From headwaters to estuary: Distribution and fate of halogenated flame retardants (HFRs) in a river basin near the largest HFR manufacturing base in China

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.

Species-specific and habitat-dependent bioaccumulation of halogenated flame retardants in marine organisms from estuary to coastal seas

Halogenated flame retardants (HFRs) have attracted global attention owing to their adverse effects on ecosystems and humans. The Shandong Peninsula is the largest manufacturing base for HFRs in East Asia, yet its impacts on marine ecosystems are unclear. Seventeen HFRs were analyzed in organisms captured from the Xiaoqing River estuary, Bohai Sea (BS), Yellow Sea and Northern East China Sea to investigate the distribution and bioaccumulation of HFRs on a broad scale. The results showed a downward trend in ΣHFR concentrations from the estuary (37.7 ng/g lw on average) to Laizhou Bay (192 ng/g lw) and to coastal seas (3.13 ng/g lw). The concentrations of ΣHFRs were significantly higher in demersal fish (0.71-198 ng/g lw) and benthic invertebrates (0.81-3340 ng/g lw) than in pelagic fish (0.30-27.6 ng/g lw), reflecting a habitat dependence. The concentrations of higher-brominated homologs were greater in benthic invertebrates, whereas a greater level of lower-brominated PBDE congeners was observed in fish, suggesting different profiles between species. Furthermore, the analogue composition of HFRs in fish was similar to that in the dissolved phase of seawater, whereas the HFR pattern in benthic invertebrates was consistent with the profile in sediment. The concentrations of HFRs in organisms vary widely depending on emissions from anthropogenic activities, whereas bioaccumulation patterns are strongly influenced by species and habitat.

Combined exposure to decabromodiphenyl ether and nano zero-valent iron aggravated oxidative stress and interfered with metabolism in earthworms

Decabromodiphenyl ether (BDE-209) is a common brominated flame retardant in electronic waste, and nano zero-valent iron (nZVI) is a new material in the field of environmental remediation. Little is known about how BDE-209 and nZVI combined exposure influences soil organisms. During the 28 days study, we determined the effects of single and combined exposures to BDE-209 and nZVI on the oxidative stress and metabolic response of earthworms (Eisenia fetida). On day 7, compared to CK, malondialdehyde (MDA) content increased in most combined exposure groups. To remove MDA and reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were induced in most combined exposure groups. On day 28, compared to CK, the activities of SOD and CAT were inhibited, while POD activity was significantly induced, indicating that POD plays an important role in scavenging ROS. Combined exposure to BDE-209 and nZVI significantly affected amino acid biosynthesis and metabolism, purine metabolism, and aminoacyl-tRNA biosynthesis pathways, interfered with energy metabolism, and aggravated oxidative stress in earthworms. These findings provide a basis for assessing the ecological impacts of using nZVI to remediate soils contaminated with BDE-209 from electronic waste.

Polybrominated diphenyl ether contamination in sediments from rivers in the western Niger Delta of Nigeria

This study investigated the concentrations of 39 polybrominated diphenyl ether (PBDE) congeners in sediments from three rivers in the western Niger Delta of Nigeria that have been affected by pollution from urbanization and industrial activities. The Σ39 PBDE concentrations in sediments from these rivers ranged from 0.29 to 95.5, 5.15 to 121, and 0.73 to 66.1 ng g-1 for the Afiesere (AR), Edor (ER), and Okpare Rivers (OR), respectively. The homologue distribution patterns indicated the prominence of tetra- and penta-BDE congeners in sediments from these rivers. The ecological risk assessment results showed that the penta-BDEs were the primary source of risk to sediment-dwelling organisms in these rivers. However, the human health risk assessment indicated negligible risks for exposure of both adults and children to PBDEs in these sediments. The source apportionment suggests that the PBDE contamination in these river sediments was derived from long-distance migration, debromination of highly brominated congeners, and commercial penta-BDEs. These results reflect the use of penta-BDE formulations in this region rather than octa- and deca-BDE formulations.

Transcriptome-based approach to identify mechanisms underlying locomotor abnormality induced by decabromodiphenyl ethane in zebrafish larvae

The brominated flame retardant decabromodiphenyl ethane (DBDPE) has been extensively used following restrictions on BDE-209 and thus, been frequently detected in aquatic environment. However, information on impact of DBDPE on fish development and the potential mechanisms remains scarce. In present study, developing zebrafish were employed as a study model. Embryos were exposed until 5 d to DBDPE at concentrations of 0, 3, 30, and 300 μg/L, following which the impact on larval development was investigated. DBDPE bioaccumulation and locomotor hyperactivity were observed in developing zebrafish exposed to DBDPE. Transcriptome and bioinformatics analyses indicated that pathways associated with cardiac muscle contraction and retinol metabolism were notably affected. The mechanisms of DBDPE to induce locomotor abnormality were further investigated by analyzing levels of retinol and retinol metabolites, eye and heart histology, heart rates, and ATPase activity. Our results indicate that locomotor hyperactivity observed in larvae exposed to DBDPE results from abnormal heartbeat, which in turn is attributable to inhibition of Na+/K+-ATPase activity. Furthermore, DBDPE did not change larval eye histology and contents of retinoid (retinol, retinal, and retinoic acid). This study provides insight into the mechanisms underlying DBDPE-induced developmental toxicity and highlights the need for addressing the environmental risks for aquatic organisms.

A review of polybrominated diphenyl ethers and novel brominated flame retardants in Chinese aquatic environment: Source, occurrence, distribution, and ecological risk assessment

Due to the widespread commercial production and use of brominated flame retardants (BFRs) in China, their potential impact on human health development should not be underestimated. This review searched the literature on Polybrominated diphenyl ethers and Novel brominated flame retardant (PBDEs and NBFRs) (broad BFRs) in the aquatic environment (including surface water and sediment) in China over the last decade. It was found that PBDEs and NBFRs entered the aquatic environment through four main pathways, atmospheric deposition, surface runoff, sewage effluent and microplastic decomposition. The distribution of PBDEs and NBFRs in the aquatic environment was highly correlated with the local economic structure and population density. In addition, a preliminary risk assessment of existing PBDEs and PBDEs in sediments showed that areas with high-risk quotient values were always located in coastal areas with e-waste dismantling sites, which was mainly attributed to the historical legacy of electronic waste. This research provides help for the human health development and regional risk planning management posed by PBDEs and NBFRs.

