Tissue concentrations of polybrominated compounds in Chinese sturgeon (Acipenser sinensis): origin, hepatic sequestration, and maternal transfer

Toxicokinetic Models for Bioconcentration of Organic Contaminants in Two Life Stages of White Sturgeon (Acipenser transmontanus)

The white sturgeon (Acipenser transmontanus) is an endangered ancient fish species that is known to be particularly sensitive to certain environmental contaminants, partly because of the uptake and subsequent toxicity of lipophilic pollutants prone to bioconcentration as a result of their high lipid content. To better understand the bioconcentration of organic contaminants in this species, toxicokinetic (TK) models were developed for the embryo-larval and subadult life stages. The embryo-larval model was designed as a one-compartment model and validated using whole-body measurements of benzo[a]pyrene (B[a]P) metabolites from a waterborne exposure to B[a]P. A physiologically based TK (PBTK) model was used for the subadult model. The predictive power of the subadult model was validated with an experimental data set of four chemicals. Results showed that the TK models could accurately predict the bioconcentration of organic contaminants for both life stages of white sturgeon within 1 order of magnitude of measured values. These models provide a tool to better understand the impact of environmental contaminants on the health and the survival of endangered white sturgeon populations.

Emerging environmental pollutants hydroxylated polybrominated diphenyl ethers: From analytical methods to toxicology research

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of particular concern due to their ubiquitous distribution and adverse health effects. Significant progress has been made in the characterization of OH-PBDEs by using mass spectrometry (MS). In this review, we summarize applications of MS-based techniques in detection, environmental and biota distribution, and potential health risk effects, hoping to unfold an overall picture on account of current knowledge of OH-PBDEs. The analytical methodologies are discussed from sample pretreatment to MS analysis. The methods including gas chromatography-MS (GC-MS), liquid chromatography-MS (LC-MS), and ion mobility spectrometry-MS (IMS-MS) are discussed. GC-MS is the most frequently adopted method in the analysis of OH-PBDEs due to its excellent chromatographic resolution, high sensitivity, and strong ability for unknown identification. LC-MS has been widely used for its high sensitivity and capability of direct analysis. As a newly developed technique, IMS-MS provides high specificity, which greatly facilitates the identification of isomers. OH-PBDEs pervasively existed in both abiotic and biotic samples, including humans, animals, and environmental matrices. Multiple adverse health effects have been reported, such as thyroid hormone disruption, estrogen effects, and neurotoxicity. The reported potential pathological mechanisms are also reviewed. Additionally, MS-based metabolomics, lipidomics, and proteomics have been shown as promising tools to unveil the molecular mechanisms of the toxicity of OH-PBDEs. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

Occurrence of Halogenated Organic Pollutants in Hadal Trenches of the Western Pacific Ocean

The hadal trenches are the most remote and inaccessible habitats on earth and were once believed to be pristine. A recent study has reported the detection of high levels of persistent organic pollutants (POPs), including polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), in endemic amphipods from two hadal trenches (Mariana and Kermadec) in the Western Pacific, implicating that the trenches are indeed polluted. However, a fundamental question remains unanswered, if and to what extent such the physical environment of the trenches is polluted by POPs. In this study, we sampled Mariana, Mussau, and New Britain trenches and analyzed samples of amphipods, sediment, and suspended particulate matter (SPM). Our results show that the amphipods contained elevated levels of PCBs and PBDEs, comparable to those reported in the earlier study. We also detected significantly high concentrations (up to 1343 ng g^-1 lw) of chlorinated pesticides, such as dichlorodiphenyltrichloroethanes and chlordanes. Furthermore, four brominated natural products (BNPs), which structurally resembled methoxylated brominated diphenyl ethers or polybrominated biphenyls, were identified in the endemic amphipods. However, neither POPs nor BNPs were detected in sediments or SPM. Taken together, we propose that the POPs detected in endemic amphipods likely resulted from bioaccumulation by feeding on polluted large detritus (e.g., carrion) falling to the trench bottoms from the surface ocean.

A density functional theory/time-dependent density functional theory study of the structure-related photochemical properties of hydroxylated polybrominated diphenyl ethers and methoxylated polybrominated diphenyl ethers and metal ion effects

As the derivatives and structural analogs of polybrominated diphenyl ethers (PBDEs), hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have attracted increasing concern. However, knowledge of the photochemical behaviors of OH-PBDEs and MeO-PBDEs in water is limited. Here, we used density functional theory and time-dependent density functional theory to examine the structure-related photochemical properties of OH-PBDEs and MeO-PBDEs in water and the effects of metal ions as environmental factors. Eight 6-OH-PBDEs with 1-8 bromine substituents and eight 6-MeO-PBDEs with 1-8 bromine substituents were selected for this study. The optimized geometries of the selected congeners and their complexes with metals in the lowest excited triplet state (T₁) showed that one C-Br bond moderately or significantly elongated. The elongated C-Br bond in the T₁ state was shown in the ortho-position for the 6-OH-PBDE congeners and the ortho-position or the meta-position for the 6-MeO-PBDE congeners. For the selected congeners, there were significant positive linear correlations between the number of bromine atoms (N_Br) and the calculated average atomic charge of bromine and maximum electronic absorbance wavelength (λ_max), and a negative linear correlation between the N_Br and average bond dissociation energy of C-O bonds (BDE_C-O). The photoreactivities of the 6-OH-PBDEs and 6-MeO-PBDEs increased with an increase in the bromination degree with or without metal ions. The calculated average atomic charge of bromine and BDE_C-O of the complexes with Mg²⁺/Zn²⁺ was higher and lower than those of the corresponding monomers, respectively, indicating that the presence of Mg²⁺/Zn²⁺ increased the photoreactivity (debromination and dissociation of C-O bond) of the selected 6-OH-PBDEs and 6-MeO-PBDEs. The effects of the coordination of Mg²⁺/Zn²⁺ may be overestimated due to their missing explicit solvation shell. These results provide vital insight into the photochemical properties of OH-PBDEs and MeO-PBDEs in water.

Health indicators and contaminant levels of a critically endangered species in the Gironde estuary, the European sturgeon

The European sturgeon, Acipenser sturio, is a highly endangered species that almost disappeared in the last decades. Thanks to yearly restocking of the population, this species is still found in the Gironde estuary (France), where juveniles grow during several years before leaving to the ocean. The aims of this study were to evaluate the pressure exerted on these fish by known organic and inorganic contaminants during their stay at the Gironde estuary, and to get information on the fish's health in this context. Monthly captures over the year 2014 provided 87 fish from the cohorts 2012 and 2013 mainly, and from cohorts 2008, 2009, and 2011, all fish born in hatchery. We report the very first analyses of contaminant levels and of biological markers measured in the blood of these fish. Low inorganic contamination was found, composed of seven metals mainly Zn (< 5 μg mL^-1), Fe (< 1.5 μg mL^-1), Cu (< 0.8 μg mL^-1), Se (< 0.8 μg mL^-1), As (< 0.25 μg mL^-1), Co (< 0.14 μg mL^-1), and Mn (< 0.03 μg mL^-1). Concerning persistent organic contaminants, the sum of seven PCBs varied from 1 to 10 ng g^-1 plasma, that of eight OCPs from 0.1 to 1 ng g^-1, and that of eight PBDEs from 10 to 100 pg g^-1. Higher levels of contaminants were measured during spring as compared to summer. The sex steroid hormone plasma levels (estradiol, testosterone, and 11-ketotestosterone) were quite low, which was predictable for juveniles. The transcription of reproduction-involved genes (EstR, AR, LHR, sox9) in blood cells was demonstrated for the first time. Some of them were correlated with organic contaminant levels PCBs and OCPs. Other gene transcriptions (sodCu and bax) were correlated with PCBs and OCPs. However, the DNA damage level measured here as comet tail DNA and micronuclei ratio in red blood cells were in the very low range of the values commonly obtained in fish from pristine areas. The data presented here can serve as a reference base for future monitoring of this population of sturgeons.

Occurrence, biomagnification and maternal transfer of legacy and emerging organophosphorus flame retardants and plasticizers in water snake from an e-waste site

Water snake and small common carp samples collected from a Chinese pond polluted with electronic waste (e-waste) were analyzed for organophosphorus flame retardants (PFRs), PFR metabolites, and plasticizers to investigate their occurrence, biomagnification, and maternal transfer in ovoviviparous species. Mean concentrations of total PFRs, PFR metabolites, and plasticizers were 2.2-16, 1.3-2.8 and 151-1320 ng/g wet weight (ww), respectively in analyzed organisms. Metabolites of PFRs were found in the same order of magnitude as or even higher than their parent compounds, indicating the importance of monitoring metabolites to evaluate the internal exposure of PFRs in organisms. Biomagnification factors (BMFs) were below 1 for all targeted chemicals and negatively correlated with metabolite/parent ratios (MPRs), suggesting a biodilution driven by metabolism. The lipid normalized concentrations were lower in eggs than in muscle for most of targeted chemicals. The maternal transfer potential was significantly and positively correlated with log K_OW (p < 0.05) when log K_OW was below 6.

