Distribution and fate of HBCD and TBBPA brominated flame retardants in North Sea estuaries and aquatic food webs

Concentrations, Distributions, and Risk Assessment of HBCD in Sediment in the Weihe River Basin in Northwest China

As one of the most widely used brominated flame retardants, hexabromocyclododecane (HBCD) is found widely in the environmental media. In this study, the content and spatial distribution of HBCD and risk posed by HBCD in surface sediment in the Weihe River Basin in Northwest China were investigated. The HBCD concentration ranged nd–4.04 ng/g dw with the mean was 0.45 ng/g dw. The major source of HBCD in surface sediment was local point discharge. The distribution profiles of α-, β-, γ-HBCD were 24.7–87.9%, 0–42.0%, and 0–67.1%, respectively. Specially, α-HBCD was the dominating isomer in most sample sites. This differed significantly from that in HBCD technical product, which might be attributed to the different degradation rates and inter-transformation of the three HBCD isomers. Risk quotient method was used to assess the potential risk posed by HBCD in sediment. HBCD do not pose strong risks to aquatic algae organisms in the Weihe River Basin.

In vitro effects of brominated flame retardants, selected metals and their mixtures on ethoxyresorufin-O-deethylase activity in Mossambica tilapia liver

The in vitro effects of individual brominated flame retardants (BFRs), selected metals, and their binary mixtures on ethoxyresorufin-O-deethylase (EROD) activity were evaluated using a plate-reader method. The BFRs, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), decabromodiphenyl oxide (BDE-209), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), were tested at doses ranging from 0.1 ng/L to 100 µg/L. Selected metals (Cu²⁺, Cd²⁺, Hg²⁺, and Zn²⁺) were screened at doses of 0.1 mg/L to 50 mg/L. The activity of EROD was significantly induced by TBBPA, BDE-209, and Zn²⁺, while HBCD, Cu²⁺, Cd²⁺, and Hg²⁺ decreased EROD activity. Moreover, following exposure to binary mixtures of metals and BFRs, the EROD activity dose-response curves were similar to those of the metals alone, indicating that EROD activity was governed by the metals.

Solvent effects on quantitative analysis of brominated flame retardants with Soxhlet extraction

Reliable quantifications of brominated flame retardants (BFRs) not only ensure compliance with laws and regulations on the use of BFRs in commercial products, but also is key for accurate risk assessments of BFRs. Acetone is a common solvent widely used in the analytical procedure of BFRs, but our recent study found that acetone can react with some BFRs. It is highly likely that such reactions can negatively affect the quantifications of BFRs in environmental samples. In this study, the effects of acetone on the extraction yields of three representative BFRs [i.e., decabrominated diphenyl ether (decaBDE), hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA)] were evaluated in the Soxhlet extraction (SE) system. The results showed that acetone-based SE procedure had no measureable effect for the recovery efficiencies of decaBDE but could substantially lower the extraction yields for both TBBPA and HBCD. After 24 h of extraction, the recovery efficiencies of TBBPA and HBCD by SE were 93 and 78% with acetone, 47 and 70% with 3:1 acetone:n-hexane, and 82 and 94% with 1:1 acetone:n-hexane, respectively. After 72 h of extraction, the extraction efficiencies of TBBPA and HBCD decreased to 68 and 55% with acetone, 0 and 5% with 3:1 acetone/n-hexane mixtures, and 0 and 13% with 1:1 acetone/n-hexane mixtures, respectively. The study suggested that the use of acetone alone or acetone-based mixtures should be restricted in the quantitative analysis of HBCD and TBBPA. We further evaluated nine alternative solvents for the extraction of the three BFRs. The result showed that diethyl ether might be reactive with HBCD and may not be considered as the alternative to acetone used solvents for the extraction of HBCD.

Chronic toxicity of hexabromocyclododecane(HBCD) induced by oxidative stress and cell apoptosis on nematode Caenorhabditis elegans

In order to gain insights into the chronic effects and mechanisms of hexabromocyclododecane (HBCD), the animal model Caenorhabditis elegans (C. elegans) was chosen for toxicity study. Multiple endpoints, including the physiological (growth and locomotion behaviors), biochemical (reactive oxygen species (ROS) production, lipofuscin accumulation, and cell apoptosis), and molecular (stress-related gene expressions) levels, were tested by chronic exposure for 10 d to low concentrations of HBCD (0.2 nM-200 nM). The results revealed that chronic exposure to HBCD at concentrations more than 20 nM would significantly influence the growth, locomotion behaviors, ROS formation, lipofuscin accumulation, and cell apoptosis of nematodes. Treatment with antioxidants of ascorbate and N-acetyl-l-cysteine (NAC) suppressed the toxicity induced by HBCD. The integrated gene expression profiles showed that the chronic exposure to 200 nM of HBCD significantly increased the expression levels of stress-related genes (e.g., hsp-16.2, hsp-16.48, sod-1, sod-3, and cep-1 genes). Among these genes, the sod-1, sod-3, and cep-1 gene expressions were significantly correlated with HBCD-induced physiological effects by the Pearson correlation test. The mutations of sod-3 and cep-1 induced more severe toxicity compared to wild-type nematodes. Therefore, HBCD exposure induced oxidative stress by ROS accumulation and cell apoptosis, which resulted in HBCD-induced toxicity on nematodes, and sod-3 and cep-1 played important roles in protecting nematodes against HBCD-induced toxicity.

Extracellular degradation of tetrabromobisphenol A via biogenic reactive oxygen species by a marine Pseudoalteromonas sp

Tetrabromobisphenol A (TBBPA) has attracted considerable attention due to its ubiquitous presence in different environmental compartments worldwide. However, information on its aerobic biodegradability in coastal environments remains unknown. Here, the aerobic biodegradation of TBBPA using a Pseudoalteromonas species commonly found in the marine environment was investigated. We found that extracellular biogenic siderophore, superoxide anion radical (O₂^•-), hydrogen peroxide (H₂O₂), and hydroxyl radical (^•OH) were involved in TBBPA degradation. Upregulation of genes (nqrA and lodA) encoding Na⁺-translocating NADH-quinone oxidoreductase and l-lysine-ε-oxidase supported the extracellular O₂^•- and H₂O₂ production. The underlying mechanism of TBBPA biodegradation presumably involves both O₂^•- reduction and ^•OH-based advanced oxidation process (AOP). Furthermore, TBBPA intermediates of tribromobisphenol A, 4-isopropylene-2,6-dibromophenol, 4-(2-hydroxyisopropyl)-2,6-dibromophenol, 2,4,6-tribromophenol (TBP), 4-hydroxybenzoic acid, and 2-bromobenzoic acid were detected in the culture medium. Debromination and β-scission pathways of TBBPA biodegradation were proposed. Additionally, membrane integrity assays revealed that the increase of intracellular catalase (CAT) activity and the extracellular polymeric substances (EPS) might account for the alleviation of oxidative damage. These findings could deepen understanding of the biodegradation mechanism of TBBPA and other related organic pollutants in coastal and artificial bioremediation systems.

Halogenated flame retardants in stranded sperm whales (Physeter macrocephalus) from the Mediterranean Sea

In recent years, decline of marine mammals' populations and increased frequency of strandings have arised the interest on the role that pollution may have in these events. The present work aimed at quantifying levels of brominated flame retardants (BFRs) and dechloranes (DECs) in tissues of 3 adult females and one foetus of sperm whales stranded in the Southern Adriatic Sea coasts (Italy). Results proved the presence of different flame retardants (FRs) in tissues of sperm whales, including various polybrominated diphenyl ethers (PBDE) congeners (47, 99, 100, 154, entering the composition of PentaBDE mixture), hexabromocyclodecanes (HBCDs), Dec 602 and methoxylated polibrominated diphenyl ethers (MeO-BDEs). In blubber, a target tissue for contaminant accumulation, ΣPBDEs reached values of 160, 158 and 183 ng/g lw, α-HBCD of 5.75 ng/g lw, Dec 602 of 1632 ng/g lw and MeO-BDEs of 563 ng/g lw. The availability of foetal tissues allowed evaluating the potential maternal transfer on many of these compounds, and to discuss the potential adverse effects on foetal health. To the best of our knowledge, obtained data are the first reporting placental transfer of FRs in sperm whales. PBDE levels detected in foetus suggested a potentially long-term exposure to BFRs, which could cause severe damages to the developing organism, likely at the cerebral, endocrine and immunologic levels. Dec 602, which was detected at the highest concentrations among all FRs considered, could potentially cause dysfunctional effects on the immune system of adult females.

