Influence of humic acid on the bioaccumulation, elimination, and toxicity of PFOS and TBBPA co-exposure in Mytilus unguiculatus Valenciennes

Tetrabromobisphenol A (TBBPA) and Perfluorooctane sulfonate (PFOS) are emerging contaminants which coexist in marine environments, posing significant risks to ecosystems and human health. The behavior of these contaminants in the presence of dissolved organic matter (DOM), specifically the co-contamination of TBBPA and PFOS, is not well understood. The bioaccumulation, distribution, elimination, and toxic effects of TBBPA and PFOS on thick-shell mussels (Mytilus unguiculatus V.), with the absence and presence of humic acid (HA), a typical DOM, were studied. The results showed that the uptake of TBBPA decreased and the uptake of PFOS increased when exposed to 1 mg/L HA. However, at higher concentrations of HA (5 and 25 mg/L), the opposite effect was observed. Combined exposure to HA, TBBPA, and PFOS resulted in oxidative stress in the digestive gland, with the severity of stress dependent on exposure time and HA dose. Histological analysis revealed a positive correlation between HA concentration and tissue damage caused by TBBPA and PFOS. This study provides insights into the influence of HA on the bioaccumulation-elimination patterns and toxicity of TBBPA and PFOS in marine bivalves, offering valuable data for ecological and health risk assessments of combined pollutants in aquatic environments rich in DOM.

The association between brominated flame retardants exposure with bone mineral density in US adults: A cross-sectional study of the national health and nutrition examination survey (NHANES) 2005-2014

BACKGROUND AND AIMS

Exposure to brominated flame retardants (BFRs) has been widely confirmed to impair the normal functioning of the human body system. However, there is a paucity of study on the effects of serum BFRs on bone mineral density (BMD). This study aims to investigate the relationship between exposure to BFRs and BMD in a nationally representative sample of U.S. adults.

METHODS

3079 participants aged between 20 and 80 years with complete data were included in the study. Serum levels of BFRs were measured using automated liquid-liquid extraction and subsequent sample clean-up. The BMD of all participants were assessed by DXA examinations. Generalize linear model, Restricted cubic spline (RCS), subgroup, weighted quantile sum (WQS) and bayesian kernel machine regression (BKMR) were used to estimate the association between serum BFRs and BMD.

RESULTS

Multivariate linear regression analyses revealed that, after adjusting for covariates, PBB153 was significantly associated with TF-BMD (β = 0.0177, 95%CI: 0.0103-0.0252), FN-BMD (β = 0.009, 95%CI: 0.0036-0.0145), TS-BMD (β = 0.0081, 95%CI: 0.0013-0.015) and L1-BMD (β = 0.0144, 95%CI: 0.0075-0.0213). However, the associations lose their statistical significance after further adjustment for sex. BFRs exhibited S-shaped or line-plateau dose-response curves with BMD. In subgroup analyses, BFRs were significantly associated with BMD in participants who were younger than 55 years, female, overweight (BMI >25 kg/m2), and less alcohol consumption. In WQS and BKMR analyses, the effects of BFRs mixtures on BMD differed by sex, and PBDE153, PBDE209 and PBB153 had the highest weights in the WQS regression model.

CONCLUSION

This study showed that serum BFRs negatively predicted BMD in men, but not in women or the general population. PBDE153, PBDE209, and PBB153 were significant BMD factors, especially in younger, overweight, and less alcohol consumption individuals.

Insight into the interaction of tetrabromobisphenol A with sediment-derived dissolved organic carbon in a multiphase system by direct immersion solid phase microextraction

Tetrabromobisphenol A (TBBPA), a ubiquitously used commercial brominated flame retardant (BFR), has been widely detected in aquatic environments, and has aroused much attention due to its potential adverse effects on aquatic organisms. However, current research on the environmental fate and transport of TBBPA in the sediment-dissolved organic carbon (DOC)-water polyphase system is lacking. In this study, the sorption behavior of TBBPA in a water-DOC-sediment system was investigated using the direct-immersion solid-phase microextraction (DI-SPME) method, and the free dissolved concentration (Cw-SPME) and DOC adsorption concentration (CDOC) of TBBPA in water were measured by applying this DI-SPME approach. In addition, the effects of pH, ionic strength, and soluble organic concentration on the adsorption of TBBPA in the multiphase system were evaluated. The adsorption kinetics experimental results show that the adsorption behavior of TBBPA on sediments conforms to a linear model, suggesting that it could be mainly absorbed by sediments. The solid-water partition coefficient (Kd) of TBBPA was artificially reduced 1.54 times using the traditional liquid-liquid extraction method because the sorption behavior of the DOC was ignored, which could be accurately corrected using the DI-SPME method. The logKd and logKOC of TBBPA in the multiphase system were 4.12 ± 0.25 and 6.48 ± 0.25, respectively. Finally, the interference experiment revealed that the sorption behavior of TBBPA was affected by the pH, ionic strength (calcium ion), and humic acid concentration, apart from the lead ion concentration itself.

Hexabromocyclododecane in sediments from riverine, port, and coastal areas of Kaohsiung, Taiwan: levels, spatial distribution, and potential ecological risk

The widespread use of hexabromocyclododecane (HBCD), a brominated flame retardant, is a major public health concern because of the toxic, persistent, and bioaccumulative nature of HBCD. However, there is limited information available regarding the distribution and transportation of HBCD in sediments across various environmental settings, spanning from riverine to marine environments in the Kaohsiung area of Taiwan. In this study, we comprehensively investigated the level and distribution of and potential ecological risk posed by HBCD in surface sediments in the Kaohsiung area of Taiwan. In sediment samples from stations on the Love River and Kaohsiung Port area, the concentrations of HBCD ranged from 10.6 to 320.1 μg/kg dry weight (dw) and nondetectable (n.d.) to 58.4 μg/kg dw, respectively. The concentrations of HBCD in sediment collected from the M1, M2, and M3 sites, located in the Cijin coastal area, were 896.2 μg/kg dw, 3.2 μg/kg dw ( 1. The M1 site had the highest risk level (RQ = 5.27). These data suggest that domestic sewage and industrial wastewater discharge pose a potential risk to marine environments. Consequently, timely measures to control HBCD-related risks are required. Our study offers insight into the environmental effects of HBCD contamination of sediment and provides valuable information that can be used to guide environmental policy and safety measures.

Hydroxylated transformation products obtained after UV irradiation of the current-use brominated flame retardants hexabromobenzene, pentabromotoluene, and pentabromoethylbenzene

Hexabromobenzene (HBB), pentabromotoluene (PBT), and pentabromoethylbenzene (PBEB) are current-use brominated flame retardants (cuBFRs) which have been repeatedly detected in environmental samples. Since information on hydroxylated transformation products (OH-TPs) was scarcely available, the three polybrominated compounds were UV irradiated for 10 min in benzotrifluoride. Fractionation on silica gel enabled the separate collection and identification of OH-TPs. For more insights, aliquots of the separated OH-TPs were UV irradiated for another 50 min (60 min total UV irradiation time). The present investigation of polar UV irradiation products of HBB, PBT, and PBEB was successful in each case. Altogether, eight bromophenols were detected in the case of HBB (three Br3-, four Br4-, and one Br5-isomer), and nine OH-TPs were observed in the case of PBT/PBEB (six Br3- and three Br4-congeners). In either case, Br➔OH exchange was more relevant than H➔OH exchange. Also, such exchange was most relevant in meta- and ortho-positions. As a further point, and in agreement with other studies, the transformation rate decreased with decreasing degree of bromination. UV irradiation of HBB additionally resulted in the formation of tri- and tetrabrominated dihydroxylated compounds (brominated diphenols) that were subsequently identified. These dihydroxylated transformation products were found to be more stable than OH-TPs.

Bioavailability of non-aromatic brominated flame retardants in rats from dust and oil vehicles

Hexabromocyclododecane (HBCD) is a brominated flame retardant (BFR) labeled by the Stockholm Convention as a persistent organic pollutant (POP) and exists primarily as three stereoisomers, i.e. α-, β-, and γ. One of the major routes of human exposure to HBCD is dust found in homes, offices, and cars and dust may be the most important route of HBCD exposure in young children. A study was conducted to determine the oral bioavailability of HBCD from household dust in rats over a 21-d feeding period relative to HBCD bioavailability from a corn oil matrix. Twenty-four hours after the last exposure, rats were sacrificed, and various tissues were collected. HBCD diastereomers were detected in adipose, blood, and liver of both dose groups, suggesting HBCD is bioavailable from both oil and dust. β-HBCD concentrations were below the limit of detection in all tissues, but α-HBCD was detected in the brain of oil-dose rats and in adipose and liver of both dose groups. γ-HBCD was the dominant diastereomer in adipose, blood, and liver samples regardless of dosing matrix. Except for γ-HBCD in muscle of the oil-dosed group, muscle did not contain measurable HBCDs. Adipose tissue accumulated HBCD to a greater extent than muscle or liver, having bioaccumulation factors greater than 1.

