Toxicity and bioaccumulation of three hexabromocyclododecane diastereoisomers in the marine copepod Tigriopus japonicas

Inventorization and ecological risk assessment of tetrabromobisphenol A and hexabromocyclododecane in sediments from Guangdong coastal area of South China Sea

Brominated flame retardants (BFRs) exhibit excellent flame retardant properties and are widely used in various industries. Among the common BFRs, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDs) pose substantial ecological and human health risks due to their extensive application and long-range transport. This study established 131 sample collection sites along the coast of the South China Sea (SCS) in Guangdong Province to assess the concentration, distribution, inventory, and ecological risk of TBBPA and HBCDs in surface sediments. The concentrations of TBBPA in SCS sediments ranged from < limit of detection (LOD) to 80 μg/kg dry weight (dw), and those of HBCDs from < LOD to 18 μg/kg dw. The diastereoisomers of HBCDs (α-, β-, and γ-HBCD) in the sediment samples accounted for 36 %, 13 %, and 51 %, respectively. Human activities, particularly those associated with nearby electronic waste disassembly and textile and garment industries, considerably influenced the dispersion of TBBPA and HBCDs. The inventories of TBBPA and HBCDs in Guangdong Province's SCS were estimated to be 3.2 × 105 kg and 7.2 × 104 kg, respectively. The average risk quotient values ranged from <0.01 to 0.016, indicating a low to negligible environmental risk. This study provides deeper insights into the distribution and scientific significance of HBCDs and TBBPA in SCS sediment samples, elucidates the current state of BFR contamination, and offers recommendations for future research on environmental safety and human health in the region.

Enantioselective biomarkers of maize toxicity induced by hexabromocyclododecane based on submicroscopic structure, gene expression and molecular docking

Hexabromocyclododecane (HBCD), as a monitored chemical of the Chemical Weapons Convention, the Stockholm Convention and the Action Plan for New Pollutants Treatment in China, raises significant concerns on its impact of human health and food security. This study investigated enantiomer-specific biomarkers of HBCD in maize (Zea mays L.). Upon exposure to HBCD enantiomers, the maize root tip cell wall exhibited thinning, uneven cell gaps, and increased deposition on the cell outer wall. Elevated malondialdehyde (MDA) indicated lipid peroxidation, with higher mitochondrial membrane potential (MMP) inhibition in (+)-enantiomer treatments (47.2%-57.9%) than (-)-enantiomers (14.4%-37.4%). The cell death rate significantly increased by 37.7%-108.8% in roots and 16.4%-62.4% in shoots, accompanied by the upregulation of superoxide dismutase isoforms genes. Molecular docking presenting interactions between HBCD and target proteins, suggested that HBCD has an affinity for antioxidant enzyme receptors with higher binding energy for (+)-enantiomers, further confirming their stronger toxic effects. All indicators revealed that oxidative damage to maize seedlings was more severe after treatment with (+)-enantiomers compared to (-)-enantiomers. This study elucidates the biomarkers of phytotoxicity evolution induced by HBCD enantiomers, providing valuable insights for the formulation of more effective policies to safeguard environmental safety and human health in the future.

Distribution characteristics and migration trends of hexabromocyclododecanes between seawater-sediment system in different seasons of fishing grounds along the Yellow sea and East China sea coasts

Pollutants in the ecological environment of fishery seawater are harmful to the survival and reproduction of aquatic organisms. Hexabromocyclododecanes (HBCDs) were 42.9% detected within ND-48.89 ng/L in 177 seawater samples and 30.7% within ND-1.07 ng/g dw in 88 sediment samples of the fisheries in the Yellow Sea and East China Sea, respectively. γ-HBCD accounted for 65% of seawater and 89% of sediment samples. HBCDs in seawater in winter (ND-48.89 ng/L) were significantly higher than in summer (ND-4.99 ng/L), possibly because the re-suspension caused by winds and waves could re-migrate HBCDs from the sediment to the seawater in winter. However, seasonal differences of HBCDs in sediment were not significant. The fugacities indicated HBCDs' migrating trend from seawater to sediment due to their hydrophobic nature. There is almost no terrestrial input of HBCDs from the Yangtze and Yellow Rivers, and currently used fishery materials in marine may compose long-lasting sources of HBCDs.