The occurrence and distribution of hexabromocyclododecanes in freshwater systems, focusing on tissue-specific bioaccumulation in crucian carp

The occurrence and distribution of hexabromocyclododecanes (HBCDs) were investigated in freshwater, sediment, and selected crucian carp (Carassius carassius) tissues (muscle, liver, egg, and blood) to evaluate the potential for HBCDs bioaccumulation. The HBCDs concentration ranged from not detected to 0.35ng/L in freshwater, and from 0.037 to 35.4ng/g-dw in sediment. The highest HBCDs concentration was detected in crucian carp liver (5.14±8.15ng/g-ww), followed by egg (3.88±10.1ng/g-ww), blood (0.61±0.63ng/mL), and muscle (0.38±0.70ng/g-ww). In all crucian carp tissues, α-HBCD was the predominant stereoisomer, and the fraction of α-HBCD as a proportion of the total HBCDs in liver tissue (96%) was higher than that in egg tissue (79%). There was a positive correlation between the HBCDs concentration in crucian carp muscle and body size (p<0.01, Spearman). The biota-sediment accumulation factor (BSAF) (0.14) and bioconcentration factor (BCF) (137,000L/kg) values were estimated in crucian carp muscle using field-based data.

Potential risk of coupling products between tetrahalobisphenol A and humic acid prepared via oxidation with a biomimetic catalyst

Tetrahalobisphenol A (TXPBAs, X = Br or Cl), TBBPA and TCBPA, which are widely used as flame retardants, ultimately disposed of in landfills. In landfills, enzymatically oxidized TXBPAs can be covalently incorporated into humic acids (HAs) to form coupling products (HA-TXBPAs). In the present study, HA-TXBPAs were prepared by catalytic oxidation with iron(III)-phthalocyanine-tetrasulfate as a model of oxidative enzymes. The stability of HA-TXBPAs was evaluated by incubating them under physicochemical conditions of landfills (pH 9 and 50 °C). For HA-TBBPA, 18-26% of TBBPA was released from HA-TBBPA, due to the acid dissociation of the loosely bound TBBPA. However, no additional release was observed, even after 30 days, indicating that 74-82% of the TBBPA was incorporated into the HA. For HA-TCBPA, 3-4% of TCBPA and a major byproduct, 4-(2-hydroxyisopropyl)-2,6-dichlorophenol, was found to be loosely incorporated into HA. For both TBBPA and TCBPA, covalently bound organo-halogens were not released during the 30 days of incubation. Inhibition of the growth of Chlamydomonas reinhardtii was indicated when trace levels of TXBPAs (approximately 0.1 μM) were present. These results suggest that HA-TXBPAs contain not only covalently incorporated TXBPAs but also loosely bound TXBPAs and halophenols. The latter in HA-TXBPAs have the potential to leach from landfills and affect aquatic ecosystems.

Debromination of Hexabromocyclododecane by Anaerobic Consortium and Characterization of Functional Bacteria

A microbial consortium which can efficiently remove hexabromocyclododecane (HBCD) under anaerobic condition have been successfully enriched over 300 days. Under the optimal conditions, the degradation efficiency was 92.4% removal after treatment of 12 days with original addition of 500 μg/L HBCD, yielding 321.7 μg/L bromide in total as well. A typical debromination product, dibromocyclododecadiene (DBCD), was detected during the degradation process. The debromination profiles of three main HBCD diastereomers fitted well with first-order model (R²: 0.96–0.99), with the rate constants ranging from 1.3 × 10^-1 to 1.9 × 10^-1. The microbial community analysis by high throughput sequencing showed that the composition of the microbial communities varied dynamically with time and the population of functional bacteria increase sharply after enrichment. The population of Bacteroidetes increased from 5 to 47%. And some bacteria which are relatively minority in population at the beginning, such as Azospira oryzae (OTU2), Microbacterium (OTU13), and Achromobacter insolitus (OTU39) increased more than 22 times after enrichment (from 0.5 to 13%, 12%, and 11%, respectively). However, no reported dehalogenating bacteria were found after enrichment. And the contribution for debromination may come from new dehalogenating bacteria. All in all, the present study provided in-depth information on anaerobic microbial communities for HBCD removal by debromination.

Complete genome sequence of Bacillus sp. HBCD-sjtu, an efficient HBCD-degrading bacterium

Environmental pollution caused by the release of industrial chemicals is currently one of the most important environmental harms. Manufacturing chemicals can be biodegraded, and valuable intermediates can be used as pharmacophores in drug targeting and have several other useful purposes. Hexabromocyclododecane (HBCD), a non-aromatic brominated flame retardant, is a toxic compound that consists of a cycloaliphatic ring of 12 carbon atoms to which six bromine atoms are attached. It is formed by bromination of cis-trans-trans-1,5,9-cyclododecatriene, but its use is now restricted in several countries, because it is an environmental pollutant. Little is known about whether bacteria can degrade HBCD. A bacterial strain that degrades HBCD was recently isolated using enrichment culture techniques. Based on morphological, biochemical and phylogenetic analysis this isolate was categorized as Bacillus cereus and named strain HBCD-sjtu. Maximum growth and HBCD-degrading activity were observed when this strain was grown at 30 °C, pH 7.0 and 200 RPM in mineral salt medium containing 0.5 mm HBCD. The genome of strain HBCD-sjtu, which consists of only one circular chromosome, was sequenced. This whole genome sequence will be crucial for illuminating the molecular mechanisms of HBCD degradation.

Complex toxicity as disruption of adipocyte or osteoblast differentiation in human mesenchymal stem cells under the mixed condition of TBBPA and TCDD

People are frequently and unintentionally exposed to many chemical compounds, such as environmental pollutants and endocrine-disrupting chemicals (EDCs), in food and from the atmosphere. In particular, endocrine-disrupting TBBPA and dioxins are found in human breast milk and in the body. Conventional studies evaluate toxicity by administering a single substance to cells or animals, but evaluation of the toxicity of mixtures of these ingested compounds is essential for “true” toxicological assessment. We evaluated toxic effects in vitro using human mesenchymal stem cells (hMSCs). TBBPA increased the number of lipid droplets, and upregulated the expression of adipocyte-related mRNA, aP2 and LPL, through a PPARγ-dependent mechanism. TCDD suppressed lipid droplets and adipocyte-related mRNA levels. Adipocyte differentiation was stimulated by TBBPA and inhibited by TCDD in a dose-dependent manner. TBBPA did not influence osteoblast differentiation, but TCDD suppressed ALP staining and activity, calcium deposition, and osteoblast-related mRNA levels. In a mixture of TBBPA and TCDD, TBBPA inhibited TCDD suppression of adipocyte and osteoblast differentiation in a dose-dependent manner. Interestingly, we observed lipid droplets in TBBPA-treated cells differentiated into osteoblasts. These results suggest that TBBPA and TCDD disrupted differentiation into adipocytes and osteoblasts and contributes to a more complete toxicological understanding of exposure to these chemical substances.