In vivo and in vitro study on hepatotoxicity of Tris-(2, 3-dibromopropyl) isocyanurate exposure via mitochondrial and death receptor pathway

Tri-(2,3-dibromopropyl) isocyanate (TBC), a newly brominated flame retardant, is widely used in the synthesis of flame retardant materials with characteristics of persistent organic pollutants. To obtain environmental exposure risks of TBC, Wistar rats and HepG2 cell were used for in vivo and in vitro studies on the toxicity of TBC and relevant ecotoxicological mechanisms of apoptosis. 80 Wistar rats were randomly selected and divided into four exposure groups (0, 0.313, 0.625, 1.250) g/(kg·bw) TBC, half male and half female, with oral administration for 28 days. Wistar rats exhibited appetite loss, weight loss, and dull hair with increasing period of TBC exposure. The pathological examinations revealed the most severe damage of liver and the ratio of liver/body weight of 35.497 × 10^-3 for high-dosed group (1.250 g/kg·bw) was higher than that of 32.792 × 10^-3 for control group in female rats with identical trend in male rats. The above indicators was fairly consistent with the serum test results which further confirmed the liver to be the target organ. The exposure dosages of HepG2 cell were (0, 12.5, 25, 50) μg/mL, individually. The HepG2 cells exposed to TBC for 72 h displayed hazy cell contour and decreased density of cell growth. And there was an inhibition detected by MTT assay, where the maximum inhibition rate was 19.93% under the dose of 50 μg/mL TBC. Apoptosis rate detected by flow cytometry which was demonstrated to be positively correlated to exposure dosage of TBC. The apoptosis rates of the low, medium and high dose groups of TBC exposure were (1.082 ± 0.109) %, (3.017 ± 0.09) % and (6.813 ± 0.233) %, individually. Targeted genes and corresponding protein expressions that triggering apoptosis both in vivo and in vitro were significantly altered. Overall, this work discloses the impacts of TBC exposure on hepatotoxicity, which provides new insights for chemical risk assessments of accelerate cell apoptosis via mitochondrial and death receptor pathway.

The disruption on gut microbiome of Decabromodiphenyl ethane exposure in the simulator of the human intestinal microbial ecosystem (SHIME)

The health risks of Decabromodiphenyl ethane (DBDPE) with its cardiovascular toxicity, liver toxicity and cytotoxicity had been generally acknowledged. However, the influence on gut microbiome and short-chain fatty acids (SCFAs) metabolism caused by DBDPE exposure remained unknown. In this study, three exposure groups (5, 50, 500 mg/L) and control group were used to investigate the effect of DBDPE by using simulator of the human intestinal microbial ecosystem (SHIME). 16S rRNA gene high-throughput sequencing illustrated that high dose DBDPE exposure increased the α-diversity of gut microbiota, while reduced the abundance of Firmicutes and Proteobacteria. In addition, the low dose (5 mg/L) DBDPE inhibited the increasing of SCFAs, but the medium and high dose (50 and 500 mg/L) DBDPE promoted the advancement, especially in ascending colon. Notably, DBDPE exposure lead a similar changing of acetic acid and butyric acid contents in different sections of the colon. This study confirmed the alternation of composition and metabolic function in gut microbial community due to DBDPE exposure, indicating an intestinal damage and appealing for more attention concentrated on the health effects of DBDPE exposure.

Removal of polybrominated diphenyl ethers in high impact polystyrene (HIPS) from waste TV sets

Most studies have shown that improper disposal of e-waste can accelerate the release of high concentrations of polybrominated diphenyl ethers (PBDEs), and this situation causes environmental pollution and human health risks. The recycling technology of waste electronic plastics based on solvent processes can reduce environmental pollution and health risks from PBDEs. In this study, high impact polystyrene (HIPS) from waste TV sets was taken as the research object, and d-limonene and n-propanol were used as solvent and precipitant, respectively. We studied the relationship between the precipitation conditions and the size of precipitate particles, and the effect laws of precipitation conditions on the removal percentage of PBDEs were discussed. Transferring behavior of PBDEs during precipitation was investigated, and the parameters suitable for removing PBDEs from HIPS solution were confirmed. Results showed that lower HIPS concentration in d-limonene, lower precipitation temperature, higher mass ratio of n-propanol to HIPS solution, and greater stirring speed were conducive to form smaller and more uniform precipitate particles. All conditions (concentration, temperature, mass ratio, and stirring rate) that could increase the solubility of PBDEs in the mixed solvent of limonene and n-propanol or decrease the swelling degree of HIPS precipitate particles, or reduce the size of particles could improve the removal percentage of PBDEs. The investigated results indicated that insoluble PBDEs (e.g., decabromodiphenyl ether) transferred into the HIPS precipitate mainly through the generated crystals and then precipitated together with the HIPS particles, and soluble PBDEs (e.g., octabromodiphenyl ether) migrated into the precipitate by the solution entrained. The precipitate particles, which measured approximately 1.0 mm (on average), were obtained when the solution containing 10% of HIPS from waste TV shell was precipitated by adding n-propanol equivalent to twice the mass of the solution at 40 °C and 3000 r/min stirring speed. The total concentration of PBDEs in the precipitate particles (dried) was reduced to 2369 mg/kg, and 88.06% of the PBDEs in the original plastic solution was successfully removed by this process.

Effect of brominated flame retardant on the pyrolysis products of polymers originating in WEEE

Chemical recycling is an environmentally friendly method, which is often used for the recycling of plastics included in waste electric and electronic equipment (WEEE), since fuels and secondary valuable materials can be produced. Brominated flame retardants (BFRs) are usually added into these plastics to reduce their flammability; but they are toxic substances. The aim of this work is to examine the thermal behaviour and the products obtained after pyrolysis of polymer blends that consist of acrylonitrile-butadiene-styrene (ABS), high-impact polystyrene (HIPS), polycarbonate (PC) and polypropylene (PP) with composition that simulates real WEEE, in the absence and presence of a common BFR, tetrabromobisphenol A (TBBPA), in order to investigate its effect on pyrolysis products. Blends were prepared via the solvent casting method and the melt-mixing in an extruder; it was revealed that the latter method may be a better choice for blends preparation, since it did not affect the products obtained. The chemical structure of each polymeric blend was identified by Fourier transform infrared spectroscopy (FTIR). Thermal degradation of the blends was evaluated by thermogravimetric (TG) experiments performed using a thermal analyser (TGA) and a pyrolyser for evolved gas analysis (EGA). It was observed that blends had a similar behaviour during their thermal degradation; and in most cases, they followed a one-step mechanism. Pyrolysis products were identified by the pyrolyser combined with a gas chromatographer/mass spectrometer (GC/MS), and comprised various useful compounds, such as monomers, aromatic hydrocarbons and phenolic compounds that could be used as chemical feedstock. Furthermore, it was found that TBBPA affected products distribution by enhancing the formation of phenolic compounds and on the other hand by resulting in brominated compounds, such as dibromophenol.

Machine learning-assisted optimization of TBBPA-bis-(2,3-dibromopropyl ether) extraction process from ABS polymer

The increasing amount of e-waste plastics needs to be disposed of properly, and removing the brominated flame retardants contained in them can effectively reduce their negative impact on the environment. In the present work, TBBPA-bis-(2,3-dibromopropyl ether) (TBBPA-DBP), a novel brominated flame retardant, was extracted by ultrasonic-assisted solvothermal extraction process. Response Surface Methodology (RSM) achieved by machine learning (support vector regression, SVR) was employed to estimate the optimum extraction conditions (extraction time, extraction temperature, liquid to solid ratio) in methanol or ethanol solvent. The predicted optimum conditions of TBBPA-DBP were 96 min, 131 mL g^-1, 65 °C, in MeOH, and 120 min, 152 mL g^-1, 67 °C in EtOH. And the validity of predicted conditions was verified.

DFT studies on pyrolysis mechanisms of tetrabromobisphenol A (TBBPA)

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant. In order to better understand the decomposition process of TBBPA and clarify the evolution process of the main pyrolysis products, the density functional theory (DFT) method PBE0/6-311G(d) has been used to investigate the pyrolysis mechanisms of TBBPA in this study. Seven possible pyrolysis reaction paths were proposed, and the kinetic parameters in all pyrolysis paths were calculated. The calculation results indicate that in initial degradation of TBBPA without the involvement of hydrogen radical, the demethylation reaction is the main pyrolysis reaction channel, and the keto-enol tautomerization reaction is the main competitive pyrolysis reaction channel. The brominated cyclohexadienone formed through the keto-enol tautomerization is prone to further debromination to generate Br radical. The involvement of hydrogen radical significantly lowers the energy barrier of TBBPA decomposition. When a hydrogen radical is involved in the pyrolysis process, the debromination reaction becomes the major pyrolysis reaction channel, and the homolytic cleavage of C_aromatic-C bond becomes the major competitive pyrolysis reaction channel.

