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

Emerging contaminants and their potential impacts on estuarine ecosystems: Are we aware of it?

Emerging contaminants (ECs) are becoming more prevalent in estuaries and constitute a danger to both human health and ecosystems. These pollutants can infiltrate the ecosystem and spread throughout the food chain. Because of the diversified sources and extensive human activities, estuaries are particularly susceptible to increased pollution levels. A thorough review on recent ECs (platinum group elements, pharmaceuticals and personal care products, pesticides, siloxanes, liquid crystal monomers, cationic surfactant, antibiotic resistance genes, and microplastics) in estuaries, including their incidence, detection levels, and toxic effects, was performed. The inclusion of studies from different regions highlights the global nature of this issue, with each location having its unique set of contaminants. The diverse range of contaminants detected in estuary samples worldwide underscores the intricacy of ECs. A significant drawback is the scarcity of research on the toxic mechanisms of ECs on estuarine organisms, the prospect of unidentified ECs, warrant research scopes.

Multi-omics analysis reveals BDE47 induces depression-like behaviors in mice by interfering with the 2-arachidonoyl glycerol-associated microbiota-gut-brain axis

2,2',4,4'-tetrabromodiphenyl ether (BDE47) is a foodborne environmental risk factor for depression, but the pathogenic mechanism has yet to be fully characterized. In this study, we clarified the effect of BDE47 on depression in mice. The abnormal regulation of the microbiome-gut-brain axis is evidenced closely associated with the development of depression. Using RNA sequencing, metabolomics, and 16s rDNA amplicon sequencing, the role of the microbiome-gut-brain axis in depression was also explored. The results showed that BDE47 exposure increased depression-like behaviors in mice but inhibited the learning memory ability of mice. The RNA sequencing analysis showed that BDE47 exposure disrupted dopamine transmission in the brain of mice. Meanwhile, BDE47 exposure reduced protein levels of tyrosine hydroxylase (TH) and dopamine transporter (DAT), activated astrocytes and microglia cells, and increased protein levels of NLRP3, IL-6, IL-1β, and TNF-α in the brain of mice. The 16 s rDNA sequencing analysis showed that BDE47 exposure disrupted microbiota communities in the intestinal contents of mice, and faecalibaculum was the most increased genus. Moreover, BDE47 exposure increased the levels of IL-6, IL-1β, and TNF-α in the colon and serum of mice but decreased the levels of tight junction protein ZO-1 and Occludin in the colon and brain of mice. In addition, the metabolomic analysis revealed that BDE47 exposure induced metabolic disorders of arachidonic acid and neurotransmitter 2-Arachidonoyl glycerol (2-AG) was one of the most decreased metabolites. Correlation analysis further revealed gut microbial dysbiosis, particularly faecalibaculum, is associated with altered gut metabolites and serum cytokines in response to BDE47 exposure. Our results suggest that BDE47 might induce depression-like behavior in mice through gut microbial dysbiosis. The mechanism might be associated with the inhibited 2-AG signaling and increased inflammatory signaling in the gut-brain axis.

Methane emission reduction oriented extracellular electron transfer and bioremediation of sediment microbial fuel cell: A review

Sediment is the internal and external source of water environment pollution, so sediment remediation is the premise of water body purification. Sediment microbial fuel cell (SMFC) can remove the organic pollutants in sediment by electroactive microorganisms, compete with methanogens for electrons, and realize resource recycling, methane emission inhibiting and energy recovering. Due to these characteristics, SMFC have attracted wide attention for sediment remediation. In this paper, we comprehensively summarized the recent advances of SMFC in the following areas: (1) The advantages and disadvantages of current applied sediment remediation technologies; (2) The basic principles and influencing factors of SMFC; (3) The application of SMFC for pollutant removal, phosphorus transformation and remote monitoring and power supply; (4) Enhancement strategies for SMFC in sediments remediation such as SMFC coupled with constructed wetland, aquatic plant and iron-based reaction. Finally, we have summarized the drawback of SMFC and discuss the future development directions of applying SMFC for sediment bioremediation.