Thyroid Disruption by Bisphenol S Analogues via Thyroid Hormone Receptor β: in Vitro, in Vivo, and Molecular Dynamics Simulation Study

Bisphenol S (4-hydroxyphenyl sulfone, BPS) is increasingly used as a bisphenol A (BPA) alternative. The global usage of BPS and its analogues (BPSs) resulted in the frequent detection of their residues in multiple environmental media. We investigated their potential endocrine-disrupting effects toward thyroid hormone receptor (TR) β. The molecular interaction of BPSs toward TRβ ligand binding domain (LBD) was probed by fluorescence spectroscopy and molecular dynamics (MD) simulations. BPSs caused the static fluorescence quenching of TRβ LBD. The 100 ns MD simulations revealed that the binding of BPSs caused significant changes in the distance between residue His435 at helix 11(H11) and residue Phe459 at H12 in comparison to no ligand-bound TRβ LBD, indicating relative repositioning of H12. The recombinant two-hybrid yeast assay showed that tetrabromobisphenol S (TBBPS) and tetrabromobisphenol A (TBBPA) have potent antagonistic activity toward TRβ, with an IC₁₀ of 10.1 and 21.1 nM, respectively. BPS and BPA have the antagonistic activity with IC₁₀ of 312 and 884 nM, respectively. BPSs significantly altered the expression level of mRNA of TRβ gene in zebrafish embryos. BPS and TBBPS at environmentally relevant concentrations have antagonistic activity toward TRβ, implying that BPSs are not safe BPA alternatives in many BPA-free products. Future health risk assessments for TR disruption and other adverse effects should focus more on the structure-activity relationship in the design of environmentally benign BPA alternatives.

Multiclass screening of >200 pharmaceutical and other residues in aquatic foods by ultrahigh-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry

A quick screening method of more than 200 pharmaceutical and other residues in aquatic foods based on ultrahigh-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry (UHPLC-Q/Orbitrap MS) was established. In this method, after the addition of 200 μL of 1 M EDTA-Na₂, 2 g of each sample homogenate was extracted successively with 10 mL of acetonitrile and 10 mL of ethyl acetate. The extracts were combined, dried under nitrogen flow, and redissolved in 0.1% formic acid in acetonitrile/water (4:6, v/v) for analysis. The prepared samples were analyzed by UHPLC- Q/Orbitrap MS system in Full MS/ddMS² (full-scan data-dependent MS/MS) mode. Compound identification was performed through comparison of the sample data with the database for standard chemicals, including the retention time, precursor ion, product ions, and isotope pattern for all 206 compounds. Five different aquatic food matrices (carp, shrimp, crab, eel, and mussel) spiked with the analytes at 1, 10, and 50 ng/g were evaluated to assess recoveries, precision, matrix effects, stability, and detection limits using the method. UHPLC analyses required 25 min, and 178-200 analytes met identification criteria at 50 ng/g depending on the matrix. Furthermore, practical application of this method for real samples displayed strong screening capability. Graphical abstract A quick screening method of >200 pharmaceutical and other residues in aquatic foods based on ultrahighperformance liquid chromatography-quadrupole-Orbitrap mass spectrometer was established. Fivedifferent aquatic food matrices, including carp, shrimp, crab, eel and mussel, were studied to evaluatescreen limit at 1, 10 and 50 μg·kg-1 level. Results suggest the high reliability, high time-efficiency and goodsimplicity of the method.

An overview of hexabromocyclododecane (HBCDs) in environmental media with focus on their potential risk and management in China

Hexabromocyclododecanes (HBCDs) are the subject of recent interest and potential risk assessment particularly in China due to its ubiquitous existence in a variety of environmental media. This paper reviews the recent studies conducted on HBCDs in different environmental media (air, soil, water, river sediment, sewage sludge, biota and daily food) in China. At the same time, human health risks via food and occupational exposure of HBCDs in production plants, expanded polystyrene (EPS) and extruded polystyrene (XPS) plants were assessed. The review reveals that HBCDs levels of air, soil, sediment, sewage sludge, biota and food presented a geographical variation in the eastern coastal regions of China. There were many factors resulting in the variation, such as sampling sites, climate and analytical method. In terms of diastereoisomer, α-HBCD and γ-HBCD were the predominant diastereoisomers in air, soil, sediment, and sewage sludge. In the water, α-HBCD and γ-HBCD shared the major proportion to the total HBCDs. However, only α-HBCD was the predominant diastereoisomer in biota. With regard to human exposure pathway to HBCDs, food was the major route for human exposure to HBCDs, especially meat. In addition, soil and road dust were also important exposure pathways. Furthermore, workers and residents, especially infants in and around waste dumping sites and industrial areas are exposed to the highest HBCDs levels among all the populations studied thus far. HBCDs posed a potential threat to the environment and human health. Therefore, risk assessment and management have an important role to play in preventing and mitigating HBCDs risks.

Sorption and bioaccumulation behavior of multi-class hydrophobic organic contaminants in a tropical marine food web

While numerous studies have demonstrated the environmental behavior of legacy persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), information regarding sorption and bioaccumulation potential of other widely used organic chemicals such as halogenated flame retardants (HFRs) is limited. This study involved a comprehensive field investigation of multi-class hydrophobic organic contaminants (HOCs) in environmental media and fish in Singapore Strait, an important tropical maritime strait in Southeast Asia. In total, 90 HOCs were analyzed, including HFRs, synthetic musks, PCBs, OCPs, as well as triclosan and methyl triclosan. The results show that the organic carbon normalized sediment-seawater distribution ratios (C_SED/C_WD) of the studied compounds are comparable to the organic carbon-water partition coefficients (K_OC), over a log K_OC range of approximately 4-11. The observed species-specific bioaccumulation factors (BAFs), biota-sediment accumulation factors (BSAFs), organism-environment media fugacity ratios (f_FISH/f_WD and f_FISH/f_SED) and trophic magnification factors (TMFs) indicate that legacy POPs and PBDE 47 show bioaccumulation behavior in this tropical marine ecosystem, while triclosan, tonalide, dodecachlorodimethanodibenzocyclooctane stereoisomers (DDC-COs), and hexabromocyclododecanes (HBCDDs) do not. Methyl triclosan and galaxolide exhibit moderate biomagnification. Tetrabromobisphenol A (TBBPA) and 1,2-bis (2,4,6-tribromophenoxy)ethane (BTBPE) were detected in environmental media but not in any of the organisms, suggesting low bioaccumulation potential of these flame retardants. The apparently low bioaccumulation potential of the studied HFRs and synthetic musks is likely because of metabolic transformation and/or reduced bioavailability due to the hydrophobic nature of these compounds.

Halogenated flame retardants (HFRs) in surface sediment from the Pearl River Delta region and Mirs Bay, South China

A total of 43 surface sediment collected from rivers and the estuaries in the Pearl River Delta (PRD) region and Mirs Bay from the South China were analyzed for twelve halogenated flame retardants (HFRs) including polybrominated diphenyl ethers (PBDEs) using liquid chromatography-tandem mass spectrometer system. Their levels, spacial distribution, congener profiles and possible sources were investigated. Decabromodiphenyl ethane (DBDPE) was the predominant contaminant (1.520-1714ng/g dw) in the study area exceeding those of PBDEs (8.090-595.8ng/g dw), implying that DBDPE has been the predominant HFR products in this region in recent years in addition to PBDEs. Whereas the ratio of [DBDPE/BDE 209] varied among samples, this is indicative of different usage patterns of HFRs between PRD region and Mirs Bay. The PBDEs congener was dominated by BDE 209, with the average value accounting for 86.8% of the total PBDE in the sediment samples.