Spatial distribution, conversion, and ecological risk assessment of hexabromocyclododecanes in the sediments of black-odorous urban rivers nationwide in China

Hexabromocyclododecanes (HBCDs) have become a global pollution problem, particularly in China-a major producer and user of HBCDs. However, little is known about the HBCD pollution status in urban rivers nationwide in China. In this study, we comprehensively investigated the pollution characteristics of HBCDs in 173 sediment samples from black-odorous urban rivers across China. Total HBCD concentrations ranged from not-detected to 848 ng/g dw, showing significant differences among the various sampling cities, but generally increasing from west to east China. This distribution pattern of HBCDs was strongly associated with the local industrial output, gross domestic product, and daily wastewater treatment capacity. α-HBCD was the predominant diastereoisomer in most sediments, with an average proportion of 63.8 ± 18.8 %, followed by γ-HBCD (23.8 ± 19.5 %) and β-HBCD (12.4 ± 6.49 %), showing a significant increase of the α-HBCD proportions relative to those in HBCD commercial mixtures and an opposite trend for that of γ-HBCD. These results suggested that HBCDs might undergo isomerization from γ- to α-HBCD and biotic/abiotic degradation with preference for γ-HBCD. Of these conversions, the microbial degradation of HBCDs was further verified by the preferential transformation of (-)-α-, (+)-β-, and (-)-γ-HBCDs and the detection of HBCD-degrading bacteria, including Dehalococcoides, Bacillus, Sphingobium, and Pseudomonas. A risk assessment indicated that HBCDs pose low to moderate risks to aquatic organisms in most black-odorous urban river sediments.

Maternal Transfer and Apical and Physiological Effects of Dietary Hexabromocyclododecane Exposure in Parental Fathead Minnows (Pimephales promelas)

Hexabromocyclododecane (HBCD) is a persistent organic pollutant that has been characterized as an endocrine disruptor, undergoes maternal transfer, and hinders development and growth in oviparous organisms. The present study examined the apical effects of dietary HBCD (11.5, 36.4, 106 mg/kg, wet wt) on adult fathead minnow exposed for 49 days and the subsequent accumulation and maternal transfer kinetics in adult tissue and eggs, respectively. Exposed adults displayed a significant increase in egg production in the medium treatment group, but no other significant effects were noted. Maternal transfer of dietary HBCD had a similar egg-to-muscle ratios (EMR) in the low and medium treatment groups (1.65 and 1.27 [wet wt], respectively). However, the high treatment group deviated from other treatments with an EMR of 4.2 (wet wt), potentially due to differences in total lipid content in food and/or reaching diffusion/lipid saturation limits in adult tissue, resulting in lower accumulation in the adult muscle tissue. A positive correlation was observed between egg HBCD concentration and time of exposure, which indicates that maternal transfer of HBCD is of concern in fish, and further studies should be conducted to fully elucidate the potential adverse effects that may be observed in the early life stage of oviparous organisms. Environ Toxicol Chem 2023;42:143-153. © 2022 SETAC.

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.