Occurrence of some legacy and emerging contaminants in feed and food and their ranking priorities for human exposure

The "feed-to-food" pathway is one of the most important routes for human exposure to manmade contaminants. The contaminants could threaten human health through the "feed-to-food" route and have recently become of great public concern. This review selects the representative legacy and emerging contaminants (ECs), such as polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate esters (OPEs), short-chain chlorinated paraffins (SCCPs), and per- and polyfluoroalkyl substances (PFASs), regarding their occurrence in feed and food, as well as their metabolites and transport in farming and livestock ecosystems. Factors that might influence their presence and behavior are discussed. This review raises an approach to rank the priority of ECs using the EC concentrations in feed and food and using the hazard quotient (HQ) method for human health. Although SCCPs have the highest levels in feed and food, their potential risks appear to be the lowest. PFASs have the highest HQs on account of human exposure risk. Future research should pay more attention to the combined effects of multiple ECs.

Biotransformation kinetics and pathways of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and its hydroxylated and methoxylated derivatives (6-OH-BDE-47 and 6-MeO-BDE-47) in earthworms (Eisenia fetida)

As a class of persistent organic pollutant, polybrominated diphenyl ethers (PBDEs) and their hydroxylated and methoxylated derivatives (OH-PBDEs and MeO-PBDEs) have been widely detected in soil environments. However, studies on the bioavailability and transformation of PBDEs and their derivatives in soil organisms remain scarce. In this study, a detailed kinetic investigation on the accumulation and biotransformations of BDE-47, 6-MeO-BDE-47 and 6-OH-BDE-47 in earthworms (Eisenia fetida) exposed to artificially contaminated soils was conducted. The uptake and elimination kinetics of BDE-47, 6-MeO-BDE-47 and 6-OH-BDE-47 by earthworms were in accordance with a one-compartment first-order kinetic model. The bioaccumulation factors (BAFs) followed the order 6-MeO-BDE-47 > 6-OH-BDE-47 > BDE-47. All three compounds could undergo step-by-step debromination to produce lower brominated analogs in earthworms. Both BDE-47 and 6-OH-BDE-47 could be transformed to MeO-PBDEs, whereas no transformation from 6-OH-BDE-47 or 6-MeO-BDE-47 to PBDEs or from BDE-47 and 6-MeO-BDE-47 to OH-PBDEs took place in the earthworms. Methoxylation was proposed as a potential metabolic pathway to form MeO-PBDEs in earthworms, with the metabolic rates for the methoxylation of BDE-47 and 6-OH-BDE-47 being 27.7 and 5.1 times greater, respectively, than that of the debromination metabolism. The isomers of 6-MeO-BDE-47 and 6-OH-BDE-47 were formed via the addition of methoxy/hydroxy groups or via bromine shifts on benzene ring in the earthworms. This study provides comprehensive information for a better understanding of the accumulation and biotransformation of PBDEs and their derivatives in earthworms.

A Review of Hydroxylated and Methoxylated Brominated Diphenyl Ethers in Marine Environments

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) are present in the marine environment worldwide. Both OH-PBDEs and MeO-PBDEs are known natural products, whereas OH-PBDEs may also be metabolites of PBDEs. There is growing concern regarding OH-PBDEs as these compounds seem to be biological active than PBDEs. In the present study, we reviewed the available data on the contamination of OH/MeO-PBDEs in the marine environment worldwide, including seawater, marine sediment, marine plants, invertebrates, fish, seabirds and mammals. Bioaccumulation and biomagnification of OH/MeO-PBDEs in the marine food web were summarized as well. This study also proposes the future research of OH/MeO-PBDEs, including the production and the synthesis pathway of OH/MeO-PBDEs, the toxicokinetics of OH/MeO-PBDEs and the toxicology and human exposure risk assessment.

