Trophodynamics of Emerging Brominated Flame Retardants in the Aquatic Food Web of Lake Taihu: Relationship with Organism Metabolism across Trophic Levels

Species-specific bioaccumulation and biotransformation of two novel brominated flame retardants in fish: Insights from isotope fractionation

1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) and 1,2-bis(2,4,6-tribromophenoxyethane) (BTBPE), two novel brominated flame retardants, have been widely detected in diverse environmental media. However, information about their fate in aquatic environments is limited. In this study, two aquatic food chains comprising a prey species (tiger barb, TB) and two predator species (oscar fish, OF, and redtail catfish, RF) were established to examine the species-specific biotransformation and bioaccumulation of TBECH and BTBPE in fish. Higher biomagnification factors of TBECH and BTBPE were observed in RF ((3.44 ± 0.31)-(3.62 ± 0.14)) compared to OF ((2.77 ± 0.06)-(3.18 ± 0.05)). Debrominated and hydroxylated biotransformation products (BPs) of BTBPE and α-/β-TBECH were identified in OF livers, whereas no debrominated BPs were detected in RF. The changes in enantiomer fractions (EFs) of α-TBECH and β-TBECH in both RF and OF indicate selective biotransformation of specific enantiomers within each fish species. Additionally, the stable carbon isotope (δ13C) of α-/β-TBECH and BTBPE, as well as α-/β-TBECH enantiomers further substantiates a higher metabolic conversion potential was observed in OF compared to RF, supports the hypothesis that debromination exclusively occurs in OF. Meanwhile, the carbon isotope enrichment factor (εC) of α-/β-TBECH, BTBPE, and α-TBECH enantiomers in OF ((-2.43 ± 0.21)-(-3.41 ± 0.16)) were significantly higher than those in RF ((-1.74 ± 0.18)-(-2.16 ± 0.22); p < 0.05), indicating potential disparities in biotransformation mechanisms between these two fish species. In vitro incubation experiments using OF liver microsomes further demonstrated that εC values of β-TBECH and BTBPE during the debromination process (-2.93 ± 0.14 and -3.55 ± 0.21) were notably higher compared to oxidative processes (-1.90 ± 0.23 and -2.74 ± 0.18). These results provided valuable insights into species-specific bioaccumulation and biotransformation of chemicals in fish, while stable carbon isotope fractionation can potentially reveal distinct transformation pathways of chemicals within fish.

Structure and Toxicity Characterization of Alkyl Hydroxylated Metabolites of 6PPD-Q

Distinct from other nontoxic phenyl-p-phenylenediamine (PPD) quinones, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) was recently discovered to be regioselectively metabolized to alkyl hydroxylated metabolites (alkyl-OH-6PPD-Q) in rainbow trout. It remains unknown whether the unique alkyl-OH-6PPD-Q contributes to the toxicity of 6PPD-Q. To test this, we herein synthesized chemical standards of alkyl-OH-6PPD-Q isomers and investigated their metabolic formation mechanism and toxicity. The predominant alkyl-OH-6PPD-Q was confirmed to be hydroxylated on the C4 tertiary carbon (C4-OH-6PPD-Q). The formation of C4-OH-6PPD-Q was only observed in microsomal but not in cytosolic fractions of rainbow trout (O. mykiss) liver S9. A general cytochrome P450 (CYP450) inhibitor fluoxetine inhibited the formation of hydroxylated metabolites of 6PPD-Q, supporting that CYP450 catalyzed the hydroxylation. This well-explained the compound- and regio-selective formation of C4-OH-6PPD-Q, due to the weak C-H bond on the C4 tertiary carbon. Surprisingly, while cytotoxicity was observed for 6PPD-Q and C3-OH-6PPD-Q in a coho salmon (O. kisutch) embryo (CSE-119) cell line, no toxicity was observed for C4-OH-6PPD-Q. To further confirm this under physiologically relevant conditions, we fractionated 6PPD-Q metabolites formed in the liver microsome of rainbow trout. Cytotoxicity was observed for the fraction of 6PPD-Q, but not the fraction of C4-OH-6PPD-Q. In summary, this study highlighted the C4 tertiary carbon as the key moiety for both metabolism and toxicity of 6PPD-Q and confirmed that alkyl hydroxylation is a detoxification pathway for 6PPD-Q.

Guidance for measuring and evaluating biomagnification factors and trophic magnification factors of difficult substances: application to decabromodiphenylethane

As field based trophic magnification factors (TMFs) and biomagnification factors (BMFs) become more prominent regulatory metrics used in bioaccumulation assessments of commercial chemicals, there is a need to develop standardized guidelines for conducting field-based bioaccumulation studies and to establish methods using weight of evidence analyses of those studies. Hence, the primary objectives of this study were (1) to compile a set of comprehensive criteria and guidelines for conducting field-based biomagnification studies and (2) to develop a weight of evidence meta-analysis for evaluating field-based biomagnification studies and their reported biomagnification metrics for assessing the biomagnification potential of substances. To test the effectiveness of our proposed guidelines and weight of evidence meta-analysis, we reviewed over 25 field studies investigating the biomagnification of decabromodiphenyl ethane (DBDPE), a substance that is considered super-hydrophobic and difficult to test in bioconcentration tests. Approximately half of the field studies that investigated trophic magnification of DBDPE in food webs or biomagnification of DBDPE in predator-prey interactions were considered of acceptable quality, whereas no studies were of high quality. Quality scores of studies statistically decreased with increasing TMF (r2 = 0.261, p = .035) and/or BMF (r2 = 0.238, p = .0024). The weight of evidence meta-analysis indicated with a high level of confidence that concentrations of DBDPE do not biomagnify in top predators and within food-webs. Given the increasing importance of the TMF and BMF for bioaccumulation assessments and the apparent deficiencies in current biomagnification studies identified in this meta-analysis for DBDPE, there is an urgent need to adopt standardized guidelines and procedures for both conducting and evaluating field-based biomagnification studies.

Novel flame retardants (NFRs) in e-waste: Environmental burdens, health implications, and recommendations for safety assessment and sustainable management

Novel flame retardants (NFRs) have emerged as chemicals of environmental health concern due to their widespread use as an alternative to polybrominated diphenyl ethers (PBDE) in electrical and electronic devices. Humans and ecosystems are under threat because of e-waste recycling procedures that may emit NFRs and other anthropogenic chemicals into the e-waste workplace and the surrounding environment. The individual toxicity of NFRs including novel brominated flame retardants (NBFRs), their combined effects and the underlying mechanisms of toxicity have remained poorly understood. Exposure assessment as well as chemical safety testing should focus on prioritizing N(B)FRs for regulation and management. Here, the occurrence of N(B)FRs in the vicinity and surroundings of e-waste recycling sites are presented. Important knowledge gaps and prospects for a more integrated, harmonized, and mechanistically positioned risk assessment strategy for N(B)FRs as well as possible economically feasible and environmentally sustainable approaches for removing them from complex matrices are highlighted. Overall, data in the ng to µg-ranges of N(B)FR in soil, dust, sediment, water and fish were found. Dust and soil sample concentrations ranged from the low ng to low µg/g range while water concentrations were always in the low ng/L range (∼0.5 to ∼4 ng/L). Concentration in fish was usually in the range of 3- ∼300 ng/g with two substances in the low to medium-high µg/g range (DBDPE, BTBPE). From the 20 N(B)FR analysed in sediment samples only 10 were above detection limit. Most chemicals were found in a low ng/g range.

Bioaccumulation of novel brominated flame retardants in a marine food web: A comprehensive analysis of occurrence, trophic transfer, and interfering factors

Although the concept of bioaccumulation for novel brominated flame retardants (NBFRs) is clear, the process and interfering factors of bioaccumulation are still not fully understood. The present study comprehensively evaluated the occurrence, transfer and interfering factors of NBFRs in a marine food web to provide new thought and perspective for the bioaccumulation of these compounds. The occurrence of 17 NBFRs were determined from 8 water, 8 sediment and 303 organism samples collected from Dalian Bay, China. The trophic magnification factor (TMF), the bioaccumulation factor (BAF) and the biota sediment accumulation factor (BSAF) were calculated in a plankton-mollusk-crustacean-fish based food webs. Results showed that among the 17 target NBFRs, 11 compounds appeared the significant trophic magnification and 2 compounds of decabromodiphenylethane (DBDPE) and octabromotrimethylphenylindane (OBIND) presented the significant trophic dilution. The significant positive correlation was found between the value of BAFs and the trophic level for 15 NBFRs (except DBDPE and OBIND), indicating that the species with high BAFs values were all at high trophic levels. The stable and rapid metabolic rates of DBDPE and OBIND constitute the main reason why they hardly accumulate in high trophic level organisms. The BSAFs of NBFRs in swimming organisms were much higher than that in mollusks and crustaceans, indicating that a large part of NBFRs accumulated from food webs. The significant positive correlation between TMF and BAF was observed in high trophic level organisms, which demonstrates the important role of high trophic level organisms in evaluating the bioaccumulation effect of NBFRs.

UV-aging process of titanium dioxide nanoparticles aggravates enterohepatic toxicity of bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate to zebrafish

The physicochemical characteristics of titanium dioxide nanoparticles (n-TiO2) may change during the aging process once discharged into aquatic environment. However, how the aging process affects their interactions with co-existing pollutants, as well as the joint toxicity has not been explored. This study investigated how UV-aging impacts n-TiO2 in aquatic environments and their interactions with bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), focusing on their joint toxicity in adult female zebrafish. UV-aging process significantly increased the specific area and hydrophobicity of n-TiO2, promoting the adsorption of TBPH. In vivo experiments revealed that aged n-TiO2 enhanced the bioaccumulation of TBPH in the liver and intestine, worsening hepatic steatosis and intestinal barrier damage. A combined analysis of hepatic lipidomic profiling and intestinal microbiota 16S rRNA sequencing revealed that co-exposure of aged n-TiO2 and TBPH altered gut microbial composition and abundances, facilitating the circulation of lipopolysaccharides (LPS) through the gut-liver axis. Subsequentially, the elevated LPS level in the liver activated the sphingolipid metabolic pathway, resulting in severer lipid metabolism disorders and hepatotoxicity. This study found that UV-aging increases the hydrophobicity and surface area of n-TiO2, enhancing their interaction with the TBPH, which leads to greater bioaccumulation and hepatoxicity through mechanisms involving changes in gut microbiomes and sphingolipid metabolism.