Emerging brominated flame retardants and dechlorane-related compounds in European eels (Anguilla anguilla) from Latvian lakes

Fifteen halogenated flame retardants (HFRs) including seven emerging brominated flame retardants (EBFRs) and eight dechlorane-related compounds (DRCs) were analyzed in eels (Anguilla anguilla) sampled from five Latvian lakes. Out of the seven EBFRs, hexabromocyclododecane (HBCD) and decabromodiphenyl ethane (DBDPE) were found in eels in quantifiable concentrations, up to 6.58 and 33.0 ng g^-1 lipid weight (l.w.), respectively. The mean total concentration of DRCs (∑_DRC) in the samples was 0.62 ng g^-1 l.w. and the geographical distribution of DRC contamination was nearly uniform among the selected lakes. Dechlorane 602 (Dec 602) was the predominant component, whereas the composition of mixture containing syn- and anti-Dechlorane Plus (DP) stereoisomers showed a pronounced enrichment of the anti-DP isomer and was close to the composition of OxyChem^® DP commercial product. The determined concentrations of HFRs were lower than in other studies of aquatic biota from Europe and Asia, and the obtained results reflect the acceptable environmental status of Latvian lakes with regard to the total content of HBCD (∑_HBCD), considering the environmental quality standards (EQS) stated in the Directive 2013/39/EU. The highest ∑_HBCD levels were observed in eels from lakes corresponding to the industrialization of those areas, while the results of principal component analysis (PCA) showed that the concentration of HBCD depended on the particular sampling lake, reflecting non-uniform contamination of the Latvian environment with this EBFR.

Occurrence of selected halogenated flame retardants in Belgian foodstuff

This paper reports on the occurrence of halogenated flame retardants (HFRs), namely PBDEs, HBCDs, TBBPA, brominated phenols (BrPhs), dechlorane plus (DP) and emerging FRs in a variety of Belgian foodstuffs. A total of 183 composite food samples were analyzed by GC-MS and LC-MS/MS techniques for the presence of HFRs. The analyses revealed that 72% of the samples was contaminated with HFRs to some extent. The highest number of contaminated samples was observed within the group 'Potatoes and derived products', 'Fish and fish products' and 'Meat and meat products', while the least contaminated group was 'Food for infants and small children'. The total HFR content ranged from <LOQ to 35.4 ng/g ww with an average content of 1.2 ng/g ww and median of 0.25 ng/g ww. The samples with the highest total HFR levels were canned king crab, fresh mackerel, Emmental cheese, fresh eel and plaice. The most frequently detected HFRs were PBDEs and BrPhs being present in almost all food groups, and among the individual HFRs, the most frequently found compounds were BDE-47 (53%), BDE-209 (46%) and 246-TBP (40%). TBBPA, DPs, TBPH and γ-HBCD occurred with a frequency of less than 5%. TBBPS, 26-DBP, HBB, TBB and BTBPE were not detected in any of the analyzed food samples.

Tetrabromobisphenol A Induces MMP-9 Expression via NADPH Oxidase and the activation of ROS, MAPK, and Akt Pathways in Human Breast Cancer MCF-7 Cells

Tetrabromobisphenol A (TBBPA), the most common industrial brominated flame retardant, acts as a cytotoxic, neurotoxic, and immunotoxicant, causing inflammation and tumors. However, the mechanism of TBBPA-induced matrix metalloproteinase-9 (MMP-9) expression in human breast cancer cells is not clear. In human breast cancer MCF-7 cells, treatment with TBBPA significantly induced the expression and promoter activity of MMP-9. Transient transfection with MMP-9 mutation promoter constructs verified that NF-κB and AP-1 response elements are responsible for the effects of TBBPA. Furthermore, TBBPA-induced MMP-9 expression was mediated by NF-κB and AP-1 transcription activation as a result of the phosphorylation of the Akt and MAPK signaling pathways. Moreover, TBBPA-induced activation of Akt/MAPK pathways and MMP-9 expression were attenuated by a specific NADPH oxidase inhibitor, and the ROS scavenger. These results suggest that TBBPA can induce cancer cell metastasis by releasing MMP-9 via ROS-dependent MAPK, and Akt pathways in MCF-7 cells.

How do measured PBDE and HCBD levels in river fish compare to the European Environmental Quality Standards?

This study evaluates the current situation regarding PBDE and HBCD levels in different river fish species. We collected published data in the last five years in different countries around the world. These levels of pollution were compared with Environmental Quality Standards (EQS) for biota established by the European Directive in the field of water policy. Although HBCD situation is not critical, with only some values exceeding the limit about 5 times, the PBDE levels clearly exceeded the established EQS, with 25% of fish samples exceeding up to ten thousand times. Although it is expected that levels of pollution by PBDEs will decrease over the next years due to the ban in their use, it is not expected that this decrease will reach the EQS values by the end of 2021, as demanded by the European Directive. Hence, it is necessary to implement new strategies in order to minimize the impact of PBDEs on the environment.

Multi-walled carbon nanotubes facilitated the removal of tetrabromobisphenol a mediated by horseradish peroxidase

In this study, we systematically investigated the effect of multiwall carbon nanotubes (MWCNTs) on the removal of tetrabromobisphenol A (TBBPA) mediated by horseradish peroxidase (HRP) at varying important conditions. The results suggested that the presence of MWCNTs significantly enhanced the removal of TBBPA mediated by HRP and the reaction rate constant was linear with the MWCNTs dosage. The enhancement of MWCNTs on the HRP-mediated reaction was attributed to two facts, one is that MWCNTs protected HRP from inactivation, the other is that the presence of MWCNTs made the homogeneous reaction of TBBPA be heterogeneous reaction by adsorbing TBBPA on its surface. Moreover, the influence of MWCNTs on TBBPA products distribution was further elucidated. We found that the species of reaction product had no difference between the HRP-mediated systems with and without the presence of MWCNTs. However, the presence of MWCNTs significantly decreased the yields of each product. These results give insight into the role of MWCNTs in HRP-mediated TBBPA reactions and provide theoretical foundation for potential development of novel enzymatic methods to control TBBPA contamination. MWCNTs enhanced the removal of TBBPA mediated by HRP/H₂O₂, because it protected HRP from inactivation and adsorbed TBBPA on its surface to form a heterogeneous reaction process.

Brominated flame retardants in marine environment focused on aquaculture area: Occurrence, source and bioaccumulation

Brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs), tetrabromobisphenol A (TBBPA), and hexabromocyclododecanes (HBCDs), were investigated in bivalve (i.e., oyster (Crassostrea gigas) and mussel (Mytilus coruscus)), sediment, and seawater samples collected from aquaculture areas in South Korea to identify their occurrence, sources, and bioaccumulation. Among the studied chemicals, HBCDs predominated in bivalves and sediment, with concentrations of ND-67.52ng/g lipid weight and 3.47-168ng/g dry weight, respectively, while TBBPA was the highest contributor in seawater (ND-2.79ng/L). Compared with a non-aquaculture area, HBCD and PBDE concentrations were significantly higher in all matrices in the aquaculture area (Mann-Whitney U test, p<0.05), suggesting that sources may be located near or associated with the aquaculture areas, such as industrial complexes and expanded polystyrene buoys. Finally, the bioconcentration factor (BCF) and biota-sediment accumulation factor (BSAF) were estimated. Among the studied BFRs, BDE-47 (BCF: 1.70×10⁶L/kg; BSAF: 20.92) and α-HBCD (BCF: 1.05×10⁶L/kg; BSAF: 0.13) showed the highest accumulation potentials in bivalves.

Different effects of bisphenol a and its halogenated derivatives on the reproduction and development of Oryzias melastigma under environmentally relevant doses

Bisphenol A (BPA) and its halogenated compounds (H-BPAs) are widely detected in the environmental media and organisms. However, their toxicological effects, especially chronic exposure at low doses, have not been fully compared. In this study, the effects of BPA and H-BPAs on the reproduction and development of Oryzias melastigma were systematically assessed and compared at various developmental stages. BPA and its derivatives tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) elicited the acceleration of embryonic heartbeat. BPA did not show any significant impact on the hatching time and rate of embryos. In contrast, both TBBPA and TCBPA led to the delayed hatching and decreased hatching rate. Accordingly, the expressions of hatching enzyme significantly decreased upon exposure and TCBPA was found to be more toxic than TBBPA. The body weight and gonadsomatic index (GSI) of the treated fish were relatively lower than the control fish upon long-term (four months from larvae to adult) exposure to BPA rather than H-BPAs. Slowed oocyte development occurred in the ovary, and the estrogen level decreased after exposure to BPA rather than H-BPAs. In male fish, no significant alteration was observed in the testis for all groups. The concentration of testosterone significantly decreased upon exposure to BPA rather than H-BPAs. The effects of these three chemicals on the estrogen-related gene expressions were different under various developmental stages. Our study indicated the importance of considering both the exposure stages and structure-activity relationship when assessing the eco-toxicological impact of pollutants.

