Polybrominated diphenyl ethers in surface sediments from fishing ports along the coast of Bohai Sea, China

The screening of priority pollutants in the Bohai Sea based on ecological risk assessment

The Bohai Sea (BS) is a semi-enclosed inland sea and China's most polluted coastal sea. With the rapid economic development of the circum-Bohai Sea region, large amounts of pollutants have been discharged into the BS, posing a significant threat to human health and the ecosystem. Great efforts have been made on investigating the levels of various pollutants in the BS; however, the priority pollutants which are required for the implementation of suitable environmental management and remediation measures in this system remain unclear. By using the risk quotient method, this study evaluated the ecological risks of various pollutants (including antibiotics, heavy metals, total petroleum hydrocarbons (TPHs), endocrine disruptors, pesticides, and persistent organic pollutants) in BS water and sediments over the past twelve years to identify the priority pollutants in this system. The results showed that 8 and 10 pollutants were at risk in BS water and sediments, respectively. Overall, 13 pollutants (arsenic (As), copper (Cu), mercury (Hg), nickel (Ni), chromium (Cr), lead (Pb), zinc (Zn), cadmium (Cd), TPHs, bisphenol A (BPA), erythromycin, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs)) in the BS were identified to have potential risks and should be included in the list of priority pollutants. The monitoring of the changes in the contents of these pollutants in BS water and sediments needs to be strengthened in the future.

Regional BDE-209 emission, environmental fate and risks: Methods establishment, data filling and feature analysis

BDE-209 is an emerging environmental contaminant that poses a significant threat to human health. Despite its inclusion in the Stockholm Convention, the current regional emission levels, environmental fate, and corresponding risks remain unclear, especially with the ongoing release of BDE-209 during the disposal of waste electrical and electronic equipment. The significant gaps in BDE-209 emission data highlight the need for a regional approach to better understand these issues. Therefore, we established a method to identify regional BDE-209 emissions, environmental fate, and risks in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) using a substance flow analysis framework, fugacity model, and risk model. Our results showed: (1) Despite the increasing pressure of electronic waste, emissions have decreased with gradual strengthening of restrictions. The stage with the highest contribution to emissions is flame-retardant plastic production, which accounts for 41 % of emissions, followed by informal treatment (36 %). (2) The largest BDE-209 emissions are into air and soil, at 7.23 t and 4.56 t, respectively, and the highest reserves are in soil and sediment. (3) Infants and young children have the highest levels of exposure and cancer risk. This research helps fill the multi-regional data gap for BDE-209 and clarify the complex regional emission situation in the GBA.

Advanced understanding of the polybrominated diphenyl ethers (PBDEs): Insights from total environment to intoxication

Polybrominated diphenyl ethers (PBDEs) are brominated compounds connected by ester bonds between two benzene rings. There are 209 congeners of PBDEs, classified according to the number and position of the bromine atoms. Due to their low cost and superior flame retardant properties, PBDEs have been extensively used as flame retardants in electronic products, plastics, textiles, and other materials since the 1970s. PBDEs are classified as persistent organic pollutants (POPs) under the Stockholm Convention because of their environmental persistence, bioaccumulation, and toxicity to both humans and wildlife. Due to their extensive use and significant quantities, PBDEs have been detected across a range of environments and biological organisms. These compounds are known to cause damage to the metabolic system, exhibit neurotoxicity, and pose reproductive hazards. This review investigates the environmental distribution and human exposure pathways of PBDEs. Using China-a country with significant PBDE use-as an example, it highlights substantial regional and temporal variations in PBDE concentrations and notes that certain environmental levels may pose risks to human health. The article then examines the toxic effects and mechanisms of PBDEs on several major target organs, summarizing recent research and the specific mechanisms underlying these toxic effects from multiple toxicological perspectives. This review enhances our understanding of PBDEs' environmental distribution, exposure pathways, and toxic mechanisms, offering valuable insights for further research and management strategies.