Multiresidue Methods for the Determination of Organic Micropollutants and Their Metabolites in Fish Matrices

Two analytical methods were developed for the determination of 48 organic compounds and 20 of their main by-products in fish matrices. The targeted compounds belong to various chemical classes of metabolizable (phthalates, polycyclic aromatic hydrocarbons, insecticides [pyrethroids and N,N-diethyl-meta-toluamide]) and legacy (organochlorine pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers) pollutants. Analyses were performed by gas and liquid chromatography-tandem mass spectrometry in multiple reaction monitoring (MRM) and dynamic MRM, respectively. Method performances were satisfactory, with results meeting the validation criteria because they achieved good linearity responses, recovery, precision, and accuracy for most of the 68 investigated compounds. The methods were then applied on 3 feral chub (Squalius cephalus) collected from the Marne hydrographic network (France). Twenty-six parent compounds and 5 metabolites were systematically detected in fish matrices, with substantial concentration variability within and among individuals. Phthalates and pyrethroids accounted for most of the pollutant load. Metabolite concentrations in liver samples exceeded those of parent molecules in fish muscle. The present study presents 2 reliable methods for the determination of a wide range of contaminants and underlines the importance of metabolite analysis for a more comprehensive understanding of pollutant bioaccumulation and fate in aquatic organisms. Environ Toxicol Chem 2019;38:1866-1878. © 2019 SETAC.

Halogenated organic pollutants in aquatic, amphibious, and terrestrial organisms from an e-waste site: Habitat-dependent accumulation and maternal transfer in watersnake

Dichlorodiphenyltrichloroethanes (DDTs), Polychlorinated biphenyls (PCBs), and halogenated flame retardants (HFRs) were measured in aquatic, amphibious, and terrestrial wildlife collected from an e-waste contaminated pond and its surrounding region. The species-specific bioaccumulation and maternal transfer of chemicals in the watersnake were investigated. Total concentrations of target chemicals ranged from 1.3 × 10³ to 4.8 × 10⁵ ng g^-1 lipid weight. PCBs were the predominant (72-95%) contaminants, followed by polybrominated biphenyl ethers (PBDEs, 4-27%). The concentrations of PCBs and HFRs except decabromodiphenyl ethane (DBDPE) were higher in aquatic organisms and terrestrial birds than in amphibians and lizards. Relatively high DDT levels were observed in the terrestrial birds and toads, but high DBDPE was found in the aquatic species except for waterbird eggs. Species-specific congeners profiles for PCB and PBDE and isomeric composition for dechlorane plus were observed. These results indicated a habitat-dependent accumulation among different species. Maternal transfer examined by the ratio of egg to carcass for watersnakes indicated multi-linear correlations between maternal transfer potential and octanol-water partition coefficient (log K_OW) of chemicals. The same maternal transfer efficiencies were found for chemicals with log K_OW between 6 and 8, then the maternal transfer potential rapidly decreased with increasing of log K_OW.

Global occurrence of polybrominated diphenyl ethers and their hydroxylated and methoxylated structural analogues in an important animal feed (fishmeal)

Polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH) and methoxylated (MeO) structural analogues have been found widely distributed in aquatic ecosystems, and may exhibit potential adverse effects to humans due to their bioaccumulative behavior through food chain. Fishmeal is an important animal feed applied around the world and is generally of marine origin. However, the levels and sources of PBDEs in fishmeal have not been thoroughly evaluated and their structural analogues have not been reported to date. The present study collected ninety-two fishmeal samples from world main fishmeal producing area to determine 27 PBDEs, 10 MeO-PBDEs and 11 OH-PBDEs. The concentrations of Σ₂₇PBDEs, Σ₁₀MeO-PBDEs and Σ₁₁OH-PBDEs were in the ranges of 0.1-1498 (mean: 75.8), 1.14-881 (37.4) and 1.00-47.5 (8.17) ng/g lipid, respectively. PBDEs were found primarily correlated with the historically commercial production, meaning higher production of certain commercial product in a country, higher corresponding PBDE congeners in local fishmeal. A market shift from penta- and octa-formulations toward deca-formulation was observed. BDE209 was identified as a major congener in fishmeal. Both the MeO-PBDEs and the OH-PBDEs were influenced by fishmeal producing areas (p < 0.001). High MeO-PBDEs were identified in the Southeast Asian fishmeal, which might be due to the suitable environmental conditions for the generation of bromoperoxidase-contained algae in local area. The ratio of two major MeO-PBDE congeners, 6-MeO-BDE47/2'-MeO-BDE68, were generally >1 in the northern hemisphere and <1 in the southern hemisphere in the present study, which was consistent with the results obtained from previous published papers. Both MeO-PBDEs and OH-PBDEs were in accordance with the specialties of naturally produced halogenated compounds.

Hydroxylated and methoxylated polybrominated diphenyl ethers in a marine food web of Chinese Bohai Sea and their human dietary exposure

Hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have been identified ubiquitous in wildlife and environment. However, understanding on their trophic accumulation and human exposure was hitherto limited. In this study, the occurrences and trophic behaviors were demonstrated for OH- and MeO-PBDEs using the biota samples collected from Dalian, a coastal city near Chinese Bohai Sea. ∑OH-PBDEs exhibited a wider concentration range (<MDL (method detection limit)-25 ng/g dry weight (dw)) compared with ∑MeO-PBDEs (<MDL-2 ng/g dw) and ∑PBDEs (<MDL-2 ng/g dw). The congener profiles and distribution patterns revealed that majority of OH- and MeO-PBDEs in marine biota were naturally produced and largely attributed to preying on lower trophic level biota. Though tertiary consumers accumulated more MeO-PBDEs and PBDEs, these chemicals did not show statistically significant biomagnification in the selected food web. Conversely, trophic dilution was determined for ortho-substituted OH-tetraBDEs and OH-pentaBDEs, revealing that trophic dilution was prevalent for naturally produced OH-PBDEs. The dietary intake evaluation of OH-PBDEs (0.4 ng/kg/d) and MeO-PBDEs (0.8 ng/kg/d) via seafood consumption showed that coastal residents were in higher exposure risks to OH-PBDEs and MeO-PBDEs via the massive seafood consumption.

Fish life-history traits are affected after chronic dietary exposure to an environmentally realistic marine mixture of PCBs and PBDEs

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that have been shown to affect fish life-history traits such as reproductive success, growth and survival. At the individual level, their toxicity and underlying mechanisms of action have been studied through experimental exposure. However, the number of experimental studies approaching marine environmental situations is scarce, i.e., in most cases, individuals are exposed to either single congeners, or single types of molecules, or high concentrations, so that results can hardly be transposed to natural populations. In the present study, we evaluated the effect of chronic dietary exposure to an environmentally realistic marine mixture of PCB and PBDE congeners on zebrafish life-history traits from larval to adult stage. Exposure was conducted through diet from the first meal and throughout the life cycle of the fish. The mixture was composed so as to approach environmentally relevant marine conditions in terms of both congener composition and concentrations. Life-history traits of exposed fish were compared to those of control individuals using several replicate populations in each treatment. We found evidence of slower body growth, but to a larger asymptotic length, and delayed spawning probability in exposed fish. In addition, offspring issued from early spawning events of exposed fish exhibited a lower larval survival under starvation condition. Given their strong dependency on life-history traits, marine fish population dynamics and associated fisheries productivity for commercial species could be affected by such individual-level effects of PCBs and PBDEs on somatic growth, spawning probability and larval survival.

Tissue Contaminant Burdens in San Francisco Estuary White Sturgeon (Acipenser transmontanus): Implications for Population Recovery

The San Francisco Estuary (SFE) is heavily influenced by anthropogenic activities, including historic and chronic contaminant inputs. These contaminants can adversely affect SFE fish populations, particularly white sturgeon, because they are a benthic dwelling, long-lived species. We measured a suite of metals and organic contaminants in liver and gonad tissues of 25 male and 32 female white sturgeon as well as several physiological indicators of sturgeon health. Most sturgeon (68% of males and 83% of females) were estimated to be between 13 and 17 years of age. Sturgeon tissues had elevated concentrations of several metals, including As, Ba, Cd, Cu, Cr, Pb, Hg, Ni, Se, and Zn. The most frequently detected organic contaminants in sturgeon livers and gonads were DDE, PCBs, PBDEs, and galaxolide. Selenium was detected at levels similar to those shown to cause impaired liver physiology and reproductive success in white sturgeon. Observed Hg levels were higher than those shown to result in lower condition factor and gonadosomatic indices in white sturgeon. Liver galaxolide levels correlated with decreased plasma estradiol levels in female sturgeon. The Cd, As, and Cu warrant further investigation, because they were detected at levels known to impair fish health. Our results suggest contaminants are negatively affecting SFE white sturgeon health and fitness. Future SFE white sturgeon contaminant research is suggested.