Evaluation of ecotoxicological effects associated with coastal sediments of the Yellow Sea large marine ecosystem using the marine copepod Tigriopus japonicus

A copepod bioassay with Tigriopus japonicus was applied to evaluate the relative ecotoxicity of sediments in the Yellow and Bohai seas, and contributions of individual PAHs to copepod toxicity were evaluated. Mean toxicity was greatest in the Yellow Sea of China, followed by the Bohai Sea and Yellow Sea of Korea. Elevated concentrations of sedimentary PAHs, alkylphenols, and styrene oligomers back-supported the significant toxicities observed in bioassay. Copepod toxicity in relation to PAHs indicated the greatest contribution by indeno[1,2,3-c,d]pyrene. However, lacked contribution by PAHs, viz., 2.4 and 3.0 % for the total immobilization and mortality, respectively, indicated a large proportion of unknown toxicants being widely distributed along the Yellow Sea Large Marine Ecosystem (YSLME) coastline. Overall, the present study provides useful baseline information for evaluating the potential sedimentary toxicants, with emphasizing further investigation to identify the unknown toxicants at an LME scale, and elsewhere.

Integrated analysis of exoskeletal surface profile and chitin-related gene expression on Macrophthalmus japonicus mud crabs exposed to hexabromocyclododecane

Hexabromocyclododecanes (HBCDs), widely used brominated flame retardants, easily accumulate in aquatic organisms such as Macrophthalmus japonicus crabs, which inhabit tidal flat sediments. To analyze the effects of HBCD exposure in chitin-formed exoskeleton, we investigated molecular responses of chitin-related genes as well as physical changes of the exoskeletal surface form as a new biological end-point on M. japonicus. The expression patterns of chitin biosynthesis-, modification-, and degradation-related genes in the gills and hepatopancreases of M. japonicus were also analyzed. Additionally, the survivability and exoskeleton surface profiles of M. japonicus crabs were evaluated. M. japonicus chitin synthase expression was significantly downregulated, whereas that of the chitinase transcript was significantly upregulated upon exposure to all HBCD concentrations on day 7. Contrastingly, the gene expression of chitin deacetylase 1 significantly increased upon exposure to all HBCD concentrations on day 1, and this increase was significantly elevated on day 4. The expression of chitin deacetylase 1 was dose-dependent. Additionally, decreased survival and exoskeleton surface profile changes were observed in M. japonicus crabs exposed to all HBCD concentrations. These results suggest that exposure to HBCD induces changes in the synthesis, modification, and degradation of chitin, a pivotal component of the cuticular exoskeleton, and may disrupt the exoskeletal surface structure in M. japonicus crabs.

Mechanochemical destruction and mineralization of solid-phase hexabromocyclododecane assisted by microscale zero-valent aluminum

Hexabromocyclododecane (HBCD) has been listed in Annex A of the Stockholm Convention as a persistent and bio-accumulative chemical. While HBCD is often present in the solid form for its low solubility, cost-effective technologies have been lacking for the degradation of solid-phase HBCD. In this work, mechanochemical (MC) destruction of high-energy ball milling was employed for direct destruction of solid-phase HBCD, where a strong reducer, microscale zero-valent aluminum (mZVAl), was used as the co-milling agent. The new mZVAl-assisted MC process achieved complete debromination and mineralization of HBCD within 3 h milling. The optimal operating parameters were determined, including the milling atmosphere, the milling speed, the mZVAl-to-HBCD molar ratio, and the ball-to-mZVAl mass ratio. Fourier transform infrared spectrometry and Raman analyses revealed that the organic structures of HBCD were destroyed and organic bromine was completely converted into inorganic bromide, accompanied by the generation of amorphous and graphite carbon. Analysis of the milled samples by GC-MS demonstrated the absence of obvious organic matter after MC treatment, also indicating the complete degradation and conversion of HBCD to inorganic compounds. Further X-ray photoelectron spectroscopic analysis indicates that the fresh surface of mZVAl was generated upon the MC treatment, and Al(0) served as a strong reducing agent (e-donor) for reductive debromination and destruction of the carbon skeleton. The mZVAl-assisted MC milling appears promising as a non-combustion approach for effective destruction and carbonization/mineralization of solid-phase HBCD or potentially other persistent organic pollutants.