Evidence for Adverse Effects on Liver Development and Regeneration in Zebrafish by Decabromodiphenyl Ethane

Decabromodiphenyl ethane (DBDPE), a ubiquitous emerging pollutant, could be enriched in the liver of organisms, but its effects and mechanisms on liver development and regeneration remain largely unknown. In the present study, we first investigated the adverse effects on liver development and found decreased area and intensity of fluorescence in transgenic zebrafish larvae exposed to DBDPE; further results in wild-type zebrafish larvae revealed a possible mechanism involving disturbed MAPK/Fox O signaling pathways and cell cycle arrest as indicated by decreased transcription of growth arrest and DNA-damage-inducible beta a (gadd45ba). Subsequently, an obstructed recovery process of liver tissue after partial hepatectomy was characterized by the changing profiles of ventral lobe-to-intestine ratio in transgenic female adults upon DBDPE exposure; further results confirmed the adverse effects on liver regeneration by the alterations of the hepatic somatic index and proliferating cell nuclear antigen expression in wild-type female adults and also pointed out a potential role of a disturbed signaling pathway involving cell cycles and glycerolipid metabolism. Our results not only provided novel evidence for the hepatotoxicity and underlying mechanism of DBDPE but also were indicative of subsequent ecological and health risk assessment.

Evaluation and Mechanistic Study of Transgenerational Neurotoxicity in Zebrafish upon Life Cycle Exposure to Decabromodiphenyl Ethane (DBDPE)

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a ubiquitous emerging pollutant in the environment, which may evoke imperceptible effects in humans or wild animals. Hence in this study, zebrafish embryos were exposed to DBDPE (0, 0.1, 1, and 10 nM) until sexual maturity (F0), and F1 and F2 generations were cultured without further exposure to study the multi- and transgenerational toxicity and underlying mechanism. The growth showed sex-different changing profiles across three generations, and the social behavior confirmed transgenerational neurotoxicity in adult zebrafish upon life cycle exposure to DBDPE. Furthermore, maternal transfer of DBDPE was not detected, whereas parental transfer of neurotransmitters to zygotes was specifically disturbed in F1 and F2 offspring. A lack of changes in the F1 generation and opposite changing trends in the F0 and F2 generations were observed in a series of indicators for DNA damage, DNA methylation, and gene transcription. Taken together, life cycle exposure to DBDPE at environmentally relevant concentrations could induce transgenerational neurotoxicity in zebrafish. Our findings also highlighted potential impacts on wild gregarious fish, which would face higher risks from predators.

Distribution, sources, and risk analysis of heavy metals in sediments of Xiaoqing River basin, Shandong province, China

The accumulation of heavy metals in river sediment poses a major threat to ecological safety. The Xiaoqing River originates in western Jinan, with higher population density and per capita gross domestic product (GDP) in its basin compared to the Shandong province average. This study analyzed the spatial characteristics, ecological risk, human health risk, and contamination sources of heavy metals by collecting sediment samples from Xiaoqing River. We use the methods such as geo-accumulation index (Igeo), ecological risk assessment based on the interval number sorting method, and health risk assessment to evaluate the risk of heavy metals in sediments. The research finding suggests heavy metals including Pb, As, Ni, and Cr are low ecological risks, while Hg and Cd have reached high and extreme ecological risks. Correlation analysis and principal component analysis were used to analyze the correlation and sources of different heavy metals. The six heavy metals were categorized into three groups. Factor 1, comprising Hg, Cr, and Pb, was identified as a mixed source with a contribution rate of 37.76%. Factor 2 is an agricultural source and comprises Ni, Cd, and As with a contribution rate of 27.05%. Factor 3 includes Pb and Ni contributing to 15.30% as a natural source. This study offers valuable insights for the prevention of heavy metal pollution, as well as promoting sustainable urban development.

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.

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.

Mitochondrial Dysfunction Was Involved in Decabromodiphenyl Ethane-Induced Glucolipid Metabolism Disorders and Neurotoxicity in Zebrafish Larvae

Decabromodiphenyl ethane (DBDPE), a novel brominated flame retardant, is becoming increasingly prevalent in environmental and biota samples. While DBDPE has been shown to cause various biological adverse effects, the molecular mechanism behind these effects is still unclear. In this research, zebrafish embryos were exposed to DBDPE (50-400 μg/L) until 120 h post fertilization (hpf). The results confirmed the neurotoxicity by increased average swimming speed, interfered neurotransmitter contents, and transcription of neurodevelopment-related genes in zebrafish larvae. Metabolomics analysis revealed changes of metabolites primarily involved in glycolipid metabolism, oxidative phosphorylation, and oxidative stress, which were validated through the alterations of multiple biomarkers at various levels. We further evaluated the mitochondrial performance upon DBDPE exposure and found inhibited mitochondrial oxidative respiration accompanied by decreased mitochondrial respiratory chain complex activities, mitochondrial membrane potential, and ATP contents. However, addition of nicotinamide riboside could effectively restore DBDPE-induced mitochondrial impairments and resultant neurotoxicity, oxidative stress as well as glycolipid metabolism in zebrafish larvae. Taken together, our data suggest that mitochondrial dysfunction was involved in DBDPE-induced toxicity, providing novel insight into the toxic mechanisms of DBDPE as well as other emerging pollutants.

Multi- and Transgenerational Developmental Impairments Are Induced by Decabromodiphenyl Ethane (DBDPE) in Zebrafish Larvae

A novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a ubiquitous emerging pollutant; hence, the knowledge of its long-term toxic effects and underlying mechanism would be critical for further health risk assessment. In the present study, the multi- and transgenerational toxicity of DBDPE was investigated in zebrafish upon a life cycle exposure at environmentally relevant concentrations. The significantly increased malformation rate and declined survival rate specifically occurred in unexposed F2 larvae suggested transgenerational development toxicity by DBDPE. The changing profiles revealed by transcriptome and DNA methylome confirmed an increased susceptibility in F2 larvae and figured out potential disruptions of glycolipid metabolism, mitochondrial energy metabolism, and neurodevelopment. The changes of biochemical indicators such as ATP production confirmed a disturbance in the energy metabolism, whereas the alterations of neurotransmitter contents and light-dark stimulated behavior provided further evidence for multi- and transgenerational neurotoxicity in zebrafish. Our findings also highlighted the necessity for considering the long-term impacts when evaluating the health of wild animals as well as human beings by emerging pollutants.