The occurrence and spatial-temporal distribution of tetrabromobisphenol A in the coastal intertidal zone of Qingdao in China, with a focus on toxicity assessment by biological monitoring

Tetrabromobisphenol A (TBBPA) is a widely used flame retardant that has increasingly been found as contaminant in aquatic environments. The main goal of this study was to evaluate the pollution level of TBBPA at six locations around Qingdao and assess its biotoxicity through a two-generation toxicity study looking at a copepod species. In the chemical monitoring, the concentration of TBBPA in seawater samples ranged from nd to 1.8 μg/L. Next, the biological indicator monitoring used 1.8 μg/L as the middle exposure concentration to perform quantitative evaluations of the influence of TBBPA on the demographic traits of Pseudodiaptomus inopinus. The results showed that copepods became more sensitive to TBBPA exposure even in environmental concentration (1.8 μg/L) as the generations developed. The detrimental effects of TBBPA further increased naupliar mortality and impaired copepodite development to adulthood. This study demonstrated that the water pollution condition of TBBPA was measured at all 6 sampling locations of Qingdao. Therefore, the present results call for a decreased discharge of TBBPA into the marine environment to avoid impairing copepod reproduction and development.

Effects of the earthworm Metaphire guillelmi on the mineralization, metabolism, and bound-residue formation of tetrabromobisphenol A (TBBPA) in soil

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants worldwide. The degradation and fate of this organic pollutant of soils is of great concern and can be strongly affected by geophagous earthworms through ingestion and burrowing activities. Using ¹⁴C-tracers, we studied the effects of the geophagous earthworm Metaphire guillelmi on the mineralization, metabolism, and bound-residue formation of TBBPA in a typical Chinese rice paddy soil during 30days of incubation in the laboratory. Earthworms significantly decreased both mineralization (from 3.9±0.3% of the initial amount to 2.6±0.2%) and dissipation (from 90.6±0.6% to 84.1±1.2%) of TBBPA in the soil, and stimulated the generation of O-methylation metabolites (TBBPA methyl ethers; from 1.4±0.4% to 15.4±0.6%). This resulted in a strong decrease in bound-residue formation of TBBPA and its metabolites in the soil (from 80.3±0.4% to 41.8±3.1%). Results from a first-order, two-compartment model that describes the fate of TBBPA in soil indicated that the TBBPA-derived bound residues were mainly attributed to the binding of metabolites to the soil matrix and not to the binding of TBBPA, and that earthworms reduced the kinetic rates of both polar metabolite generation and their bound-residue formation. Our results suggested that the geophagous earthworm Metaphire guillelmi strongly influenced the fate of TBBPA by altering the composition of metabolites and therefore bound-residue formation. The increased persistence of TBBPA and the formation of persistent O-methylation metabolites by M. guillelmi would increase the environmental risk of TBBPA.

Abiotic transformation of hexabromocyclododecane by sulfidated nanoscale zerovalent iron: Kinetics, mechanism and influencing factors

Recent studies showed that sulfidated nanoscale zerovalent iron (S-nZVI) is a better reducing agent than nanoscale zerovalen iron (nZVI) alone for reductive dechlorination of several organic solvents such as trichloroethylene (TCE) due to the catalytic role of iron sulfide (FeS). We measured the rates of transformation of hexabromocyclododecane (HBCD) by S-nZVI and compared them to those by FeS, nZVI, and reduced sulfur species. The results showed that: i) HBCD (20 mg L^-1) was almost completely transformed by S-nZVI (0.5 g L^-1) within 12 h; ii) the reaction with β-HBCD was much faster than with α- and γ-HBCD, suggesting the diastereoisomeric selectivity for the reaction by S-nZVI; and iii) the reaction with S-nZVI was 1.4-9.3 times faster than with FeS, S^2- and nZVI, respectively. The study further showed that the HBCD reaction by S-nZVI was likely endothermic, with the optimal solution pH of 5.0, and could be slowed in the presence of Ca²⁺, Mg²⁺, NO₃^-, HCO₃^- and Cl^-, and by increasing ionic strength, solvent content and initial HBCD concentration, or decreasing the S-nZVI dosage. GC-MS analysis showed that tetrabromocyclododecene and dibromocyclododecadiene were the products. XPS spectra indicated that both Fe(II) and S(-II) on the S-nZVI surface were oxidized during the reaction, suggesting that FeS might act as both catalyst and reactant. The study not only demonstrated the superiority of S-nZVI over other well-known reactive reagents, but also provided insight to the mechanisms of the reaction.

Adipose Tissue as a Site of Toxin Accumulation

We examine the role of adipose tissue, typically considered an energy storage site, as a potential site of toxicant accumulation. Although the production of most persistent organic pollutants (POPs) was banned years ago, these toxicants persist in the environment due to their resistance to biodegradation and widespread distribution in various environmental forms (e.g., vapor, sediment, and water). As a result, human exposure to these toxicants is inevitable. Largely due to their lipophilicity, POPs bioaccumulate in adipose tissue, resulting in greater body burdens of these environmental toxicants with obesity. POPs of major concern include polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), and polybrominated biphenyls and diphenyl ethers (PBBs/PBDEs), among other organic compounds. In this review, we (i) highlight the physical characteristics of toxicants that enable them to partition into and remain stored in adipose tissue, (ii) discuss the specific mechanisms of action by which these toxicants act to influence adipocyte function, and (iii) review associations between POP exposures and the development of obesity and diabetes. An area of controversy relates to the relative potential beneficial versus hazardous health effects of toxicant sequestration in adipose tissue. © 2017 American Physiological Society. Compr Physiol 7:1085-1135, 2017.

Occurrence and effects of plastic additives on marine environments and organisms: A review

Plastics debris, especially microplastics, have been found worldwide in all marine compartments. Much research has been carried out on adsorbed pollutants on plastic pieces and hydrophobic organic compounds (HOC) associated with microplastics. However, only a few studies have focused on plastic additives. These chemicals are incorporated into plastics from which they can leach out as most of them are not chemically bound. As a consequence of plastic accumulation and fragmentation in oceans, plastic additives could represent an increasing ecotoxicological risk for marine organisms. The present work reviewed the main class of plastic additives identified in the literature, their occurrence in the marine environment, as well as their effects on and transfers to marine organisms. This work identified polybrominated diphenyl ethers (PBDE), phthalates, nonylphenols (NP), bisphenol A (BPA) and antioxidants as the most common plastic additives found in marine environments. Moreover, transfer of these plastic additives to marine organisms has been demonstrated both in laboratory and field studies. Upcoming research focusing on the toxicity of microplastics should include these plastic additives as potential hazards for marine organisms, and a greater focus on the transport and fate of plastic additives is now required considering that these chemicals may easily leach out from plastics.

Fate and O-methylating detoxification of Tetrabromobisphenol A (TBBPA) in two earthworms (Metaphire guillelmi and Eisenia fetida)

Tetrabromobisphenol A (TBBPA) is the world's most widely used brominated flame retardant but there is growing concern about its fate and toxicity in terrestrial organisms. In this study, two ecologically different earthworms, Metaphire guillelmi and Eisenia fetida, were exposed to soil spiked with ¹⁴C-labeled TBBPA for 21 days. M. guillelmi accumulated more TBBPA than E. fetida, evidenced by a 2.7-fold higher ¹⁴C-uptake rate and a 1.3-fold higher biota-soil accumulation factor. Considerable amounts of bound residues (up to 40% for M. guillelmi and 18% for E. fetida) formed rapidly in the bodies of both earthworms. ¹⁴C accumulated mostly in the gut of M. guillemi and in the skin of E. fetida, suggesting that its uptake by M. guillelmi was mainly via gut processes whereas in E. fetida epidermal adsorption predominated. The TBBPA transformation potential was greater in M. guillelmi than in E. fetida, since only 5% vs. 34% of extractable ¹⁴C remained as the parent compound after 21 days of exposure. Besides polar metabolites, the major metabolites in both earthworms were TBBPA mono- and dimethyl ethers (O-methylation products of TBBPA). Acute toxicity assessments using filter paper and natural soil tests showed that the methylation metabolites were much less toxic than the parent TBBPA to both earthworms. It indicated that earthworms used O-methylation to detoxify TBBPA, and M. guillelmi exhibited the higher detoxification ability than E. fetida. These results imply that if only the free parent compound TBBPA is measured, not only bioaccumulation may be underestimated but also its difference between earthworm species may be misestimated. The species-dependent fate of TBBPA may provide a better indicator of the differing sensitivities of earthworms to this environmental contaminant.