Uptake and biotransformation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in four marine microalgae species

Hydroxylated- and methoxylated- polybrominated diphenyl ethers (OH-PBDEs and MeO-PBDEs) are more toxic than PBDEs and occur widely in the marine environment, and yet their origins remain controversial. In this study, four species of microalgae (Isochrysis galbana, Prorocentrum minimum, Skeletonema grethae and Thalassiosira pseudonana) were exposed to BDE-47, which is synthetic and is the predominant congener of PBDEs in the environment. By chemical analysis after incubation of 2 to 6 days, the efficiency of uptake of BDE-47 and, more importantly, the potential of undergoing biotransformation to form OH-PBDEs and MeO-PBDEs by the microalgae were investigated. Growth rates of these axenic microalgae were not affected upon exposure to environmentally relevant concentrations (0.2–20 μg BDE-47 L⁻¹), and accumulation ranged from 0.772 ± 0.092 μg BDE-47 g⁻¹ lipid to 215 ± 54 μg BDE-47 g⁻¹ lipid within 2 days. Debromination of BDE-47 and formation of BDE-28 occurred in all microalgae species (0.01 to 0.87%), but biotransformation to OH-PBDEs was only found in I. galbana upon exposure to extremely high concentration. The results of this study showed that biotransformation of microalgae species is unlikely an explanation for the OH-PBDEs and MeO-PBDEs found in the marine environment.

Occurrence, spatial distribution, and ecological risks of typical hydroxylated polybrominated diphenyl ethers in surface sediments from a large freshwater lake of China

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been frequently observed in marine aquatic environments; however, little information is available on the occurrence of these compounds in freshwater aquatic environments, including freshwater lakes. In this study, we investigated the occurrence and spatial distribution of typical OH-PBDEs, including 2'-OH-BDE-68, 3-OH-BDE-47, 5-OH-BDE-47, and 6-OH-BDE-47 in surface sediments of Taihu Lake. 3-OH-BDE-47 was the predominant congener, followed by 5-OH-BDE-47, 2'-OH-BDE-68, and 6-OH-BDE-47. Distributions of these compounds are drastically different between sampling site which may be a result of differences in nearby point sources, such as the discharge of industrial wastewater and e-waste leachate. The positive correlation between ∑OH-PBDEs and total organic carbon (TOC) was moderate (r = 0.485, p < 0.05), and site S3 and S15 were excluded due to point source pollution, suggesting that OH-PBDEs concentrations were controlled by sediment TOC content, as well as other factors. The pairwise correlations between the concentrations of these compounds suggest that these compounds may have similar input sources and environmental behavior. The target compounds in the sediments of Lake Taihu pose low risks to aquatic organisms. Results show that OH-PBDEs in Lake Taihu are largely dependent on pollution sources. Because of bioaccumulation and subsequent harmful effects on aquatic organisms, the concentrations of OH-PBDEs in freshwater ecosystems are of environmental concern.

Formation of brominated phenolic contaminants from natural manganese oxides-catalyzed oxidation of phenol in the presence of Br(.)

Brominated phenolic compounds (BPCs) are a class of persistent and potentially toxic compounds ubiquitously present in the aquatic environment. However, the origin of BPCs is not clearly understood. In this study, we investigated the formation of BPCs from natural manganese oxides (MnOx)-catalyzed oxidation of phenol in the presence of Br(-). Experiments at ambient temperature clearly demonstrated that BPCs were readily produced via the oxidation of phenol by MnOx in the presence of Br(-). In the reaction of MnOx sand with 0.213 μmol/L phenol and 0.34 mmol/L Br(-) for 10 min, more than 60% of phenol and 56% of Br(-) were consumed to form BPCs. The yield of BPCs increased with increasing concentrations of phenol and Br(-). Overall, a total of 14 BPCs including simple bromophenols (4-bromophenol, 2,4-dibromophenol, and 2,4,6-tribromophenol), hydroxylated polybrominated diphenyl ethers (OH-PBDEs), and hydroxylated polybrominated biphenyls (OH-PBBs) were identified. The production of BPCs increased with increasing concentrations of Br(-) or phenol. It was deduced that Br(-) was first oxidized to form active bromine, leading to the subsequent bromination of phenol to form bromophenols. The further oxidation of bromophenols by MnOx resulted in the formation of OH-PBDEs and OH-PBBs. In view of the ubiquity of phenol, Br(-), and MnOx in the environment, MnOx-mediated oxidation may play a role on the natural production of BPCs.

Thermal degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) over synthesized Fe-Al composite oxide

A series of Fe-Al composite oxides were synthesized by the hydrothermal method using different urea dosages and examined towards the degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) at 300 °C. The as-prepared oxides were characterized by field-emission scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology and composition of the prepared materials could be regulated by controlling the urea concentration. Interestingly, these properties influenced the nature and amount of the hydrodebromination products generated during the degradation of BDE-47. The degradation of BDE-47 over the composite oxide prepared at a urea dosage of 3 mmol generated BDE-17 as the major isomer product, followed by BDE-28/33, -30, and -32, among the tribromodiphenyl ethers (tri-BDEs). Regarding the dibromodiphenyl ethers (di-BDEs) produced, the amount of the isomers decreased in the order of BDE-8/11 > BDE-7 > BDE-15 > BDE-10. And the BDE-1 among monobromodiphenyl was determined. In contrast, over the composite oxides prepared at urea dosages greater than 3 mmol, BDE-28/33 gradually become the major isomer product instead of BDE-17 among tri-BDEs. The amount of the other di-BDEs isomer such as BDE-15 and -10 approach to be comparable to that BDE-8/11. However, regardless of the urea dosage, BDE-47 converted into BDE-75 via an isomerization reaction. Based on these intermediate products identification, a possible hydrodebromination mechanism of BDE-47 over Fe-Al composite oxide was comprehensively traced.

Trophic transfer of naturally produced brominated aromatic compounds in a Baltic Sea food chain

Brominated aromatic compounds (BACs) are widely distributed in the marine environment. Some of these compounds are highly toxic, such as certain hydroxylated polybrominated diphenyl ethers (OH-PBDEs). In addition to anthropogenic emissions through use of BACs as e.g. flame retardants, BACs are natural products formed by marine organisms such as algae, sponges, and cyanobacteria. Little is known of the transfer of BACs from natural producers and further up in the trophic food chain. In this study it was observed that total sum of methoxylated polybrominated diphenyl ethers (MeO-PBDEs) and OH-PBDEs increased in concentration from the filamentous red alga Ceramium tenuicorne, via Gammarus sp. and three-spined stickleback (Gasterosteus aculeatus) to perch (Perca fluviatilis). The MeO-PBDEs, which were expected to bioaccumulate, increased in concentration accordingly up to perch, where the levels suddenly dropped dramatically. The opposite pattern was observed for OH-PBDEs, where the concentration exhibited a general trend of decline up the food web, but increased in perch, indicating metabolic demethylation of MeO-PBDEs. Debromination was also indicated to occur when progressing through the food chain resulting in high levels of tetra-brominated MeO-PBDE and OH-PBDE congeners in fish, while some penta- and hexa-brominated congeners were observed to be the dominant products in the alga. As it has been shown that OH-PBDEs are potent disruptors of oxidative phosphorylation and that mixtures of different congener may act synergistically in terms of this toxic mode of action, the high levels of OH-PBDEs detected in perch in this study warrants further investigation into potential effects of these compounds on Baltic wildlife, and monitoring of their levels.

Simultaneous Determination of Perfluorinated Compounds in Edible Oil by Gel-Permeation Chromatography Combined with Dispersive Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry

A simple analytical method was developed for the simultaneous analysis of 18 perfluorinated compounds (PFCs) in edible oil. The target compounds were extracted by acetonitrile, purified by gel permeation chromatography (GPC) and dispersive solid-phase extraction (DSPE) using graphitized carbon black (GCB) and octadecyl (C18), and analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ES-MS/MS) in negative ion mode. Recovery studies were performed at three fortification levels. The average recoveries of all target PFCs ranged from 60 to 129%, with an acceptable relative standard deviation (RSD) (1-20%, n = 3). The method detection limits (MDLs) ranged from 0.004 to 0.4 μg/kg, which was significantly improved compared with the existing liquid-liquid extraction and cleanup method. The method was successfully applied for the analysis of all target PFCs in edible oil samples collected from markets in Beijing, China, and the results revealed that C6-C10 perfluorocarboxylic acid (PFCAs) and C7 perfluorosulfonic acid PFSAs were the major PFCs detected in oil samples.