DBDPE and ZnO NPs synergistically induce neurotoxicity of SK-N-SH cells and activate mitochondrial apoptosis signaling pathway and Nrf2-mediated antioxidant pathway

Decabromodiphenyl ethane (DBDPE), a new brominated flame retardant, could negatively affect neurobehavior and pose health risks to humans. Humans are also exposed to widely used nanomaterials. This study investigated the combined toxic effects and action types of DBDPE and Zinc oxide nanoparticles (ZnO NPs) on human neuroblastoma SK-N-SH cells and the toxicity mechanisms. DBDPE inhibited the viability of SK-N-SH cells by 21.87% at 25 mg/L. ZnO NPs synergistically exacerbated the toxic effects of DBDPE. DBDPE and ZnO NPs caused excessive ROS production and inhibition of antioxidant enzyme (SOD and GSH) activity in cells, thus causing oxidative cellular damage. Moreover, DBDPE and ZnO NPs caused apoptosis by disrupting mitochondrial kinetic homeostasis, reducing mitochondrial membrane potential (MMP), increasing cytochrome C release and regulating Bax/Bcl-2 and Caspase-3 mRNA and protein expression. DBDPE and ZnO NPs increased the mRNA expression of nuclear factor erythroid 2- related factor (Nrf2) and its downstream genes. The molecular mechanisms revealed that oxidative stress, apoptosis and mitochondrial dysfunction were the critical factors in combined cytotoxicity. The bioinformatics analysis further indicated that co-exposure affected Nrf2 activation, apoptotic factors expression and mitochondrial fusion. The findings enrich the risk perception of neurotoxicity caused by DBDPE and ZnO NPs.

Decabromodiphenyl ethane induces locomotion neurotoxicity and potential Alzheimer's disease risks through intensifying amyloid-beta deposition by inhibiting transthyretin/transthyretin-like proteins

As a major alternative to traditional brominated flame retardants (BFRs), decabromodiphenyl ethane (DBDPE) is widely used and has been commonly detected in various environmental media and organisms. Few previous studies have focused on DBDPE-induced locomotion neurotoxicity, and the exact molecular mechanisms and related health risks remain unclear. In this study, we first analyzed the locomotion indicators of nematodes following DBDPE exposure, demonstrated that DBDPE caused locomotion neurotoxicity, and identified that a series of the transthyretin (TTR)-like genes participated in the regulation of nematode motility by transcriptomic analysis, gene transcription validation and TTR-like mutant verification. Subsequently, this study demonstrated that DBDPE exacerbated amyloid-beta (Aβ) deposition by repressing TTR/TTR-like gene transcription based on Alzheimer's disease (AD) model nematodes and human SH-SY5Y cells following DBDPE exposure and further revealed that DBDPE reduced the binding between TTR and Aβ by competing with the strand G region sites on the TTR/TTR-like protein, ultimately exacerbating Aβ deposition and the risk of AD. In short, our study demonstrated that DBDPE induced locomotion neurotoxicity and potential AD risks through intensifying Aβ deposition by inhibiting TTR/TTR-like proteins, providing reference support for risk management and policy formulation related to DBDPE and similarly structured novel BFRs.

Thyroid-disrupting effects caused by exposure to alternative flame retardants from groundwater contamination in rural central China

Accumulating evidence reveals that exposure to alternative flame retardants (AFRs) results in defective thyroid functions. AFRs are detectable in various environmental media in developed cities in China. However, few studies have reported the contamination levels of AFR in groundwater in rural areas, indicating an urgent need to investigate exposure of AFRs and perform health risk assessment for populations that use groundwater as the main source of drinking water. This study investigated the concentrations of AFRs in groundwater in rural areas of central China. Moreover, Nthy-ori-3-1 cells were used to determine the thyroid cytotoxicities and thyroid-interfering effects of a single AFR as well as the mixtures of AFRs based on the AFR contamination levels in real-world. The results revealed that all classes of AFRs were detectable in rural areas in central China. Dechlorane plus, hexabromocyclododecane, bromophenols (BPs), novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) exhibited spatial contamination patterns, with an average concentrations (median) of 157.89 ± 88.61 (185.47) pg/L, 0.09 ± 0.29 (not detectable) ng/L, 5.20 ± 5.92 (3.43) ng/L, 3338.11 ± 3758.78 (2836.72) pg/L, and 79.35 ± 97.19 (53.62) ng/L, respectively. The half maximal effective concentrations (EC₅₀) of BPs, OPFRs, and NBFRs ranged 98.4-4012 μM, 42.0-2506 μM, and 10.1-203.7 μM, respectively. Several AFRs exhibited more cytotoxic effects than did traditional brominated flame retardants. It is intriguing that several single AFRs and mixtures at environmentally-relevant exposure levels promoted the viability of Nthy-ori-3-1 cells. Taken together, our study demonstrates that AFRs are present in the groundwater in rural areas in central China and AFRs exhibit thyroid disrupting effects.

Fat mass and obesity-associated gene (FTO) hypermethylation induced by decabromodiphenyl ethane causing cardiac dysfunction via glucolipid metabolism disorder