Contamination characteristics and dietary intake risk of brominated flame retardants in fishes around a typical e-waste dismantling site in Southern China

Polybrominated diphenyl ethers (PBDEs) and their substitutes, novel brominated flame retardants (NBFRs), are ubiquitously present in the aquatic environment of electronic waste (e-waste) dismantling region, leading to their inevitable absorption and accumulation by aquatic organisms, which can be transferred to human via directly aquatic product consumption or through food chain, thereby posing potential health risks. This study focused on fish samples from Guiyu and its surrounding areas, and found the total PBDEs concentrations were 24-7400 ng/g lw (mean: 1800 ng/g lw) and the total NBFRs concentrations were 14 to 2300 ng/g lw (mean: 310 ng/g lw). Significant positive correlations were found among PBDE congeners, among different NBFRs, and between NBFRs and commercial PBDEs that they replace. ΣPBDEs and ΣNBFRs in the intestine were 620-350,000 and 91-81,000 ng/g lw (mean: 83000 and 12,000 ng/g lw, respectively), significantly exceeding those in the gills, where ΣPBDEs and ΣNBFRs were 14-37,000 and 39-45,000 ng/g lw (mean: 9200 and 2400 ng/g lw, respectively). The ΣPBDEs and ΣNBFRs showed no non-carcinogenic risks to the target population through dietary intake. Despite the significantly higher daily intake of decabromodiphenyl ethane (DBDPE) compared to decabromodiphenyl ether (BDE209), the non-carcinogenic risk associated with BDE209 remained higher than that of DBDPE. Our findings can assist researchers in understanding the presence of BFRs in aquatic organisms, inhabiting e-waste dismantling areas, and in evaluating the associated health risks posed to humans through dietary exposure.

Fugacity- and biotransformation-based mechanistic insights into the trophic transfer of organophosphate flame retardants in a subtropical coastal food web from the Northern Beibu Gulf of China

The bioaccumulation and trophic transfer of organophosphate flame retardants (OPFRs) in marine ecosystems have attracted great attention in recent research, but our understanding of the trophic transfer mechanisms involved is limited. In this study, we investigated the trophodynamics of OPFRs and their metabolites in a subtropical coastal food web collected from the northern Beibu Gulf, China, and characterized their trophodynamics using fugacity- and biotransformation-based approaches. Eleven OPFRs and all seven metabolites were simultaneously quantified in the shellfish, crustacean, pelagic fish, and benthic fish samples, with total concentrations ranging from 164 to 4.11 × 104 and 4.56-4.28 × 103 ng/g lipid weight, respectively. Significant biomagnification was observed only for tris (phenyl) phosphate (TPHP) and tris (2-ethylhexyl) phosphate (TEHP), while other compounds except for tris(2-chloroethyl) phosphate (TCEP) displayed biomagnification trends based on Monte Carlo simulations. Using a fugacity-based approach to normalize the accumulation of OPFRs in biota to their relative biological phase composition, storage lipid is the predominant biological phase for the mass distribution of 2-ethylhexyl diphenyl phosphate (EHDPHP) and TPHP. The water content and structure protein are equally important for TCEP, whereas lipid and structure protein are the two most important phases for other OPFRs. The mass distribution of these OPFRs along with TLs can explain their trophodynamics in the food web. The organophosphate diesters (as OPFR metabolites) also displayed biomagnification trends based on bootstrapped estimation. The correlation analysis and Korganism-water results jointly suggested the metabolites accumulation in high-TL organisms was related to biotransformation processes. The metabolite-backtracked trophic magnification factors for tri-n‑butyl phosphate (TNBP) and TPHP were both greater than the values that accounted for only the parent compounds. This study highlights the incorporation of fugacity and biotransformation analysis to characterize the trophodynamic processes of OPFRs and other emerging pollutants in food webs.

A review of occurrence, bioaccumulation, and fate of novel brominated flame retardants in aquatic environments: A comparison with legacy brominated flame retardants

Novel brominated flame retardants (NBFRs) have been developed as replacements for legacy brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs). The prevalence of NBFRs in aquatic environments has initiated intense concerns that they resemble to BFRs. To comprehensively elucidate the fate of NBFRs in aquatic environments, this review summarizes the physico-chemical properties, distribution, bioaccumulation, and fates in aquatic environments. 1,2-bis(2,3,4,5,6-pentabromophenyl) ethane (DBDPE) as the major substitute for PBDEs is the primary NBFR. The release from industrial point sources such as e-waste recycling stations is the dominant way for NBFRs to enter the environment, which results in significant differences in the regional distribution of NBFRs. Sediment is the major sink of NBFRs attributed to the high hydrophobicity. Significantly, there is no decreasing trend of NBFRs concentrations, while PBDEs achieved the peak value in 1970-2000 and decreased gradually. The bioaccumulation of NBFRs is reported in both field studies and laboratory studies, which is regulated by the active area, lipid contents, trophic level of aquatic organisms, and the log KOW of NBFRs. The biotransformation of NBFRs showed similar metabolism patterns to that of BFRs, including debromination, hydroxylation, methoxylation, hydrolysis, and glycosylation. In addition, NBFRs show great potential in trophic magnification along the aquatic food chain, which could pose a higher risk to high trophic-level species. The passive uptake by roots dominates the plant uptake of NBFRs, followed by acropetal and basipetal bidirectional transportation between roots and leaves in plants. This review will provide the support to understand the current pollution characteristics of NBFRs and highlight perspectives for future research.

Metabolic activity of gut microbial enrichment cultures from different marine species and their transformation abilities to plastic additives

The role of the gut microbiota in host physiology has been previously elucidated for some marine organisms, but little information is available on their metabolic activity involved in transformation of environmental pollutants. This study assessed the metabolic profiles of the gut microbial cultures from grouper (Epinephelus coioides), green mussel (Perna viridis) and giant tiger prawn (Penaeus monodon) and investigated their transformation mechanisms to typical plastic additives. Community-level physiological profiling analysis confirmed the utilization profiles of the microbial cultures including carbon sources of carbohydrates, amines, carboxylic acids, phenolic compounds, polymers and amino acids, and the plastic additives of organophosphate flame retardants, tetrabromobisphenol A derivates and bisphenols. Using in vitro incubation, triphenyl phosphate (TPHP) was found to be rapidly metabolized into diphenyl phosphate by the gut microbiota as a representative ester-containing plastic additive, whereas the transformation of BPA (a representative phenol) was relatively slower. Interestingly, all three kinds of microbial cultures efficiently transformed the hepatic metabolite of BPA (BPA-G) back to BPA, thereby increasing its bioavailability in the body. The specific enzyme analysis confirmed the ability of the gut microbiota to perform the metabolic reactions. The results of 16S rRNA sequencing and network analysis revealed that the genera Escherichia-Shigella, Citrobacter, and Anaerospora were functional microbes, and their collaboration with fermentative microbes played pivotal roles in the transformation of the plastic additives. The structure-specific transformations by the gut microbiota and their distinct bioavailability deserve more attention in the future.

Bioaccumulation and Trophodynamics of Novel Brominated Flame Retardants (NBFRs) in Marine Food Webs from the Arctic and Antarctic Regions

The pervasive contamination of novel brominated flame retardants (NBFRs) in remote polar ecosystems has attracted great attention in recent research. However, understanding regarding the trophic transfer behavior of NBFRs in the Arctic and Antarctic marine food webs is limited. In this study, we examined the occurrence and trophodynamics of NBFRs in polar benthic marine sediment and food webs collected from areas around the Chinese Arctic Yellow River Station (n = 57) and Antarctic Great Wall Station (n = 94). ∑7NBFR concentrations were in the range of 1.27-7.47 ng/g lipid weight (lw) and 0.09-1.56 ng/g lw in the Arctic and Antarctic marine biota, respectively, among which decabromodiphenyl ethane (DBDPE) was the predominant compound in all sample types. The biota-sediment bioaccumulation factors (g total organic carbon/g lipid) of NBFRs in the Arctic (0.85-3.40) were 4-fold higher than those in the Antarctica (0.13-0.61). Trophic magnification factors (TMFs) and their 95% confidence interval (95% CI) of individual NBFRs ranged from 0.43 (95% CI: 0.32, 0.60) to 1.32 (0.92, 1.89) and from 0.34 (0.24, 0.49) to 0.92 (0.56, 1.51) in the Arctic and Antarctic marine food webs, respectively. The TMFs of most congeners were significantly lower than 1, indicating a trophic dilution potential. This is one of the very few investigations on the trophic transfer of NBFRs in remote Arctic and Antarctic marine ecosystems, which provides a basis for exploring the ecological risks of NBFRs in polar regions.