Reducing baseline toxicity in fishery product-related sediments from land to sea: Region-specific solutions are required

Eastern China is a major producer of fishery products (including inland aquaculture, coastal mariculture, and coastal fishing products). The quality of the products is affected by hydrophobic organic contaminants (HOCs) in the sediments. Based on in-vitro luminescent bacterial assay, the baseline toxicity (BEQBio) of 56 common HOCs were assessed in the present study. Specifically, the BEQBio of sediments declined from land (31-400 mg/kg) to sea (9.1-270 mg/kg). However, the toxicity contribution explained by the HOCs increased gradually from land (0.70 %) to sea (10 %) using Iceberg Modeling. In the inland pond, current use HOCs (pyrethroid pesticide (PEs), organic tin (OTCs), and antibiotic) exhibited considerable concentrations, although their toxicity contribution was very small (0.076 %), thus more regulations on the use of HOCs should be proposed and further screening is needed to confirm the major toxicants. In coastal mariculture area, the toxicity contribution of current use HOCs further declined (0.010 %), whereas environmental background HOCs, such as polycyclic aromatic hydrocarbons (PAHs), became increasingly significant, with the contribution ratio increasing from 0.37 % to 2.4 %. To minimize the negative impacts of PAHs, optimization of energy structure in transportation and coastal industry is required. In the coastal fishing area, the phased-out persistent organic pollutants (POPs) remained a major concern, in terms of both concentration and toxicity contribution. The phased-out POPs explained 7.0 % of the toxic effects of the sediments from the coastal fishing area, due to historical residue, industrial emissions, and their high toxicities. For this reason, it is critical to improve the relevant emission regulations and standards, so as to eventually reduce the unintentional discharges of POPs.

Five coexisting brominated flame retardants in a water-sediment-Vallisneria system: Bioaccumulation and effects on oxidative stress and photosynthesis

The pollution of various brominated flame retardants (BFRs) is concurrence, while their environmental fate and toxicology in water-sediment-submerged plant systems remain unclear. In this study, Vallisneria natans plants were co-exposed to 2,3,4,5,6-pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ether (BDE209), and decabromodiphenyl ethane (DBDPE). The ∑BFRs concentration in the root was 2.15 times higher than that in the shoot. Vallisneria natans accumulated more BTBPE and HBB in 0.2, 1, and 5 mg/kg treatments, while they accumulated more DBDPE and BDE209 in 25 and 50 mg/kg treatments. The bioaccumulation factors in the shoot and root were 1.08-96.95 and 0.04-0.70, respectively. BFRs in sediments had a more pronounced effect on bioaccumulation levels than BFRs in water, and biotranslocation was another potential influence factor. The SOD activity, POD activity, and MDA content were significantly increased under co-exposure. The DBDPE separate exposure impacted the metabolism of substances and energy, inhibited mismatch repair, and disrupted ribosomal functions in Vallisneria natans. However, DBDPE enhanced their photosynthesis by upregulating the expression level of genes related to the light reaction. This study provides a broader understanding of the bioaccumulation and toxicity of BFRs in submerged plants, shedding light on the scientific management of products containing BFRs.

Long-term dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) reduced feeding in common carp (Cyprinus carpio): Via the JAK-STAT signaling pathway

Polybrominated diphenyl ethers (PBDEs) are widely present in water ecosystems where they pose a significant threat to aquatic life, but our knowledge about how PBDEs affect feeding is limited. Therefore, this study explored the effects of continuous dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) (40 and 4000 ng/g) on the feeding in common carp (Cyprinus carpio) and the underlying mechanism. BDE-47 significantly decreased the food intake of carp. Transcriptome analysis of brain tissue showed that BDE-47 mainly affected the nervous, immune, and endocrine systems. Further examination of the expression levels of appetite factors in the brain revealed that BDE-47 caused dysregulation of appetite factors expressions such as agrp, pomc, cart, etc. In addition, the JAK-STAT signaling pathway was activated under BDE-47 exposure. It can be concluded from these findings that BDE-47 activated the JAK-STAT signaling pathway, causing imbalanced expression of appetite factors, leading to disordered feeding behavior and decreased food intake in carp. These results provide an important reference for a more comprehensive understanding of the hazards posed by BDE-47 on animal feeding and the associated mechanisms.

Dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) induces oxidative damage promoting cell apoptosis primarily via mitochondrial pathway in the hepatopancreas of carp, Cyprinus carpio

To investigate the mechanisms of BDE-47 on hepatotoxicity in fish, this study examined the effects of dietary exposure to BDE-47 (40 and 4000 ng/g) on carp for 42 days. The results showed that BDE-47 significantly increased carp's condition factor and hepatosomatic index. Pathological results revealed unclear hepatic cord structure, hepatocytes swelling, cellular vacuolization, and inflammatory cell infiltration in the hepatopancreas of carp. Further investigation showed that ROS levels significantly increased on days 7, 14, and 42. Moreover, the activities of antioxidant enzymes SOD, GSH, CAT, and GST increased significantly from 1 to 7 days, and the transcription levels of antioxidant enzymes CAT, Cu-Zn SOD, Mn-SOD, GST, and GPX, and antioxidant pathway genes Keap1, Nrf2, and HO-1 changed significantly at multiple time-points during the 42 days. The results of apoptosis pathway genes showed that the mitochondrial pathway genes Bax, Casp3, and Casp9 were significantly upregulated and Bcl2 was significantly downregulated, while the transcription levels of FADD and PERK were significantly enhanced. These results indicate that BDE-47 induced oxidative damage in hepatopancreas, then it promoted cell apoptosis mainly through the mitochondrial pathway. This study provides a foundation for analyzing the mechanism of hepatotoxicity induced by BDE-47 on fish.

Spatiotemporal transitions of organophosphate esters (OPEs) and brominated flame retardants (BFRs) in sediments from the Pearl River Delta, China

Recent regulations on the use of brominated flame retardants (BFRs, especially polybrominated diphenyl ethers, PBDEs) have led a sharp increase in the use of organophosphate esters (OPEs), which have become the subject of widespread environmental concern. To gain insights into their environmental transitions, we investigated the spatiotemporal trends and sources of 25 OPEs and 23 BFRs (21 PBDEs and two alternative BFRs) in sediments from the Pearl River Delta (PRD), the second economic/industrial region of China. Among them, PBDEs showed higher mean concentrations than OPEs and alt-BFRs in PRD sediments, a continual increase in most PRD areas, and positive correlations with most local socioeconomic parameters. The source analysis results indicated that all of these changes resulted from the substantial use/stock of PBDEs (especially deca-BDE) in this region, and BDE-209 displayed debromination in most sediments. OPEs demonstrated obvious increases in sediments from all major PRD rivers, especially those located in less-developed regions. This distribution might be related to the large-scale industry relocation from the central PRD area to its vicinities. Unexpectedly, decabromodiphenyl ethane (DBDPE), an important deca-BDE substitute, presented considerable declines in the PRD sediments while several novel OPEs showed considerably high proportions, especially aryl-substituted OPEs, which merit further screening analysis.

The effect of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) on locomotor behaviour and muscle physiology of the sea cucumber Apostichopus japonicus

The 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is the predominant congener of polybrominated diphenyl ethers, and it is also a persistent organic pollutant that with a higher detection rate in samples from environment and animals. To date, there have been few studies of the effects of BDE-47 on locomotion in sea cucumbers. In this study, we investigated the influence of different concentrations of BDE-47 (low: 0.1 μg/L; moderate: 1.0 μg/L; high: 10.0 μg/L) on locomotion of Apostichopus japonicus and evaluated changes in their muscle physiology using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The behavioural studies showed that the average and maximum velocity of movement decreased significantly in both the moderate and high BDE-47 groups after 1 day of exposure. In addition, levels of 55 metabolites were identified and characterized in the longitudinal muscle of A. japonicus exposed to BDE-47. The alteration of taurine and norepinephrine levels indicated that BDE-47 had drastic physiological effects on the longitudinal muscle of A. japonicus.