Decabromodiphenyl ethane (DBDPE) is a major alternative to BDE-209 owing to its lower toxicity. However, the mass production and increased consumption of DBDPE in recent years have raised concerns related to its adverse health effects. However, the effect and mechanism of DBDPE on cardiotoxicity have rarely been studied. In the present study, we investigated the impacts of DBDPE on the cardiovascular system in male SD rats and then explored the underlying mechanisms to explain the cardiotoxicity of DBDPE using AC16 cells. Under in vivo conditions, male rats were administered with an oral dosage of DBDPE at 0, 5, 50, and 500 mg/kg/day for 28 days, respectively. Histopathological analysis demonstrated that DBDPE induced cardiomyocyte injury and fibrosis, and ultrastructural observation revealed that DBDPE could induce mitochondria damage and dissolution. DBDPE could thus decrease the level of MYH6 and increase the level of SERCA2, which are the two key proteins involved in the maintenance of homeostasis during myocardial contractile and diastolic processes. Furthermore, DBDPE could increase the serum levels of glucose and low-density lipoprotein but decrease the content of high-density lipoprotein. In addition, DBDPE could activate the PI3K/AKT/GLUT2 and PPARγ/RXRα signaling pathways in AC16 cells. In addition, DBDPE decreased the UCP2 level and ATP synthesis in mitochondria both under in vitro and in vivo conditions, consequently leading to apoptosis via the Cytochrome C/Caspase-9/Caspase-3 pathway. Bisulfite sequencing PCR (BSP) identified the hypermethylation status of fat mass and obesity-associated gene (FTO). 5-aza exerted the opposite effects on the PI3K/AKT/GLUT2, PPARγ/RXRα, and Cytochrome C/Caspase-9/Caspase-3 signaling pathways induced by DBDPE in AC16 cells. In addition, the DBDPE-treated altered levels of UCP2, ATP, and apoptosis were also found to be significantly reversed by 5-aza in AC16 cells. These results suggested that FTO hypermethylation played a regulative role in the pathological process of DBDPE-induced glycolipid metabolism disorder, thereby contributing to the dysfunction of myocardial contraction and relaxation through cardiomyocytes fibrosis and apoptosis via the mitochondrial-mediated apoptotic pathway resulting from mitochondrial dysfunction.

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.

Decabromodiphenyl Ethane Mainly Affected the Muscle Contraction and Reproductive Endocrine System in Female Adult Zebrafish

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a widespread environmental pollutant. However, the target tissue and toxicity of DBDPE are still not clear. In the current study, female zebrafish were exposed to 1 and 100 nM DBDPE for 28 days. Chemical analysis revealed that DBDPE tended to accumulate in the brain other than the liver and gonad. Subsequently, tandem mass tag-based quantitative proteomics and parallel reaction monitoring verification were performed to screen the differentially expressed proteins in the brain. Bioinformatics analysis revealed that DBDPE mainly affected the biological process related to muscle contraction and estrogenic response. Therefore, the neurotoxicity and reproductive disruptions were validated via multilevel toxicological endpoints. Specifically, locomotor behavioral changes proved the potency of neurotoxicity, which may be caused by disturbance of muscular proteins and calcium homeostasis; decreases of sex hormone levels and transcriptional changes of genes related to the hypothalamic-pituitary-gonad-liver axis confirmed reproductive disruptions upon DBDPE exposure. In summary, our results suggested that DBDPE primarily accumulated in the brain and evoked neurotoxicity and reproductive disruptions in female zebrafish. These findings can provide important clues for a further mechanism study and risk assessment of DBDPE.

Determination of multiple organic flame retardants in maricultural water using High-volume/High-throughput Solid-phase extraction followed by liquid/gas chromatography tandem mass spectrometry

A rapid and efficient analytical method is proposed and optimized for the enrichment, extraction and instrument analysis of four typical organic flame retardants (OFRs), including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDs) and dechlorane compounds (Dechloranes) in maricultural waters using High-volume/High-throughput Solid-phase extraction with in-situ ultrasonic technique followed by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and gas chromatography tandem mass spectrometry (GC-MS) instrumental detection. The optimized pretreatment conditions were that the analytes were enriched by XAD-2 resins and eluted repeatedly with 50 mL hexane/acetone (1:1, v:v) for 5 min. The results of method validation exhibited that the developed method can be used for quantitative detection of 11 OPEs, 13 PBDEs, 3 HBCDs and 5 Dechloranes in water samples. The method detection limits (MDLs) and limits of quantification (LOQs) are 0.4-26.2 pg/L and 1.5-87.4 pg/L for OPEs, 23.3-35.4 pg/L and 77.5-117.9 pg/L for HBCDs, 0.8-97.4 pg/L and 2.6-324.7 pg/L for PBDEs and 9.3-78.5 pg/L and 31.0-261.8 pg/L for Dechloranes, respectively. The method was successfully applied in lagoon maricultural areas in Hainan province, and the results showed that 4 OFRs were detected in almost all water samples. Total concentrations of 18 water samples were 1.89-39.97 ng/L for OPEs, 0.18-5.40 ng/L for PBDEs, ND-0.24 ng/L for HBCDs and 0.01-1.77 ng/L for Dechloranes, respectively. The optimized analytical method is highly sensitive and efficient with expectation to play an essential role in monitoring the ultra-trace organic pollutants and providing an effective risk assessment in ecological environment.

Organophosphate flame retardants, tetrabromobisphenol A, and their transformation products in sediment of e-waste dismantling areas and the flame-retardant production base

Due to the prohibition of polybrominated diphenyl ethers, organophosphate flame retardants (OPFRs) and tetrabromobisphenol A (TBBPA) have become emerging flame retardants. However, knowledge about their occurrence, especially their transformation products, is still limited. This study collected sediment samples from two rivers, i.e., Lianjiang River (located at an e-waste dismantling area) and Xiaoqing River (situated at a flame retardant production base), to investigate the occurrence, composition, and spatiality distribution of OPFRs, TBBPA, and their transformation products. Both targets were detected in the Lianjiang River in the range of 220-1.4 × 10⁴ and 108-3.1 × 10³ ng/g dw (dry weight) for OPFRs and TBBPA, and 0.11-2.35 and 4.8-414 ng/g dw for their respective transformation products, respectively. The concentrations of OPFRs and TBBPA in the Xiaoqing River ranged from 4.15 to 31.5 and 0.76-2.51 ng/g dw, respectively, and no transformation products were detected. Different compositional characteristics of OPFRs and distinct spatial distribution from mainstream and tributary observed between the two rivers are attributed to the difference in the local industries. Spatial distribution and principal component analysis indicated that e-waste dismantling activities could be a vital source of local pollution. Besides, the confluence of tributaries seemed to determine the contaminant levels in the Xiaoqing River. Also, concentration ratios and Spearman's correlation between metabolites and parent chemicals were analyzed. Low concentration ratios (3.6 ×10^-4 to 0.16) indicated a low transformation degree, and Spearman's correlation analysis suggested transformation products were partly stemming from commercial products. Considering the limited study of these transformation products, more studies on their sources, transform mechanism, and toxicity are required.