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

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

Simultaneous determination of polybrominated diphenyl ethers and hexabromocyclododecane in plastic waste by short-column gas-chromatography-quadrupole mass spectrometry and electron capture detector

To avoid recycling plastic waste containing polybrominated diphenyl ethers (PBDEs) or hexabromocyclododecane (HBCD), which are listed in the Stockholm Convention on Persistent Organic Pollutants (POPs), a simple method to determine their contents at the time of waste disposal is needed. Herein, we developed a rapid analytical method using a gas chromatograph coupled with quadrupole mass spectrometry or electron capture detection to simultaneously detect PBDEs and HBCD in plastic waste. PBDEs and HBCD were ultrasonically extracted from plastic samples using toluene. The dissolved polymer matrix was then removed using n-hexane and 44% H₂SO₄-impregnated silica gel before analysis of the extract. A run time of less than 10 min was achieved using a custom, short GC column (5 m). The detection limits of the method were below the upper threshold of the low POP content limits defined by the Basel Convention (<1000 mg kg^-1 for both PBDEs and HBCD). The accuracy of the method was confirmed by analyzing seven polymer reference materials. The determined PBDE and HBCD concentrations in most of these reference materials were within 30% of the certified values; the coefficients of variation in triplicate analysis were also within 30%. The concentrations of PBDEs and HBCD in actual plastic waste measured by this method were comparable with those obtained by more sophisticated and expensive methods, such as GC-high-resolution MS for PBDEs and liquid chromatography-tandem mass spectrometry for HBCD. Hence, the method developed herein is a less expensive alternative for identifying PBDE- and HBCD-containing wastes.

Global distribution and trends of polybrominated diphenyl ethers in human blood and breast milk: A quantitative meta-analysis of studies published in the period 2000-2019

Polybrominated diphenyl ethers (PBDEs) are a class of flame-retardants that are found throughout the human body. However, global trends and diversity of the concentrations in human body and the potential risks remain largely unresolved. Based on published data during 2000-2019, we conducted a systematic meta-analysis to understand the burden and risks of PBDEs in humans and their spatiotemporal variations. The report provides a global picture of PBDE concentrations in human blood and breast milk. We found the levels of body PBDE burden in the North American population were higher than those from Asia and Europe. However, high concentrations of blood PBDEs in occupational population from Asia were observed, largely because of poorly controlled e-waste recycling operations. Penta- and deca-BDE were the main contributors in North America and Asia, respectively, reflecting the difference in the production and use of these chemicals. On a global scale, no substantial decreases in the concentrations of PBDEs in the blood and breast milk were observed, although most of the chemicals have been phased out. The results suggested that humans will be exposed to PBDEs with relatively high concentrations in a certain period because of the legacy in products and the environmental media. And the potential health risks necessitate careful study in the future. Our results also remind that the uses of degradation-resistant chemicals should be attached great importance to their safety.

Aqueous photodecomposition of the emerging brominated flame retardant tetrabromobisphenol S (TBBPS)

As an emerging brominated flame retardant (BFR), tetrabromobisphenol S (TBBPS) has been frequently detected in the environmental media and organisms. Knowledges on the transformation and fate of TBBPS in both environment and engineering systems are essential to its ecological risk assessment. Herein, we reported the photochemical decomposition of TBBPS in aqueous solution upon 254 nm ultraviolet irradiation (UV₂₅₄). Results show that TBBPS was highly photoreactive, most likely due to the presence of four ortho-bromine substituents. The molar absorption coefficient and quantum yield of TBBPS were found to be pH-dependent, with the monoanionic form being most photoreactive. A series of photoproducts were identified by solid phase extraction (SPE) combined with liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI(+)-MS/MS. The photolysis of TBBPS likely proceeded through photonucleophilic substitution, photoreductive debromination, and β-scission reactions. A ketocarbene, possibly derived from the lower lying excited triplet state, was proposed to be involved in the photolysis of TBBPS. Ion chromatography analysis revealed that debromination occurred quickly, and the yield of bromide (Br^-) approached 100% after 90 min irradiation. The presence of SRNOM and MRNOM inhibited the photodegradation rate of TBBPS, which is likely due to the light-screening and physical quenching effects of natural organic matter (NOM). Our results reveal that photolysis is an important process for the attenuation of TBBPS in aquatic system; however, naturally occurring species such as NOM can appreciably retard the decay of TBBPS.

On-line spectroscopic study of brominated flame retardant extraction in supercritical CO2

Removal of brominated flame retardants (BFRs) from polymers before disposal or recycling will alleviate negative environmental effects and ensure safe usage of recycled products. Extraction of BFRs in supercritical CO₂ is appealing but also presents challenges to industries due to limited solubility and lack of kinetic studies. For a more comprehensive evaluation of supercritical extraction potentialities, we (i) developed an on-line pressure apparatus that is compatible with both the FTIR and UV-vis spectrometers to enable kinetic and thermodynamic studies; (ii) studied kinetic extraction involving three conventional and two novel BFRs as well as three typical polymeric matrix. Solubilities were determined using the gravimetric method or X-ray fluorescence. FTIR exhibited a superior applicability compared to UV-vis in the following BFR extraction's time-dependency binary and ternary systems. We observed that faster stirring speed, higher temperature, and finer particle size can accelerate the overall extraction kinetics. In binary systems, it took less than 2 h to achieve equilibrium for each BFR at 60 °C, 25 MPa and 1000 rpm. In the presence of polymeric matrix, slower extraction kinetics were observed due to the occurrence of competitive dissolution and molecular diffusion within the matrix. Mathematical models derived from irreversible desorption and Fick's diffusion laws fitted well with the observed extraction kinetics of BFRs, thus enabling us to identify the rate-determining step. The high solubilization rate coefficients that we measured for BFRs revealed that the dynamic extraction process in up-scaling design could compensate for the low solubility with flowing supercritical CO₂.

Tetrabromobisphenol A and hexabromocyclododecanes in sediments and biota from two typical mangrove wetlands of South China: Distribution, bioaccumulation and biomagnification

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) were examined in sediments and biota species from two mangrove wetlands of the Pearl River Estuary (PRE) and the Jiulong River Estuary (JRE), South China, to investigate their distribution, bioaccumulation and biomagnification in mangrove food webs. Levels of TBBPA and ΣHBCD (sum of α-, β- and γ-HBCDs) ranged from 0.003 to 0.31 and not detected (nd) to 1.11 ng/g dry weight in the sediments, and from 0.56 to 22.1 and nd to 56.3 ng/g lipid weight in the biota species, respectively. γ-HBCD was the major diastereoisomer in the PRE sediments, while α- and γ-HBCDs predominated in the JRE sediments. In contrast, α-HBCD was dominant in the biota. Mean enantiomeric fractions (EFs) of α-, β- and γ-HBCDs in the sediments all followed the trend of JRE > racemic standard > PRE. A significant enrichment of (-)-α-HBCD was found in the biota (p = 0.04), with EFs in the range of 0.297-0.485. Bioaccumulations were seen for TBBPA and α-HBCD as their biota-sediment accumulation factors (BSAFs) were greater than 1. (-)-α-HBCD had significantly greater BSAFs than (+)-α-HBCD (p = 0.04), indicating the preferential bioaccumulation of (-)-α-HBCD. Biomagnification factors (BMFs) of TBBPA ranged from 0.83 to 1.51, which varied among feeding relationships and mangroves. Positive relationships were found between TBBPA concentrations and trophic levels of the biota species with trophic magnification factors of 2.17 for the PRE and 1.22 for the JRE, suggesting that TBBPA biomagnifies in the mangrove food webs. No biomagnifications were observed for ΣHBCD, α-HBCD and its enantiomers.

Bioconcentration of 2,4,6-tribromophenol (TBP) and thyroid endocrine disruption in zebrafish larvae

2,4,6-tribromophenol (TBP) is generally used as a brominated flame retardant but is produced in the degradation of tetrabromobisphenol-A. Although TBP is frequently detected in the environment and in various biota, including fish species, we still know little about its toxicity and environmental health risk. Here we investigated the bioconcentration and effects of TBP on the thyroid endocrine system by using zebrafish as a model. Zebrafish embryos (2 h post-fertilization, hpf) were exposed to five concentrations of TBP (0, 0.3, 1, 10, and 100 μg/L) until 144 hpf. According to our chemical analysis, TBP underwent bioconcentration in zebrafish larvae. However, acute exposure to TBP did not affect the hatching of embryos or their risk of malformation, nor the growth and survival of larvae, indicating low developmental toxicity of TBP. The whole-body thyroxine (T4) contents were significantly increased in zebrafish larvae after exposure to TBP, indicating thyroid endocrine disruption occurred. Gene transcription levels in the hypothalamic-pituitary-thyroid (HPT) axis were also examined in larvae; these results revealed that the transcription of corticotrophin-releasing hormone (crh), thyrotropin-releasing hormone (trh), and thyroid-stimulating hormone (tshβ) were all significantly downregulated by exposure to TBP. Likewise, genes encoding thyronine deiodinases (dio1, dio2, and dio3a/b) and thyroid hormone receptors (trα and trβ) also had their transcription downregulated in zebrafish. Further, the gene transcription and protein expression of binding and transport protein transthyretin (TTR) were significantly increased after TBP exposure. Taken together, our results suggest the bioavailability of and potential thyroid endocrine disruption by TBP in fish.