Aggravated visual toxicity in zebrafish larvae upon co-exposure to titanium dioxide nanoparticles and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate

The bioavailability and toxicity of organic pollutants in aquatic organisms can be largely affected by the co-existed nanoparticles. However, the impacts of such combined exposure on the visual system remain largely unknown. Here, we systematically investigated the visual toxicity in zebrafish larvae after single or joint exposure to titanium dioxide nanoparticles (n-TiO2) and bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) at environmentally relevant levels. Molecular dynamics simulations revealed the enhanced transmembrane capability of the complex than the individual, which accounted for the increased bioavailability of both TBPH and n-TiO2 when combined exposure to zebrafish. Transcriptome analysis showed that co-exposure to n-TiO2 and TBPH interfered with molecular pathways related to eye lens structure and sensory perception of zebrafish. Particularly, n-TiO2 or TBPH significantly suppressed the expression of βB1-crystallin and rhodopsin in zebrafish retina and lens, which was further enhanced after co-exposure. Moreover, we detected disorganized retinal histology, stunted lens development and significant visual behavioral changes of zebrafish under co-exposure condition. The overall results suggest that combined exposure to water borne n-TiO2 and TBPH increased their bioavailability, resulted in severer damage to optic nerve development and ultimately abnormal visual behavior patterns, highlighting the higher potential health risks of co-exposure to aquatic vertebrates.

Bis(2-ethylhexyl)-tetrabromophthalate Poses a Higher Exposure Risk and Induces Gender-Specific Metabolic Disruptions in Zebrafish Liver

Bis(2-ethylhexyl)-tetrabromophthalate (TBPH), a typical novel brominated flame retardant, has been ubiquitously identified in various environmental and biotic media. Consequently, there is an urgent need for precise risk assessment based on a comprehensive understanding of internal exposure and the corresponding toxic effects on specific tissues. In this study, we first investigated the toxicokinetic characteristics of TBPH in different tissues using the classical pseudo-first-order toxicokinetic model. We found that TBPH was prone to accumulate in the liver rather than in the gonad, brain, and muscle of both female and male zebrafish, highlighting a higher internal exposure risk for the liver. Furthermore, long-term exposure to TBPH at environmentally relevant concentrations led to increased visceral fat accumulation, signaling potential abnormal liver function. Hepatic transcriptome analysis predominantly implicated glycolipid metabolism pathways. However, alterations in the profile of associated genes and biochemical indicators revealed gender-specific responses following TBPH exposure. Besides, histopathological observations as well as the inflammatory response in the liver confirmed the development of nonalcoholic fatty liver disease, particularly in male zebrafish. Altogether, our findings highlight a higher internal exposure risk for the liver, enhancing our understanding of the gender-specific metabolic-disrupting potential associated with TBPH exposure.

Bioaccumulation and biotransformation of 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) in zebrafish (Danio rerio)

Despite the increasing production, use, and ubiquitous occurrence of novel brominated flame retardants (NBFRs), little information is available regarding their fate in aquatic organisms. In this study, the bioaccumulation and biotransformation of two typical NBFRs, i.e., 1,2-bis (2,4,6-tribromophenoxyethane) (BTBPE) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH), were investigated in tissues of zebrafish (Danio rerio) being administrated a dose of target chemicals through their diet. Linear accumulation was observed for both BTBPE and TBECH in the muscle, liver, gonads, and brain of zebrafish, and the elimination of BTBPE and TBECH in all tissues followed pseudo-first-order kinetics, with the fastest depuration rate occurring in the liver. BTBPE and TBECH showed low bioaccumulation potential in zebrafish, with biomagnification factors (BMFs) < 1 in all tissues. Individual tissues' function and lipid content are vital factors affecting the distribution of BTBPE and TBECH. Stereoselective accumulation of TBECH enantiomers was observed in zebrafish tissues, with first-eluting enantiomers, i.e. E1-α-TBECH and E1-β-TBECH, preferentially accumulated. Additionally, the transformation products (TPs) in the zebrafish liver were comprehensively screened and identified using high-resolution mass spectrometry. Twelve TPs of BTBPE and eight TPs of TBECH were identified: biotransformation pathways involving ether cleavage, debromination, hydroxylation, and methoxylation reactions for BTBPE and hydroxylation, debromination, and oxidation processes for TBECH. Biotransformation is also a vital factor affecting the bioaccumulation potential of these two NBFRs, and the environmental impacts of NBFR TPs should be further investigated in future studies. The findings of this study provide a scientific basis for an accurate assessment of the ecological and environmental risks of BTBPE and TBECH.

Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate Enhances foxo1-Mediated Lipophagy to Remodel Lipid Metabolism in Zebrafish Liver

An emerging environmental contaminant, bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), can bioaccumulate in the liver and affect hepatic lipid metabolism. However, the in-depth mechanism has yet to be comprehensively explored. In this study, we utilized transgenic zebrafish Tg (Apo14: GFP) to image the interference of TBPH on zebrafish liver development and lipid metabolism at the early development stage. Using integrated lipidomic and transcriptomic analyses to profile the lipid remodeling effect, we uncovered the potential effects of TBPH on lipophagy-related signaling pathways in zebrafish larvae. Decreased lipid contents accompanied by enhanced lipophagy were confirmed by the measurements of Oil Red O staining and transmission electron microscopy in liver tissues. Particularly, the regulatory role of the foxo1 factor was validated via its transcriptional inhibitor. Double immunofluorescence staining integrated with biochemical analysis indicated that the enhanced lipophagy and mitochondrial fatty acid oxidation induced by TBPH were reversed by the foxo1 inhibitor. To summarize, our study reveals, for the first time, the essential role of foxo1-mediated lipophagy in TBPH-induced lipid metabolic disorders and hepatoxicity, providing new insights for metabolic disease studies and ecological health risk assessment of TBPH.

Integrated Studies on Male Reproductive Toxicity of Bis(2-ethylhexyl)-tetrabromophthalate: in Silico, in Vitro, ex Vivo, and in Vivo

Bis(2-ethylhexyl)tetrabromophthalate (TBPH) has been widely detected in the environment and organisms; thus, its toxic effects on male reproduction were systematically studied. First, we found that TBPH can stably bind to the androgen receptor (AR) based on in silico molecular docking results and observed an antagonistic activity, but not agonistic activity, on the AR signaling pathway using a constructed AR-GRIP1 yeast assay. Subsequently, we validated the adverse effects on male germ cells by observing inhibited androgen production and proliferation in Leydig cells upon in vitro exposure and affected general motility and motive tracks of zebrafish sperm upon ex vivo exposure. Finally, the in vivo reproductive toxicity was demonstrated in male zebrafish by reduced mating behavior in F0 generation when paired with unexposed females and abnormal development of their offspring. In addition, reduced sperm motility and impaired germ cells in male zebrafish were also observed, which may be related to the disturbed homeostasis of sex hormones. Notably, the specifically suppressed AR in the brain provides further evidence for the antagonistic effects as above-mentioned. These results confirmed that TBPH affected male reproduction through a classical nuclear receptor-mediated pathway, which would be helpful for assessing the ecological and health risks of TBPH.

Occurrence, Distribution, and Trophic Transfer of Pharmaceuticals and Personal Care Products in the Bohai Sea

The ubiquitous presence of pharmaceuticals and personal care products (PPCPs) in environments has aroused global concerns; however, minimal information is available regarding their multimedia distribution, bioaccumulation, and trophic transfer in marine environments. Herein, we analyzed 77 representative PPCPs in samples of surface and bottom seawater, surface sediments, and benthic biota from the Bohai Sea. PPCPs were pervasively detected in seawater, sediments, and benthic biota, with antioxidants being the most abundant PPCPs. PPCP concentrations positively correlated between the surface and bottom water with a decreasing trend from the coast to the central oceans. Higher PPCP concentrations in sediment were found in the Yellow River estuary, and the variations in the physicochemical properties of PPCPs and sediment produced a different distribution pattern of PPCPs in sediment from seawater. The log Dow, but not log Kow, showed a linear and positive relationship with bioaccumulation and trophic magnification factors and a parabolic relationship with biota-sediment accumulation factors. The trophodynamics of miconazole and acetophenone are reported for the first time. This study provides novel insights into the multimedia distribution and biomagnification potential of PPCPs and suggests that log Dow is a better indicator of their bioaccumulation and trophic magnification.

Bioaccumulation of novel brominated flame retardants in crucian carp (Carassius auratus): Implications for electronic waste recycling area monitoring

Bioaccumulation factor (BAF) of pollutants is an important parameter for evaluating their bioaccumulation potential and an important indicator for evaluating their environmental risks. However, little study exits on the BAF of novel brominated flame retardants (NBFRs). The present study determined 17 NBFRs in 24 water samples in dissolved phase and 93 crucian carp samples collected from an electronic waste recycling site in northern China, in order to examine their contamination, distribution and bioaccumulation. The results showed that the targeted NBFRs were widely detectable in the dissolved phase and crucian carps. In dissolved phase, allyl 2,4,6-tribromophenyl ether (ATE) had the highest detectable rate (100%) and concentration (mean: 1.3 ± 0.62 ng/L), but in crucian carp, hexachlorocyclopentenyl-dibromocyclooctane (HCDBCO) was the one with the highest detectable rate (89%) and concentration (mean: 16 ± 9.2 ng/g wet weight (ww)) among all 17 NBFRs. The discharge and water solubility of NBFRs determined their concentration in the dissolved phase, while the concentration of NBFRs in crucian carp was the results of their discharge and food exposure. The estimated BAFs exceeded 5000 L/kg for petabromoethylbenzene (PBEB), pentabromotoluene (PBT), HCDBCO, pentabromobenzyl acrylate (PBBA), 1,2,3,4,5-pentabromobenzene (PBBZ), 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), hexabromobenzene (HBBZ), and α-1,2,5,6-tetrabromocyclooctane (α-TBCO), suggesting that these compounds were above the hazard standard of bioaccumulation. Although the BAFs of 2,3,5,6-tetrabromo-p-xylene (p-TBX), 1,2-bis(2,4,6-tribromophenoxy)-ethane (BTBPE), α-/β-tetrabromoethylcyclohexane (α-/β-TBECH) and ATE were less than 5000, the potential of bioaccumulation cannot be ignored. The log BAF of tested NBFRs showed a pattern of first increasing and then decreasing with the increase of log KOW, the water solubility of NBFRs, the exposure to fish, the uptake and depuration of fish were the key factor to this pattern. To our knowledge, the BAF values of the most of NBFRs calculated in this study were not reported in the published work previously.