Severe contamination and time trends of legacy and novel halogenated flame retardants in multiple environmental media from Lake Shihwa, Korea: Effectiveness of regulatory action

Novel halogenated flame retardants (HFRs) were introduced to industrial markets as alternatives to legacy brominated FRs (BFRs), such as polybrominated diphenyl ethers (PBDEs). In the present study, PBDEs and their brominated and chlorinated alternatives, novel BFRs (NBFRs) and dechlorane plus (DP), were measured in multiple environmental matrices in a highly industrialized lake in Korea. Legacy and novel HFRs were detected in multiple samples, indicating ubiquitous contamination. Concentrations of HFRs in water and sediment observed in creeks running through machine, textiles, and automobile industrial complexes were significantly higher than those observed in inside and outside of the lake. Higher bioaccumulation levels of HFRs were observed in inshore compared with offshore waters. Results suggest that multi-matrix distribution of legacy and novel HFRs was dependent on the geographical proximity to industrial sources. Compared with previous studies, the highest levels of PBDEs and NBFRs were recorded in water samples on a global scale, implying on-going emissions from industrial activities. Decabromodiphenyl ethane (DBDPE) was a dominant compound in water samples, whereas the concentrations of PBDEs, NBFRs, and DP in sediment were similar to each other. This suggests a shift in consumption from legacy to novel HFRs, preferentially in water environments. A significant declining trend in PBDEs was observed in water and sediment collected between 2008 and 2015, indicating the effectiveness of regulatory actions. Based on their environmental occurrence and bioaccumulation potential, pentabromoethylbenzene and bis(2-ethylhexyl) tetrabromophthalate may pose emerging concerns regarding contamination of aquatic environments.

Spatio-temporal variations and input patterns on the legacy and novel brominated flame retardants (BFRs) in coastal rivers of North China

Decabromodiphenyl ether (BDE209) has been subject to restrictions since 2018 in developed countries but is still manufacturing in China. Decabromodiphenyl ethane (DBDPE) is widely used as a replacement for BDE209. To better understand the behaviors and fates of these legacy and novel brominated flame retardants (BFRs), water samples were collected from the estuaries of 36 rivers that drain into the Bohai Sea (BS) and North Yellow Sea (NYS) in 2017 and 2018. The results showed that BDE209 was still the predominant compound with a median concentration of 2470 pg L^-1, whereas DBDPE had a median concentration of 129 pg L^-1. Spatially, relatively high concentrations were observed in the rivers near Laizhou Bay (LB), which is the manufacturing hub of BFRs. BDE209 concentrations were significantly higher in dry season than in wet season, which indicates a dominant process of dilution by precipitation during the wet season. DBDPE concentration showed no significant seasonal difference. This implies that wet deposition was the major additional source of DBDPE during the wet season, and the concentration increased further during the autumn as a result of a time-lag effect. The BFR concentrations in urban rivers were lower than those reported by a study undertaken in August 2013. An increase in the BFR concentrations in rural rivers since 2013 suggested increases in the use and non-point source emissions of BFRs in some remote aquatic environments. The estimated annual inputs of BDE209 and DBDPE into the BS were ∼95.9 kg yr^-1 and ∼26.8 kg yr^-1, respectively, whereas those into the NYS were ∼24.1 kg yr^-1 and ∼8.38 kg yr^-1. The results revealed an ecological risk of BDE209 in winter especially in the Xiaoqing River, thus suggesting the impact of BDE209 on the aquatic environment and human health.

Decabromodiphenyl Ether versus Decabromodiphenyl Ethane: Source, Fate, and Influencing Factors in a Coastal Sea Nearing Source Region

Both decabromodiphenyl ether (BDE 209) and decabromodiphenyl ethane (DBDPE) are still produced in large quantities in China, especially in the Shandong Province closed to the Bohai Sea (BS). This study conducted a comprehensive investigation of the distribution and budget of brominated flame retardants (BFRs) in the BS. BDE 209 was the predominant BFR in most of the investigated rivers flowing into the BS, although DBDPE exceeded BDE 209 in certain rivers as a result of the replacement of BDE 209 with DBDPE in North China. The spatial distributions of BFRs in the rivers were controlled by the proximity of the BFR manufacturing base and the extent of urbanization. BFRs' spatial distribution in the BS was influenced by a combination of land-based pollution sources, environmental parameters (e.g., suspended particulate matter, particulate organic carbon, and particulate black carbon), and hydrodynamic conditions. The spatial variation trend of BDE 209/DBDPE ratios in various environmental media provided useful information. Vertically, the BDE 209/DBDPE ratio decreased from the seawater surface layer to the sediment, indicating their differential transport in the BS. A multi-box mass balance model and analysis of BDE 209 showed that degradation was the primary sink of BFRs in seawater (∼68%) and surface sediment (∼72%) in the BS.

Distribution behavior and risk assessment of emerging perfluoroalkyl acids in multiple environmental media at Luoma Lake, East China

Perfluoroalkyl acids (PFAAs) are ubiquitous in various environments. This has caused great public concern, particularly in the shallow freshwater lake region, where the lake, rivers, and estuaries form a highly interconnected continuum. However, little is known about the environmental behaviors of PFAAs in the continuum. For the first time, a high-resolution monitoring framework covering the river-estuary-lake continuum of Luoma Lake was built, and the concentrations, sources, and environmental fates of PFAAs were identified and analyzed. The results revealed that the total concentration of PFAAs was at a moderate level in the water and at a high level in the sediment compared to global levels respectively. Perfluorooctanesulfonate (PFOS) was the most abundant PFAA in the continuum. In particular, the ∑PFAA concentration in the particle phase was much higher than that in the sediment phase. Distinct spatial heterogeneities were observed in the behaviors of distribution and the multiphase fate of PFAAs in the continuum, mainly driven by the turbulent mixing during transport, dilution of lake water, and spatial differences of hydrodynamic features and sedimentary properties among the sub-regions. Interestingly, the pH of the sediment and water had significant effects on the water-sediment portioning of PFAAs in contrasting ways. Furthermore, based on the composition of the sediments, four possible migration paths for PFAAs were deduced and the main sources of PFAAs were identified as sewage, domestic, and industrial effluents using the positive matrix factorization model. During the human health assessment, no risk was found under the median exposure scenario; however, under the high exposure scenario, PFAAs posed uncertain risks to human health, which cannot be ignored. This study provides basic information for simulating the fate and transport of PFAAs in the continuum and is significant for developing cost-effective control and remediation strategies in the near future.