Polybrominated diphenyl ethers in plastic waste of electrical and electronic equipment: a case study in Belarus

Plastic waste of electrical and electronic equipment (WEEE) can contain polybrominated diphenyl ethers (PBDEs) that have been used as fire retardants for a long time. PBDEs were listed in the Stockholm Convention as persistent organic pollutants, so PBDE-containing plastic waste should be separated and disposed of in an ecologically sound manner. In the article, the results of bromine and PBDE content in plastic samples of WEEE collected in Belarus are presented. The screening method for bromine identification and HRGC/HRMS for PBDE identification were applied. It is shown that bromine is present in 43% of the 111 studied samples. Most often, Br-containing plastic was found in CRT monitor, CRT TVs and LCD monitor (about 50%), printers (35%), and LCD TVs (25%). PBDEs were revealed in 12 Br-containing samples, representing TVs, monitors, and printers. The sum of ∑10PBDEs varied from 6.6 to 21,000 μg/kg. BDE-209 dominated in 9 samples (75% of cases); BDE-183, in two; and BDE-47 and BDE-99, in one sample. Based on the low content of PBDEs in the plastic, year of equipment production, and year of restriction of PBDEs applied in the countries-manufacturers, it was concluded that the presence of PBDEs in plastic is a consequence of contaminated waste recycling. Despite the relatively low concentrations of PBDEs (below the limit values established by the Stockholm and Basel conventions for POP wastes), further research is necessary with an extension of the list of analyzed types of equipment and identification of other brominated flame retardants.

Biodegradation of hexabromocyclododecane by Rhodopseudomonas palustris YSC3 strain: A free-living nitrogen-fixing bacterium isolated in Taiwan

The persistent organic pollutant, brominated flame retardant, hexabromocyclododecane (HBCD), identified as an emerging contaminant has been detected in various environmental matrix. The increased level of this toxic organic compound in the environment has been associated with serious human health risks. The results obtained from this study revealed that various Rhodopseudomonas palustris strains isolated from paddy soil in Taiwan possessed good HBCD biodegradation capability when they were cultured aerobically. Among these strains, YSC3 was considered as one of the most potential isolates for HBCD degradation. The optimum HBCD biodegradation occurred at neutral pH and at 35 °C in all our pH and temperature tests at an initial HBCD concentration of 1 ppm. HBCD degradation kinetics generally decreased with the increase of initial HBCD concentration. The study also suggested that the cultivation temperature played a vital role on YSC3 for its initiation of cellular HBCD degradation. The relative-molar ratio of the released bromide ions during the biodegradation of HBCD was observed in the range between 1 and 3.5, suggesting that the debromination reactions occurred. Concomitant with the loss of HBCD, there was a concurrent production of two metabolites, pentabromocyclododecanol and pentabromocyclododecene, which were determined by liquid chromatography and mass spectrometry techniques. On the basis of the obtained results, the possible biodegradation pathways were also proposed in this study.

Acute β-tetrabromoethylcyclohexane (β-TBECH) treatment inhibits the electrical activity of rat Purkinje neurons

Brominated flame-retardants are environmentally pervasive and persistent synthetic chemicals, some of which have been demonstrated to disrupt neuroendocrine signaling and electrical activity of neurons. 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) lacks the toxicity of other classes of BFRs, however its safety is still questioned, as little is known of its neurological effects. Therefore, we sought to determine if TBECH could acutely alter the electrical activity of Purkinje neurons maintained in vitro. Briefly, cerebella from gestational day 20 rats were dissociated and maintained for up to three weeks in culture. Action potentials of Purkinje neurons were detected by cell-attached patch clamp before, during, and after application of β-TBECH. β-TBECH decreased action potential activity in a dose-dependent manner with an apparent EC₅₀ of 396 nM. β-TBECH did not significantly alter the coefficient of variation, a measure of the regularity of firing, suggesting that the mechanism of β-TBECH's effects on firing frequency may be independent of Purkinje neuron intracellular calcium handling. Because levels of β-TBECH in exposed individuals may not approach the EC₅₀, these data suggest that any abnormal neurodevelopment or behavior linked with β-TBECH exposure may result from endocrinological effects as opposed to direct disruption of electrical activity.

Aerobic cometabolism of tetrabromobisphenol A by marine bacterial consortia

The coastal environments worldwide are subjected to increasing TBBPA contamination, but current knowledge on aerobic biodegradability of this compound by marine microbes is lacking. The aerobic removal of TBBPA using marine consortia under eight different cometabolic conditions was investigated here. Results showed that the composition and diversity of the TBBPA-degrading consortia had diverged after 120-day incubation. Pseudoalteromonas, Alteromonas, Glaciecola, Thalassomonas, and Limnobacter were the dominant genera in enrichment cultures. Furthermore, a combination of beef extract- and peptone-enriched marine consortia exhibited higher TBBPA removal efficiency (approximately 60%) than the other substrate amendments. Additionally, Alteromonas macleodii strain GCW was isolated from a culture of TBBPA-degrading consortium. This strain exhibited about 90% of degradation efficiency toward TBBPA (10 mg L^-1) after 10 days of incubation under aerobic cometabolic conditions. The intermediates in the degradation of TBBPA by A. macleodii strain GCW were analyzed and the degradation pathways were proposed, involving β-scission, debromination, and nitration routes.

Inhomogeneity of sediment samples in analysis of hexabromocyclododecane

The repeatability test of the analytical method for hexabromocyclododecane (HBCD) was conducted with sediment sample. The maximum HBCD concentration exceeded the minimum by a factor of 90 even though the identical sediment samples were used. Therefore, we examined which step of the analytical method was the factor causing variability. We examined the blank test, and confirmation test of the extraction and purified procedure. From these results, we confirmed that there was nothing wrong with the accuracy of our analytical method. These results indicate that the variability of HBCD concentration in the repeatability test was attributed not to the analytical method, but to the inhomogeneity of the sediment sample. Aluminum, silicon, and organic carbon in sediments were measured to compare the variability of these concentrations with that of HBCD concentration. These concentrations were similar values within identical samples which showed variability in HBCD concentration. HBCD concentration in several samples did not correlate with organic carbon content. These results suggests that sediment samples were homogeneous by itself, and HBCD was heterogeneously distributed in spite of homogeneity of organic carbon in sediment. The sediment sample with variability in HBCD concentration showed different HBCD diastereomer compositions in identical sediment. It implies that the sample contained HBCD derived from different histories or point sources. Even though we increased sample amounts to analyze the homogeneity of the sample, HBCD concentration varied within identical samples if the sample had a hot spot. Past monitoring data may contain overestimation or underestimation of HBCD concentration in sediment.

Molecular mechanisms and tissue targets of brominated flame retardants, BDE-47 and TBBPA, in embryo-larval life stages of zebrafish (Danio rerio)

Brominated flame retardants are known to disrupt thyroid hormone (TH) homeostasis in several vertebrate species, but the molecular mechanisms underlying this process and their effects on TH-sensitive tissues during the stages of early development are not well characterised. In this study, we exposed zebrafish (Danio rerio) embryo-larvae to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and tetrabromobisphenol A (TBBPA) via the water for 96 h from fertilisation and assessed for lethality, effects on development and on the expression of a suite of genes in the hypothalamic-pituitary-thyroid (HPT) axis via both real time quantitative PCR (qRT-PCR) on whole body extracts and whole mount in situ hybridisation (WISH) to identify tissue targets. The 96-h lethal median concentration (96h-LC₅₀) for TBBPA was 0.9 μM and mortality was preceded by retardation of development (smaller animals) and morphological deformities including, oedemas in the pericardial region and tail, small heads, swollen yolk sac extension. Exposure to BDE-47 did not affect zebrafish embryo-larvae survival at any of the concentrations tested (1-100 μM) but caused yolk sac and craniofacial deformities, a curved spine and shorter tail at the highest exposure concentration. TBBPA exposure resulted in higher levels of mRNAs for genes encoding deiodinases (dio1), transport proteins (ttr), the thyroid follicle synthesis protein paired box 8 (pax8) and glucuronidation enzymes (ugt1ab) and lower levels of dio3b mRNAs in whole body extracts, with responses varying with developmental stage. BDE-47 exposure resulted in higher levels of thrb, dio1, dio2, pax8 and ugt1ab mRNAs and lower levels of ttr mRNAs in whole body extracts. TBBPA and BDE-47 therefore appear to disrupt the TH system at multiple levels, increasing TH conjugation and clearance, disrupting thyroid follicle development and altering TH transport. Compensatory responses in TH production/ metabolism by deiodinases were also evident. WISH analyses further revealed that both TBBPA and BDE-47 caused tissue-specific changes in thyroid receptor and deiodinase enzyme expression, with the brain, liver, pronephric ducts and craniofacial tissues appearing particularly responsive to altered TH signalling. Given the important role of TRs in mediating the actions of THs during key developmental processes and deiodinases in the control of peripheral TH levels, these transcriptional alterations may have implications for TH sensitive target genes involved in brain and skeletal development. These findings further highlight the potential vulnerability of the thyroid system to disruption by BFRs during early developmental windows.