Effects of carbon source on electricity generation and PAH removal in aquaculture sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) have been used for treating pollutants in sediment or overlying water. This study investigated the feasibility of constructing SMFCs under aquaculture conditions by employing indigenous carbohydrates as substrates to enhance the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) in sediment, as well as the correlation between PAHs removal and electricity generation in SMFCs. The results showed that adding glucose could allow SMFCs to generate more electrical power and increase the removal efficiency of PAHs (by 57.2% for naphthalene, 41.3% for acenaphthene, and 36.5% for pyrene). In addition, starch enhanced PAHs removal by 49.9%, 35.8%, and 31.2%, respectively, whereas cellulose enhanced removal by 44.3%, 29.3%, and 26.9%, respectively. Pearson correlation coefficients between the level of electrical power generated and the removal masses of the three PAHs were 0.485, 0.830**, and 0.851**. Thus, the use of SMFCs could be an effective approach for PAH treatment in aquaculture, and the electrical power generated could be used as an in-situ indicator for the biodegradation rate of SMFCs.

Widespread occurrence of emerging E-waste contaminants - Liquid crystal monomers in sediments of the Pearl River Estuary, China

Liquid crystal monomers (LCMs), commonly used in screens of electronic devices, have recently been identified as a group of emerging chemicals of concern associated with e-waste. They are potentially persistent, bioaccumulative, and toxic substances, and may pose a threat to the marine ecosystem. The Pearl River Estuary (PRE) receives organic contaminants discharged from the Pearl River Delta region, where primitive handling of e-waste is widespread. However, information on the pollution status of LCMs in the PRE is absent. Herein, a rapid and robust analytical method was established using ultrasonic extraction, solid phase extraction cleanup, and GC-Orbitrap-MS analysis. The spatial distribution of 39 target LCMs was investigated in 45 surface sediment samples from the PRE. Ten LCMs were detected, with ΣLCMs ranged from 0.9 to 31.1 ng/g dry weight. Our results demonstrated a widespread occurrence of LCMs in the sediments of the PRE, and a gradient of their contamination from inshore to offshore regions, indicating land-based origins. Our reported ΣLCMs concentrations were relatively higher compared to many other legacy and emerging pollutants found in the same investigated area. Preliminary risk assessment showed 3VbcH, Pe3bcH and tFMeO-3bcHP might be the top 3 risk contributors in the PRE. Further investigation on the ecological impact of LCMs on marine benthic ecosystems, as well as identification of their sources and control measures are warranted.

Human exposure to polybrominated diphenyl ethers (PBDEs) through the diet: An update of the scientific literature

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame-retardants (BFRs). As for other persistent organic pollutants, dietary intake (followed by dust inhalation) is the main route of human exposure to PBDEs. In 2012, we reviewed the scientific literature on the concentrations of PBDEs in foodstuffs and their dietary exposure. The current review is aimed at updating the results of recent studies (2012-2022) focused on determining the levels of PBDEs in food samples, as well as the dietary intake of these compounds. We have revised studies conducted over the world. The current information on the concentrations of PBDEs in food and their dietary intake is now much more notable than that available in our previous review, being China the country contributing with the highest number of studies. Because of the important differences in materials and methods used in the available studies, the comparison of results is certainly complicated. However, there seems to be a general trend towards a decrease in the levels of PBDEs in foods, and consequently, in the dietary intake of these contaminants. The lack of tolerable daily intakes of PBDEs is an issue that needs to be solved for assessing human health risks of these BFRs.

Effect of starch-derived organic acids on the removal of polycyclic aromatic hydrocarbons in an aquaculture-sediment microbial fuel cell

This study constructed sediment microbial fuel cells (SMFCs) for polycyclic aromatic hydrocarbons (PAHs) removal in contaminated aquaculture sediment. Starch, a waste deposited in aquaculture sediment, was employed as the co-substrate for electricity generation and PAHs removal, and the effect of starch-derived organic acids on SMFC performance was assessed. The results indicated that sufficient starch promoted PAHs removal (69.9% for naphthalene, 55.6% for acenaphthene, and 46.8% for pyrene) in dual-chamber SMFC, whereas excessive starch attenuated SMFC performance because the organic acids accumulation reduced anode pH, decreased species diversity, and changed the microbial communities. The electricity generation and PAHs removal were positively correlated (R > 0.96), and both of them were related to Macellibacteroides belonging to Bacteroidetes. However, a larger single-chamber SMFC device did not obtain enhanced PAHs removal owing to the restricted "effective range" of the anode. Hence, more challenges need to be addressed to realize the practical application of SMFC.