Source, fate and budget of Dechlorane Plus (DP) in a typical semi-closed sea, China

Dechlorane Plus (DP), which has severe effects on marine ecosystems, has been proposed for listing under the Stockholm Convention as a persistent organic pollutant (POPs). This study was the first comprehensive investigation of the concentration and fate of DP in the Bohai Sea (BS) based on determination of river estuary water, river estuary sediment, surface seawater, bottom seawater, and sea sediments samples. The highest water DP levels were found in river estuary in Tianjin in North China due to the huge usage of DP in recent years, and spatial distribution analysis indicates it was mainly affected by regional high urbanization and emission of E-waste. The spatial distribution of DP in the BS was mainly affected by a combination of coastal hydrodynamics and land anthropogenic activities. On the basis of multi-box mass balance, simulations of DP in seawater showed an increase from 2014 to 2025, before leveling off at 184 pg L ^-1 by a constant DP input to the BS. Riverine discharge almost contributed to the total input (∼99%) and dominated the DP levels in the BS. Degradation of DP accounted for 55.3% and 78.1% of total DP output in seawater and sediment, respectively, indicating that degradation mainly affected decline of DP in the environment.

Distributions, transports and fates of short- and medium-chain chlorinated paraffins in a typical river-estuary system

Chlorinated paraffins (CPs) are widely employed in a variety of domestic and industrial products, and are ubiquitously detected in the environment. Short-chain chlorinated paraffins (SCCPs) have been listed in the Stockholm Convention as persistent organic pollutants (POPs), but not medium-chain chlorinated paraffins (MCCPs), even though they exhibit physicochemical properties and environmental behaviors similar to SCCPs. However, very limited data are available regarding their environmental behaviors and fates in river-estuary systems. China is the major producer of chlorinated paraffins (CPs), and Shandong Province is the main producer of CPs in China. Here, we investigated the distribution, transport, and fate of SCCPs and MCCPs in a heavily polluted river in Shandong Province, aiming to explore the distributions of CPs between dissolved and particulate phases, and between water and sediment phases, as well as the transport of CPs from river headwaters to estuaries and the roles of the estuarine turbidity maximum zone (ETM) on the fate of CPs. CP concentrations in sediments were 9.1-16,000 ng/g dw (mean value: 1000 ng/g dw) for SCCPs and 2.4-27,000 ng/g dw (mean value: 4400 ng/g dw) for MCCPs. In the water column, CP concentrations were 7.4-470 ng/L for SCCPs (mean value: 43 ng/L) and 4.0-120 ng/L for MCCPs (mean value: 27 ng/L). CP concentrations in riverine sediments were among the highest worldwide. SCCPs accounted for 95% of CPs (sum of SCCPs and MCCPs) in the dissolved phase. Cities around the river basin were found to be important pollution sources for CPs. Long-chained and more chlorinated congeners with larger LogKow values might be more likely to be 'salted-out', and thus, will be sequestrated in sediments in the ETM, while those lighter congener groups with relatively high water solubility were prone to be transported by water flow to larger distances.

Polybrominated diphenyl ethers, decabromodiphenyl ethane and dechlorane plus in aquatic products from the Yellow River Delta, China

Aquatic biota including fish, shrimp and bivalves were collected from the Yellow River Delta (YRD), China to investigate the levels, composition profile and dietary exposure of polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) and dechlorane plus (DP). The concentrations of PBDEs, DBDPE and DP in the organisms ranged from 5.3 to 149, not detected (nd) - 49, and 0.5-29 ng/g lipid weight, respectively. Higher levels of PBDEs and DP were found in mullet (Liza haematocheila).PBDEs were the major pollutants and BDE 209 was the predominant congener of PBDEs suggesting the great production and application of deca-BDE in YRD. The average f_anti values for different species were similar to or a little lower than that of the commercial DP, suggesting syn-DP might be selectively accumulated by the organisms. The estimated daily intake values of HFRs suggested consuming fish was the main pathway for the exposure of halogenated flame retardants.

Developing interim water quality criteria for emerging chemicals of concern for protecting marine life in the Greater Bay Area of South China

This study aimed to establish marine water quality criteria (MWQC) for emerging chemicals of concern (ECCs) for protecting aquatic life in the Greater Bay Area (GBA) of South China. Despite the frequent occurrence and elevated concentrations of these ECCs in the GBA, there is a lack of regional MWQC for these contaminants. We screened 21 common ECCs that were classified into the following six groups: (1) new persistent organic contaminants; (2) brominated flame retardants; (3) perfluoroalkyl and polyfluoroalkyl substances; (4) pharmaceutically active compounds (PhACs); (5) plasticizers; and (6) personal care products. Globally, MWQC for PhACs remain largely unavailable despite their increasing occurrence in marine environments. Using an integrative scientific approach, we derived interim MWQC for the GBA with specific protection goals. The approach described herein can be applied for the derivation of MWQC for ECCs and the establishment of guidelines for ecological risk assessment in the GBA and other regions.

Legacy and novel halogenated flame retardants in seawater and atmosphere of the Bohai Sea: Spatial trends, seasonal variations, and influencing factors

Seventeen halogenated flame retardants (HFRs) were concurrently analyzed in surface seawater and low atmospheric samples from the Bohai Sea during four research cruises. HFRs mainly existed in particulate phases, and in general decabromodiphenyl ethane (DBDPE) was the predominant compound in both air and water samples. Relatively high concentrations were observed in the water of Laizhou Bay (LB), where the largest manufacturing base of brominated flame retardants (BFRs) in China is located and weak water exchange occurs. Transport from LB by coastal currents may be the main source of BFRs in some areas without emission sources. The HFRs in seawater exhibited distinct seasonal variation, with significantly higher concentrations in winter than those in summer. The controlling factors include the resuspension of sediment induced by large wind waves in winter and phytoplankton scavenging in spring and seawater stratification in summer. HFRs composition varied largely in different seasons, due to the different extents of riverine input and atmospheric deposition. Normally, for air masses passing through the nearby industrial regions, high concentrations of DBDPE (up to 1780 pg m^-3) co-existed with high total suspended particle (TSP) levels (up to 150 μg m^-3). The estimated atmospheric deposition fluxes of HFRs were 19, 51, and 80 kg season^-1 in spring, summer, and winter, respectively, indicating that the Bohai Sea is a sink of HFRs via atmospheric deposition. This study has increased our understanding of the behaviors and fates of the legacy and novel HFRs in the shallow coastal sea.