Dermal disposition of Tetrabromobisphenol A Bis(2,3-dibromopropyl) ether (TBBPA-BDBPE) using rat and human skin

Tetrabromobisphenol A Bis(2,3-dibromopropyl) ether (TBBPA-BDBPE) is a high production volume brominated flame retardant (BFR) used in consumer products, resulting in ubiquitous human exposure. Although the major route of exposure for this chemical is believed to be via ingestion, dermal contact is likely via contaminated dust. Independent trials of a single dose of 100 nmol/cm² (∼1 μCi [¹⁴C]/cm²) of [¹⁴C]-radiolabeled TBBPA-BDBPE was applied to whole rat skin (in vivo) or split-thickness human and rat skin (ex vivo) to estimate in vivo human percutaneous uptake. [¹⁴C]-radioactivity was quantified to determine dermal absorption (dose retained in dosed skin) and penetrance (dose recovered in receptor fluid [ex vivo] or tissues/excreta [in vivo]) over 24 h. In vivo absorption and penetration for rat skin was 26% and 1%, with a maximum flux of 44 ± 9 pmol/cm²/h. In ex vivo rat skin, absorption and penetration and absorption values were 23% and 0.3% (flux = 26 ± 8 pmol/cm²/h). In ex vivo human skin, 53% was absorbed and penetration was 0.2% with a maximal flux of 16 ± 12 pmol/cm²/h. Computed maximal flux for in vivo human skin was 21 ± 9 pmol/cm²/h with expected total absorption of ∼80% and a penetration of <1%. HPLC-radiometric analyses of samples showed that TBBPA-BDBPE was not metabolized in ex vivo or in vivo studies. These studies indicate that TBBPA-BDBPE is likely to be dermally bioavailable even after washing and dermal contact with this chemical should be considered an important route of exposure.

Decabromodiphenyl ether exacerbates hyperglycemia in diet-induced obese mice. Toxicology. 2019;412:12-18. [PMID: 30468867 DOI: 10.1016/j.tox.2018.11.004]

Decabromodiphenyl ether (decaBDE) is a brominated flame retardant used in plastic and textile articles. It has become a ubiquitous environmental contaminant, however; the relationship between decaBDE and obesity remains to be elucidated. We aimed to clarify if oral decaBDE exposure can be a factor in obesity and its related metabolic dysfuctions. Male C57BL/6 J mice were fed a normal (ND, 9.0 kcal% fat) or high-fat (HFD, 62.2 kcal% fat) diet and treated with decaBDE (the equivalent of three doses of 0, 0.5 (L-DecaBDE), and 10 (H-DecaBDE) μg/kg body weight/day) ad libitum in drinking water from 5 to 20 weeks of age. In HFD-fed mice, decaBDE exposure markedly increased both fasting blood glucose levels compared with vehicle exposure, which was more prominent in H-DecaBDE-exposed mice. DecaBDE exposure significantly reduced mRNA levels of glucose transporter 4 and thyroid hormone receptor alpha in skeletal muscle and mechanistic target of rapamycin complex 2 in brown adipose tissue compared with vehicle exposure under HFD-feeding. The tendency for hyperglycemia and the remarkable activation of insulin signaling pathway-related genes were observed in ND + DecaBDE mice compared to the ND + Vehicle mice. These results demonstrate that decaBDE can contribute to the enhancement of diet-induced hyperglycemia through disruption of glucose homeostasis.

Deriving aquatic life criteria for PBDEs in China and comparison of species sensitivity distribution with TBBPA and HBCD

Polybrominated diphenyl ethers (PBDEs) are important industrial brominated flame retardants. PBDEs have raised great concerns for their persistence, bioaccumulation, and harm to aquatic life and human health. Pentabromodiphenyl ether (PeBDE), octabromodiphenyl ether (OcBDE), and decabromodiphenyl ether (DeBDE) are three main commercial PBDEs congeners. In this study, published ecotoxicity data of these three PBDEs congeners for Chinese freshwater species were collected, and several acute and chronic toxicity tests for the three PBDEs congeners were performed. Using the derivation method for aquatic life criteria developed by the United States Environmental Protection Agency (USEPA), we determined that the criterion maximum concentration (CMC) for PeBDE, OcBDE and DeBDE for protection of freshwater organisms were 0.0492 mg/L, 0.197 mg/L and 0.239 mg/L, respectively. The criterion continuous concentration (CCC) for PeBDE, OcBDE and DeBDE were 0.0103 mg/L, 0.0224 mg/L and 0.0267 mg/L, respectively. The results provided a good reference for the derivation of PBDEs' water quality criteria and a basis for ecological risk assessment of PBDEs. In addition, the results of species sensitivity distribution comparison showed that the toxicity rank of five brominated flame retardants was TBBPA > PeBDE > OcBDE > DeBDE > HBCD.

Polybrominated diphenyl ethers and perfluorinated alkyl substances in blood serum of New Zealand adults, 2011-2013

A national survey was conducted in 2011-2013 to assess serum concentrations of brominated flame retardants (BFRs) and perfluorinated alkyl substances (PFASs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 geographic regions, 2 ethnic groups (Māori/non-Māori) and sex. Eligible participants (n = 734; response rate of contacted individuals = 37%) donated up to 30 mL of blood, after which serum was pooled (49 pools for BFRs, 63 pools for PFASs) according to demographic strata. BFRs were analysed by GC-HRMS and PFASs by LC-MS/MS. Associations between serum BFRs and PFASs and demographic variables (age, region, ethnicity, sex) were assessed using regression analysis. The weighted geometric mean (GM) serum concentrations of BDE47, BDE99, BDE100, and BDE153 were 2.0, 0.66, 0.43, and 1.2 ng/g lipid, respectively. The weighted geometric mean (GM) serum concentrations of PFOS, PFOA, PFHxS, and PFNA were 3.4, 2.4, 1.0, and 0.66 ng/mL, respectively. The majority of BFRs showed higher serum concentrations in younger age groups. Conversely, the four PFASs showed higher serum concentrations in older age groups. Concentrations of BFRs and PFASs were generally lower in females compared to males. In New Zealand, both age and sex are important determinants of BFR and PFAS serum concentrations.

Enhancement of copper, nickel, and gallium recovery from LED waste by adaptation of Acidithiobacillus ferrooxidans

This paper is the first study on the extraction of Cu, Ni, and Ga from Light Emitting Diode (LED) waste by bio-hydrometallurgy technology. LEDs have a high concentration of metals and various types of brominated flame retardants (BFRs). This study demonstrates the need for strains with resistance to high concentrations of LED powder. The adaptation of Acidithiobacillus ferrooxidans to LED powder was done through a serial acclimatisation procedure in five steps of 5, 10, 15, 20, and 25 g/l. The results indicated that the heavy metals tolerance of Acidithiobacillus ferrooxidans decreased as the pulp density increased from 5 to 20 g/l. The pulp density > 20 g/l of LED powder caused a toxic response resulting in an evident inhibitory effect on bacterial activity. In the presence of 20 g/l of LED powder, adapted Acidithiobacillus ferrooxidans exhibits higher Fe³⁺ level, cell amount, ORP, and lower pH than the non-adapted cells. The recovery of copper, nickel, and gallium were higher by adapted bacteria compared to non-adapted bacteria. The adapted A. ferrooxidans leached approximately 84%, 96%, and 60%, copper, nickel, and gallium, respectively. It could be concluded that adaptation can be an effective tool for enhancement of copper, nickel, and gallium bioleaching from LED powder and adapted Acidithiobacillus ferrooxidans would be a suitable strain in LED waste bioleaching.

Complete genome sequence of Bacillus sp. HBCD-sjtu, an efficient HBCD-degrading bacterium

Environmental pollution caused by the release of industrial chemicals is currently one of the most important environmental harms. Manufacturing chemicals can be biodegraded, and valuable intermediates can be used as pharmacophores in drug targeting and have several other useful purposes. Hexabromocyclododecane (HBCD), a non-aromatic brominated flame retardant, is a toxic compound that consists of a cycloaliphatic ring of 12 carbon atoms to which six bromine atoms are attached. It is formed by bromination of cis-trans-trans-1,5,9-cyclododecatriene, but its use is now restricted in several countries, because it is an environmental pollutant. Little is known about whether bacteria can degrade HBCD. A bacterial strain that degrades HBCD was recently isolated using enrichment culture techniques. Based on morphological, biochemical and phylogenetic analysis this isolate was categorized as Bacillus cereus and named strain HBCD-sjtu. Maximum growth and HBCD-degrading activity were observed when this strain was grown at 30 °C, pH 7.0 and 200 RPM in mineral salt medium containing 0.5 mm HBCD. The genome of strain HBCD-sjtu, which consists of only one circular chromosome, was sequenced. This whole genome sequence will be crucial for illuminating the molecular mechanisms of HBCD degradation.