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

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

Concentration profile, spatial distributions and temporal trends of polybrominated diphenyl ethers in sediments across China: Implications for risk assessment

Polybrominated diphenyl ethers (PBDEs) in sediments of China have been extensively investigated; however, most studies conducted to date have focused on specific locations, and the pollution and risk posed by these chemicals in sediments at the national scale remain unknown. Therefore, we analyzed the concentrations and risks of PBDEs in sediments in China and their spatiotemporal variations based on available literature. Overall, the sediments across China contain moderate to high levels of PBDEs, with BDE-209 being the dominant congener, followed by BDE-47 and BDE-99. The sediment concentrations of PBDEs were highest in southern China and lowest in northeastern China. Additionally, based on their PBDE concentrations, 18.4%, 30.0%, and 11.9% of sediment samples from rivers, lakes, and coastal waters, respectively, posed low to moderate eco-toxicological risks, but 6.90% of river sediments posed high risks. Between 2001 and 2017, the concentrations and risks of PBDEs in the sediments from rivers and coastal waters tended to decrease gradually. Additionally, there were low to moderate risks from PBDEs in lake sediments, and the risks in 2012-2017 were 3.30 times higher than those in 2006-2011. However, more studies about the spatial and temporal trends in PBDEs in sediment across China and their impacts on aquatic organisms are needed because there is still a general lack of relevant information.

Effects of cooking on oral bioaccessibility of PBDEs, MeO-PBDEs, and OH-PBDEs in fish (tilapia) and chicken egg

Human health concerns are rising with polybrominated diphenyl ethers' (PBDEs) analogues, methoxylated and hydroxylated PBDEs (MeO-PBDEs and OH-PBDEs), due to their occurrences in foods and greater potential toxicological effects than PBDEs. While the oral bioaccessibilities (BA%) of PBDEs in foods are available, such information on MeO-PBDEs and OH-PBDEs, and the effects of cooking on them have not been adequately addressed. The present study was conducted with fish and chicken egg as typical foods to assess the bioaccessibility (BA%) of PBDEs, MeO-PBDEs, and OH-PBDEs using the colon extended physiologically based extraction test and examine the effects of cooking processes (boiling, frying, and steaming) on them. The results showed that thermal degradation or transformation of the target compounds did not occur during boiling and frying of fish. The BA% of individual PBDEs, MeO-PBDEs, and OH-PBDEs were 20-51% for boiled fish, 11-20% for pan-fried fish, 15-77% for steamed egg, and 42-68% for pan-fried egg. Cooking decreased the BA% of all target compounds in fish due to protein denaturation. However, the BA% of OH-PBDEs in pan-fried egg were greater than those in steamed egg. In addition, the substituent groups of CH₃O- and OH- did not pose any effects on the BA% of BDE-47 in fish, but OH-group decreased its BA% in egg. These findings suggested that MeO-PBDEs and OH-PBDEs exhibited the similar oral BA% in fish to PBDEs, but the underlying mechanism for the effects of cooking on BA% of OH-PBDEs in egg needs to be further investigated.

Bioaccumulation and Trophic Transfer of Polybrominated Diphenyl Ethers and Their Hydroxylated and Methoxylated Analogues in Polar Marine Food Webs