Evaluating phospholipid- and protein-water partitioning of two groups of chemicals of emerging concern: Diastereo- and enantioselectivity

The partitioning between phospholipids/proteins and water can be used to predict the bioaccumulation potential of chemicals with better accuracy compared with n-octanol-water partition coefficient. However, such partitioning is poorly understood for chiral chemicals, many of which exhibit differential bioaccumulation and toxicity potential between enantiomers. In this study, the enantiospecific liposome-water and bovine serum albumin (BSA)-water partition coefficients (Klip/w and KBSA/w, determined at 25 ℃ and 37 ℃, respectively) were measured by equilibrium dialysis for α-, β-, and γ-hexabromocyclododecane (HBCD) and three β-blockers (propranolol, metoprolol, and sotalol). Raman and fluorescence analyses and molecular docking were conducted to provide additional insights into the partitioning process. Results showed α- and β-HBCD displayed stronger enantioselective partitioning to liposomes with the (-)-form, while (-)-α-HBCD, R-(+)-propranolol, R-(+)-metoprolol, and E2-sotalol favored partitioning to BSA compared with their antipodes. Raman spectra revealed α- and γ-HBCD enhanced and reduced the organization of liposome acyl chains, respectively, and polar interactions enhanced the liposome partitioning of β-blockers. Fluorescence spectra indicated the changed tryptophan microenvironment might influence the BSA steric effect toward HBCD, and electrostatic interactions dominated the formation of BSA-β-blocker complexes. Molecular docking results supported the difference in the thermodynamic nature of interaction between the studied enantiomers and BSA.

Multi-matrix distribution and contamination profiles of HBCDD isomers in a man-made saltwater lake near industrial complexes with high flame retardant consumption in Korea

South Korea is one of the largest consumers of flame-retardants worldwide. In this study, water, sediment, and biota samples were collected from a highly industrialized lake to investigate contamination, isomeric profiles, source, and the bioaccumulation potential of hexabromocyclododecanes (HBCDDs). Almost all of the sediments were severely contaminated by HBCDDs, which were some of the highest global levels compared to those found in previous studies. The highest concentrations and similar profiles to those of technical mixtures of HBCDDs were observed in creeks passing through industrial complexes, indicating on-going contamination by high consumption of HBCDDs from industrial activities. γ-HBCDD was dominant in water and sediment, whereas α-HBCDD was dominant in fish and shellfish. The diastereoisomeric profiles of HBCDDs in multiple matrices were influenced by proximity to industry and chemical properties. In-situ biota-sediment accumulation factors of α-HBCDDs were > 1 in benthic species, implying that HBCDDs are of great concern in sedimentary environments.

Susceptibility of the Non-Targeted Crustacean Eurytemora affinis to the Endocrine Disruptor Tebufenozide: A Transcriptomic Approach

Copepods are zooplanktonic crustaceans ubiquitously widespread in aquatic systems. Although they are not the target, copepods are exposed to a wide variety of pollutants such as insect growth regulators (IGRs). The aim of this study was to investigate the molecular response of a non-targeted organism, the copepod Eurytemora affinis, to an IGR. Adult males and females were exposed to two sub-lethal concentrations of tebufenozide (TEB). Our results indicate a sex-specific response with a higher sensitivity in males, potentially due to a differential activation of stress response pathways. In both sexes, exposure to TEB triggered similar pathways to those found in targeted species by modulating the transcription of early and late ecdysone responsive genes. Among them were genes involved in cuticle metabolism, muscle contraction, neurotransmission, and gametogenesis, whose mis-regulation could lead to moult, locomotor, and reproductive impairments. Furthermore, genes involved in epigenetic processes were found in both sexes, which highlights the potential impact of exposure to TEB on future generations. This work allows identification of (i) potential biomarkers of ecdysone agonists and (ii) further assessment of putative physiological responses to characterize the effects of TEB at higher biological levels. The present study reinforces the suitability of using E. affinis as an ecotoxicological model.