Contamination trends and factors affecting the transfer of hexabromocyclododecane diastereomers, tetrabromobisphenol A, and 2,4,6-tribromophenol to breast milk in Japan

This study investigated contamination trends and factors affecting the levels of brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) diastereomers, tetrabromobisphenol A (TBBP-A), and 2,4,6-tribromophenol (2,4,6-TBP), in breast milk in Japan. Breast milk samples (n = 64) were collected from mothers living in six prefectures in Japan. The mean concentrations were 2.2, 0.19, 0.29, 3.0, and 0.59 ng/g lipid weight for α-HBCD, β-HBCD, γ-HBCD, TBBP-A, and 2,4,6-TBP, respectively. Based on the previous studies, the levels of ΣHBCD in Japanese women's milk appear to be increasing, and the levels of TBBP-A are higher than those in other Asian countries. Although ΣHBCD were not correlated to phenolic BFRs, the concentration of β-HBCD was significantly correlated to the concentrations of TBBP-A (r = 0.440, p < 0.01) and 2,4,6-TBP (r = 0.320, p < 0.01). The concentration of γ-HBCD increased significantly with maternal age (r = 0.378, p < 0.01), but the concentrations of the other analytes were not dependent on age. The concentration of α-HBCD was higher in primiparae than in multiparae (p < 0.05), while TBBP-A was higher in multiparae. No significant correlation was found between the phenolic BFR levels in milk and mothers' age, working place, and drinking/smoking habits. These results suggest that exposure to α- and γ-HBCD diastereomers could be affected by maternal age and parity, respectively, because of their different kinetics and sources. Therefore, these factors should be considered when conducting infant risk assessments.

Novel approach for removing brominated flame retardant from aquatic environments using Cu/Fe-based metal-organic frameworks: A case of hexabromocyclododecane (HBCD)

Cu and Fe based metal-organic frameworks (Cu-BTC and Fe-BTC) were synthesized via a simple solvothermal method and innovatively utilized to remove a typical nonionic brominated flame retardant, hexabromocyclododecane (HBCD), from aquatic environment. Results show that over 80% of HBCD was removed by Cu-BTC within 5h, which is 1.3 times higher than removal by Fe-BTC. Thermodynamic analysis confirms spontaneous adsorption of HBCD onto the metal-organic frameworks (MOFs). Furthermore, the Gibbs free energy of Cu-BTC (-9.11kJ/mol) is more negative than that of Fe-BTC (-5.04kJ/mol). Both adsorption isotherms of HBCD onto Cu-BTC and Fe-BTC followed the Langmuir model, indicating a typical monomolecular-layer adsorption mechanism. In addition, the water stability test of these MOFs shows that the collapse of the Cu-BTC crystal structure is significantly hindered in the aquatic environment due to adsorption of the hydrophobic HBCD. The proposed adsorption mechanism includes van der Waals and hydrophobic interactions. These findings demonstrate that Cu/Fe-BTC are promising adsorbents for the removal of hydrophobic organic pollutants from aquatic environments, and may further improve the understanding of MOF materials for environmental applications.

TBBPA disposition and kinetics in pregnant and nursing Wistar Han IGS rats

Tetrabromobisphenol-A (TBBPA) is a brominated flame retardant (BFR) commonly used in electronics to meet fire safety standards and has the largest worldwide production of any BFR. TBBPA has been detected in human breast milk and maternal/cord serum, indicating exposure to mothers, fetuses, and breastfeeding newborns although exposure to fetuses and newborns is poorly understood. Pregnant or nursing Wistar Han IGS rats were administered [14C]-TBBPA in a single dose (25 mg/kg, 2.5 μCi/kg) and euthanized between 0.5&24 h post dose to determine disposition in pregnant and nursing rats and their pups. Systemic exposure was largely unchanged between 1&8 h post dose in pregnant rats; [14C]-radioactivity in blood varied only slightly between 0.5&8 h (2.6 ± 0.6 → 2.6 ± 0.8 nmol-eq/mL) but was below the limit of detection at 24 h with an absorption half-life of 16min and elimination half-life of 17 h. Cmax was observed at 30min in lactating rats and concentrations fell steadily through 8 h. Plasma from pregnant rats contained a mixture of TBBPA and TBBPA-conjugates at 30min but only metabolites in subsequent samples. TBBPA was not detected in lactating dam plasma in this study. Placental concentrations increased through 8 h while whole-fetus Cmax occurred at 2 h post dose. In lactating animals, liver, uterus, and mammary time-concentration curves lagged slightly behind blood-concentration curves. It was clear from these studies that TBBPA is available to both the developing fetus and nursing pup following maternal exposure, and nursing pups are continuously exposed via contaminated milk produced by their mother. This research was supported in part by the Intramural Research Program of NIH/NCI.

Transport of Hexabromocyclododecane (HBCD) into the soil, water and sediment from a large producer in China

Hexabromocyclododecane (HBCD) is used as a flame retardant with extensive industrial applications, which is mainly produced at facilities on the coast of China. Radially distributed soil samples and equidistant paired water and sediment samples were taken around one of the biggest HBCD production enterprises to reflect its environmental behavior via air deposition and wastewater discharge of HBCD diastereoisomers (α-, β- and γ-HBCD). Worldwide high concentrations of HBCD (11,700ng/g in the soil, 5080ng/L in the water and 6740ng/g in the sediment) were detected in these environmental samples. Concentrations dropped by two orders of magnitude over several kilometers distance from the plant. The diastereoisomer pattern varied in the three environmental compartments examined, such that γ-HBCD was the predominant diastereoisomer in the soil and sediment whilst α- and γ-HBCD shared the predominance in the water. The mass inventories of HBCD in the local soil and sediment were estimated to be 5006kg and 30kg respectively, suggesting that soil was the major sink of HBCD in the production area. As for the soil, the environmental burdens in the areas with radiuses of 2, 4 and 6km were 3210, 3770 and 4590kg respectively.

Hens can ingest extruded polystyrene in rearing buildings and lay eggs contaminated with hexabromocyclododecane

The overall concentration of hexabromocyclododecane (HBCDD) in eggs is low although abnormally high concentrations exceeding 3000 ng g^-1 lw have been reported. In order to test whether these contaminations may originate from the ingestion of insulating materials in rearing buildings, a group of 55 hens raised in a collective cage was provided with a 64-g piece of extruded polystyrene (XPS, 2.59% HBCDD of which 75, 15 and 10% as α-, β- and γ-HBCDD, respectively). Hens entirely consumed the piece within 3 days, leading to a mean daily exposure of 4.7 mg HBCDD per kg body weight. Whole egg HBCDD concentration reached a maximum of 1037 ng HBCDD g^-1 fresh weight (fw), recorded 2 days after the piece had disappeared, and decreased down to 86 ng g^-1 fw within the 19 following days. In all these samples, HBCDD was made of 98.7 ± 0.7 and 1.3 ± 0.6% α- and β-HBCDD, respectively, and 0.1% γ-HBCDD when quantified; it was enriched in (-)α- and (+)β-HBCDD with enantiomeric fractions of 0.438 ± 0.009 and 0.579 ± 0.030, respectively. HBCDD was quantified in all the individual eggs collected the last day of experiment at concentrations ranging between 0.47 and 1361 ng g^-1 fw, according to a lognormal distribution. The ingestion of XPS in degraded rearing buildings is thus a plausible cause of on-farm egg contamination by HBCDD which should be strictly avoided.

Functional genomic assessment of 2, 2-bis (bromomethyl)-1, 3-propanediol induced cytotoxicity in a single-gene knockout library of E. coli

Functional gene fingerprinting of chemicals could be used to understand the direct gene-chemical interaction in the process of toxification from a genome-wide scale. 2, 2-bis (bromomethyl)-1, 3-propanediol (BMP) is a brominated flame retardant with widespread production but with very limited toxicological data. Here the cytotoxicity of BMP was assessed by Escherichia coli (E. coli) functional genome-wide knockout mutants screening and the underlying molecular mechanism was investigated. The median inhibition concentration (IC50) of BMP was 1.608 ± 0.078 mg/ml after 24 h exposure. 119 initial, including 66 sensitive and 53 resistant single gene mutants, were identified by a full library screening of BMP at the concentration of IC50. The resistant genes were significantly enriched in nucleobase-containing compound biosynthetic process (GO: 0034654) by gene ontology (GO) biological process analyses, which suggested that the pathway of DNA repair is a critical cellular process in the survival of cells exposed to BMP. Meanwhile, function annotation of all BMP responsive genes suggested the mechanism of BMP was associated with DNA damage, oxidative stress and cellular transmembrane transport process. Many genes were exclusively responsive to BMP comparing with other chemicals that has been assessed by E. coli mutant screening approach, which indicated that BMP has a distinct mode of toxic action. Overall, the functional genomic screening approach presented here provides a great tool to assess the cellular toxicological mechanism of environmental chemicals.