Arctic and Antarctic marine ecosystems, which are important components of global biodiversity, have been severely threatened by environmental pollutants in recent decades. In this study, polybrominated diphenyl ethers (PBDEs) and their hydroxylated and methoxylated analogues (OH-PBDEs and MeO-PBDEs) were analyzed in seawater, sediment, and marine organisms (algae, invertebrates, and fishes) collected surrounding the Arctic Yellow River Station (n = 83) and the Antarctic Great Wall Station (n = 72). PBDEs and the analogues were detectable in all polar marine matrices, except MeO-PBDEs in seawater. The concentrations of ∑PBDEs, ∑MeO-PBDEs, and ∑OH-PBDEs in the marine organisms were in the range of 0.33-16 ng/g lipid weight (lw), n.d.-2.6 ng/g lw, and 0.12-2.3 ng/g lw in the Arctic and 0.06-31 ng/g lw, n.d.-5.8 ng/g lw, and 0.17-35 ng/g lw in Antarctica, respectively. Biota-sediment bioaccumulation factor (BSAF, g TOC/g lipid) values of MeO-PBDEs (0.002-0.14) and OH-PBDEs (0.004-0.18) were lower than the BSAF values of PBDEs (0.85-12). Trophic magnification was found for ∑MeO-PBDEs, whereas trophic dilution was observed for ∑OH-PBDEs in both regions. This is one of very few investigations on trophic transfer of PBDE metabolites in the Antarctic and Arctic regions and will further strengthen concerns about the ecological risk of PBDE metabolites in remote areas.

Inevitable human exposure to emissions of polybrominated diphenyl ethers: A perspective on potential health risks

Polybrominated diphenyl ethers (PBDEs) serve as flame retardants in many household materials such as electrical and electronic devices, furniture, textiles, plastics, and baby products. Though the use of PBDEs like penta-, octa- and deca-BDE greatly reduces the fire damage, indoor pollution by these toxic emissions is ever-growing. In fact, a boom in the global market projections of PBDEs threatens human health security. Therefore, efforts are made to minimize PBDEs pollution in USA and Europe by encouraging voluntary phasing out of the production or imposing compelled regulations through Stockholm Convention, but >500 kilotons of PBDEs still exist globally. Both 'environmental persistence' and 'bioaccumulation tendencies' are the hallmarks of PBDE toxicities; however, both these issues concerning household emissions of PBDEs have been least addressed theoretically or practically. Critical physiological functions, lipophilicity and toxicity, trophic transfer and tissue specificities are of utmost importance in the benefit/risk assessments of PBDEs. Since indoor debromination of deca-BDE often yields many products, a better understanding on their sorption propensity, environmental fate and human toxicities is critical in taking rigorous measures on the ever-growing global deca-BDE market. The data available in the literature on human toxicities of PBDEs have been validated following meta-analysis. In this direction, the intent of the present review was to provide a critical evaluation of the key aspects like compositional patterns/isomer ratios of PBDEs implicated in bioaccumulation, indoor PBDE emissions versus human exposure, secured technologies to deal with the toxic emissions, and human toxicity of PBDEs in relation to the number of bromine atoms. Finally, an emphasis has been made on the knowledge gaps and future research directions related to endurable flame retardants which could fit well into the benefit/risk strategy.

Insight into the transplacental transport mechanism of methoxylated polybrominated diphenyl ethers using a BeWo cell monolayer model

Methoxylated polybrominated diphenyl ethers (MeO-PBDEs), a type of emerging environmental contaminants, can accumulate through the food chain and eventually enter the human body. For pregnant women, these chemicals may be transplacentally transported to their fetuses, causing early intrauterine exposure. This study was designed to explore the transport process and characteristics of MeO-PBDEs using a BeWo cell monolayer model to simulate the placental barrier effect. Concentration-dependent transplacental transport indicates that the transport of MeO-PBDEs may be dominated by passive diffusion within the studied concentration range. According to the apparent permeability coefficients, MeO-BDE congeners investigated can be classified as poorly transported compounds, with the exception of MeO-BDE28. Time-dependent transplacental transport was observed (R² = 0.97-0.99), which showed that the intracellular accumulation of MeO-PBDEs followed pseudo-first-order kinetics process. The transport process of MeO-PBDEs in the BeWo cell assay was not found to be sensitive to the pH of 6.5-7.4. An efflux transporter, breast cancer resistance protein, may be involved in the transport process of some MeO-PBDE congeners, and influx transporters, including organic anion transporters and organic cation transporters, may also be involved in the transport process. Although the present results indicated the possible transplacental transport mechanism, more molecular biological studies should be conducted to advance the understanding of the transport mechanisms.