Treatment of PBDEs from Soil-Washing Effluent by Granular-Activated Carbon: Adsorption Behavior, Influencing Factors and Density Functional Theory Calculation

Soil-washing is a potential technology for the disposal of soil contaminated by e-waste; however, the produced soil-washing effluent will contain polybrominated diphenyl ethers (PBDEs) and a large number of surfactants, which are harmful to the environment, so the treatment of PBDEs and the recycling of surfactants are the key to the application of soil-washing technology. In this study, coconut shell granular-activated carbon (GAC) was applied to remove PBDEs from Triton X-100 (TX-100) surfactant which simulates soil-washing effluent. The adsorption results show that, GAC can simultaneously achieve effective removal of 4,4′-dibromodiphenyl ether (BDE-15) and efficient recovery of TX-100. Under optimal conditions, the maximum adsorption capacity of BDE-15 could reach 623.19 μmol/g, and the recovery rate of TX-100 was always higher than 83%. The adsorption process of 4,4′-dibromodiphenyl ether (BDE-15) by GAC could best be described using the pseudo-second-order kinetic model and Freundlich isothermal adsorption model. The coexistence ions had almost no effect on the removal of BDE-15 and the recovery rate of TX-100, and the solution pH had little effect on the recovery rate of TX-100; BDE-15 had the best removal effect under the condition of weak acid to weak base, indicating that GAC has good environmental adaptability. After adsorption, GAC could be regenerated with methanol and the adsorption effect of BDE-15 could still reach more than 81%. Density functional theory (DFT) calculation and characterization results showed that, Van der Waals interaction and π–π interaction are dominant between BDE-15 and GAC, and hydrogen bond interactions also exist. The existence of oxygen-containing functional groups is conducive to the adsorption of BDE-15, and the carboxyl group (-COOH) has the strongest promoting effect. The study proved the feasibility of GAC to effectively remove PBDEs and recover surfactants from the soil-washing effluent, and revealed the interaction mechanism between PBDEs and GAC, which can provide reference for the application of soil-washing technology.

Tetrabromobisphenol A and hexabromocyclododecanes in sediments from fishing ports along the coast of South China: Occurrence, distribution and ecological risk

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDDs) have attracted extensive attention due to their strong persistence and toxicity. However, little has been known about their pollution status in fishing ports, which are typical sinks of land-sourced pollutants. In this study, we investigated the occurrence, distribution and ecological risk of TBBPA and HBCDDs in sediments from fishing ports along the coast of South China. The concentrations of TBBPA and ΣHBCDD (sum of α-, β-, and γ-HBCDD) in the fishing-port sediments were in the ranges of 0.02-21.5 ng/g dw and 1.06-14.1 ng/g dw, respectively. γ-HBCDD was the predominant diastereoisomer in most fishing-port sediments. The enantiomeric analysis indicated a preferential enrichment of (-)-enantiomers for α-, β-, and γ-HBCDD. The geographical location of fishing ports is a significant determinant of distribution for TBBPA and HBBCDs. The concentrations of TBBPA and HBCDDs in fishing-port sediments were strongly associated with local population density, but weakly correlated with total organic carbon content of the sediment. The mass inventories of TBBPA and ΣHBCDD were estimated to be 77.0 ng/cm² and 141 ng/cm², respectively. The ecological risk assessment demonstrated that TBBPA and HBCDDs in fishing-port sediments exhibited low risks to marine organisms. This study contributes to the understanding pollution situation of fishing ports, and provides a reference for environmental safety assessment and environmental pollution control.