Occurrence, composition, source, and regional distribution of halogenated flame retardants and polybrominated dibenzo-p-dioxin/dibenzofuran in the soils of Guiyu, China

Guiyu, China, is well-known for the crude disposal of electronic waste (EW) and severe persistent organic pollutants (POPs). Therefore, in this study, the occurrence, composition, and source of polybrominated diphenyl ethers (PBDEs), 2,2',4,4',5,5'-hexabromobiphenyl (BB153), some novel brominated flame retardants (NBFRs), Dechlorane Plus (DP) and polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) in farmland soils covering Guiyu were studied. In EW disposal area soils, PBDEs were the most abundant FRs, with concentrations of 13-1014 ng g^-1. The primary PBDE sources were technical Penta- and Deca-BDE mixtures in northern and southern Guiyu, respectively. The levels of BB153 were relatively low, possibly because it has been banned in the 1970s. The concentrations of hexabromobenzene (HBB) were 0.048-3.3 ng g^-1, while pentabromoethylbenzene (PBEB) was almost not detected in the soils. Two alternatives to commercial PBDEs, decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), were the primary NBFRs, with concentrations of 1.8-153 ng g^-1 and 0.43-15 ng g^-1, respectively. DP was another primary FR, with concentrations of 0.57-146 ng g^-1. Moreover, syn-DP and anti-DP isomers were not stereoselectively decomposed during the EW disposal process and were therefore present in their original fractions in the soils. The levels of PBDD/Fs in EW disposal area soils were 2.5-17 pg TEQ g^-1. 1,2,3,4,6,7,8-HpBDF and OBDF were the dominant congeners, mainly derived from processing, pyrolysis and combustion of BFRs. The regional distribution of pollutants was shown to be related to the disposal manner of EW, with their open thermal disposal tending to release more highly brominated compounds such as BDE209, DBDPE, and 1,2,3,4,6,7,8-HpBDF. Additionally, some riverbank sites were heavily polluted because of nearby point sources, downwind Simapu (SMP) town without EW disposal activity was also contaminated by these pollutants.

Occurrence and effects of plastic additives on marine environments and organisms: A review

Plastics debris, especially microplastics, have been found worldwide in all marine compartments. Much research has been carried out on adsorbed pollutants on plastic pieces and hydrophobic organic compounds (HOC) associated with microplastics. However, only a few studies have focused on plastic additives. These chemicals are incorporated into plastics from which they can leach out as most of them are not chemically bound. As a consequence of plastic accumulation and fragmentation in oceans, plastic additives could represent an increasing ecotoxicological risk for marine organisms. The present work reviewed the main class of plastic additives identified in the literature, their occurrence in the marine environment, as well as their effects on and transfers to marine organisms. This work identified polybrominated diphenyl ethers (PBDE), phthalates, nonylphenols (NP), bisphenol A (BPA) and antioxidants as the most common plastic additives found in marine environments. Moreover, transfer of these plastic additives to marine organisms has been demonstrated both in laboratory and field studies. Upcoming research focusing on the toxicity of microplastics should include these plastic additives as potential hazards for marine organisms, and a greater focus on the transport and fate of plastic additives is now required considering that these chemicals may easily leach out from plastics.

Accumulation of α-hexabromocyclododecane (α-HBCDD) in tissues of fast- and slow-growing broilers (Gallus domesticus)

The aim of the current study was to describe the fate of ingested α-hexabromocyclododecane (α-HBCDD) in fast-growing (FG) and slow-growing (SG) broilers, through an exposure to a dietary concentration of 50 ng α-HBCDD g^-1 feed during 42 and 84 days, respectively. Depuration parameters were assessed in SG broilers successively exposed during 42 days and depurated during 42 days. At market age, SG broilers had ingested 42% more feed than FG broilers, while their body weight gain per g of feed ingested was 34% lower. No isomerization of α- to β- or γ-HBCDD forms occurred, while OH-HBCDD was identified as a product of α-HBCDD metabolism. Irrespective of the strain, abdominal fat displayed the highest α-HBCDD concentration on a lipid weight basis, followed leg muscles and then breast muscle, liver and plasma. The accumulation ratios of α-HBCDD were slightly higher in SG (6.7, 2.1, 2.6 and 9.9 in leg muscles, breast muscle, liver and abdominal fat, respectively) than in FG broilers (5.2, 2.2, 1.1 and 8.4, respectively). The elimination half-lives in SG broilers were 20, 12 and 19 d in leg muscles, breast muscle and abdominal fat, respectively, to which dilution through growth contributed for around 50%. The overall assimilation efficiency of α-HBCDD was estimated at 58 and 50% in FG and SG broilers, respectively, while 22 and 17% of α-HBCDD ingested were estimated to be eliminated in excreta as metabolites.

Complete catalytic debromination of hexabromocyclododecane using a silica-supported palladium catalyst in alkaline 2-propanol

Although the brominated flame retardant 1,2,5,6,9,10-hexabromocyclododecane (HBCD) has been widely used to reduce the flammability of polymeric materials, it is a toxic and persistent organic compound. In this paper, we report an efficient method for the debromination of HBCD by using a Pd-catalyzed system. HBCD was completely debrominated to the C₁₂ cyclic compounds such as cyclododecatriene, cyclododecadiene, and cyclododecene in a solution of 2-propanol/methanol (99:1, v/v) containing dissolved NaOH in the presence of a silica-supported Pd catalyst (Pd/SiO₂) at 35 °C. The reaction achieved product yields of 92% for the bromine-free products and 94% for the released Br ions. In the absence of Pd/SiO₂, HBCD was partially debrominated to yield penta-, tetra-, and tribrominated C₁₂ cyclic compounds. The HBCD debromination pathway seems to involve both HBr elimination by reaction with NaOH and Pd-catalyzed hydrodebromination by hydrogen transfer from 2-propanol.

A review of the environmental distribution, fate, and control of tetrabromobisphenol A released from sources

Tetrabromobisphenol A (TBBPA), a high use brominated flame retardant (BFR), raising concerns of widespread pollution and harm to human and ecological health. BFR manufacturing, TBBPA-based product manufacturing, e-waste recycling, and wastewater treatment plants have been identified as the main emission point sources. This paper discusses the occurrence, distribution, and fate of TBBPA from source to the environment. After release to the environment, TBBPA may undergo adsorption, photolysis, and biological degradation. Exposure of humans and biota is also discussed along with the role of treatment and regulations in reducing release of TBBPA to the environment and exposure risks. In general this review found stronger enforcement of existing legislation, and investment in treatment of e-waste plastics and wastewater from emission point sources could be effective methods in reducing release and exposure of TBBPA in the environment.

Estimation of human percutaneous bioavailability for two novel brominated flame retardants, 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (EH-TBB) and bis(2-ethylhexyl) tetrabromophthalate (BEH-TEBP)

2-Ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and bis(2-ethylhexyl)tetrabromophthalate (BEH-TEBP) are novel brominated flame retardants used in consumer products. A parallelogram approach was used to predict human dermal absorption and flux for EH-TBB and BEH-TEBP. [¹⁴C]-EH-TBB or [¹⁴C]-BEH-TEBP was applied to human or rat skin at 100nmol/cm² using a flow-through system. Intact rats received analogous dermal doses. Treated skin was washed and tape-stripped to remove "unabsorbed" [¹⁴C]-radioactivity after continuous exposure (24h). "Absorbed" was quantified using dermally retained [¹⁴C]-radioactivity; "penetrated" was calculated based on [¹⁴C]-radioactivity in media (in vitro) or excreta+tissues (in vivo). Human skin absorbed EH-TBB (24±1%) while 0.2±0.1% penetrated skin. Rat skin absorbed more (51±10%) and was more permeable (2±0.5%) to EH-TBB in vitro; maximal EH-TBB flux was 11±7 and 102±24pmol-eq/cm²/h for human and rat skin, respectively. In vivo, 27±5% was absorbed and 13% reached systemic circulation after 24h (maximum flux was 464±65pmol-eq/cm²/h). BEH-TEBP in vitro penetrance was minimal (<0.01%) for rat or human skin. BEH-TEBP absorption was 12±11% for human skin and 41±3% for rat skin. In vivo, total absorption was 27±9%; 1.2% reached systemic circulation. In vitro maximal BEH-TEBP flux was 0.3±0.2 and 1±0.3pmol-eq/cm²/h for human and rat skin; in vivo maximum flux for rat skin was 16±7pmol-eq/cm²/h. EH-TBB was metabolized in rat and human skin to tetrabromobenzoic acid. BEH-TEBP-derived [¹⁴C]-radioactivity in the perfusion media could not be characterized. <1% of the dose of EH-TBB and BEH-TEHP is estimated to reach the systemic circulation following human dermal exposure under the conditions tested.

CHEMICAL COMPOUNDS STUDIED IN THIS ARTICLE

2-Ethylhexyl 2,3,4,5-tetrabromobenzoate (PubChem CID: 71316600; CAS No. 183658-27-7 FW: 549.92g/mol logP_est: 7.73-8.75 (12)) Abdallah et al., 2015a. Other published abbreviations for 2-ethylhexyl-2,3,4,5-tetrabromobenzoate are TBB EHTeBB or EHTBB Abdallah and Harrad, 2011. bis(2-ethylhexyl) tetrabromophthalate (PubChem CID: 117291; CAS No. 26040-51-7 FW: 706.14g/mol logP_est: 9.48-11.95 (12)). Other published abbreviations for bis(2-ethylhexyl)tetrabromophthalate are TeBrDEPH TBPH or BEHTBP.