Trophodynamics of halogenated organic pollutants (HOPs) in aquatic food webs

Halogenated organic pollutants (HOPs) represent hazardous and persistent compounds characterized by their capacity to accumulate within organisms and endure in the environment. These substances are frequently transmitted through aquatic food webs, engendering potential hazards to ecosystems and human well-being. The trophodynamics of HOPs in aquatic food webs has garnered worldwide attention within the scientific community. Despite comprehensive research endeavors, the prevailing trajectory of HOPs, whether inclined toward biomagnification or biodilution within global aquatic food webs, remains unresolved. Furthermore, while numerous studies have probed the variables influencing the trophic magnification factor (TMF), the paramount determinant remains elusive. Collating a compendium of pertinent literature encompassing TMFs from the Web of Science between 1994 and 2023, our analysis underscores the disparities in attention accorded to legacy HOPs compared to emerging counterparts. A discernible pattern of biomagnification characterizes the behavior of HOPs within aquatic food webs. Geographically, the northern hemisphere, including Asia, Europe, and North America, has demonstrated greater biomagnification than its southern hemisphere counterparts. Utilizing a boosted regression tree (BRT) approach, we reveal that the food web length and type emerge as pivotal determinants influencing TMFs. This review provides a valuable basis for gauging ecological and health risks, thereby facilitating the formulation of robust standards for managing aquatic environments.

Multi-process regulation of novel brominated flame retardants: Environmentally friendly substitute design, screening and environmental risk regulation

Novel brominated flame retardants (NBFRs), one of the most widely used synthetic flame-retardant materials, have been considered as a new group of pollutants that potentially affect human health. To overcome the adverse effects of NBFRs, a systematic approach for molecular design, screening, and performance evaluation was developed to generate environmentally friendly NBFR derivatives with unaltered functionality. In the present study, the features of NBFRs (long-distance migration, biotoxicity, bioenrichment, and environmental persistence) were determined and characterized by the multifactor comprehensive characterization method with equal weight addition, and the similarity index analysis (CoMSIA) model was constructed. Based on the three-dimensional equipotential diagram of the target molecule 2-ethylhexyl tetrabromobenzoic acid (TBB), 23 TBB derivatives were designed. Of these, 22 derivatives with decreased environmental impact and unaltered functional properties (i.e., flame retardancy and stability) were selected using 3D-QSAR models and density functional theory methods. The health risks of these derivatives to humans were assessed by toxicokinetic analysis; the results narrowed down the number of candidates to three (Derivative-7, Derivative-10, and Derivative-15). The environmental impact of these candidates was further evaluated and regulated in the real-world environment by using molecular dynamics simulation assisted by the Taguchi experimental design method. The relationship between the binding effects and the nonbonding interaction resultant force (TBB derivatives-receptor proteins) was also studied, and it was found that the larger the modulus of the binding force, the stronger the binding ability of the two. This finding indicated that the environmental impact of the designed NBFR derivatives was decreased. The present study aimed to provide a new idea and method for designing NBFR substitutes and to provide theoretical support for restraining the potential environmental risks of NBFRs.

Targeted and non-targeted screening of flame retardants in rural and urban honey

Flame retardants (FRs) are often added to commercial products to achieve flammability resistance, but they are not chemically bonded to the materials, so, they can be easily released into the environment during the production and disposal processes. When honeybees travel to collect nectar during the pollination process, they are prone to be contaminated by chemicals in the air. Therefore, honey contamination has been proposed as an indicator of the pollution status in a particular region. To date, the occurrence of flame retardants in urban honey has yet to be explored. In this study, a direct injection method was used, coupled with LC-QTOF-MS, to analyze honey samples. This method was applied to urban (n = 100) and rural (n = 100) honey samples from the Quebec province (Canada), and the levels of flame retardants in urban and rural honey samples were not significantly different. In the targeted approach, two of the target FRs, tris(2-butoxyethyl) phosphate (TBOEP) and triphenyl phosphate (TPHP), were detected and confirmed at an average trace concentration (<1 ng mL-1). Additionally, a non-targeted screening workflow with an in-house-built library was developed and validated to screen for flame retardants in honey. Tris (2-chloropropyl) phosphate (TCIPP) was identified in honey using the non-targeted screening workflow and confirmed using a pure analytical standard, but there are other compounds detected in the non-targeted analysis that have yet to be validated. This study was the first to report FR compounds based on a direct injection method, coupled with a non-targeted screening workflow, at a trace level in a honey matrix. It also showed that a non-targeted workflow was effective to detect and identify unknown compounds present in the honey sample; hence, this provided a novel angle for the occurrence of FRs in air, with honey as a bio-indicator.

Dietary Uptake of Highly Hydrophobic Chemicals by Rainbow Trout (Oncorhynchus Mykiss)

Rainbow trout (Oncorhynchus mykiss) was exposed through the diet to a mixture of non-ionic organic chemicals for 28 d, followed by a depuration phase, in accordance with OECD method 305. The mixture included hexachlorobenzene (HCB), 2,2',5,5'-tetrachlorobiphenyl (PCB-52), 2,2',5,5'-hexachlorobiphenyl (PCB-153), decachlorobiphenyl (PCB-209), decabromodiphenyl ether (BDE209), decabromodiphenyl ethane (DBDPE), bis-(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (TBPH), perchloro-p-terphenyl (p-TCP), perchloro-m-terphenyl (m-TCP), and perchloro-p-quaterphenyl (p-QTCP), the latter six of which are considered highly hydrophobic based on n-octanol/water partition coefficients (KOW) greater than 108. All chemicals had first-order uptake and elimination kinetics except p-QTCP, whose kinetics could not be verified due to limitations of analytical detection in the elimination phase. For HCB and PCBs, the growth-corrected elimination rates (k2g), assimilation efficiencies (α), and biomagnification factors (BMFL) corrected for lipid content compared well with literature values. For the highly hydrophobic chemicals, elimination rates were faster than the rates for HCB and PCBs, and α's and BMFLs were much lower than those of HCB and PCBs, i.e., ranging from 0.019 to 2.8%, and from 0.000051 to 0.023 (g-lipid/g-lipid), respectively. As a result, the highly hydrophobic organic chemicals were found be much less bioavailable and bioaccumulative than HCB and PCBs. Based on the current laboratory dietary exposures, none of the highly hydrophobic substances would be expected to biomagnify, but Trophic Magnification Factors (TMFs) > 1 have been reported from field studies for TBPH and DBDPE. Additional research is needed to understand and reconcile the apparent inconsistencies in these two lines of evidence for bioaccumulation assessment.

New brominated flame retardant decabromodiphenyl ethane (DBDPE) in water sediments: A review of contamination characteristics, exposure pathways, ecotoxicological effects and health risks

As an alternative to polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) has become one of the most important new brominated flame retardants (NBFRs). However, little is known about whether this emerging contaminant may has an environmental fate similar to PBDEs. Sediments are the main sink for DBDPE in the aqueous phase. Worldwide concentration data, since it was first found in sediments to date, have been collated, and the following conclusions have been drawn. (1) DBDPE concentrations in sediments have increased rapidly, often with a higher risk of contamination in source discharge areas. Compared with other countries, DBDPE contamination in China is more severe, especially in Guangdong Province, which is closely related to its being an e-waste dismantling area. (2) The amount of DBDPE in surface sediments has exceeded that of legacy brominated flame retardants (BFRs), and data recorded in sediment cores also corroborate that DBDPE is replacing decabromodiphenyl ether (BDE-209) as one of the most dominant NBFRs in the environment. (3) The exposure pathways of DBDPE include dietary intake, air or indoor dust intake, cutaneous absorption and endogenous exposure. For sediments, dietary exposure and endogenous exposure pathways need to be considered. Sediment DBDPE can enter the human body through bioenrichment such as contaminated seafood and the food chain. (4) DBDPE can exhibit neurotoxicity, thyrotoxicity, reproductive and developmental toxicity, hepatotoxicity and oxidative stress in organisms. Long-term DBDPE exposure may increase hyperthyroidism risk and inhibit normal cells activity. This review focuses on the distribution characteristics and exposure risks of DBDPE in global water sediments, providing a strong reference for environmental management and related legal policy formulation. The next steps are to focus on continuous source monitoring, process control and sediment clean-up of DBDPE. The development of sustainable water management options for waste microplastics (MPs) and e-waste spiked with DBDPE is a priority.

Occurrence and accumulation characteristics of legacy and novel brominated flame retardants in surface soil and river sediments from the downstream of Chuhe River basin, East China

Surface soil and river sediment samples were collected from the downstream of Chuhe River basin, East China, to investigate the occurrence and accumulation characteristics of legacy and novel brominated flame retardants (NBFRs). The respective concentrations of BDE-209 and nine NBFRs ranged from n.d. to 41.4 ng/g dry weight (dw) and from 0.35 to 362.78 ng/g dw in the collected surface soil samples and ranged from 0.29 to 19.73 ng/g dw and from 0.70 to 66.83 ng/g dw in the collected river sediment samples. Soil samples exhibited a higher potential to accumulate BTBPE while the relative abundance of PBT in the collected sediment samples was significantly higher than that in soils. Even so, BTBPE was the predominant NBFR in both soil and sediment samples. The concentrations and relative abundances of legacy and NBFRs exhibited large spatial variation. The calculated concentration ratios of the total of the nine NBFRs (∑9NBFRs) to BDE-209 (∑9NBFRs/BDE-209) in most of the analyzed samples far exceeded 1, implying a clear shift from legacy brominated flame retardants to NBFRs in the downstream of Chuhe River basin.