Effects of salinity on the chronic toxicity of 4-methylbenzylidene camphor (4-MBC) in the marine copepod Tigriopus japonicus

Organic ultraviolet filters are widely used in personal care products. 4-methylbenzylidene camphor (4-MBC) is one of the most frequently used UV filters. Due to its widespread usage 4-MBC has been detected at high concentrations in offshore waters. Previous toxicological studies have suggested that 4-MBC might induce much higher toxicity in marine organisms than freshwater species. To explore the effects of salinity on 4-MBC toxicity, the marine copepod Tigriopus japonicus was used as the model species, as it plays an important role in marine ecosystems and can be adapted to a wide range of salinity conditions. T. japonicus were adapted to three different salinity conditions (i.e., 20, 30 and 40 ppt) prior to exposure to 0, 1, and 5 μg L-1 4-MBC for multiple generations (F0-F3). Results showed that environmentally relevant concentrations of 4-MBC had toxic effects on T. japonicus and therefore, can pose a significant risk to marine copepods in the natural environment. In addition, increasing salinity levels increased the lethal, developmental and reproductive toxicities of 4-MBC in T. japonicus. This was because that higher salinity levels increased the uptake rate constant and bioconcentration factor of 4-MBC and also further exacerbated the oxidative stress induced by exposure to 4-MBC in T. japonicus. Our study demonstrated that understanding how salinity affects the toxicity of 4-MBC is important for accurate assessment of the risk of 4-MBC in the aquatic environments.

Tetrabromobisphenol A and hexabromocyclododecane isomers in breast milk from the general population in Beijing, China: Contamination levels, temporal trends, nursing infant's daily intake, and risk assessment

Two currently used brominated flame retardants (BFRs), α, β, γ-hexabromocyclododecane (HBCDD) and tetrabromobisphenol A (TBBPA), were measured in 111 breast milk samples from 37 Beijing mothers. Each mother provided one milk sample per month for 3 months. HBCDD was detected in almost all samples, and the median level reached 5.67 ng g^-1 lipid weight (lw). α- HBCDD was the most abundant isomer (median: 4.23 ng g^-1 lw), followed by γ- and β-HBCDD. For TBBPA, a relatively lower detecting frequency (64%) and contamination level (median: 1.57 ng g^-1 lw) were obtained. A comparison to our previous study revealed that the occurrence of TBBPA and HBCDD in Beijing human milk significantly rose from 2011 to 2014, whereas another commonly used class of BFRs, polybrominated diphenyl ethers (PBDEs), showed significantly decreased during this period. However, a comparison among currently used BFRs showed that levels of some BFRs, such as HBCDD, surpassed those of PBDEs, which indicated that PBDEs were no longer the primarily used BFR in China. However, no significant temporal trends for BFR levels were observed over the 3 months of lactation. Daily intakes of TBBPA and HBCDD were calculated for nursing infants and the median TBBPA and HBCDD intakes via breastfeeding were 6.62 and 26.4 ng kg^-1 bw day^-1, respectively. These values were several times higher than those for adults via food consumption. However, risk assessment using the margin of exposure approach indicated that intakes of TBBPA and HBCDD via breastfeeding can scarcely cause significant health risks to infants.

Degradation of hexabromocyclododecane (HBCD) by nanoscale zero-valent aluminum (nZVAl)

