercial PCB mixture Aroclor 1242. Stereoselective elimination of the chiral PCB congeners 91, 95, and 136 was observed, indicating a stereoselective biotransformation process. The δ(13)C values of PCBs 5/8, 18, and 20/33 in fish were increased compared with those in the spiked food, while PCBs 47/48 and 49 showed significant heavy isotope depletion. These results suggested a significant biotransformation of the corresponding individual PCB congeners although the potential PCB metabolites, hydroxylated PCBs (OH-PCBs) and methylsulfone PCBs (MeSO2-PCBs), were not detected in the fish tissue samples throughout this experiment. The results of the present study demonstrated that a combination of chiral analysis and CSIA is a promising new approach for investigating the biotransformation of PCBs in biota.

Perfluoroalkylated substances (PFASs) and legacy persistent organic pollutants (POPs) in halibut and shrimp from coastal areas in the far north of Norway: Small survey of important dietary foodstuffs for coastal communities

Halibut (Hippoglossus hippoglossus) and shrimps (Pandalus borealis) are regular foodstuffs for communities in northern Norway and important species for the coastal fishing industry. This is the first study to present a comprehensive overview of the contaminant status of these species, with emphasis on unregulated perfluoroalkylated substances (PFAS). The contaminant concentrations were low and within tolerable levels for human dietary exposure. Median Σpolychlorinated biphenyls (PCB) were 4.9 and 2.5ng/g ww for halibut and unpeeled shrimps, respectively. Concentrations of perfluorooctane sulfonate (PFOS) - the most abundant PFASs - were 0.9 and 2.7ng/g ww in halibut and shrimp, respectively. The halibut fillets were dominated by PCBs, which contributed to 50% of the total POPs load, followed by ΣDDTs; 26% and PFASs (18%), whereas shrimps were dominated by PFASs (74%). ΣPBDEs (polybrominated diphenyl ethers) contributed to 1-4% of the total POP load. Local sources are not contributing significantly to the contaminant burden in these species.

Persistent halogenated compounds in fish from rivers in the Pearl River Delta, South China: Geographical pattern and implications for anthropogenic effects on the environment

Three fish species, mud carp (Cirrhinus molitorella), tilapia (Tilapia nilotica), and plecostomus (Hypostomus plecostomus), from rivers in the Pearl River Delta (PRD) were analyzed for dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), and Dechlorane Plus (DP). The concentrations of DDTs, HCHs, PCBs, PBDEs, DBDPE, and DP ranged from 380-57,000, 5.5-100, 30-4200, 6.9-690, 0.29-460, and 0.09-20ng/g lipid weight, respectively. Congener profiles or chemical compositions of PBDEs, DPs, DDTs, and HCHs in plecostomus differed significantly from those in the other two fish species, which can be ascribed to species-specific metabolism. DDTs derived from historical residue and land erosion remained the predominant pollutants in the PRD, while industrial and urban activities resulted in elevated levels of PCBs and PBDEs in the metropolitan area. E-waste recycling activities have greatly impacted on the adjacent aquatic environment, and the potential point source for DBDPE was also revealed.

Trophic magnification of polychlorinated biphenyls and polybrominated diphenyl ethers in an estuarine food web of the Ariake Sea, Japan

To evaluate trophic biomagnification of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in an estuary of the Ariake Sea, Japan, we measured concentrations of 209 PCB congeners and 28 PBDE congeners, and nitrogen stable isotope (δ(15)N) levels in living aquatic organisms. The trophic magnification factor (TMF) for ΣPCBs (all 209 congeners) was 1.52, and TMFs for 58 PCB congeners ranged from 0.90 to 3.28. In contrast, TMF for ΣPBDEs was 1.17, and TMFs for 7 PBDE congeners ranged from 0.46 to 1.66. TMFs of PCB and PBDE congeners in this study were lower than those in marine food webs, and were similar to those in a lake food web. However, although negative relationships were observed between TMF and log octanol-water partition coefficient (KOW) values among PCB congeners in this study (log KOW up to 7), positive relationships have been reported in several other studies. In the present estuary, PCB concentrations in sea bass may not reach a steady state because sea bass are migratory species. Therefore, TMFs of highly chlorinated congeners with high log KOW values take longer to reach the steady state and may not increase with increasing log KOW.

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 (δ(13)C) 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 (13)C 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.