Preliminary study on brominated dioxins/furans and hydroxylated/methoxylated PBDEs in Baltic cod (Gadus morhua) liver. Comparison to the levels of analogue chlorinated co-occurring pollutants

Low pg levels of PBDD/Fs in 0.8-38.9 pg g(-1) (fat) range (mean 14.2 pg g(-1)) observed in the tested cod liver samples were significantly lower than levels of their chlorinated analogues (25.1-95.9 range, 37.7 mean pg g(-1) fat). Brominated furans dominated the congener profile. Elevated levels of OH-/MeO-BDE were however observed with mean concentrations at 2769±1319 and 5441±2918 pg g(-1) (fat) respectively. The observed congener profiles with the predominance of 6-OH-BDE 47 and the relatively high proportion between the native and hydroxylated compounds indicate on natural origin of those compounds or at least presence of various exposure sources. A large fraction of studied samples did not comply with the currently standing EU regulations concerning PCBs and chlorinated dioxins (11%), especially as regards non-dioxin like PCBs (88%).

Temporal trends of polychlorinated biphenyls, polybrominated diphenyl ethers, and perfluorinated compounds in Chinese sturgeon (Acipenser sinensis) eggs (1984-2008)

Because investigation on the temporal trends of persistent halogenated compounds (PHCs) is necessary to predict their future impacts on the environment and human health and evaluate the effectiveness of regulations on their production and usage, it is of concern to investigate annual temporal trends of PHCs in biota samples. This study examined the temporal trends of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and perfluorinated compounds (PFCs) in Chinese sturgeon (Acipenser sinensis) eggs over a period of 25 years (1984-2008), and 62 PCBs (19.2-1030 ng/g dw for total PCBs), 16 PBDEs (4.7-572 ng/g dw for total PBDEs), and 14 PFCs (26-46 ng/g dw for total PFCs) were detected. Although a decreasing temporal trend was observed for total PCBs with annual reduction rate of 3.4% (ρ = 0.005), a clear break point was observed around 1991, indicating their continuing emission in the 1980s in China. All major PBDEs showed increasing temporal trends, with annual change rates at 3.5-10.2% over the 25 years, but a sharp decreasing trend was observed after 2006, indicating a rapid response to the banning of PBDE usage in China in 2004. The greatest annual rate of increase was observed for BDE-28 (10.2%) followed by BDE-100 (7.7%), which would be due to metabolism input from higher brominated PBDEs. Significantly increasing temporal trends were observed for all PFCs, and the annual rates of increase were 7.9% and 5.9% for total perfluorinated carboxylic acids and perfluorooctanesulfonate (PFOS), respectively. A peak concentration for PFOS was observed in 1989, which may be related to the import history of PFCs in China. The present study is the first report of systematic temporal trends of PHCs in biota samples from China and shows that regulatory policy is needed to reduce their potential health and ecological risk in China considering the increasing temporal trends of PBDEs and PFCs.

Effects of the bioaccumulative polybrominated diphenyl ether flame retardant congener BDE-47 on growth, development, and reproductive success in zebra finches

This study investigated the effects of the polybrominated diphenyl ether congener, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on the growth and development, and subsequent breeding success of exposed zebra finches (Taeniopygia guttata). Using oral dosing procedures and treatments adjusted by weight, we treated newly hatched chicks daily for the first 20-days-post-hatch (dph) with varying treatments of BDE-47 (0, 5, 50, and 500 ng/g bw/day). Weight and tarsal measurements were monitored from hatch to 90 dph, but no differences were observed between treatment groups at any age. Treated females that reached sexual maturity were mated with untreated males; however, again no treatment effects were observed on breeding success. Analysis of tissue samples at 21 dph did indicate that debromination of BDE-47 had occurred resulting in BDE-28 and BDE-17 metabolites.

Structure-dependent activities of polybrominated diphenyl ethers and hydroxylated metabolites on zebrafish retinoic acid receptor

Polybrominated diphenyl ethers (PBDEs), a group of potential endocrine-disrupting chemicals (EDCs) have been shown to disrupt retinoid homeostasis in different species in both laboratory and field studies. However, the molecular mechanisms of interactions with the retinoic acid receptor (RAR) are not fully understood. Zebrafish have proven useful for investigating mechanisms of chemical toxicity. In the present study, a reporter gene assay was used to investigate the activities of 11 PBDEs and six OH-PBDEs with different degrees of bromination on zebrafish RAR. All tested OH-PBDEs induced RAR transcriptional activity; however, of the 11 PBDEs examined, only BDE28 and BDE154 affected the RAR transcriptional activity. Homology modeling and molecular docking were employed to simulate the interactions of PBDEs/OH-PBDEs with zebrafish RARs and to identify binding affinities to analyze the specialization of the interaction between RARs and PBDEs/OH-PBDEs. The results showed that although these compounds could bind with RARs, the effects of PBDEs/OH-PBDEs on RAR transcriptional activity did not depend on their RAR-binding abilities. The present study is the first attempt to demonstrate that OH-PBDEs could induce RAR transcriptional activity by binding directly with RAR; these effects are possibly related to the structure of the compounds, especially their hydroxylation and bromination. Most of the PBDEs could not directly interact with the RAR.

Transformation pathways of MeO-PBDEs catalyzed by active center of P450 enzymes: a DFT investigation employing 6-MeO-BDE-47 as a case

Recent in vivo and in vitro experiments indicated that methoxylated polybrominated diphenyl ethers (MeO-PBDEs) can be biotransformed into hydroxylated PBDEs (HO-PBDEs) that are more toxic than PBDEs and MeO-PBDEs. Nevertheless, the enzymatic transformation mechanism is not clear. We hypothesized that cytochrome P450 enzymes (CYPs) play a key role in the transformation and employed the density functional theory calculations to unveil the mechanism. The transformation of a model compound, 6-MeO-BDE-47, catalyzed by the active center of CYPs (Compound I), was computed. For the first time, our results show that the energy barriers for the addition of Compound I to the C atoms on the phenyl of 6-MeO-BDE-47 are much higher than that for hydroxylation of the methoxyl, indicating that O-demethylation is a dominating metabolic pathway. This is in line with experimental observations performed by others. The pathways for the transformation of 6-MeO-BDE-47 catalyzed by Compound I were clarified. A C-H bond of the methoxyl is activated by Compound I, followed by radical rebound to form carbinol intermediates, then the carbinols decompose to form 6-HO-BDE-47 with the assistance of water molecules. The computational method can be potentially employed to develop models that predict biotransformation of xenobiotics catalyzed by CYPs.

Maternal transfer, distribution, and metabolism of BDE-47 and its related hydroxylated, methoxylated analogs in zebrafish (Danio rerio)

OH-PBDEs have been reported to be more potent than the postulated precursor PBDEs or corresponding MeO-PBDEs. However, there are contradictory reports for transformation of these compounds in organisms, particularly, for biotransformation of OH-PBDEs and MeO-PBDEs, only one study reported transformation of 6-OH-BDE-47 and 6-MeO-BDE-47 in Japanese medaka. In present study zebrafish (Danio rerio) were exposed to BDE-47, 6-OH-BDE-47, 6-MeO-BDE-47, 2'-OH-BDE-28 and 2'-MeO-BDE-28 in the diet for 20 d. Concentrations of each exposed compound were measured in eggs collected on days 0, 5, 10, 15 or 20. After 20 d exposure, concentrations of precursor and biotransformation products in liver and liver-free residual carcass were measured by use of GC-MS/MS. Total mass of the five compounds in bodies of adults were: 2'-MeO-BDE-28 ∼ 6-MeO-BDE-47>BDE-47>2'-OH-BDE-28>6-OH-BDE-47. MeO-PBDEs were also accumulated more into parental fish body than in liver, while OH-PBDEs accumulated in liver more than in liver-free residual carcass. Concentrations in liver of males were greater than those of females. This result suggests sex-related differences in accumulation. Ratios between concentration in eggs and liver (E/L) were: 2.9, 1.7, 0.8, 0.4 and 0.1 for 6-MeO-BDE-47, BDE-47, 6-OH-BDE-47, 2'-MeO-BDE-28 and 2'-OH-BDE-28, respectively. This result suggests transfer from adult females to eggs. BDE-47 was not transformed into OH-PBDEs or MeO-PBDEs. Inter-conversions of 6-OH-BDE-47 and 6-MeO-BDE-47, 2'-OH-BDE-28 and 2'-MeO-BDE-28 were observed, with metabolite/precursor concentration ratios for 6-OH-BDE-47, 6-MeO-BDE-47, 2'-OH-BDE-28 and 2'-MeO-BDE-28 being 3.8%, 14.6%, 2.9% and 76.0%, respectively. Congener-specific differences were observed in distributions between liver and carcass, maternal transfer and transformation. The two MeO-PBDEs were accumulated into adults, transferred to eggs, and were transformed to the structural similar OH-PBDEs, which might be more toxic. BDE-47 was accumulated into adults and transferred from females to eggs, but not transformed to MeO-PBDEs and/or OH-PBDEs. Accumulation of OH-PBDEs into adults as well as rates of transformation of OH-PBDEs to MeO-PBDEs were all several orders of magnitude less. Thus, MeO-PBDEs are likely to present more of a risk in the environment.