Legacy and novel brominated flame retardants in a lab-constructed freshwater ecosystem: Distribution, bioaccumulation, and trophic transfer

The extensive utilization of both legacy and novel brominated flame retardants (BFRs) leads to high environmental concentrations, which would be bioaccumulated by organisms and further transferred through the food webs, causing potential risks to humans. In this study, five BFRs, that showed high detection frequencies and concentrations in sediments from an e-waste dismantling site in Southern China, namely 2,3,4,5,6-pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ethane (DBDPE), and decabromodiphenyl ether (BDE209), were selected as target pollutants in the lab-constructed aquatic food web as part of a micro-ecosystem, to investigate their distribution, bioaccumulation, and trophic transfer patterns. The significant correlations between different samples in the food web indicated that the dietary uptake appeared to influence the levels of BFRs in organisms. Significant negative correlations were observed between the trophic level of organisms and the lipid-normalized concentrations of BTBPE and DBDPE, indicating the occurrence of trophic dilution after 5-month exposure. However, the average values of bioaccumulation factors (BAFs) were from 2.49 to 5.17 L/kg, underscoring the importance of continued concern for environmental risks of BFRs. The organisms occupying higher trophic levels with greater bioaccumulation capacities may play a pivotal role in determining the trophic magnification potentials of BFRs. This research provides a helpful reference for studying the impacts of feeding habits on bioaccumulation and biomagnification, as well as for identifying the fate of BFRs in aquatic environment.

Temporal Trends and Suspect Screening of Halogenated Flame Retardants and Their Metabolites in Blubbers of Cetaceans Stranded in Hong Kong Waters during 2013-2020

Halogenated flame retardants (HFRs) are a large class of chemical additives intended to meet flammability safety requirements, and at present, they are ubiquitous in the environment. Herein, we conducted the target analysis and suspect screening of legacy and novel HFRs and their metabolites in the blubber of finless porpoises (Neophocaena phocaenoides; n = 70) and Indo-Pacific humpback dolphins (Sousa chinensis; n = 35) stranded in Hong Kong, a coastal city in the South China Sea, between 2013 and 2020. The average concentrations of total target HFRs (ΣHFRs) were 6.48 × 10³ ± 1.01 × 10⁴ and 1.40 × 10⁴ ± 1.51 × 10⁴ ng/g lipid weight in porpoises and dolphins, respectively. Significant decreasing temporal trends were observed in the concentrations of tetra-/penta-/hexa-bromodiphenyl ethers (tetra-/penta-/hexa-BDEs) in adult porpoises stranded from 2013-2015 to 2016-2020 (p < 0.05), probably because of their phasing out in China. No significant difference was found for the concentrations of decabromodiphenyl ether and hexabromocyclododecane, possibly due to their exemption from the ban in China until 2025 and 2021, respectively. Eight brominated compounds were additionally identified via suspect screening. A positive correlation was found between the concentrations of tetra-BDE and methyl-methoxy-tetra-BDE (Me-MeO-tetra-BDE) (p < 0.05), indicating that the metabolism of tetra-BDE may be a potential source of Me-MeO-tetra-BDE in marine mammals.

Enzyme-Catalyzed Hydrogen-Deuterium Exchange between Environmental Pollutants and Enzyme-Regulated Endogenous Metabolites

Environmental pollutants can disrupt the homeostasis of endogenous metabolites in organisms, leading to metabolic disorders and syndromes. However, it remains highly challenging to efficiently screen for critical biological molecules affected by environmental pollutants. Herein, we found that enzyme could catalyze hydrogen-deuterium (H-D) exchange between a deuterium-labeled environmental pollutant [D₃₈-bis(2-ethylhexyl) phthalate (D₃₈-DEHP)] and several groups of enzyme-regulated metabolites [cardiolipins (CLs), monolysocardiolipins (MLCLs), phospholipids (PLs), and lysophospholipids (LPLs)]. A high-throughput scanning identified the D-labeled endogenous metabolites in a simple enzyme [phospholipase A₂ (PLA₂)], enzyme mixtures (liver microsomes), and living organisms (zebrafish embryos) exposed to D₃₈-DEHP. Mass fragmentation and structural analyses showed that similar positions were D-labeled in the CLs, MLCLs, PLs, and LPLs, and this labeling was not attributable to natural metabolic transformations of D₃₈-DEHP or incorporation of its D-labeled side chains. Molecular docking and competitive binding analyses revealed that DEHP competed with D-labeled lipids for binding to the active site of PLA₂, and this process mediated H-D exchange. Moreover, competitive binding of DEHP against biotransformation enzymes could interfere with catabolic or anabolic lipid metabolism and thereby affect the concentrations of endogenous metabolites. Our findings provide a tool for discovering more molecular targets that complement the known toxic endpoints of metabolic disruptors.

Trophodynamic of endocrine disrupting compounds in the aquatic food webs: Association with hydrophobicity and biota metabolic rate

Increasing concentration of endocrine disrupting compounds (EDCs) are released into the aquatic environment, resulting in irreversible effects on the endocrine and reproductive systems of biota. How the liver enzymes affect metabolic rate of these compounds and thus their structure-related trophic transfer in aquatic food webs remains largely unknown. In this study, the concentrations of seven common EDCs were measured in 15 species of fish, 7 invertebrate species and plankton collected from Liuxi River to Pearl River, South China. The mean ΣEDC concentrations generally were found to increase as follows: plankton (29.59 ng g^-1 dw) < invertebrate species (50.69 ng g^-1 dw) < fish (122.56 ng g^-1 dw), with 4-nonylphenol (4-NP) and bisphenol S (BPS) as the predominant components. Trophic magnification factors (TMFs) values were >1.0 ranged from 1.30 (BPS) to 4.07 (4-NP), indicating trophic magnification potential. Measurement of metabolism and activities of microsomal CYP450 enzymes were performed in the fish liver microsomes of Hypophthalmichthys molitrix ([TL] = 2.27), Cirrhinus mrigala (TL = 3.87) and Odontamblyopus rubicundus (TL = 4.73). TMFs were significantly negatively correlated with the obtained in vitro biotransformation clearance rates (CL _{in vitro}) of EDCs and CYP450 enzymes activities. A multiple linear regression model indicated that biotransformation clearance is a more powerful predictor for TMFs than the hydrophobicity (Kow) to drive changes in the studied aquatic food web trophodynamics.

Temporal trends in concentrations of brominated flame retardants in UK foodstuffs suggest active impacts of global phase-out of PBDEs and HBCDD

Global restrictions on use of legacy brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) have generated demand for novel BFRs (NBFRs) as substitutes. Our research group has previously reported decreased concentrations of PBDEs and HBCDD and increased concentrations of NBFRs in UK indoor environments, suggesting that restrictions on PBDEs and HBCDD are exerting an impact. In this study, we analysed UK foodstuffs collected in 2020-21 and compared the BFR concentrations found with those found in similar samples collected in 2015 to investigate whether similar trends in BFR concentrations would be observed. Concentrations of PBDEs and HBCDD isomers detected in our samples had declined by 78-92 % and 59-97 % since the 2015 study, respectively. Moreover, concentrations of NBFRs (dominated by 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE or TBE), and bis(2-ethyl hexyl) tetrabromophthalate (BEH-TEBP or TBPH)) in UK foodstuffs increased significantly (28-1400 %) between 2015 and 2020-21. Combined, these findings suggest that restrictions on use of PBDEs and HBCDD have had a discernible impact on concentrations of these legacy BFRs and their NBFR replacements in UK foodstuffs. Interestingly, given recent reports of a significant increase in concentrations of decabromodiphenyl ethane (DBDPE) in UK house dust between 2014 and 2019, a significant decline (70-84 %) in concentrations of DBDPE was observed in UK foodstuffs.

Bioaccumulation and Trophic Transfer of Organophosphate Flame Retardants and Their Metabolites in the Estuarine Food Web of the Pearl River, China

The accumulation and trophodynamics of organophosphate flame retardants (OPFRs) and their metabolites were investigated in the estuarine food web of the Pearl River, China. The mean ∑OPFR concentration among the investigated species increased in the following order: fish [431 ± 346 ng/g lipid weight (lw)] < snail (1310 ± 621 ng/g lw) < shrimp (1581 ± 1134 ng/g lw) < crab (1744 ± 1397 ng/g lw). The di-alkyl phosphates (DAPs) of di-(n-butyl) phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), and diphenyl phosphate (DPHP) were the most abundant metabolites, with concentrations same as or even higher than their corresponding parent compounds. The log bioaccumulation factors for most OPFRs were lower than 3.70, and significant biomagnification was only found for trisphenyl phosphate [TPHP, with the trophic magnification factors (TMFs) > 1]. The TMFs of OPFRs, except for TPHP and tributyl phosphate had a positive correlation with lipophilicity (log K_OW, p ≤ 0.05) and a negative correlation with the biotransformation rate (log K_M, p ≤ 0.05). The mean TMF > 1 was observed for all of the OPFR metabolites based on the bootstrap regression method. The "pseudo-biomagnification" of OPFR metabolites might be attributed to the biotransformation of OPFRs in organisms at high trophic levels.