Hexabromocyclododecane (HBCD) has been listed in Annex A of the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2013, but till now there is a lack of efficient methods for its degradation. In this study, nanoscale zero-valent aluminum (nZVAl), an excellent reductant with a very low redox potential of E⁰(Al³⁺/Al⁰) = -1.662 V and strong electron transfer ability, was used to reductively degrade HBCD. Nearly 100% HBCD was degraded within 8 h reaction at 25 °C in ethanol/water (v/v, 50/50) solution without pH adjustment. And about 67% cyclododecatriene (CDT) was obtained, which is the complete debromination product. What's more, the yield of Br^- could achieve nearly 100% after optimizing conditions. The reaction was strongly promoted by increasing the dosages of nZVAl or decreasing the initial concentration of HBCD. The temperature had the most significant influence and the degradation was completed in 40 min with elevating the reaction temperature to 45 °C. The reaction mechanism was further revealed through the characterization of nZVAl particles before and after the reaction by SEM-EDS, TEM, HRTEM, XRD, and XPS. It was found that, after corrosion of the oxide film on the surface of nZVAl, metallic aluminum inside was exposed. The reactive sites were provided and electrons released were transferred from nZVAl to HBCD, causing HBCD degraded to dibromocyclododecadiene (DBCD) and then CDT by reductive debromination. These findings imply that nZVAl can degrade HBCD efficiently with no extra energy input and this offers a new idea for better treatment of HBCD.

Integrated Assessment of Bioconcentration, Toxicity, and Hazards of Chlorobenzenes in the Aquatic Environment

The evaluation of bioconcentration, toxicity, and hazard (BTH) of persistent lipophilic organic compounds (LOCs) are generally performed as separate rather than integrated assessments. There are adequate data sets in the literature for chlorobenzenes (CBs) consisting of (a) concentrations in aquatic biota (C_B) and water (C_w) in the natural environment, (b) laboratory-derived bioconcentration factors (K_B) and field concentration ratios (CR), the field equivalent factor of K_B, (c) measured internal lethal concentrations (ILC₅₀) and model estimated ILC₅₀ calculated from K_B and lethal concentrations (LC₅₀), and (d) calculated hazard quotients in aquatic biota (HQ_B) and in water (HQ_W). However, there have been no integrated studies of those parameter values based on the respective lipid-based parameters (C_BL, K_BL, CR_L, ILC_50L, HQ_BL) performed. This study utilized the lipid-based parameters for CBs; a group of widely occuring, bioaccumulative, and toxic LOCs, and integrated those parameters into a bioconcentration-toxicity-hazard (BTH_L) index. The values of the parameters were obtained from selected literature with known lipid contents of the aquatic biota. The results showed that the laboratory derived bioconcentration factors, K_BLs, were comparable to the corresponding field based factors, CR_Ls, and the measured internal lethal concentrations, ILC_50L, showed comparable values with the estimated ones. The integrated BTH_L index was less than an order of magnitude or moderately acceptable for the assessment of variability, uncertainty, and predictive power of the index. This integrated assessment can be used to support decision making dealing with CBs in specific and LOCs in general, both in regional and global aquatic environments.

Diastereoisomer-specific neurotoxicity of hexabromocyclododecane in human SH-SY5Y neuroblastoma cells

Hexabromocyclododecane (HBCD) is a widely applied brominated flame retardant (BFR) and is regarded as a persistent organic pollutant. It has been found in human tissues and has the potential to cause neurological disorders. However, our understanding of HBCD neurotoxicity at the diastereoisomer level remains lacking. Here, we investigated the neurotoxicity of three HBCD diastereoisomers, i.e., α-, β-, and γ-HBCD, in SH-SY5Y human neuroblastoma cells. Results showed that the HBCD diastereoisomers decreased cell viability, increased lactate dehydrogenase (LDH) release, and impaired cytoskeleton development. Typical morphological features and apoptosis rates showed that the HBCD diastereoisomers induced SH-SY5Y cell apoptosis. The expression levels of several cell apoptosis-related genes and proteins, including Bax, caspase-3, caspase-9, cytochrome c, Bcl-2, and X-linked inhibitor of apoptosis (XIAP), as well as the cell cycle arrest, DNA damage, adenosine triphosphate (ATP) consumption, reactive oxygen species (ROS) levels, and intracellular calcium ion (Ca²⁺) levels, were examined. Results showed that the HBCD diastereoisomer neurotoxicity was ranked β-HBCD > γ-HBCD > α-HBCD. The cell apoptosis and caspase expression levels of the three HBCD diastereoisomers followed the same order, suggesting that caspase-dependent apoptosis may be one mechanism responsible for the structure-selective HBCD diastereoisomer neurotoxicity. The levels of intracellular Ca²⁺ and ROS increased significantly. The ROS levels were ordered β-HBCD > γ-HBCD > α-HBCD, whereas those of intracellular Ca²⁺ were γ-HBCD > β-HBCD > α-HBCD. Thus, ROS may be a key factor regulating the neurotoxicity of HBCD diastereoisomers. To the best of our knowledge, this is the first study to report on the diastereoisomer-specific toxicity of HBCD in human neural cells and on the possible mechanisms responsible for the selective neurotoxicity of HBCD diastereoisomers.