Changes of polybrominated diphenyl ether concentrations in ducks with background exposure level and time

To reveal what degree bioaccumulation of polybrominated diphenyl ethers (PBDEs) depends on exposure time and other factors, we conducted a semi-field experiment for a year (June 2008-June 2009) in a village in an e-waste recycling site in Taizhou, China. Approximately one hundred of juvenile ducks (Anas domestica Linnaeus) were entrusted to a villager. The ducks lived and forged in a PBDE-polluted pond from the late March to the end of November. Fish and mudsnails that were heavily polluted by PBDEs were main food. In cold days (from December to the middle March), the ducks lived in the villager' house, and mainly fed on paddy, which contained lower concentrations of PBDEs than fish and mudsnails. The female ducks were sampled for PBDE analysis every three months. We found that the ∑PBDE concentrations in duck liver, muscle, lung and brain fluctuated greatly with the changes of exposure levels that were determined by the environment and diets, but the ∑PBDE concentrations in fat tissue increased successively with time. Congener analysis demonstrated that the successive increase in the ∑PBDE concentrations with time in fat tissue was due to the successive increase in BDE-209, -183 and -153 concentrations, with large fluctuations of low brominated congeners. The results show that PBDE concentrations in liver, muscle, lung and brain tissues heavily depends on exposure levels rather than exposure time. In fat tissue, by contrast, PBDE concentrations (mainly high brominated congeners) slightly depends on exposure levels but heavily depend on time relative to other tissues, implying that high brominated congeners seem to have longer half-lives than low brominated congeners in fat tissue.

Spatial distributions of methoxylated and hydroxylated polybrominated diphenyl ethers in the East China Sea--a seaward increasing trend

Methoxylated (MeO-) and hydroxylated (OH-) polybrominated diphenyl ethers (PBDEs) in marine environments have been of increasing concern due to their potential ecological toxicities and worldwide occurrence. However, few reports have been referred to their occurrence and distributions in marine sediments despite large numbers of studies on marine organisms have been reported. In the present paper, nine MeO-BDEs, ten OH-BDEs and three phytoplankton biomarkers (PBs) of brassicasterol, dinosterol and alkenones have been measured in surface sediments from the East China Sea. 6-MeO-BDE47, 2'-MeO-BDE68 and 6-OH-BDE47 were predominant congeners, ranging from 5.2 to 599.5 pg g(-1)dw, 5.2 to 562.4 pg g(-1)dw, and 11.4 to 129.1 pg g(-1)dw, respectively. Their spatial patterns all presented a seaward increasing trend and higher levels of these compounds were mainly concentrated in the outer shelf influenced by the Kuroshio Current. The patterns further prove that these ortho-substituted MeO-BDEs and OH-BDEs in marine sediments are natural compounds. Furthermore, alkenones also presented a seaward increasing trend. Statistical analysis shows that there are significant correlations between MeO-BDEs, OH-BDEs and alkenones, impling the potential of coccolithophorids for producing these natural compounds and their global distribution, especially in open oceans. Comparison between TOC and the ratio of 6-MeO-BDE47/6-OH-BDE47 suggests that TOC should be a potential controlling factor of the conversion between MeO-BDE and OH-BDE pairs.

PBDEs, hydroxylated PBDEs and methoxylated PBDEs in bivalves from Beijing markets

The structural analogues of polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) have been attracting increasing concern in recent years. Five bivalve species (blue mussel, short-necked clam, surf clam, ark shell and razor clam) were collected from Beijing markets, and the concentrations of seven PBDEs, four OH-PBDEs and fourteen MeO-PBDEs in the bivalves were measured. The seasonal variations of these three types of polybrominated compound in blue mussels were also monitored. The results indicate that the levels of ΣPBDEs in this study were comparable to those in short-necked clams from Liaodong Bay, China, with BDE47 as the dominant congener. For the ortho-MeO-PBDEs, 6-MeO-BDE47 was found at higher concentrations than the others, while for the meta- and para-MeO-PBDEs, 4'-MeO-BDE17 was found at higher concentrations. 6-OH-BDE-47 was the most abundant congener among the 4 measured OH-PBDEs, followed by 6-OH-BDE-137 and 6-OH-BDE-85. The levels of OH-PBDEs and MeO-PBDEs in bivalves from Beijing markets were much lower than the corresponding compounds in blue mussels from the Baltic Sea. In the blue mussels collected in April, June and September of 2012, apparent seasonal variations were observed for these three types of polybrominated compounds, but the acidic components displayed different trends from the neutral components, with PBDEs and MeO-PBDEs showing the highest concentrations in June, while OH-PBDEs had the lowest concentrations in June. This difference in seasonal variations between the neutral components and the acidic components may be explained by their different sources and transformation/elimination mechanisms.

Major sources of MeO/OH-BDEs in the East China Sea elucidated from their records and phytoplankton biomarkers

Hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have caused much concern because of their potential toxicity and worldwide distribution. These compounds are recently suggested to originate from the natural process in the ocean. However, their source remains highly controversial. In this study, we analyzed the contents of nine MeO-BDEs, ten OH-BDEs, and phytoplankton biomarkers (PBs) in two sediment cores collected from the East China Sea (ECS). The detection of 6-MeO-BDE-47, 2'-MeO-BDE-68, and 6-OH-BDE-47 have been reported since the 1920s, prior to the production of PBDEs. Significant relations were found between MeO/OH-BDEs and indicators of marine organic matters. The similar down-core variations and significant correlations between MeO/OH-BDEs and PBs suggest the possibility that phytoplankton produced these natural compounds. Laboratory incubation further demonstrates that phytoplankton can produce MeO-BDEs. Comparisons between the content ratios of 6-MeO-BDE-47/2'-MeO-BDE-68 and brassicasterol/dinosterol indicate that the signature of MeO-BDEs is controlled by the phytoplankton community structure.

Sedimentary records of hydroxylated and methoxylated polybrominated diphenyl ethers in the southern Yellow Sea

Although hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDEs) have caused much concern in recent years, few reports had discussed on their input history. In this study, we measured the contents of nine MeO-BDEs, ten OH-BDEs, and total organic carbon (TOC) of two sediment cores from the southern Yellow Sea. 6-MeO-BDE-47, 2'-MeO-BDE-68, 6-OH-BDE-47, and 2'-OH-BDE-68 were the predominant congeners in HH12, while only 2'-OH-BDE-68 and 6-OH-BDE-47 were frequently detected in core HH11. The records showed that OH-/MeO-BDEs in both cores had increased rapidly since the 1950s. Their existence was detected at the bottom layers (∼1800 s) prior to the production of PBDEs (1960s), thus OH-/MeO-BDEs originate from natural origins rather than artificial PBDEs. Comparisons between TOC and OH-/MeO-BDEs indicated that TOC is a potential factor affecting the accumulation of OH-/MeO-BDEs in marine environments. Similar trends and significant correlations between OH-BDEs and MeO-BDEs suggest their common origins or interconversion.

Halogenated phenolic contaminants in the blood of marine mammals from Japanese coastal waters

Information on accumulation of halogenated phenolic contaminants in the blood of marine mammal is limited. The present study, we determined the residue levels and patterns of chlorinated and brominated phenolic contaminants (OH-PCBs, OH-PBDEs and bromophenols) in the blood collected from pinnipeds (northern fur seal, spotted seal, Steller sea lion and ribbon seal) and small cetaceans (harbor porpoise and Dall's porpoise) from Japanese coastal waters. Concentrations of PCBs and OH-PCBs found in pinnipeds were the same as in small cetaceans living in the same coastal area. However, significantly lower concentrations of brominated compounds (PBDEs, MeO-PBDEs, OH-PBDEs) were found in the blood of pinnipeds than the levels found in cetacean species which live same area (p < 0.05). This difference of accumulation pattern suggested pinnipeds have an enhanced capability to degrade organobromine compounds relative to cetaceans.