Enantiomer-specific accumulation and depuration of α-hexabromocyclododecane (α-HBCDD) in chicken (Gallus gallus) as a tool to identify contamination sources

A LC-ESI(-)-HRMS method dedicated to the analysis of 6 HBCDD enantiomers at trace levels in animal matrices was developed, using a cellulose based stationary phase with a particle size of 2.5 μm. This method was applied to a sample set derived from a kinetic study of α-HBCDD previously conducted in fast- and slow-growing chickens (Gallus gallus domesticus, n = 49, plus controls), in order to study the enantiomer specific accumulation and depuration of α-HBCDD in various tissues. Regarding abdominal adipose tissue, muscle and liver, the average enantiomeric fractions of α-HBCDD (EF_α) for continuously exposed groups ranged between 0.434 and 0.467, with standard deviations below 0.014, showing a significant enrichment in (-)α enantiomer even accentuated for slow growing individuals during depuration with EF_α reduced by about 0.020. Similar trends were observed for pooled plasma. Then, EF_α of circulating plasma α-HBCDD appeared to closely reflect EF_α in storage tissues and liver, suggesting some equilibrium. The racemic elimination of α enantiomer in excreta during the contamination phase indicated that no preferential gastrointestinal absorption took place. By contrast, preferential excretion of (-)α-HBCDD from the circulating compartment to the intestinal lumen occurred during the depuration. Finally, the method was applied to samples collected in three chicken farms, selected for total HBCDD levels in muscle in the ng/g range, as a tool to determine whether the contamination occurred ante- or post-mortem, according to the chiral signature. Ante-mortem contamination was hypothesised for 2 farms, with feed being excluded as contamination source.

Hexabromocyclododecane diastereomers in fish and suspended particulate matter from selected European waters-trend monitoring and environmental quality standard compliance

The brominated flame retardant hexabromocyclododecane (HBCD) was monitored in fish and sediment (from one lake) or suspended particulate matter (SPM; from five rivers) at European freshwater sites to study the effects of reduction measures implemented by HBCD producers and users in recent years. Bream (Abramis brama) were sampled annually between 2007 and 2013 in the rivers Götaälv/SE, Rhône/FR, Western Scheldt/NL, Mersey/UK, and Tees/UK and in Lake Belau/DE. Sediment/SPM was taken every second year between 2008 and 2014. HBCD was analyzed by LC/MS/MS allowing the determination of the alpha-, beta-, and gamma-diastereomers. For most sites, a decrease in ∑HBCD was observed in fish (e.g., in the Rhône and Western Scheldt by about 80 and 60%, respectively, with significantly decreasing trends, p < 0.01). In the Rhône, HBCD also decreased in SPM. At the sampling site in the Tees which was impacted by a former HBCD point source, fish HBCD levels decreased only after a major flood event in 2013. While fish data indicate a decline in environmental HBCD concentrations at most sites with diffuse emissions, SPM data were less conclusive. The European environmental quality standard for HBCD in fish of 167 μg kg^-1 wet weight was met by all fish samples in 2013.

Preliminary screening of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA) flame retardants in landfill leachate

The occurrence of selected brominated flame retardants, including nine polybrominated diphenyl ether (PBDE) congeners, hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA) in leachate samples from eight landfill sites in South Africa, were investigated. In addition, the possible influences of dissolved organic carbon on their levels were also evaluated. Filtered leachate samples were subjected to solid-phase extraction to isolate the various target compounds. PBDEs with six bromine substituents and above, as well as α-HBCDD, β-HBCDD and TBBPA, were generally found below the detection limit. However, the mean value of the total lower PBDE congeners ranged between 0.04 and 0.48 μg L^-1, and the concentrations of γ-HBCDD ranged from not detectable (ND) to 0.05 μg L^-1. No significant correlation was observed between the target compounds and dissolved organic carbon, although weak to moderate correlations were mostly observed for the lower PBDEs.

Distribution of PBDEs, HBCDs and PCBs in the Brisbane River estuary sediment

To date, very little or no data exist in literature for some brominated flame retardants (BFRs) and polychlorinated biphenyls in Queensland sediments. These pollutants were measured in the sediments along the Brisbane River estuary. The target compounds were regularly detected in measurable concentrations: PBDEs=33.3-97.8% (n=45), PCBs=94.1-100% (n=51) and HBCDs=79-98% (n=48). Consistently, >90% of the observed ∑₈PBDE concentration was attributed to BDE-209. Mean PBDE levels (ng/g dry wt.) were: 4.4±3.2 (∑₈PBDE) and 4.4±3.0 (BDE-209) across 22 sampling sites. The mean ∑₇PCB and ∑HBCD were 5.4±4.5 and 1.0±1.5ng/g dry wt. respectively. The 25% (α-HBCD), 8% (β-HBCD) and 67% (γ-HBCD) diastereoisomer contributions observed were consistent with values reported in the literature. Contaminant levels are fairly distributed along the River and were generally low compared to similar studies around the world.

Matrix-specific distribution and diastereomeric profiles of hexabromocyclododecane (HBCD) in a multimedia environment: Air, soil, sludge, sediment, and fish

Hexabromocyclododecane (HBCD) contamination and its diastereomeric profile were investigated in a multi-media environment along a river at the local scale in air, soil, sludge, sediment, and fish samples. The spatial distribution of HBCD in each matrix showed a different result. The highest concentrations of HBCD in air and soil were detected near a general industrial complex; in the sediment and sludge samples, they were detected in the down-stream region (i.e., urban area). Each matrix showed the specific distribution patterns of HBCD diastereomers, suggesting continuous inputs of contaminants, different physicochemical properties, or isomerizations. The particle phases in air, sludge, and fish matrices were dominated by α-HBCD, owing to HBCD's various isomerization processes and different degradation rate in the environment, and metabolic capabilities of the fish; in contrast, the sediment and soil matrices were dominated by γ-HBCD because of the major composition of the technical mixtures and the strong adsorption onto solid particles. Based on these results, the prevalent and matrix-specific distribution of HBCD diastereomers suggested that more careful consideration should be given to the characteristics of the matrices and their effects on the potential influence of HBCD at the diastereomeric level.

The fate and transformation of tetrabromobisphenol A in natural waters, mediated by oxidoreductase enzymes

In this study, we examined the fate and transformation of tetrabromobisphenol A (TBBPA), mediated by the representative oxidoreductases (laccase and horseradish peroxidase (HRP)) in natural waters. Both enzymes could readily degrade TBBPA at environmentally relevant concentrations (e.g., 10 nmol L^-1) in natural waters. After 2 hour treatment, 0.5-25% and 35-65% of TBBPA were degraded in municipal wastewater and natural surface waters by a laccase or HRP-catalyzed reaction, respectively. Enzyme kinetics evaluations indicated that the k_CAT/K_M ratio of HRP (1.01 μM^-1 s^-1) was much higher than that of laccase (0.032 μM^-1 s^-1) for TBBPA degradation, suggesting that the catalytic performance of HRP towards TBBPA was more efficient than that of laccase. The effects of pH and organic matter on the enzymatic degradation efficiency were explored. Organic matter in the water inhibited the enzymatic degradation efficiency and the degree of inhibition was proportional to the UV₂₅₄ values of water. Product identification indicated that the product distribution of TBBPA at low concentration (10 nmol L^-1) was similar to that of TBBPA at high concentration (10 μmol L^-1). The degradation intermediates underwent further enzymatic reaction to yield higher molecular weight secondary products. Toxicity assessment showed that TBBPA toxicity was effectively eliminated by the oxidoreductase-catalyzed reaction.