Occurrence, bioaccumulation and trophic transfer of organophosphate esters in marine food webs: Evidence from three bays in Bohai Sea, China

Due to the widespread use of organophosphate esters (OPEs), the occurrence and trophic transfer of OPEs have attracted attentions in ecosystems. However, as the final sink for these chemicals, the bioaccumulations and trophodynamics of OPEs in marine ecosystems are still not clear. In this study, seawater, sediment and marine organisms collected from Bohai Bay (BHB), Laizhou Bay (LZB), and Liaodong Bay (LDB) in Bohai Sea (BS), China were analyzed to investigate the occurrence, bioaccumulation and trophic transfer of typical OPEs. Total concentration of OPEs (∑₉ OPEs) in surface water in LZB (255.8 ± 36.44 ng/L) and BHB (209.6 ± 35.61 ng/L) was higher than that in LDB (170.0 ± 63.73 ng/L). Marine organisms in LZB accumulated the highest concentrations of OPEs among the 3 bays (∑₁₀OPEs, 70.56 ± 61.36 ng/g ww). Average bioaccumulation factor (BAF) of OPEs in marine organism in BHB, LZB, and LDB was ranged from -2.48 to 0.16, from -2.96 to 1.78, and from -2.59 to 0.59. We also found that trophic magnification factors (TMF) are generally <1, which suggested trophic dilutions of OPEs in BS, China. Nevertheless, the relatively high OPEs levels in BS still may bring potential risks to ecosystem and human health.

Distinct biomagnification of chlorinated persistent organic pollutants in adjacent aquatic and terrestrial food webs

Biomagnification of persistent organic pollutants (POPs) in food webs has been studied for many years. However, the different processes and influencing factors in biomagnification of POPs in aquatic and terrestrial food webs still need clarification. Polychlorinated biphenyls (PCBs) and short-chain chlorinated paraffins (SCCPs) were measured in organisms from adjacent terrestrial and aquatic environment in this study. The median levels of PCBs in terrestrial and aquatic organisms were 21.7-138 ng/g lw and 37.1-149 ng/g lw, respectively. SCCP concentrations were 18.6-87.3 μg/g lw and 21.4-93.9 μg/g lw in terrestrial and aquatic organisms, respectively. Biomagnification factors (BMFs) of PCBs increased with higher log K_OW in all food chains. BMFs of SCCPs were negatively correlated with log K_OW in aquatic food chains, but positively correlated with log K_OW in terrestrial food chains. The terrestrial food web had similar trophic magnification factors (TMFs) of PCBs, and higher TMFs of SCCPs than the aquatic food web. Biomagnification of PCBs was consistent in aquatic and terrestrial food webs, while SCCPs had higher biomagnification potential in terrestrial than aquatic organisms. The distinct biomagnification of SCCPs was affected by the respiratory elimination for terrestrial organisms, the different metabolism rates in various species, and more homotherms in terrestrial food webs. Fugacity model can well predict levels of less hydrophobic chemicals, and warrants more precise toxicokinetic data of SCCPs.

Quinolone distribution, trophodynamics, and human exposure risk in a transit-station lake for water diversion in east China

Quinolone antibiotics (QNs) pollution in lake environments is increasingly raising public concern due to their potential combined toxicity and associated risks. However, the spatiotemporal distribution and trophodynamics of QNs in transit-station lakes for water diversion are not well documented or understood. In this study, a comprehensive investigation of QNs in water, sediment, and aquatic fauna, including norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL), was conducted in Luoma Lake, a major transit station for the eastern route of the South-to-North Water Diversion Project in China. The target QNs were widely distributed in the water (∑QNs: 70.12 ± 62.79 ng/L) and sediment samples (∑QNs: 13.35 ± 10.78 ng/g dw) in both the non-diversion period (NDP) and the diversion period (DP), where NOR and ENR were predominant. All the QNs were detected in all biotic samples in DP (∑QNs: 80.04 ± 20.59 ng/g dw). The concentration of ∑QNs in the water in NDP was significantly higher than those in DP, whereas the concentration in the sediments in NDP was comparable to those in DP. ∑QNs in the water-sediment system exhibited decreasing trends from northwest (NW) to southeast (SE) in both periods; however, the K_oc (organic carbon normalized partition coefficients) of individual QNs in DP sharply rose compared with those in NDP, which indicated that water diversion would alter the environmental fate of QNs in Luoma Lake. In DP, all QNs, excluding NOR, were all biodiluted across the food web; whereas their bioaccumulation potentials in the SE subregion were higher than those in the NW subregion, which was in contrast to the spatial distribution of their exposure concentrations. The estimated daily QN intakes via drinking water and aquatic products suggested that residents in the SE side were exposed to greater health risks, despite less aquatic pollution in the region.

Fate and toxicity of legacy and novel brominated flame retardants in a sediment-water-clam system: Bioaccumulation, elimination, biotransformation and structural damage

Due to the characteristics of persistent organic pollutants (POPs), some legacy brominated flame retardants (LBFRs) were prohibited from use, and then gradually replaced by novel brominated flame retardants (NBFRs). However, till now little research focused on the effects of NBFRs on the benthos. In the present study, 0.5, 5, and 50 mg/kg dw of pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ethane (DBDPE) and decabromodiphenyl ether (BDE209) were added into sediments to test freshwater clams (Corbicula fluminea). In the 35-day exposure experiment, C. fluminea had different enrichment behaviors in three treatment groups. It was conjectured that in the lower dose group, the clams ingested contaminants and tended to be stable over time. While in higher dose groups, the clams were induced by the chemicals, leading to the changes in physiological activities so that the concentrations showed a downward trend first and then went up. The half-lives of contaminants in freshwater clams were between 0.911 and 11.6 days. DBDPE showed stronger bioaccumulation ability than BDE209 in this study. Parabolic relationships were observed between log BSAF and log K_ow values in clam tissues. Debromination, hydroxylation, and methoxylated products were detected. Additionally, the gill samples of C. fluminea exposed to 50 mg/kg dw of single substance were observed by scanning electron microscope (SEM), indicating that the adhesions, tissue hyperplasia, and messy cilia occurred on the surface. Our research potentially contributes to further evaluations of the environmental risks posed in sediments contaminated by PBT, HBB, BTBPE, DBDPE, and BDE209, particularly the benthic organisms.

Metabolic perturbations in human hepatocytes induced by bis (2-ethylhexyl)-2,3,4,5-tetrabromophthalate exposure: Insights from high-coverage quantitative metabolomics

Bis (2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) is an extensively used novel brominated flame retardant that is present ubiquitously in the environment and in biota. However, there is inadequate data on its potential hepatotoxicity to humans. In this study, high-coverage quantitative metabolomics based on ¹²C-/¹³C-dansylation labeling LC-MS was performed for the first time to assess the metabolic perturbations and underlying mechanisms of TBPH on human hepatocytes. HepG2 cells were exposed to TBPH at dosages of 0.1,1,10 μM for 24 or 72 h. Overall, 1887 and 1364 amine/phenol-containing metabolites were relatively quantified in cells and culture supernatant. Our results revealed that exposure to 0.1 μM TBPH showed little adverse effects, whereas exposure to 10 μM TBPH for 24 h enhanced intracellular protein catabolism and disrupted energy and lipid homeostasis-related pathways such as histidine metabolism, pantothenate and CoA biosynthesis, alanine, aspartate and glutamate metabolism. Nevertheless, most of these perturbations returned to the same levels as controls after 72 h of exposure. Additionally, prolonged TBPH exposure increased oxidative stress, as reflected by marked disturbances in taurine metabolism. This study sensitively revealed the dysregulations of intracellular and extracellular metabolome induced by TBPH, providing a comprehensive understanding of metabolic responses of cells to novel brominated flame retardants.

Photodegradation Kinetics and Solvent Effect of New Brominated Flame Retardants (NBFRS) in Liquid Medium

The photolysis of four typical NBFRs, hexabromobenzene (HBB), pentabromotoluene (PBT), pentabromobenzyl acrylateare (PBBA) and pentabromoethylbenzene (PBEB), were explored under different irradiation light wavelengths, initial concentrations and organic solvents. Density functional theory was used for chemical calculation to explore the internal mechanism of solvent effect. All degradation kinetics conformed to the first-order kinetic model. Under different irradiation light wavelengths, the degradation rates were in the following order: 180~400 nm (0.1702~0.3008 min^-1) > 334~365 nm (0.0265~0.0433 min^-1) > 400~700 nm (0.0058~0.0099 min^-1). When the initial concentration varied from 0.25 mg/L to 1 mg/L, the degradation rate decreased from 0.0379~0.0784 min^-1 to 0.0265~0.0433 min^-1 under 334~365 nm irradiation, which might be attributed to the reduction in light energy received per unit area and competition from intermediate metabolites. In different organic solvents, the degradation rates were in the order of acetone (0.1702~0.3008 min^-1) > toluene (0.0408~0.0534 min^-1) > n-hexane (0.0124~0.0299 min^-1). Quantum chemical calculation and analysis showed that the energy change in electron transfer between solvent and NBFRs was the key factor to solvent effect in the degradation of NBFRs. The active sites and degradation pathways of NBFRs were also speculated, the nucleophilic reaction of the Br atom on a benzene ring was the main process of photodegradation and it was preferential to remove the bromine and then the ethyl group on the benzene ring. Our research will be helpful in predicting and evaluating their photochemical behavior in different environment conditions.

In utero exposure to decabromodiphenyl ethane causes rapid growth in mice cubs by activating glycogenolysis and lipid synthesis

Decabromodiphenyl ethane (DBDPE) as a novel brominated flame retardant is frequently detected in environmental media due to its widespread use. Studies have shown that exposure to environmental pollutants in utero could lead to weight loss in newborns and obesity in adulthood. However, the mechanisms of how the cubs grow rapidly from low birth weight to obesity remain unclear. Although it has been reported that perinatal DBDPE exposure caused obesity in the offspring of mice in adulthood, its metabolic changes in offspring juvenile are unknown. Here, we monitored changes of body weight in cubs following exposure to DBDPE in utero. Furthermore, ¹H NMR-based metabolomics was used to investigate the effects of in utero DBDPE exposure on the metabolic profile of neonates included days 1 and 25. Additionally, the expression levels of key genes in the relevant pathways were quantified. The results showed that exposure to high levels of DBDPE in utero caused cubs to be smaller at birth and grow rapidly during lactation. Metabolomics analysis showed that cubs in the exposed group consistently accelerated glycogenolysis and lipid synthesis to promote appetite and energy absorption, and achieved rapid growth in the subsequent lactation, which was further evidenced by the expression levels of genes related to glycolipid metabolism. These results reveal the mechanism for the first time how the weight loss of newborns in utero environmental pollutant exposure transformed into obesity in adulthood, although the exposures here were much higher than would be anticipated from the environment.