Source identification of chromium in the sediments of the Xiaoqing River and Laizhou Bay: A chromium stable isotope perspective

Hexavalent chromium, Cr(VI), is a heavy metal contaminant and the reduction of Cr(VI) is accompanied by large isotopic fractionation. In this study, the sources of Cr were explored using the Cr isotopic composition of sediments from the Xiaoqing River, a heavily polluted river located in the Shandong Province of China, which flows into Laizhou Bay. The results show that δ⁵³Cr values of the sediments are the highest upstream near the pollution source, and gradually decrease along the river toward the range for igneous reservoirs observed near the estuary. Based on the calculation of authigenic Cr isotopic composition (δ⁵³Cr_auth) using the detrital index and leaching experiments, we suggest that the authigenic Cr in the sample near the pollution source with the highest δ⁵³Cr_auth value mainly comes from the reduction of Cr(VI) discharged by anthropogenic activity, and authigenic Cr in other samples in the midstream with δ⁵³Cr_auth values slightly higher than the range of igneous reservoirs may come from natural oxidative Cr weathering products. By introducing a Rayleigh model, we calculate that at least 31%-55% of Cr(VI) in the river water had been reduced to Cr(III) near the pollution source. Due to the self-purification ability of the river, Cr(VI) was reduced; thus, there is no record of high δ⁵³Cr_auth values in the downstream of the Xiaoqing River and Laizhou Bay, indicating no obvious Cr pollution in these locations. The limited variation of δ⁵³Cr values for samples from a sediment core in Laizhou Bay is also indicative of no obvious Cr pollution in the history. The Cr isotopic compositions of the river sediments are useful for the identification of Cr sources and can be used to advise environmental remediation on Cr pollution.

Polybrominated diphenyl ethers in the environment and human external and internal exposure in China: A review

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants. Because of their toxicity and persistence, some PBDEs were restricted under the Stockholm Convention in 2009. Since then, many studies have been carried out on PBDEs in China and in many other countries. In the present review, the occurrences and contamination of PBDEs in air, water, sediment, soil, biota and daily food, human blood, hair, and other human tissues in China are comprehensively reviewed and described. The human exposure pathways and associated health risks of PBDEs are summarized. The data showed no obvious differences between North and South China, but concentrations from West China were generally lower than in East China, which can be mainly attributed to the production and widespread use of PBDEs in eastern regions. High levels of PBDEs were generally observed in the PBDE production facilities (e.g., Jiangsu Province and Shandong Province, East China) and e-waste recycling sites (Taizhou City, Zhejiang Province, East China, and Guiyu City and Qingyuan City, both located in Guangdong Province, South China) and large cities, whereas low levels were detected in rural and less-developed areas, especially in remote regions such as the Tibetan Plateau. Deca-BDE is generally the major congener. Existing problems for PBDE investigations in China are revealed, and further studies are also discussed and anticipated. In particular, non-invasive matrices such as hair should be more thoroughly studied; more accurate estimations of human exposure and health risks should be performed, such as adding bioaccessibility or bioavailability to human exposure assessments; and the degradation products and metabolites of PBDEs in human bodies should receive more attention. More investigations should be carried out to evaluate the quantitative relationships between internal and external exposure so as to provide a scientific basis for ensuring human health.

Halogenated flame retardants in the sediments of the Chinese Yellow Sea and East China Sea

With the phasing out of traditional polybrominated diphenyl ethers (PBDEs), significant volumes of alternative brominated flame retardants (aBFRs) are being used and released into the environment compartment, especially in coastal regions. The levels and distribution of PBDEs, aBFRs, and dechlorane plus (DPs) were investigated in the surface sediments of the Yellow Sea (YS) and East China Sea (ECS) to examine the distribution and sources of these hydrophobic contaminants. The level and distribution of pollutants in the sediments of YS and ECS show obvious regional differences. As a major replacement for decabromodiphenyl ether (BDE 209), decabromodiphenyl ethane (DBDPE) was the dominant compound observed in the surface sediments, with a concentration one order of magnitude higher than that of BDE 209. High concentrations were found in the depositional zones of the YS, indicating that these contaminants may originate from land-based pollution sources (likely from the Laizhou Bay manufacturing base) near the Bohai Sea. The pollutants can be carried by the coastal current together with the sediment from the Yellow River, transported through the Bohai Strait and deposited in the mud zone of Northern and Southern YS. Low levels of halogenated flame retardants (HFRs) were found in the estuary of the Yangtze River and ECS, indicating that Yangtze River contributes less HFRs to the region. Riverine discharge, atmospheric deposition, surface runoff, ocean current system, and mud area deposition effects may be significant factors influencing the distributions of HFRs.

Fates and ecological effects of current-use pesticides (CUPs) in a typical river-estuarine system of Laizhou Bay, North China

Current-use pesticides (CUPs) are widely applied in agriculture; however, little is known about their environmental behaviors, especially in the freshwater-seawater transitional zone. Water and sediment samples were collected in an intensively human impacted river (Xiaoqing River) from the headwaters to Laizhou Bay to investigate the distributions and environmental fates of four CUPs: trifluralin, chlorothalonil, chlorpyrifos, and dicofol. These CUPs were frequently detected in water and sediment samples. ∑CUPs in water and sediment samples ranged from 1.20 to 100.2 ng L^-1 and 6.6-2972.5 ng g^-1 dry weight (dw), respectively. Chlorpyrifos and chlorothalonil were the most abundant CUPs in water and sediment samples, respectively. Spatial distribution of CUPs in the Xiaoqing River aquatic ecosystem was mainly influenced by point sources, agricultural activities, the dilution effect by seawater, and environmental parameters. Field-based sediment water partitioning coefficients, normalized by organic carbon (log Koc), were calculated. Interestingly, temperature and salinity exhibited significant impacts on the distribution of log Koc of the four CUPs. The effect of temperature on the distribution of log Koc of the four CUPs varied between the CUPs. In most water samples, the levels of chlorpyrifos exceed the freshwater screening benchmarks. Hence, urgent control measures need to be devised and implemented.