Production of hydroxylated polybrominated diphenyl ethers (OH-PBDEs) from bromophenols by manganese dioxide

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are of significant concern because of their enhanced toxicological effects compared to PBDEs. Research to date has attributed the origin of OH-PBDEs to biological metabolism of PBDEs and natural production in the environment. However, it is unclear how OH-PBDEs are formed naturally. In this study, we explored the formation of OH-PBDEs via the oxidative transformation of simple bromophenols (BPs, e.g., 4-BP, 2,4-DBP, and 2,4,6-TBP) by birnessite (δ-MnO2). Results showed that OH-PBDEs were readily produced by δ-MnO2 with BPs as precursors. For example, oxidation of 2,4-DBP by δ-MnO2 yielded 2'-OH-BDE-68 and 2',5'-OH-BDE-25. Other OH-PBDEs, such as 6-OH-BDE-13, 2',5'-OH-BDE-3, 4'-OH-BDE-121, and 2',5'-OH-BDE-69, were detected from the reaction with 4-BP and 2,4,6-TBP. The formation of OH-PBDEs likely resulted from the oxidative coupling of bromophenoxy radicals. Mild acidic conditions enhanced while coexisting cations (e.g., Na(+), Mg(2+), and Ca(2+)) suppressed the transformation. Given the ubiquity of BPs and δ-MnO2, oxidation of BPs by δ-MnO2 and other metal oxides is likely an abiotic route for the formation of OH-PBDEs in the environment.

Use of impact fees to incentivize low-impact development and promote compact growth

Low-impact development (LID) is an innovative stormwater management strategy that restores the predevelopment hydrology to prevent increased stormwater runoff from land development. Integrating LID into residential subdivisions and increasing population density by building more compact living spaces (e.g., apartment homes) can result in a more sustainable city by reducing stormwater runoff, saving infrastructural cost, increasing the number of affordable homes, and supporting public transportation. We develop an agent-based model (ABM) that describes the interactions between several decision-makers (i.e., local government, a developer, and homebuyers) and fiscal drivers (e.g., property taxes, impact fees). The model simulates the development of nine square miles of greenfield land. A more sustainable development (MSD) scenario introduces an impact fee that developers must pay if they choose not to use LID to build houses or apartment homes. Model simulations show homeowners selecting apartment homes 60% or 35% of the time after 30 years of development in MSD or business as usual (BAU) scenarios, respectively. The increased adoption of apartment homes results from the lower cost of using LID and improved quality of life for apartment homes relative to single-family homes. The MSD scenario generates more tax revenue and water savings than does BAU. A time-dependent global sensitivity analysis quantifies the importance of socioeconomic variables on the adoption rate of apartment homes. The top influential factors are the annual pay rates (or capital recovery factor) for single-family houses and apartment homes. The ABM can be used by city managers and policymakers for scenario exploration in accordance with local conditions to evaluate the effectiveness of impact fees and other policies in promoting LID and compact growth.

Ligninase-mediated transformation of 4,4'-dibromodiphenyl ether (BDE 15)

The structurally related hydroxylated polybrominated diphenyl ether (PBDE) like hydroxylated 4,4'-dibromodiphenyl ether widely occur in precipitation, surface water, and biotic media. The origins of hydroxylated PBDEs (OH-PBDEs) are of particular interest due to their greater toxic potencies than the corresponding PBDEs. We studied the transformation behavior and products of 4,4'-dibromodiphenyl ether (BDE 15) mediated by lignin peroxidase (LiP), an extracellular enzyme that is produced by certain white rot fungus and is widely present in the natural environment. We found that BDE 15 can be effectively transformed through the reaction mediated by LiP, and two different mono-OH-dibromodiphenyl ethers were identified by using gas chromatography-mass spectrometry (GC-MS) and GC-MS/MS. In particular, we compared the reaction behavior for systems variously containing natural organic matter (NOM) and/or veratryl alcohol (VA), a metabolite that certain fungus produces along with LiP in nature. It was found that the VA's enhancement effect on LiP performance was impaired by the presence of NOM. The findings in this study provide useful information for better understanding the origins of OH-PBDEs found in the environment.

Policy interactions and underperforming emission trading markets in China

Emission trading is considered to be cost-effective environmental economic instrument for pollution control. However, the ex post analysis of emission trading program found that cost savings have been smaller and the trades fewer than might have been expected at the outset of the program. Besides policy design issues, pre-existing environmental regulations were considered to have a significant impact on the performance of the emission trading market in China. Taking the Jiangsu sulfur dioxide (SO2) market as a case study, this research examined the impact of policy interactions on the performance of the emission trading market. The results showed that cost savings associated with the Jiangsu SO2 emission trading market in the absence of any policy interactions were CNY 549 million or 12.5% of total pollution control costs. However, policy interactions generally had significant impacts on the emission trading system; the lone exception was current pollution levy system. When the model accounted for all four kinds of policy interactions, the total pollution control cost savings from the emission trading market fell to CNY 39.7 million or 1.36% of total pollution control costs. The impact of policy interactions would reduce 92.8% of cost savings brought by emission trading program.

Hydroxylated and methoxylated polybrominated diphenyl ethers in mollusks from Chinese coastal areas

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs), methoxylated PBDEs (MeO-PBDEs) and PBDEs were determined in three mollusk species collected from three Chinese coastal regions in 2007, 2009, 2010 and 2011. The dominant MeO- and OH-PBDEs isomers detected in mollusks were 6-MeO-BDE-47, 2'-MeO-BDE-68, 6-OH-BDE-47 and 2'-OH-BDE-68. Concentrations of ΣMeO-PBDEs ranged from 9.20 to 2090pgg(-1) dry weight (mean: 450pgg(-1) dry weight). Concentrations of ΣOH-PBDEs ranged from 118 to 2540pgg(-1) dry weight (mean: 534pgg(-1) dry weight). Species differences in accumulation were found for the three mollusk species. Spatial distribution showed that OH- and MeO-PBDEs levels were higher in Weihai than in Tianjin. The temporal trends of OH- and MeO-PBDEs in mollusks were studied during period of 2007 to 2011, rising of ΣOH-PBDEs in Rap from Penglai and Ost from Weihai and declining of ΣMeO-PBDEs in Ost in Penglai were observed. Significant correlations were found between OH- and MeO-PBDEs, but neither between PBDEs and OH-PBDEs, nor between PBDEs and MeO-PBDEs, suggesting that OH- and MeO-PBDEs may have a common source or similar accumulation behavior in mollusks. OH- and MeO-PBDEs were likely not to originate from PBDE precursors.

Accumulation of polybrominated diphenyl ethers (PBDEs) in mudsnails (Cipangopaludina cahayensis) did not increase with age

In this study, we examined concentrations of polybrominated diphenyl ethers (PBDEs) in mudsnails (Cipangopaludina cahayensis) and sediment samples from an electronic waste recycling area to investigate the correlation between PBDE accumulation and age. The results showed that PBDE accumulation did not increase with age, suggesting a dynamic balance between the uptake, depuration and biotransformation of PBDEs relative to growth dilution in mudsnails. We infer that this phenomenon is associated with low absorption efficiencies, rapid depuration rates and high biotransformation rates of PBDEs. BDE-209 contributed only up to about 5 %, whereas BDE-209 was the dominant congener and contributed up to 90 % of the total PBDEs in surface sediments. The difference in PBDE congener pattern between mudsnails and sediments showed a low bioaccumulation potential for these compounds in mudsnails.

Persistent toxic burdens of halogenated phenolic compounds in humans and wildlife

Halogenated phenolic compounds (HPCs) including hydroxylated polychlorobiphenyls (OH-PCBs) and hydroxylated polybromodiphenyl-ethers (OH-PBDEs) can be persistent organic pollutant (POP) metabolites or natural marine compounds. Structurally similar to thyroid hormones (THs), they are retained in blood, transported through selective barriers, and the cause of endocrine and neuronal POP effects. This study presents a meta-analysis of HPC burdens in human and wildlife tissues, including OH-PCBs, OH-PBDEs, Pentachlorophenol, and polybromophenols. HPC blood plasma levels were also compared to known in vitro and in vivo toxicological effect concentrations. Blood, highly perfused, and fetal tissues contained the highest levels of HPCs. Plasma concentrations of analyzed OH-PCBs/PBDEs ranged from 0.1 to 100 nM in humans and up to 240, 454, 800, and 7650 nM for birds, fish, cetaceans, and other mammals, respectively. These concentrations fully fall within the in vitro effect concentrations reported in literature for HPCs of 0.05-10000 nM. We strongly advise further study of HPC blood levels in the general population, children, and fetal tissue to establish background levels and the risk at sensitive development stages. As not all HPCs are, or can be, chemically analyzed, the application of additional bioanalysis might reveal an even greater toxicological relevance of HPCs. In addition, metabolic activation should always be included within in vitro hazard assessment of POPs.