Diastereomer- and enantiomer-selective accumulation and depuration of 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexanes (DBE-DBCHs) and 1,2,5,6-tetrabromocyclooctanes (TBCOs) in earthworms (Eisenia fetida)

Due to the regulation of hexabromocyclododecane (HBCD), much attention has been paid to its potential substitutes, 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (DBE-DBCH) and 1,2,5,6-tetrabromocyclooctane (TBCO). DBE-DBCH and TBCO contain several diastereomers and enantiomers, which may exhibit different environmental behaviors and biological effects. In this study, the accumulation and depuration of individual DBE-DBCH and TBCO diastereomers by earthworms (Eisenia fetida) from diastereomer-contaminated soils were evaluated. The accumulation and depuration kinetics of DBE-DBCH and TBCO diastereomers followed one-compartment first-order kinetics. The biota soil accumulation factor (BSAF) of β-DBE-DBCH (2.74 g_oc g_lip^-1) was 1.26 times that of α-DBE-DBCH (2.18 g_oc g_lip^-1), while the BSAF of β-TBCO (2.15 g_oc g_lip^-1) was 1.62 times that of α-TBCO (1.3 g_oc g_lip^-1), showing the diastereomer-specific accumulation of DBE-DBCH and TBCO. DBE-DBCH and TBCO diastereomers appeared to be transformed in earthworm-soil systems; however, no evidence of bioisomerization of the four diastereomers in earthworms was found, and no potential metabolites of debromination and hydroxylation were detected. Furthermore, the selective enrichment of E₁-α-DBE-DBCH and E₁-β-DBE-DBCH (E₁ represents the first enantiomer eluted) occurred in earthworms as the enantiomer fractions (EFs) for α-DBE-DBCH (0.562-0.763) and β-DBE-DBCH (0.516-0.647) were significantly greater than those in the technical products (0.501 for α-DBE-DBCH and 0.497 for β-DBE-DBCH, p < 0.05), especially in the depuration stage. The results demonstrated the diastereomer- and enantiomer-selective accumulation of DBE-DBCH and the diastereomer-selective accumulation of TBCO in the earthworm.

Bioavailability and trophic magnification of antibiotics in aquatic food webs of Pearl River, China: Influence of physicochemical characteristics and biotransformation

Information on trophodynamics of antibiotics and subsequent relationships to antibiotic metabolism in river ecosystem is still unavailable, limiting the evaluation of their bioaccumulation and trophodynamics in aquatic food webs. In the present study, concentrations and relative abundance of 11 antibiotics were investigated in surface water, sediment and 22 aquatic taxa (e.g., fish, invertebrates and plankton) from Pearl River, South China. The logarithmic bioaccumulation factors (log BAFs) of antibiotics generally showed positive relationships with their log D (pH-adjusted log Kow), implying that their bioaccumulation of ionizable antibiotics depends on it is in an ionized form. Higher BAFs of antibiotics in benthic biota were observed than those in fish, indicating that sediment ingestion was a possible route of antibiotic exposure. The logarithmic biota-sediment accumulation factors (log BSAFs) of benthic biota increased when log D increased from -4.79 to -0.01, but declined thereafter. Trophodynamics of antibiotics was investigated, and intrinsic clearance were measured in liver microsomes of Tilapia zillii (trophic level [TL]: 2.5), Anabas testudineu (TL: 3.9), and Coilia grayi (TL: 5.0). Only ciprofloxacin (CFX) showed significant trophic magnification (Trophic Magnification Factor [TMF] = 1.95), and a higher metabolism rate in lower trophic levels suggest that metabolic biotransformation play a significant role in driving biomagnification of antibiotics.

Effects of nano-TiO2 on the bioavailability and toxicity of bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH) in developing zebrafish

Nanoparticles like nano-TiO₂ are suspected to influence the bioavailability and toxicity of co-existing organic or inorganic pollutants differently in aquatic environment. Recently, bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a novel brominated flame retardants (NBFRs) with potential lipid-metabolism disruptive effects, has been detected prevalently in multiple environments including where nano-TiO₂ was also observed. However, their interaction in aqueous phase and modification of nano-TiO₂ on biological processes and toxicity of TBPH at environmental relevant levels remain unknown. Accordingly, we exposed zebrafish embryos to TBPH (1, 10, 100 and 1000 μg/L) alone or with nano-TiO₂ (100 μg/L) until 72 h post-fertilization (hpf) with emphasis on their physicochemical interactions in solutions and variations of bioavailability and toxicity regarding lipid metabolism in vivo. Zeta potential, fourier transform infrared (FTIR) spectroscopy and TEM-EDS revealed adsorption and agglomeration between TBPH and nano-TiO₂in vitro. Decreased body contents of nano-TiO₂ and TBPH implied a reduction of TBPH in bioavailability. The enhanced lipid metabolism and reduced fat storage by TBPH alone were all alleviated by co-exposure to nano-TiO₂. The overall results indicate that nano-TiO₂ adsorbed TBPH to form size-enlarged agglomerates and led to decreased bioavailability and consequently mitigated lipid metabolism disorders in developing zebrafish embryo/larvae.

Habitat-dependent trophic transfer of legacy and emerging halogenated flame retardants in estuarine and coastal food webs near a source region

With the phase-out of legacy halogenated flame retardants (HFRs), such as decabromodiphenyl ether (BDE-209), emerging ones, such as decabromodiphenyl ethane (DBDPE), are being widely produced. We conducted field campaigns to assess the trophic transfer of legacy and emerging HFRs in estuarine and coastal food webs of Laizhou Bay, which are located near the largest HFR manufacturing base in China. Seawater, sediment, plankton, invertebrates, and fish were collected from both sites. BDE-209 was the predominant compound in the estuary, whereas DBDPE was the main contributor to HFRs in the bay, followed by BDE-209. Invertebrates, especially bivalves and sea cucumbers, showed higher levels of BDE-209 and DBDPE than fish. The HFR levels in the organisms of the two coastal zones were comparable to each other, although their concentrations in the estuarine water were one order of magnitude higher than those in the bay. The HFR profiles in benthic organisms were similar to those in the sediments, indicating that the bioaccumulation of HFRs in coastal food webs depended on the habitat. The ΣHFR concentrations followed the order filter-feeding > carnivorous for invertebrates, and demersal non-migratory fish showed higher HFR levels than oceanodromous fish. The trophic magnification factors estimated for BDE-209, dechlorane plus, and DBDPE were lower than 1, suggesting biodilution potential in both food webs, whereas several PBDE congeners exhibited biomagnification capacity. Feeding habits, habitats, hydrophobicity, bioavailability, and metabolism may be the main factors impacting the bioaccumulation of HFRs in organisms in estuarine-coastal ecosystems of northern China.

Novel Brominated Flame Retardants (NBFRs) in a Tropical Marine Food Web from the South China Sea: The Influence of Hydrophobicity and Biotransformation on Structure-Related Trophodynamics

The increasing discharge and ubiquitous occurrence of novel brominated flame retardants (NBFRs) in aquatic environments have initiated intense global concerns; however, little information is available regarding their structure-related trophodynamics in marine food webs. In this study, a tropical marine food web including 29 species (18 fish and 11 invertebrate species) was collected from coral reef waters of the Xisha Islands, the South China Sea, for an analysis of 11 representative NBFRs. The mean ∑NBFR concentrations generally increased in the following sequence: sea cucumbers (0.330 ng/g lw) < crabs (0.380 ng/g lw) < shells (2.10 ng/g lw) < herbivorous fishes (2.30 ng/g lw) < carnivorous fishes (4.13 ng/g lw), with decabromodiphenyl ethane (DBDPE) and hexabromobenzene (HBB) as the predominant components. Trophic magnification was observed for all of the investigated NBFRs, with trophic magnification factors (TMFs) ranging from 1.53 (tetrabromobisphenol A bis(dibromopropyl ether)) to 5.32 (HBB). Significant negative correlations were also found between the TMFs and the tested in vitro transformation clearance rates (CL_in vitro) for the target NBFRs except for bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (TBPH) (p < 0.05). Multiple linear regression analysis confirmed that the transformation rate is a more powerful predictor for TMFs than the hydrophobicity of NBFRs in this marine food web.

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

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

Biodegradation of decabromodiphenyl ethane (DBDPE) by white-rot fungus Pleurotus ostreatus: Characteristics, mechanisms, and toxicological response

Decabromodiphenyl ethane (DBDPE) can pose a potential toxic threat to human beings and the environment. P. ostreatus, as one of the typical white-rot fungi, can effectively degrade various refractory pollutants. The biodegradable characteristics of DBDPE by P. ostreatus, as well as the mechanisms, and toxicological response were investigated in this study. The removal rate reached 47.73% and 43.20%, respectively, for 5 and 20 mg/L DBDPE after 120-h degradation by P. ostreatus. As a coexisting substance, Pb could inhibit the biodegradation. It is found that both the intracellular enzyme (P450) and extracellular enzymes (manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase (Lac)) played a very important role in the biodegradation of DBDPE, of which Lac dominated the degradation. The toxic response was monitored during the degradation. The activities of SOD and CAT were enhanced to eliminate excess ROS in P. ostreatus triggered by DBDPE. In addition, debromination, hydroxylation, and oxidation were inferred as the main degradation pathways preliminarily. The findings provide a theoretical basis for the application of microbial degradation of DBDPE contamination.