Bioconcentration, Biotransformation, and Thyroid Endocrine Disruption of Decabromodiphenyl Ethane (Dbdpe), A Novel Brominated Flame Retardant, in Zebrafish Larvae

The brominated flame retardant decabromodiphenyl ethane (DBDPE), an alternative to decabrominated diphenyl ether (BDE209), has become a widespread environmental contaminant, but its possible toxic effects to wildlife remain unknown. Using zebrafish as a model, we investigated the bioconcentration and impact of DBDPE on thyroid endocrine function after water-borne exposure, compared to BDE209. Zebrafish embryos were exposed to DBDPE or BDE209 (0, 3, 10, 30, 100, 300 nM) for 6 or 14 days. Chemical analysis revealed that DBDPE and BDE209 were bioconcentrated in zebrafish larvae, with similar magnitudes of accumulated concentrations. Based on screened by chromatograms, at least seven unknown compounds were observed in DBDPE-treated larvae, indicating biotransformation of the chemical. Significant increases in whole body content of triiodothyronine (T3) and thyroxine (T4) were detected in DBDPE-treated larvae, but decreased in BDE209-treated groups. Alterations in gene transcription along the related hypothalamic-pituitary-thyroid (HPT) axis were observed. Furthermore, the binding and transport protein transthyretin (TTR) was significantly increased in DBDPE exposure groups. Histological examination and stereological analysis showed no obvious pathological changes in the thyroid gland. The present study demonstrates for the first time the bioavailability, biotransformation and thyroid endocrine disruption associated with DBDPE exposure in fish. Further studies are warranted to identify the metabolites of DBDPE and to define its environmental risks to aquatic organisms.

Brominated flame retardants in atmospheric fine particles in the Beijing-Tianjin-Hebei region, China: Spatial and temporal distribution and human exposure assessment

Atmospheric fine particle (PM_2.5) samples were collected over a whole year (April 2016 - March 2017) across five sampling locations in the Beijing-Tianjin-Hebei (BTH) region, to investigate the occurrence of novel brominated flame retardants (NBFRs) and polybrominated diphenyl ethers (PBDEs). The concentrations of ∑₉NBFRs were in the range of 0.63-104 pg/m³ (15.6 ± 16.8 pg/m³) in atmospheric PM_2.5, while the levels of ∑₉PBDEs (excluding BDE-209) ranged from 0.05 to 19.1 pg/m³ (2.9 ± 3.8 pg/m³) and BDE-209 concentrations ranged from 0.88 to 138 pg/m³ (22 ± 28 pg/m³). Relatively higher levels of NBFRs and PBDEs were found at urban sampling sites in Beijing City and Shijiazhuang City. Decabromodiphenylethane (DBDPE) and BDE-209 were the dominant compounds with the relative abundances of 72% in ∑₉NBFRs and 90% in ∑₁₀PBDEs, respectively. Generally, the levels of most target BFRs in summer were lower than those in other seasons. However, there were no notable seasonal differences in levels of DBDPE and BDE-209 in atmospheric PM_2.5 samples across the BTH region. Significant and positive correlations were found between the concentrations of BFRs and PM_2.5. Daily human exposure via inhalation revealed that children have a higher probability of suffering from the adverse effects of BFRs than that of adults. In addition, residents living near sampling locations across the BTH region may suffer high exposure risks to BDE-209 and NBFRs.

From headwaters to estuary: distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons in an intensively human-impacted river, China

Located in the Shandong Province, North China, the Xiaoqing River is heavily contaminated by industrial wastewater and domestic sewage. However, it plays a significant role with regard to irrigation for agriculture in the river basin. In this study, spatial distribution, sources, and the ecological risk of aqueous polycyclic aromatic hydrocarbons (PAHs) in the Xiaoqing River Basin were investigated from the headwaters to the estuary. Fifteen USEPA priority PAHs (except naphthalene) were quantified in water particulate and soluble phases and in sediment samples. Σ₁₅PAHs concentrations in the sediment varied from 17.15 to 3808.01 ng/g dry weight (dw), with an average of 988.72 ng/g dw, suggesting severe pollution of the Xiaoqing River in comparison with other rivers worldwide. The composition of PAHs was characterized by the high abundance of 4-ring and 5-ring PAHs in sediments and 2-ring and 3-ring PAHs in water. Industrial wastewater is a significant source of PAHs. In the river section, point source was the main factor affecting the distribution of PAHs, while in the estuary region, estuarine turbidity maximum zone (ETM), riverine flow and discharge, and its hydrodynamic parameters play more key roles on PAH levels. Molecular diagnostic ratios have proved that PAHs in sediments were derived from mixed sources, primarily a combination of several combustion processes. Toxicity equivalency concentrations (TEQs) and Ecological risk assessment by Sediment Quality Guidelines indicated that PAHs in sediments might have certain unfavorable effects on ecosystems in certain sites.

Screening of organic flame retardants in Swedish river water

Alternative flame retardants (FRs) have now replaced legacy FRs (such as polybrominated diphenyl ethers, PBDEs), but little is known about their fate in the aquatic environment. In this study, a range of legacy FRs (n=10) and alternative FRs, including halogenated FRs (HFRs, n=32) and organophosphorus FRs (OPFRs, n=19), were screened in water samples collected from 23 rivers covering the whole latitudinal range of Sweden. Of the 61 targeted FRs, 26 were detected in at least one of the river samples, with ΣFR concentrations ranging up to 170ngL^-1 (mean 31±45ngL^-1). In general, higher concentrations and a larger variety of FRs were detected in southern Sweden (ΣFR=60±56ngL^-1) compared with the north (ΣFR=9.0±16ngL^-1). In the south, HFRs were dominant, constituting on average 59% of ∑FRs, whereas in the north, OPFRs were dominant, constituting on average 82% of ∑FRs. This difference was best explained by higher population density in the south. The total daily flux of FRs into the Baltic Sea was estimated to be ~31kg and comprised mainly tetrabromobisphenol-A (TBBPA), 3,4,5,6-tetrabromophthalic anhydride (TEBP-Anh), and 2,4,6-tribromophenol (TBP). To the best of our knowledge, this is the first report of environmental occurrence of TEBP-Anh, which was detected in two rivers and is suggested to originate from airports located near the sampling sites.