Dietary exposure and risk assessment of exposure to hexabromocyclododecanes in a Taiwan population

Hexabromocyclododecane (HBCD) is commonly used in commercial products and factories. HBCDs can be detected in the air, bioaccumulated deposits, water, soil, sediments, and in biota and foodstuffs in the food-chain because they are not chemically bound to the polymer. We determined the levels of α-, β-, and γ-HBCDs in 270 foodstuffs and the doses of HBCDs Taiwanese are normally exposed to. We also wanted to create a strategy of risk management for HBCDs based on margins of exposure (MOE). HBCDs were frequently detectible in fish, seafood, and poultry. Their highest concentrations were in fish, oil, poultry, and livestock. The highest estimated daily intake was in 0- to 3-year-olds (1.576 ng/kg/day), and lower in 3- to 6- (1.064 ng/kg/day), 6- to 12- (0.899 ng/kg/day), and lowest in 12- to 16- (0.632 ng/kg/day) year-olds. The exposure doses to HBCDs indicated no health concern for Taiwanese. Except for fish, significant concentrations of α- and γ-HBCDs were detected in many other foodstuffs, which might indicate that exposure to HBCD is a relatively recent problem. Therefore, one goal of a management policy should be to follow-up the flow direction of HBCDs in Taiwan.

Effects of penthiopyrad on the development and behaviour of zebrafish in early-life stages

The agricultural use of succinate dehydrogenase inhibitor (SDHI) fungicides has increased dramatically in the US and Europe. As the SDHI fungicides, boscalid, flutolanil and thifluzamide had been reported to induce a series of toxic effects on zebrafish. However, the toxic effects of penthiopyrad on zebrafish have not been reported yet. This study aimed to assess the acute toxicity of penthiopyrad to zebrafish in early-life stages and investigate behavioural response of larvae and the effects on lipid metabolism and pigmentation under sub-lethal exposure of penthiopyrad. Based on results of the acute toxicity tests of zebrafish embryo and larvae, penthiopyrad had an acute toxicity to early-life stages of zebrafish and induced a series of deformities during development. Based on the results of sub-lethal exposure for 8 days, penthiopyrad resulted in significant decreases in swimming velocity, acceleration speed, distance moved and inactive time of larvae at 0.3, 0.6 and 1.2 mg/L. Penthiopyrad induced the disorders of lipid metabolism via affecting fatty acid synthesis and β-oxidation, in accordance with remarkable changes in the content of triglycerides and cholesterol and the expression of key genes (hmgcrα, pparα1, srebf1, cyp51 and acca1) at 1.2 mg/L. In addition, the disorder of melanin synthesis and distribution was caused by penthiopyrad in larvae in accordance with changes in body colour and related gene expression at 8 dpe.

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.