Bioaccumulation and trophic transfer of organic ultraviolet absorbents in the food web of a freshwater lake: Implications for risk estimation

Organic ultraviolet absorbents (UVAs) are increasingly reported in environmental matrices and organisms. However, available information on the bioaccumulation of UVAs in freshwater species is insufficient and their trophodynamics in lake food webs remain unknown. We measured the concentrations of twelve UVAs in the wild species from Lake Chaohu. Except for UV-320 not detected, the other UVAs were prevalent in the study species and their total concentrations were in the range of 5.44-131 ng/g dry weight, which were comparable to the concentrations reported in other waters. Compound and species-specific accumulations of UVAs in the organisms were observed. In the lake, the log-transformed concentrations of 4-methyl benzylidene camphor, octyl p-dimethylaminobenzoate, UV-326, and UV-327 related significantly to the trophic levels of species separately. The calculated trophic magnification factors (TMFs) of the four UVAs were 3.79, implying trophic magnification, and 0.18, 0.40 and 0.58, suggesting trophic dilution, respectively. These suggested that the magnification potential and the associated risks of individual UVAs in freshwater lake differed. To our knowledge, this is the first report of these TMFs in lake food webs. However, more investigation is needed to characterize their trophodynamic behaviors in lakes because food web characteristics likely affect trophic transfer of these chemicals.

Bis(2-ethylhexyl)-tetrabromophthalate induces zebrafish obesity by altering the brain-gut axis and intestinal microbial composition

Multiple environmental stressors, including chemicals termed obesogens, contribute to the susceptibility of organisms to obesity. Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a novel brominated flame retardant, is an environmental contaminant that may disrupt lipid metabolism. However, the risk of TBPH leading to obesity remains unknown. Herein, adult female zebrafish fed a normal-fat diet (NFD) or high-fat diet (HFD) were exposed to 0, 0.02 and 2.0 μM TBPH for 6 weeks. The results showed that chronic TBPH exposure lead to significant weight gain, adipocyte hypertrophy, and subcutaneous fat accumulation, which could be enhanced by HFD feeding. HFD individuals also showed significant visceral fat accumulation. Transcription of the main adipokines regulating lipid metabolism associated with the brain-gut axis were significantly affected by TBPH, especially leptin (brain) and adiponectin (intestine). Additionally, peroxisome proliferator-activated nuclear receptor gamma (PPAR-γ) was significantly upregulated in intestine. TBPH increased the abundance of Firmicutes and Bacteroidetes in the gut microbiota in both NFD and HFD groups, resulting in obesity. Interestingly, population diversity analysis indicated that TBPH alone had a comparable impact on gut microbiota composition to that of HDF controls. Thus, TBPH increased the susceptibility of female zebrafish to obesity by disrupting brain-gut axis regulation and gut microbial composition, leading to enhanced fat accumulation under HFD conditions.

Sublethal effects of DBE-DBCH diastereomers on physiology, behavior, and gene expression of Daphnia magna

1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH) is a brominated flame retardant used in commercial and industrial applications. The use of DBE-DBCH containing products has resulted in an increased release into the environment. However, limited information is available on the long-term effects of DBE-DBCH and its effects in aquatic invertebrates. Thus, the present study was aimed at determining how DBE-DBCH diastereomers (αβ and γδ) affects aquatic invertebrates using Daphnia magna as a model organism. Survival, reproduction, feeding, swimming behavior and toxicogenomic responses to environmental relevant concentrations of DBE-DBCH were analyzed. Chronic exposure to DBE-DBCH resulted in decreased lifespan, and reduced fecundity. Expression of genes involved in reproductive processes, vtg1 and jhe, were also inhibited. DBE-DBCH also induced hypoxia by inhibiting the transcription of genes involved in heme biosynthesis and oxygen transport. Furthermore, DBE-DBCH also inhibited feeding resulting in emptiness of the alimentary canal. Increased expression of the stress response biomarkers was observed following DBE-DBCH exposure. In addition, DBE-DBCH diastereomers also altered the swimming behavior of Daphnia magna. The present study demonstrates that DBE-DBCH cause multiple deleterious effects on Daphnia magna, including effects on reproduction and hormonal systems. These endocrine disrupting effects are in agreement with effects observed on vertebrates. Furthermore, as is the case in vertebrates, DBE-DBCH γδ exerted stronger effects than DBE-DBCH αβ on Daphnia magna. This indicate that DBE-DBCH γδ has properties making it more toxic to all so far studied animals than DBE-DBCH αβ.

Occurrence, bioaccumulation, fate, and risk assessment of novel brominated flame retardants (NBFRs) in aquatic environments - A critical review

Novel brominated flame retardants (NBFRs), which have been developed as replacements for legacy flame retardants such as polybrominated diphenyl ethers (PBDEs), are a class of alternative flame retardants with emerging and widespread applications. The ubiquitous occurrence of NBFRs in the aquatic environments and the potential adverse effects on aquatic organisms have initiated intense global concerns. The present article, therefore, identifies and analyzes the current state of knowledge on the occurrence, bioaccumulation, fates, and environmental and health risks of NBFRs in aquatic environments. The key findings from this review are that (1) the distribution of NBFRs are source-dependent in the global aquatic environments, and several NBFRs have been reported at higher concentrations than that of the legacy flame retardants; (2) high bioaccumulative properties have been found for all of the discussed NBFRs due to their strong hydrophobic characteristics and weak metabolic rates; (3) the limited information available suggests that NBFRs are resistant to biotic and abiotic degradation processes and that sorption to sludge and sediments are the main fate of NBFRs in the aquatic environments; (4) the results of ecological risk assessments have indicated the potential risks of NBFRs and have suggested that source areas are the most vulnerable environmental compartments. Knowledge gaps and perspectives for future research regarding the monitoring, toxicokinetics, transformation processes, and development of ecological risk assessments of NBFRs in aquatic environments are proposed.

Brominated flame retardants (BFRs) in marine food webs from Bohai Sea, China

In this study, brominated flame retardants (BFRs), including 13 polybrominated diphenyl ethers (PBDEs) and 17 novel brominated flame retardants (NBFRs) are determined in 18 species (including plankton, invertebrate, and fish) from Bohai Sea, China. Trophic transfer of these compounds is also assessed in the marine food web. Significant trophic magnification (p < 0.01) for 11 PBDE congeners (BDE-17, BDE-28, BDE-47, BDE-49, BDE-66, BDE-85, BDE-99, BDE-100, BDE-153, BDE154 and BDE-183) is observed. No significant correlation is observed for BDE-138 (p = 0.06), and significant trophic dilution is observed for BDE-209 (p < 0.0001). In PBDEs, BDE-66 has the highest TMF value of 3.9 (95% confidence interval (CI): 3.2-4.7), followed by BDE-47 (TMF: 3.8, 95% CI: 2.6-5.4) and BDE-28 (3.0, 2.2-4.1). For NBFRs, ATE, TBECH (include α- and β-isomer), PBBZ, TBCO (include α- and β-isomer), PBT, DPTE, HBBZ, PBBA, BTBPE, PBEB and HCDBCO are observed significant trophic magnification (p < 0.01), significant trophic dilution is observed for BATE (p < 0.01), DBDPE (p < 0.001) and OBIND (p < 0.0001), no significant correlation is observed for p-TBX (p = 0.77). In NBFRs, PBT has the highest TMF value of 4.5 (95% CI: 3.1-6.3), followed by PBEB (TMF: 4.0, 95% CI: 2.1-7.6) and HCDBCO (3.9, 3.1-5.0). Regression analysis between K_OW and TMF values of BFRs suggest that TMF values have a trend of first rising and then falling against the values of log K_OW. Generally, chemicals with higher K_OW value have stronger trophic magnification capacity than those with lower ones, but due to the influence of bioavailability, the trophic magnification ability of the superhydrophobic compounds may be inhibited. To our best knowledge, this is the first report of trophic transfer of NBFRs in marine food web and trophic transfer of 9 NBFRs (α-TBECH, p-TBX, BATE, PBBZ, α-TBCO, β-TBCO, DPTE, OBIND, and HCDBCO) in aquatic food web.

Nonalcoholic Fatty Liver Disease Development in Zebrafish upon Exposure to Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate, a Novel Brominated Flame Retardant

Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (TBPH), a novel brominated flame retardant, can potentially cause lipid metabolism disorder; however, its biological effects on lipid homeostasis remain unknown. We investigated its ability to cause nonalcoholic fatty liver disease (NAFLD) in zebrafish. Female zebrafish were fed a high-fat diet (HFD, 24% crude fat) or normal diet (ND, 6% crude fat), and exposed to TBPH (0.02, 2.0 μM) for 2 weeks. Consequently, HFD-fed fish showed a higher measured concentration of TBPH than ND-fed fish. Further, TBPH-treated fish in the HFD group showed higher hepatic triglyceride levels and steatosis. In comparison to ND-fed fish, treating HFD-fed fish with TBPH led to an increase in the concentration of several proinflammatory markers (e.g., TNF-α, IL-6); TBPH exposure also caused oxidative stress. In addition, the mRNA levels of genes encoding peroxisome proliferator-activated receptors were increased, and the transcription of genes involved in lipid synthesis, transport, and oxidation was upregulated in both ND- and HFD-fed fish. Both the ND and HFD groups also showed demethylation of the peroxisome proliferator-activated receptor-γ coactivator 1-α gene promoter, accompanied by the upregulation of tet1 and tet2 transcription. To summarize, we found that TBPH amplified the disruption of lipid homeostasis in zebrafish, leading to the enhancement of diet-induced NAFLD progression.