Detection of tetrabromobisphenol A and its mono- and dimethyl derivatives in fish, sediment and suspended particulate matter from European freshwaters and estuaries

An analytical method was developed for the determination of tetrabromobisphenol A (TBBPA), 3,3′,5,5′-tetrabromobisphenol-A-monomethyl ether (MM-TBBPA) and 3,3′,5,5′-tetrabromobisphenol-A-dimethyl ether (DM-TBBPA), and its valid application on fish muscle matrix (bream and sole), suspended particulate matter (SPM) and surface sediment layer samples, using only 0.5 g sample material, is demonstrated. Here, for the first time, DM-TBBPA could be determined by an LC-MS/MS-based method applying atmospheric pressure photoionization (APPI), using the same sample extracts for all three analytes. Samplings covered freshwater fish (bream; annually, period 2007–2013) and SPM or sediment (every second year in the period 2008–2014) at selected European sites (rivers: Tees/UK, Mersey/UK, Western Scheldt/NL, Götaälv/SE, Rhône/FR; Lake Belau/DE). TBBPA could be quantified in 13 of 36 bream samples (range about 0.5–1.2 μg kg⁻¹ ww) and 7 of 7 sole muscle samples (range about 0.5–0.7 μg kg⁻¹ ww). Further, it could be quantified in 11 of the 14 SPM samples (range about 0.5–9.4 μg kg⁻¹ dw) and in both of the surface sediment layer samples (2.3–2.6 μg kg⁻¹ dw). MM-TBBPA could be quantified in 12 of 36 bream and 4 of 7 sole muscle samples (range about 0.8–1.8 μg kg⁻¹ ww). Further, it could be quantified in 10 of the 14 river SPM samples (range about 2.3–4.5 μg kg⁻¹ dw) and in both lake surface sediment layer samples (5.2–5.5 μg kg⁻¹ dw). DM-TBBPA was rarely detectable and could not be quantified above the limit of quantification in any sample.

Anaerobic co-metabolic biodegradation of tetrabromobisphenol A using a bioelectrochemical system

Tetrabromobisphenol A(TBBPA), a pollutant in industrial wastewaters, needs to be removed due to its high toxicity and persistence. The main biodegradation pathway for TBBPA has been studied, and bisphenol A(BPA), which is toxic to the environment, is recognized as the general terminal product. In this study, we explored a new approach for the anaerobic biodegradation of TBBPA in a bioelectrochemical system (BES) through co-metabolic degradation of TBBPA with glucose. The half-life of TBBPA was significantly reduced to 13.5h^-1 at 25μg/l of TBBPA. With an increase in the concentration of TBBPA, the removal rates of TBBPA rose to more than eighty percent. Based on the analysis of the products, we found that the degradation products of TBBPA were 2,6-dibromo-4-(1-methyl-1-phenylethyl) phenol, (double-benzenes product) and 2,6-dibromo-4-(prop-1-en-2-yl) phenol (single-benzene product), rather than BPA. Simultaneously, we proposed two degradation pathways for TBBPA in a BES system. According to the microbial diversity analysis of the anode biofilm, we speculated that the microorganism responsible for the biodegradation of TBBPA was Azoarcus. Additionally, we briefly analyzed the effect of TBBPA on the performance of BES system to pave the way for the further analysis of the interaction between the TBBPA and the BES system.

The potential ecological risk of multiwall carbon nanotubes was modified by the radicals resulted from peroxidase-mediated tetrabromobisphenol A reactions

Extensive studies have been conducted on the environmental degradation of multiwall carbon nanotubes (MWCNTs), but primarily focused on the extent and rate of MWCNTs mineralization. Few studies have explored possible structural changes that may occur to MWCNTs during natural or engineered processes. We systematically examined MWCNTs in oxidative coupling reactions in the presence of a common contaminant tetrabromobisphenol A (TBBPA). MWCNTs was modified by the radicals of TBBPA resulting from peroxidase-mediated coupling reaction. Interactions between TBBPA radicals and MWCNTs were definitely confirmed by analyzing the characteristic mass spectrometry response of bromine in TBBPA and the structures of MWCNTs. After reaction with TBBPA radicals for 60 min, the content of bromine contained in MWCNTs was 6.84(±0.12)%, a quantity equivalent to a 501.65(±2.19) mg loading of TBBPA per gram MWCNTs. Modified MWCNTs had better stability and smaller sizes than that of MWCNTs and TBBPA-adsorbed MWCNTs. Assessment using zebrafish embryos revealed that the modified MWCNTs passed through the chorion and entered the embryo inducing acute toxicity, while the MWCNTs/TBBPA-adsorbed MWCNTs was trapped by chorion. These findings indicated that MWCNTs was modified in peroxidase-mediated coupling reactions, and suggested that such modifications may have an influence on the ecological risks of MWCNTs.

Legacy and emerging flame retardants (FRs) in the freshwater ecosystem: A review

In this review article, we have compiled and reviewed the previously published available literature on environmental distribution, behaviour, fate and regional trends of legacy and emerging flame retardants (FRs) including brominated (BFRs), organo-phosphate (OPFRs), novel brominated flame retardants (NBFRs) and dechlorane plus (DP) in the freshwater ecosystem. Transport and fate is discussed briefly with the evidences of de-bromination, sedimentation and accumulation in biota. De-bromination of BDE-209 is considered of concern because the lower brominated congeners are more toxic and mobile thus posing increased risk to the freshwater ecosystem. The available data on temporal and spatial trends as yet, is too few to show any consistent trends, enabling only general conclusions to be drawn. There is a lack of temporal studies in Asia, while, overall the trends are mixed, with both increasing and decreasing concentrations of BFRs and OPFRs. OPFRs and NBFRs have replaced classical BFRs (polybrominated diphenyl ethers (PBDEs)) in some countries but the amount of PBDEs in the environment is still considerable. Knowledge gaps and recommendations for future research are discussed emphasizing on further monitoring, advanced analytical methodologies, and risk assessment studies to completely understand the science of flame retardants in the freshwater ecosystem.

Effects of hydrodynamic disturbances and resuspension characteristics on the release of tetrabromobisphenol A from sediment

Tetrabromobisphenol A (TBBPA) exists widely in river and lake sediments; it has raised growing attention in recent years as emerging contaminant due to its possible threats to the aquatic environment and human health. Using a specialized simulator, the relationships between hydrodynamic disturbances and resuspension characteristics were simulated, with an emphasis on microscopic characteristics. Furthermore, TBBPA release from sediment was studied in relation to hydrodynamic disturbances and resuspension characteristics. The results show that stronger water disturbances caused an increase in suspended solids concentration (SSC) and produced different behaviors of particle size distribution (PSD) and media diameter (D₅₀) in the slight and large-scale resuspension situations. As for microscopic resuspension characteristics, the specific surface area (SSA) of suspended particulate matter (SPM) was very different from that of smooth particles. This difference may result from the fractal nature of the SPM. The fractal dimension (FD) of SPM was found to have a significant correlation with turbulent kinetic energy. TBBPA release into overlying water and adsorption onto SPM both increased with hydrodynamic disturbances; but the release into overlying water is more dominant. The TBBPA concentrations in SPM under different hydrodynamic conditions were significant related to SSA, indicating that SSA is a key factor affecting the TBBPA adsorption capacity of SPM. TBBPA concentrations in sediment decreased slightly with the increased hydrodynamic dispersion. Findings from this research show the importance of considering the hydrodynamic disturbance and resuspension characteristics in understanding TBBPA release behavior in aquatic environment.