Biomagnification of Hexabromocyclododecane (HBCD) in a coastal ecosystem near a large producer in China: Human exposure implication through food web transfer

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant which is mainly produced in China. Many HBCD facilities are located at the coast and the released HBCD may enter into the coastal ecosystem. There is a risk that HBCD can transfer through the food web to the diet of local population. Therefore, the coastal organisms near one of the biggest HBCD facilities in China were investigated. Variation was observed for the bioaccumulation of HBCD between the detrital food chain and the grazing food chain. In the studied species, the mullet was most contaminated which may be caused by its feeding on detritus. At the same time, the transfer of HBCD along the food web was investigated, and HBCD was biomagnified from the prey to the predator in the grazing food chains. Among the three diastereoisomers, α-HBCD was biomagnified with increasing trophic levels in the food web while β- and γ-HBCD were not. To assess the human dietary exposure, the dietary intake of HBCD from seafood was estimated, and the estimated daily intake (EDI) was 5.22ng/kg/day for adults, and 16.39ng/kg/day for children. The EDI for local residents were tens of times higher than that for general population in China, but the risk through dietary intake was very low in terms of existing reference dose.

Hexabromocyclododecane in polystyrene packaging: A downside of recycling?

While there are no regulatory fire safety obligations for polystyrene (PS) when used as packaging material, concerns exist that such packaging material may contain the flame retardant hexabromocyclododecane (HBCDD) as a result of uncontrolled recycling activities. To evaluate these concerns, we collected 50 samples of PS packaging materials from the UK and 20 from Ireland. HBCDD was detected in 63 (90%) of samples, with concentrations in 4 samples from Ireland exceeding the EU's low POP concentration limit (LPCL) of 0.1% above which articles may not be recycled. Moreover, 2 further samples contained HBCDD >0.01%. While our samples were obtained in the 12 month period prior to the March 2016 introduction of the EU's 0.01% concentration limit above which articles may not be placed on the market, our data suggest that continued monitoring is required to assess compliance with this limit value. Ratios of α vs. γ-HBCDD in our EPS packaging samples (average = 0.63) exceeded significantly (p = 0.025) those in EPS building insulation material samples (average = 0.24) reported previously for Ireland. This shift towards α-HBCDD in packaging EPS is consistent with the additional thermal processing experienced by recycled PS and suggests the source of HBCDD in PS packaging is recycled PS insulation foam. This is of concern owing to the higher bioavailability and lower metabolic clearance of α-HBCDD compared to the β- and γ-isomers.

Multigenerational effects of 4-methylbenzylidene camphor (4-MBC) on the survival, development and reproduction of the marine copepod Tigriopus japonicus

One of the most widely used organic UV filters, 4-methylbenzylidene camphor (4-MBC), is present at high concentrations in offshore waters. The marine copepod Tigriopus japonicus was exposed to different concentrations of 4-MBC (i.e., 0, 0.5, 1, 5 and 10μgL^-1) for 4 consecutive generations (F0-F3) to evaluate the impact of 4-MBC on marine ecosystems. The results showed that in the F0 generation, 4-MBC caused significant lethal toxicity in T. japonicas at concentrations of 5 and 10μgL^-1 and the nauplii were more sensitive to 4-MBC toxicity than the adults. However in the F1-F3 generations, 4-MBC exposure did not affect the survival rate. The hatching rate and the developmental duration from the nauplii to the copepodite (N-C) and from the nauplii to adult (N-A) decreased significantly in the F1-F2 generations and in the F2-F3 generations, respectively, even at the lowest exposure concentration (0.5μgL^-1). In the subsequent two generations (i.e., the F4-F5 generations) of recovery exposure in clean seawater, the growth rates of the original 4-MBC exposure groups were still faster than the control in both the N-C and N-A stages, suggesting possible transgenerational genetic and/or epigenetic changes upon chronic 4-MBC exposure. The expression of the ecdysone receptor gene was up-regulated by 4-MBC, which was consistent with the decrease of the N-C/N-A duration. In addition, 4-MBC may induce oxidative stress and trigger apoptosis in T. japonicas, resulting in developmental, reproductive and even lethal toxicity. A preliminary risk assessment suggested that under environmentally realistic concentrations, 4-MBC had significant potential to pose a threat to marine crustaceans and marine ecosystems.