Organochlorine pesticides, brominated flame retardants, synthetic musks and polycyclic aromatic hydrocarbons in shrimps. An overview of occurrence and its implication on human exposure

Shrimps are widely distributed in coastal areas, estuaries and rivers. Although this shellfish is a good source of nutrients, it can also accumulate environmental contaminants, such as organochlorine pesticides (OCPs), brominated flame retardants (BFRs), synthetic musks (SMs) and polycyclic aromatic hydrocarbons (PAHs). Due to their bioaccumulative properties, these pollutants are endocrine disruptors. In this review, an overview of the world's shrimp market, pollutants legislation and values found in shrimp samples will be discussed. Shrimps analysed from all continents showed the presence of contaminants, Asia being the continent with the highest values reported. The concentration values reached a maximum of 26100 ng/g wet weight (ww) for OCPs, of 226.45 ng/g ww for BFRs, of 12.1 ng/g ww for SMs and of 50650 ng/g ww for PAHs. Exposure data and risk, taken from different studies, are very variable and indicate that shrimp's consumption may represent a risk especially in certain geographic areas.

Occupational and dietary differences in hydroxylated and methoxylated PBDEs and metals in plasma from Puget Sound, Washington, USA region volunteers

Electronic waste (E-waste) recycling is a rapidly growing occupation in the USA with the potential for elevated exposure to flame retardants and metals associated with electronic devices. We previously measured polybrominated diphenyl ethers (PBDEs) in plasma from E-waste workers and found them similar to non-E-waste workers. This study focused on structurally related PBDE derivatives, the hydroxylated (OH-PBDEs) and methoxylated (MeO-PBDEs) forms along with metals known to occur in E-waste. Humans can metabolize PBDEs and some MeO-PBDEs into OH-PBDEs, which is a concern due to greater health risks associated with OH-PBDEs. We measured 32 different OH-PBDEs and MeO-PBDEs in plasma samples provided by 113 volunteers living in the greater Puget Sound region of Washington State, USA. We measured 14 metals in a subset of 10 E-waste and 10 non-E-waste volunteers. Volunteers were selected based on occupational and dietary habits: work outdoors and consume above average amounts of seafood (outdoor), electronic waste recycling (E-waste) or non-specific indoor occupations (indoor). A two-week food consumption diary was obtained from each volunteer prior to blood sampling. OH-PBDEs were detected in all volunteers varying between 0.27 and 102 ng/g/g-lipid. The MeO-PBDEs were detected in most, but not all volunteers varying between n.d. - 60.4 ng/g/g-lipid. E-waste recyclers had OH-PBDE and MeO-PBDE plasma levels that were similar to the indoor group. The outdoor group had significantly higher levels of MeO-PBDEs, but not OH-PBDEs. Comparison of plasma concentrations of BDE-47 with its known hydroxylated metabolites suggested OH-PBDE levels were likely determined by biotransformation and at least two subpopulations identified differing in their apparent rates of OH-PBDE formation. The metals analysis indicated no significant differences between E-waste workers and non-E-waste workers. Our results indicate E-waste workers do not have elevated plasma levels of these contaminants relative to non-E-waste workers.

Legacy and Emerging Brominated Flame Retardants in Bizerte Lagoon Murex (Hexaplex Trunculus): Levels and Human Health Risk Assessment

Occurrence of traditional (PBDEs) and novel (HBB, PBEB, DBDPE) brominated flame retardants, as well as the natural compounds of MeO-PBDEs, were studied in a shellfish species (Hexaplex trunculus) sampled from Bizerte Lagoon. PBDE and MeO-PBDE mean concentrations in murex soft tissues were 187 and 264 ng g^-1 lw respectively. The alternative flame retardants were not identified. The sum of PBDE and MeO-PBDE levels recorded in murex from the investigated aquatic ecosystem were comparable or a relatively lower than those reported for other organisms from other regions across the world. The amount of PBDE and MeO-PBDE concentrations from the Bizerte Lagoon recorded in murex were comparable or a relatively lower than those recorded from other areas across the world for other species. There is not a danger to the population health with regard to PBDE intakes associated with the consumption of murex in Bizerte city. We believe that this is the first study of the analysis of these pollutants in marine gastropod mollusks from Tunisian aquatic areas.