Distribution is a major factor affecting bioaccumulation of decabrominated diphenyl ether: Chinese sturgeon (Acipenser sinensis) as an example

While decabromodiphenyl ether (BDE-209) has very low bioavailability and a rapid biotransformation rate, it exhibits high bioaccumulation in wildlife. To explore the bioaccumulation mechanism of BDE-209 in organisms, its toxicokinetic processes were investigated in Chinese sturgeons from the Yangtze River. Different from less brominated BDEs, lipids did not play an important role in the distribution of BDE-209 with relatively high concentrations detected in liver (54.5 ± 3.3 ng/g wet weight (ww)), gills (47.4 ± 2.9 ng/g ww), and intestine (41.9 ± 3.0 ng/g ww), followed by stomach (21.9 ± 9.0 ng/g ww), muscle (19.1 ± 5.6 ng/g ww), heart (7.5 ± 5.2 ng/g ww), gonad (6.8 ± 4.9 ng/g ww), adipose (4.9 ± 1.2 ng/g ww), and egg (2.8 ± 2.3 ng/g ww). In vitro metabolism of BDE-209 by microsomal fractions of Chinese sturgeon found that BDE-209 was biotransformed rapidly with the rate constant (K) of 0.039 h(-1) in liver. BDE-126, BDE-154, BDE-188, BDE-184, BDE-183, BDE-202, BDE-201, and BDE-204/197 were observed as debrominated products of BDE-209 after incubation, and their formation rates were 0.026, 0.016, and 0.006 h(-1) for BDE-126 BDE-184, and BDE-154, respectively. The concentration ratios between heart and intestine for individual PBDEs suggested slow delivery of BDE-209 among tissues after absorption. A Bayesian hierarchical model was further developed to estimate partition coefficients in a physiologically based pharmacokinetic model of BDE-209 in Chinese sturgeon. The estimated partition coefficients between tissues and blood were higher than those of less brominated BDE or PCBs in various animals, suggesting that the low partition ratios from blood to tissues would lead to high bioaccumulation of BDE-209, especially in absorbing organs.

Species-specific differences in the accumulation features of organohalogen contaminants and their metabolites in the blood of Japanese terrestrial mammals

Residue levels and patterns of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), their hydroxylated metabolites (OH-PCBs, OH-PBDEs), and methoxylated PBDEs (MeO-PBDEs) in the blood of various terrestrial mammals in Japan, including cats, raccoon dogs, dogs, masked palm civets, foxes, raccoons, badgers, and mongooses were determined. Tri- through penta-chlorinated OH-PCBs were predominant in cat blood, whereas hexa- through octa-chlorinated OH-PCBs were found in other species. High proportion of BDE209 was found in all species, suggesting exposure to municipal waste and soil containing higher levels of deca-BDE products. 6OH-/MeO-BDE47 and 2'OH-/MeO-BDE68 were dominant in all terrestrial mammals. This is first report on the detection of OH-/MeO-PBDEs in the blood of terrestrial mammals. High concentrations of OH-/MeO-PBDEs were found in cats, suggesting the intake of these compounds from seafood. Cats exhibited higher accumulation and specific patterns of OH-PCBs, OH-PBDEs, and MeO-PBDEs, they may be at a high risk from these metabolites.

Effects of acute exposure to polybrominated diphenyl ethers on retinoid signaling in zebrafish larvae

The objectives of the present study were to investigate the effects of acute exposure to PBDEs on retinoid signaling in fish. Zebrafish embryos (2h post-fertilization, hpf) were exposed to DE-71 (0, 31.0, 68.7, and 227.6μg/L) until 120hpf. Retinoid profiles showed the content of retinal and retinoic acid was reduced significantly. While a significant up-regulation was observed in the transcription of retinal dehydrogenase (raldh2), the transcription of retinol binding protein (rbp1a), retinol dehydrogenase (rdh1), cellular retinoic acid binding protein (crabp1a and crabp2a) and retinoic acid receptor subunit (raraa) were down-regulated significantly, indicating disruption of retinoid signaling. However, the transcriptions of five opsin genes (zfrho, zfuv, zfred, zfblue, and zfgr1) were up-regulated. Furthermore, whole mount immunostaining and western blotting demonstrated increased rhodopsin protein expression in the exposure groups. Overall, the results indicated that acute exposure to PBDEs could disturb retinoid signaling and may impact on eye development of zebrafish larvae.

Relationship between BDE 209 metabolites and thyroid hormone levels in rainbow trout (Oncorhynchus mykiss)

Decabromodiphenyl ether (BDE 209), the primary component in a commonly used flame retardants, has recently been shown to be metabolized by organisms. In the present study, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to BDE 209 at five nominal gradient concentrations from 50 to 1000 ng/g wet weight for 21 days via a single intraperitoneal injection. Then the liver, kidney and blood samples were collected to analyze for its debrominated, hydroxylated and methoxylated metabolites. The relationships between levels of BDE 209 metabolites in different tissues and thyroid hormone (TH) levels in plasma were evaluated. The results showed that BDE 209 could be metabolized into debrominated BDEs, methoxylated BDEs (MeO-BDEs) and hydroxylated BDEs (OH-BDEs). Levels of these three metabolites were tissue-dependent. The TH levels, including total thyroxine (TT(4)), free thyroxine (FT(4)), total triiodothyronine (TT(3)) and free triiodothyronine (FT(3)) in plasma, were significantly affected by BDE 209 metabolism. However, only FT(4) levels showed a negative correlation with MeO-BDE and OH-BDE metabolites, among which the correlation between FT(4) and OH-BDEs was the most significant.

Hydroxylated and methoxylated polybrominated diphenyl ethers in blood plasma of humans in Hong Kong

Hydroxylated (OH-) and methoxylated (MeO-) polybrominated diphenyl ethers (PBDE) are suspected endocrine disruptors. Little is known about the accumulation or sources of these chemicals in tissues of humans, particularly those residing in Hong Kong, which is one of the most densely populated cities in the world. Seven MeO-BDEs, fifteen OH-BDEs and three bromophenols (BRPs) were analyzed in blood plasma of 116 humans that had been collected by the Hong Kong Red Cross. Total concentrations of MeO-BDEs, OH-BDEs and BRPs ranged from 3.8×10² to 52×10³ pg g⁻¹ lipid (median 4.5×10³ pg g⁻¹), 5.3 to 4.9×10² pg g⁻¹ lipid (81 pg g⁻¹) and ND to 1.1×10² pg g⁻¹ lipid (3.7 pg g⁻¹), respectively. 3-MeO-BDE-47, 6-OH-BDE-47 and 2, 4, 5-TBP were the predominant MeO-BDEs, OH-BDEs and BRPs, respectively. These results are consistent with accumulation of MeO-BDEs, OH-BDEs and BRPs in human plasma being primarily from natural products and inter-conversion of natural products. Coefficients of determination for some pairs of congeners such as 3-OH-BDE-100 and 6-OH-BDE-47, 6-OH-BDE-85 and 5'-OH-BDE-99, and 2, 4-DBP and 6-OH-BDE-85, were near 1.0, which is consistent with them having common sources. Patterns of relative concentrations of the target analytes were similar in the diet, particularly fish, as in blood plasma of humans, which suggests that the diet and particularly seafood might be a source of these compounds and PBDEs. Furthermore, biotransformation of natural chemicals such as OH-BDEs to BRPs might be the primary route of their elimination from humans.

Tissue distribution, maternal transfer, and age-related accumulation of dechloranes in Chinese sturgeon

While dechloranes have been detected in environmental media and wildlife, limited information was available on their tissue distribution in wildlife. Syn-dechlorane plus (syn-DP), anti-DP, syn-undecachloropentacyclooctadecadiene (syn-Cl(11)DP), anti-Cl(11)DP, dechlorane 602, dechlorane 603 and mirex were measured in 13 organs of 17 female Chinese sturgeon (Acipenser sinensis). Dechloranes were detected in all tissues and the highest concentrations of total dechloranes were detected in heart (87 pg/g ww, 4.5-645 pg/g ww), followed by adipose (61 pg/g ww, 14-531 pg/g ww) and eggs (57 pg/g ww, 13-261 pg/g ww). The tissue distribution of DP was mainly determined by lipid partition, while Dec 602 and Dec 603 preferred to accumulate in the intestine and stomach. The values of f(anti) (the concentration of anti-DP relative to the sum concentration of DP) in maternal tissues (0.72 ± 0.03 in muscle) were significantly higher than those found in eggs (0.65 ± 0.04) (p < 0.001), while f(anti-Cl11DP) (the concentration of anti-Cl(11)DP relative to the sum concentration of Cl(11)DP) in maternal tissues (0.59 ± 0.10 in muscle) was significantly lower than that in eggs (0.75 ± 0.13) (p < 0.05). High maternal transfer efficiencies of dechloranes were observed in eggs, which accounted for 49% of the total body burden, and the ratios of concentrations in eggs to maternal tissues (EMR) for mirex, Dec 602, Dec 603, syn-Cl(11)DP, anti-Cl(11)DP, syn-DP, and anti-DP were 18, 8.8, 5.2, 2.6, 5.2, 5.5 and 3.7, respectively, which are dependent on their K(OW) values (r = -0.66, p < 0.01). Negative age-related trends were observed for mirex, Dec 603, syn-Cl(11)DP and anti-Cl(11)DP in eggs (R(2) = 0.28-0.38, p = 0.02-0.05), which were possibly due to their high transfer efficiencies to eggs from maternal body (49%).