A review of the environmental distribution, fate, and control of tetrabromobisphenol A released from sources

Tetrabromobisphenol A (TBBPA), a high use brominated flame retardant (BFR), raising concerns of widespread pollution and harm to human and ecological health. BFR manufacturing, TBBPA-based product manufacturing, e-waste recycling, and wastewater treatment plants have been identified as the main emission point sources. This paper discusses the occurrence, distribution, and fate of TBBPA from source to the environment. After release to the environment, TBBPA may undergo adsorption, photolysis, and biological degradation. Exposure of humans and biota is also discussed along with the role of treatment and regulations in reducing release of TBBPA to the environment and exposure risks. In general this review found stronger enforcement of existing legislation, and investment in treatment of e-waste plastics and wastewater from emission point sources could be effective methods in reducing release and exposure of TBBPA in the environment.

Reductive transformation of tetrabromobisphenol A by sulfidated nano zerovalent iron

Recent studies showed that sulfidated nano zerovalent iron (S-nZVI) is a better alternative to non-sulfidated nano zerovalent iron (NS-nZVI) commonly used for contaminated site remediation. However, its reactivity with different halogenated pollutants such as tetrabromobisphenol A (TBBPA) remains unclear. In this study, we explored the reductive transformation of TBBPA by S-nZVI and compared it with that by NS-nZVI. The results showed that over 90% of the initial TBBPA (20 mg L(-1)) was transformed by S-nZVI within 24 h of reaction, which was 1.65 times as high as that for NS-nZVI. The TBBPA transformation by S-nZVI was well described by a pseudo-first-order kinetic model, whilst that by NS-nZVI was well fitted by a three-parameter single exponential decay model. After 11 weeks of aging, S-nZVI was still able to transform up to 56% of the initial TBBPA within 24 h of reaction; by contrast, the two-week aged NS-nZVI lost more than 95% of its original capacity to transform TBBPA. Moreover, S-nZVI showed only an approximately 20% decrease in its capacity to transform TBBPA in the seventh cycle, while NS-nZVI was no longer able to transform TBBPA in the fourth cycle. XPS analysis suggested the formation of FeS layer on S-nZVI surface and electrochemical analysis revealed an elevated electron transfer capacity of S-nZVI, which were likely responsible for the superior performances of S-nZVI in TBBPA transformation. While the transformation rate of TBBPA by S-nZVI decreased with increasing initial concentration of TBBPA, it showed an increasing trend with increasing S/Fe ratio and initial concentration of S-nZVI. The study indicated that S-nZVI has the potential to be a promising alternative to NS-nZVI for remediation of TBBPA-contaminated aquatic environments.

Hexabromocyclododecane and tetrabromobisphenol A in sediments and paddy soils from Liaohe River Basin, China: Levels, distribution and mass inventory

Hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) are two kinds of brominated flame retardants and widely present in the environment and biota. The levels, spatial distributions and mass inventories of HBCD and TBBPA were investigated in sediments and paddy soils from the Liaohe River Basin in northeast China. The concentrations of ΣHBCD and TBBPA were in the range of not detected (nd) to 4.02ng/g dry weight (dw) and 0.03 to 4.06ng/g dw, respectively. γ-HBCD was dominated in sediments, while the abundance of α-HBCD was relatively high in paddy soils. The spatial distributions of HBCD and TBBPA in surface sediments and paddy soils indicated that the local point-input was their major source. The significant correlation between total organic carbon (TOC) contents and the HBCD levels suggested that TOC content also exerted an influence on the distribution of HBCD in sediments. Meanwhile, it was found that the irrigation with river water was not the major transportation pathway of HBCD and TBBPA in paddy soils. Based on the study, it was estimated that there were about 1.67tons HBCD and 2.20tons TBBPA deposited into sediments of the Liaohe River system every year. The total mass inventories of HBCD and TBBPA in sediments were far higher than that in paddy soils.

Occurrence and fate of PBDEs and novel brominated flame retardants in a wastewater treatment plant in Harbin, China

Wastewater treatment plant (WWTP) is considered to be an important medium for the transport and transformation of organic pollutants. This study attempted to comprehensively investigate polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in a WWTP in Harbin, one of the main "Old Industrial Base" in China. The mean concentrations of the total PBDEs in the influent, effluent, and sludge were 152 ng/L, 16.2 ng/L, and 503 g/g dw, respectively, which were at the low end of the global range. BDE-209 was the most abundant congener, with contributions to the total PBDE ranging from 90.5 to 98.5 %. The level of the total NBFRs ranged from 24.5 to 107 ng/L, 0.95 to 20.3 ng/L, and 305 to 1202 ng/g dw in the influent, effluent, and sludge, respectively. For NBFRs, DBDPE was the most abundant congener (38.8-50.5 %), followed by BEHTBP (11.0-35.0 %). The ratio for DBDPE/BDE-209 (0.62 ± 0.42) was found less than 1 in sludge, which indicated that Deca-BDE is still the major BFR product in this city. Source identification suggested that indoor dust should be an important source of BFRs in the WWTP. Approximately 20.8 and 7.79 kg of PBDEs and NBFRs on annual basis were removed with the sludge. Biodegradation could play an important role on the fate of BFRs in the WWTP, which is required for future research.

Biogenic Fenton-like Reaction Involvement in Cometabolic Degradation of Tetrabromobisphenol A by Pseudomonas sp. fz

Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant (BFR) that has frequently been detected in various environmental compartments. Although TBBPA biotransformation has been observed under both aerobic and anaerobic conditions, knowledge of the detailed mechanism of direct aerobic TBBPA biodegradation still remains limited. In this study, the underlying mechanism of cometabolic degradation of TBBPA by Pseudomonas sp. fz under aerobic conditions was investigated. Two key degradation pathways (beta scission and debromination) were proposed based on triple quadrupole liquid chromatography-mass spectrometry (LC-MS) analysis. TBBPA degradation by strain fz was demonstrated to be an extracellular process associated with the low-molecular-mass component (LMMC). Moreover, LMMC was preliminarily identified as oligopeptides, mainly consisting of glycine, proline, and alanine in a 2:1:1 molar ratio. Quenching studies suggested the involvement of hydroxyl radicals ((•)OH) in extracellular TBBPA degradation. To the best of our knowledge, we provide the first evidence that TBBPA was degraded by a biogenic Fenton-like reaction mediated via extracellular H2O2 and Fe(II)-oligopeptide complexes by the genus Pseudomonas. This study provides a new insight into the fate and biodegradation of TBBPA and other organic pollutants in natural and artificial bioremediation environments.

Reductive transformation of hexabromocyclododecane (HBCD) by FeS

Both iron monosulfide (FeS) and brominated flame retardants (BFRs) are widely found at relatively high levels in anoxic sediments, but little is known about the reactions of FeS with BFRs. Prior studies showed that FeS was variously reactive with chlorinated organic pollutants in many anoxic environments. It is intuitive that FeS is also reactive with BFRs under anoxic conditions. This study was initiated to test such a hypothesis by quantifying the rates of reductive transformation of tetrabromobisphenol A (TBBPA), decabrominated diphenyl ether (decaBDE) and hexabromocyclododecane (HBCD) using synthetic FeS as the reactive agent. The results showed that over 90% of HBCD was transformed by FeS within 24 h, whereas both TBBPA and decaBDE were found nonreactive within 2 days. The transformation of HBCD followed a pseudo-first-order rate kinetic and the observed rate constants were dependent on the initial concentrations of FeS and HBCD. The transformation rates of β- and γ-HBCD were significantly faster than that of α-HBCD. Analysis of bromine ion and other transformation products suggested that sequential dibromoelimination to form 1,5,9-cyclododecatriene was likely to be a dominant pathway for the reductive transformation of HBCD by FeS. Surface characterization of FeS by XPS indicated that both Fe(II) and S(-II) on the FeS surface might have contributed considerably to the transformation of HBCD. These findings imply that FeS may play an important role in natural attenuation of HBCD and that it may be used as a reactive agent for treating HBCD-contaminated sediments.