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

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

Sponge-derived polybrominated diphenyl ethers and dibenzo-p-dioxins, irreversible inhibitors of the bacterial α-d-galactosidase

An integrated in vitro and in silico approach was applied to evaluate the potency of hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and spongiadioxins (OH-PBDDs) isolated from Dysidea sponges on the activity of the recombinant α-d-galactosidase of the GH36 family. It was revealed for the first time that all compounds rapidly and apparently irreversibly inhibited the bacterial α-d-galactosidase. The structure-activity relationship study in the series of OH-PBDEs showed that the presence of an additional hydroxyl group in 5 significantly enhanced the potency (IC50 4.26 μM); the increase of bromination in compounds from 1 to 3 increased their potency (IC50 41.8, 36.0, and 16.0 μM, respectively); the presence of a methoxy group decreased the potency (4, IC50 60.5 μM). Spongiadioxins 6, 7, and 8 (IC50 16.6, 33.1, and 28.6 μM, respectively) exhibited inhibitory action comparable to that of monohydroxylated diphenyl ethers 1-3. Docking analysis revealed that all compounds bind in a pocket close to the catalytic amino acid residues. Molecular docking detected significant compound-enzyme interactions in the binding sites of α-d-galactosidase. Superimposition of the enzyme-substrate and the enzyme-inhibitor complexes showed that their binding sites overlap.

Species and habitat-dependent accumulation and biomagnification of brominated flame retardants and PBDE metabolites

The occurrence, species- and habitat-dependent distribution of brominated flame retardants (BFRs) and PBDE metabolites comprising 27 polybrominated diphenyl ethers (PBDEs), 3 hexabromocyclododecanes (HBCDs), tetrabromobisphenol A (TBBPA), 17 methoxylated (MeO-) BDEs, and 8 hydroxylated (OH-) BDEs were determined in marine environments (sediment and seawater) and 20 biota species in food web in the southern part of Korea. The concentration of HBCDs was statistically higher in both pelagic (5.73-60.1 ng/g lipid weight [lw]) and demersal fish (2.45-31.3 ng/g lw), whereas a higher level of OH-BDEs was observed in benthic invertebrates (2.48-40.7 ng/g lw), suggesting different composition of BFRs and PBDE metabolites between species. The concentrations of TBBPA and MeO-BDEs were significantly higher in pelagic fish (1.31-11.3, 6.15-61.5 ng/g lw) than in demersal fish (not detected [N.D.]-4.45, 0.956-8.52 ng/g lw) and benthic invertebrates (N.D.-8.11, 0.182-4.65 ng/g lw), reflecting a dependence on habitat. Additionally, analogue distribution of PBDEs in pelagic fish was similar to that in seawater, whereas the distribution in demersal fish and benthic invertebrates was similar to the distribution in sediment. The bioconcentration factor (BCF) and trophic magnification factor (TMF) of α-HBCD, some of PBDEs, and 6-MeO-BDE47 were up to 5000 and 1, respectively, suggesting strong bioaccumulation and biomagnification.

Brominated Flame Retardants, Microplastics, and Biocides in the Marine Environment: Recent Updates of Occurrence, Analysis, and Impacts

Emerging contaminants (ECs) may pose adverse effects on the marine ecosystem and human health. Based on the analysis of publications filed in recent years, this paper provides a comprehensive overview on three prominent groups of ECs, i.e., brominated flame retardants, microplastics, and biocides. It includes detailed discussions on: (1) the occurrence of ECs in seawater, sediment, and biota; (2) analytical detection and monitoring approaches for these target ECs; and (3) the biological impacts of the ECs on humans and other trophic levels. This review provides a summary of recent advances in the field and remaining knowledge gaps to address, to enable the assessment of risk and support the development of regulations and mitigation technologies for the control of ECs in the marine environment.