Multi-species comparison of the mechanism of biotransformation of MeO-BDEs to OH-BDEs in fish

Polybrominated diphenyl ethers (PBDEs) and their methoxylated- (MeO-) and hydroxylated- (OH-) analogs are ubiquitously distributed in the environment worldwide. The OH-BDEs have greater potency than PBDEs and can be produced from the transformation of MeO-BDEs. The objectives of the current study were to (1) identify the enzyme(s) that catalyze biotransformation of 6-MeO-BDE-47 to 6-OH-BDE-47 in livers from rainbow trout, and (2) compare biotransformation of 6-MeO-BDE-47 to 6-OH-BDE-47 among rainbow trout, white sturgeon and goldfish. Cytochrome P450 1A (CYP1A) enzymes did not catalyze the biotransformation reaction. However, biotransformation was significantly inhibited by the CYP inhibitors clotrimazole and 1-benzylimidazole but not gestodene. Therefore, the reaction is likely catalyzed by CYP2 enzymes. When biotransformation was compared among species, concentrations of 6-OH-BDE-47 were significantly 3.4- and 9.1-fold greater in microsomes from rainbow trout compared to goldfish or white sturgeon, respectively. Concentrations of 6-OH-BDE-47 in microsomes from goldfish were non-significantly 2.7-fold greater than in sturgeon. The initial rate of biotransformation in microsomes from livers of rainbow trout was significantly 2.0- and 6.2-fold greater than the initial rate of biotransformation in microsomes from livers of goldfish or sturgeon, respectively, while the initial rate in goldfish was significantly 3.1-fold greater than in sturgeon. It is hypothesized that differences in CYP-mediated biotransformation of MeO-BDEs to OH-BDEs could influence concentrations of OH-BDEs in different species of fish.

Desorption behaviors of BDE-28 and BDE-47 from natural soils with different organic carbon contents

Desorption kinetic and isothermal characteristics of BDE-28 and BDE-47 were investigated using natural soils with different organic carbon fractions. The results indicated that a two-compartment first-order model with dominant contribution of slow desorption could adequately describe the released kinetics of studied PBDEs. Desorption isotherms of different samples could be fitted well by linear distribution model or nonlinear Freundlich model. Moreover, most desorption procedures roughly exhibited hysteresis with respect to preceding sorption ones. At the statistically significant level of 0.05 or 0.1, total organic carbon content (f(OC)) exhibited significant correlations with the fitted parameters by the isothermal models. The correlations of f(OC) and SOM fractions (e.g., fulvic acid and humin) with the single point desorption coefficients at lower aqueous concentrations of studied PBDEs were significant; while at higher aqueous concentrations, the relationships were less significant or insignificant. Our findings may facilitate a comprehensive understanding on behaviors of PBDEs in soil systems.

Acute toxicity of polybrominated diphenyl ethers (PBDEs) for turbot (Psetta maxima) early life stages (ELS)

BACKGROUND, AIM AND SCOPE

The environmental presence of polybrominated diphenyl ethers (PBDEs), among which BDE-47 and BDE-99 are particularly abundant, makes toxicity data necessary to assess the hazard risk posed by PBDE to aquatic organisms. This study examines the effects of BDE-47 and BDE-99 on embryo-larval stages of the marine flatfish turbot.

MATERIALS AND METHODS

The turbot embryos were exposed at nominal concentrations of BDE-47 and BDE-99 for 6 days. Selected dose levels were relevant for investigating sublethal and lethal effects.

RESULTS

Both tested compounds caused lethal toxicity as well as non-lethal malformations during embryo development. We found a high toxic potency of BDE-47 compared to BDE-99 (LC₅₀ values for embryos and larvae, respectively, BDE-47: 27.35 and 14.13 μg L⁻¹; BDE-99: 38.28 and 29.64 μg L⁻¹).

DISCUSSION

The present study shows high sensitivity of fish early life stages (ELS) to PBDE compounds. Based on environmental concentrations of dissolved PBDEs from various aquatic ecosystems, waterborne BDE-47 and BDE-99 pose little risk of acute toxicity to marine fish at relevant environmental concentrations.

CONCLUSIONS

Turbot fish ELS proved to be an excellent model for the study of ecotoxicity of contaminants in seawater. The results demonstrate harmful effects of PBDE on turbot ELS at concentrations in the range of parts per billion units.

RECOMMENDATIONS AND PERSPECTIVES

In the perspective of risk assessment, ELS endpoints provide rapid, cost-effective and ecologically relevant information, and links should be sought between these short-term tests and effects of long-term exposures in more realistic scenarios.

Occurrences and fates of hydroxylated polybrominated diphenyl ethers in marine sediments in relation to trophodynamics

While occurrences and origins of hydroxylated (OH-) polybrominated diphenyl ethers (PBDEs) in organisms have been reported, the fates of these compounds in abiotic matrixes and related trophodynamics are unclear. The present study measured concentrations of nine OH-PBDEs, twelve methoxylated (MeO-) PBDEs, and eleven PBDEs in marine sediments and explored the trophodynamics of OH-PBDEs in five invertebrates, eight fish, and two species of birds from Liaodong Bay, north China. While concentrations of PBDEs were less than the limit of quantification in sediments, concentrations of ΣOH-PBDEs and ΣMeO-PBDEs were 3.2-116 pg/g dry weight (dw) and 3.8-56 pg/g dw, respectively. When the detected compounds were incubated in native marine sediments the interconversion between 6-OH-BDE47 and 6-MeO-BDE47 was observed. This result is consistent with the similar spatial distributions and significant correlation between the concentrations of these naturally occurring compounds. 6-OH-BDE47 and 2'-OH-BDE68 were detected as the two major congeners in organisms collected from Liaodong Bay, and concentrations were 0.24 ± 0.005 ng/g lw (lipid weight) and 0.088 ± 0.006 ng/g lw, respectively. Biota-sediment accumulation factors (BSAFs) for invertebrates of 6-OH-BDE47 and 2'-OH-BDE68 were 0.017-0.96 and 0.19-1.5 (except for short-necked clam: 6.3), respectively. Lipid-normalized concentrations of 6-OH-BDE47 and 2'-OH-BDE68 decreased significantly with trophic level with TMFs of 0.21 and 0.15, respectively. The fates of OH-PBDEs in sediment together with their trophodynamics in marine food webs suggested that OH-PBDEs are partitioned into sediment and undergo biodilution in the marine food web.

Anthropogenic and naturally occurring polybrominated phenolic compounds in the blood of cetaceans stranded along Japanese coastal waters

We determined the residue levels and patterns of hydroxylated polybrominated diphenyl ethers (OH-PBDEs), and related compounds, such as PBDEs, methoxylated PBDEs (MeO-PBDEs), and bromophenols (BPhs) in the blood of eleven cetacean species stranded along the Japanese coasts. The dominant OH- and MeO-PBDE isomers found in all cetaceans were 6OH-BDE47 and 6MeO-BDE47. Additionally, 2,4,6-triBPh was dominant isomer in all cetaceans. In contrast, specific differences in the distribution of para- and meta- OH-PBDE isomers and some BPhs (potential PBDEs metabolites) were found among the cetaceans. Residue levels of ΣMeO-PBDEs and 6OH-BDE47 + 2'OH-BDE68, and 2,4,6-triBPh and 6OH-BDE47 + 2'OH-BDE68 showed a significant positive correlation. These results may suggest that the large percentages of OH-PBDEs, MeO-PBDEs and 2,4,6-triBPh might share common source (i.e. biosynthesis by marine organisms), or metabolic pathway in cetacean species. Significant correlations were found between the concentrations of BDE99 and 2,4,5-triBPh. This result suggested that 2,4,5-triBPh in cetaceans could be a metabolite of BDE99.