Sex-specific changes in thyroid gland function and circulating thyroid hormones in nestling American kestrels (Falco sparverius) following embryonic exposure to polybrominated diphenyl ethers by maternal transfer

High concentrations of polybrominated diphenyl ethers (PBDEs) accumulate in predatory birds. Several PBDE congeners are considered thyroid disruptors; however, avian studies are limited. The authors examined circulating thyroid hormones and thyroid gland function of nestling American kestrels (Falco sparverius) at 17 d to 20 d of age, following embryonic exposure by maternal transfer only to environmentally relevant levels of PBDEs (DE-71 technical mixture). Nestlings were exposed to in ovo sum (Σ) PBDE concentrations of 11 301 ± 95 ng/g wet weight (high exposure), 289 ± 33 ng/g wet weight (low exposure), or 3.0 ± 0.5 ng/g wet weight (controls, background exposure). Statistical comparisons are made to controls of the respective sexes and account for the relatedness of siblings within broods. Circulating concentrations of plasma total thyroxine (TT4 ) and total triiodothyronine (TT3 ) in female nestlings were significantly influenced overall by the exposure to DE-71. Following intramuscular administration of thyroid-stimulating hormone, the temporal response of the thyroid gland in producing and/or releasing TT4 was also significantly affected by the females' exposure to DE-71. The altered availability of T4 for conversion to T3 outside of the gland and/or changes in thyroid-related enzymatic activity may explain the lower TT3 concentrations (baseline, overall) and moderately altered temporal TT3 patterns (p = 0.06) of the treatment females. Controlling for the significant effect on TT3 levels of the delayed hatching of treatment females, baseline TT3 levels were significantly and positively correlated with body mass (10 d, 15 d, 20 d), with PBDE-exposed females generally being smaller and having lower TT3 concentrations. Given that exposure concentrations were environmentally relevant, similar thyroidal changes and associated thyroid-mediated processes relating to growth may also occur in wild female nestlings. Environ Toxicol Chem 2016;35:2084-2091. © 2016 SETAC.

Brominated flame retardant emissions from the open burning of five plastic wastes and implications for environmental exposure in China

Based on the most widely used plastics in China, five plastic wastes were selected for investigation of brominated flame retardant (BFR) emission behaviors during open burning. Considerable variations were observed in the emission factors (EF) of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) from the combustion of different plastic wastes. Distribution of BFR output mass showed that ΣPBDE was emitted mainly by the airborne particle (51%), followed by residual ash (44%) and the gas phase (5.1%); these values for ΣHBCD were 62%, 24%, and 14%, respectively. A lack of mass balance after the burning of the plastic wastes for some congeners (output/input mass ratios>1) suggested that formation and survival exceeded PBDE decomposition during the burns. However, that was not the case for HBCD. A comparison with literature data showed that the open burning of plastic waste is major source of PBDE compared to regulated combustion activities. Even for state-of-the-art waste incinerators equipped with sophisticated complex air pollution control technologies, BFRs are released on a small scale to the environment. According to our estimate, ΣPBDE release to the air and land from municipal solid waste (MSW) incineration plants in China in 2015 were 105 kg/year and 7124 kg/year. These data for ΣHBCD were 25.5 and 71.7 kg/year, respectively. Considering the fact that a growing number of cities in China are switching to incineration as the preferred method for MSW treatment, our estimate is especially important. This study provides the first data on the environmental exposure of BFRs emitted from MSW incineration in China.

Airborne polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), and dechlorane plus (DP) in concentrated vehicle parking areas

This study investigated polybrominated diphenyl ethers (PBDEs), polybrominated dibenzo-p-dioxins/furans (PBDD/Fs), and dechlorane plus (DP) in air around three concentrated vehicle parking areas (underground, indoor, and outdoor) in a metropolitan of South China. The parking areas showed higher concentrations of PBDEs, PBDD/Fs, and DP than their adjacent urban area or distinct congener/isomer profiles, which indicate their local emission sources. The highest PBDE and DP concentrations were found in the outdoor parking lot, which might be related to the heating effect of direct sunlight exposure. Multi-linear regression analysis results suggest that deca-BDEs without noticeable transformation contributed most to airborne PBDEs in all studied areas, followed by penta-BDEs. The statistically lower anti-DP fractions in the urban area than that of commercial product signified its degradation/transformation during transportation. Neither PBDEs nor vehicle exhaust contributed much to airborne PBDD/Fs in the parking areas. There were 68.1-100 % of PBDEs, PBDD/Fs, and DP associated with particles. Logarithms of gas-particle distribution coefficients (K ps) of PBDEs were significantly linear-correlated with those of their sub-cooled vapor pressures (p Ls) and octanol-air partition coefficients (K OAs) in all studied areas. The daily inhalation doses of PBDEs, DP, and PBDD/Fs were individually estimated as 89.7-10,741, 2.05-39.4, and 0.12-4.17 pg kg(-1) day(-1) for employees in the parking areas via Monte Carlo simulation.

Hexabromocyclododecanes (HBCDDs) in surface soils from coastal cities in North China: Correlation between diastereoisomer profiles and industrial activities

Hexabromocyclododecane (HBCDD) is a brominated flame retardant with a wide range of industrial applications, although little is known about its patterns of spatial distribution in soils in relation to industrial emissions. This study has undertaken a large-scale investigation around an industrialized coastal area of China, exploring the concentrations, spatial distribution and diastereoisomer profiles of HBCDD in 188 surface soils from 21 coastal cities in North China. The detection frequency was 100% and concentrations of total HBCDD in the surface soils ranged from 0.123 to 363 ng g(-1) and averaged 7.20 ng g(-1), showing its ubiquitous existence at low levels. The spatial distribution of HBCDD exhibited a correlation with the location of known manufacturing facilities in Weifang, suggesting the production of HBCDD as major emission source. Diastereoisomer profiles varied in different cities. Diastereoisomer compositions in soils were compared with emissions from HBCDD industrial activities, and correlations were found between them, which has the potential for source identification. Although the contemporary concentrations of HBCDD in soils from the study were relatively low, HBCDD-containing products (expanded/extruded polystyrene insulation boards) would be a potential source after its service life, and attention needs to be paid to prioritizing large-scale waste management efforts.

Concentrations of "legacy" and novel brominated flame retardants in matched samples of UK kitchen and living room/bedroom dust

Concentrations of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDDs) and 5 novel brominated flame retardants (NBFRs) were measured in paired samples of kitchen and living room/bedroom dust sampled in 2015 from 30 UK homes. BDE-209 was most abundant (22-170,000 ng/g), followed by γ-HBCDD (1.7-21,000 ng/g), α-HBCDD (5.2-4,900 ng/g), β-HBCDD (2.3-1,600 ng/g), BDE-99 (2.6-1,440 ng/g), BDE-47 (0.4-940 ng/g), decabromodiphenyl ethane (DBDPE) (nd-680 ng/g) and bis(2-ethylhexyl)-3,4,5,6-tetrabromo-phthalate (BEH-TEBP) (2.7-630 ng/g). The concentrations in kitchens and living rooms/bedrooms are moderate compared with previous studies. Concentrations of BDE-209 in living room/bedroom dust were significantly lower and those of DBDPE significantly higher (p < 0.05) compared to concentrations recorded in UK house dust in 2006 and 2007. This may reflect changes in UK usage of these BFRs. All target BFRs were present at higher concentrations in living rooms/bedrooms than kitchens. With the exception of BDE-28, pentabromoethylbenzene (PBEB) and DBDPE, these differences were significant (p < 0.05). No specific source was found that could account for the higher concentrations in living rooms/bedrooms.

Childhood exposure to polybrominated diphenyl ethers and neurodevelopment at six years of age

Mixtures of polybrominated diphenyl ethers (PBDEs) are present in indoor environments. Studies of the developmental effects of exposure to these chemicals in large prospective mother-child cohorts are required, with data on prenatal exposure and long-term follow-up of the children. We aimed to investigate the relationship between prenatal and childhood exposure to PBDEs and neurodevelopment at the age of six years. We determined the levels of PBDEs and other neurotoxicants in cord blood and dust collected from the homes of children for 246 families included in the PELAGIE mother-child cohort in France. We assessed two cognitive domains of the six-year-old children using the Wechsler Intelligence Scale for Children-IV. Verbal comprehension scores were lower in children from homes with higher concentrations of BDE99 (βDetects<median_vs_NonDetects=-1.6; 95% CI: -6.1, 2.9; βDetects≥median_vs_NonDetects=-5.4; -9.9, -1.0; p trend=0.02) and of BDE209 (β2nd_vs_1st_tertile=-1.8; 95% CI: -6.1, 2.5; β3rd_vs_1st_tertile=-3.2; -7.5, 1.2; p trend=0.15) in dust, particularly for boys (p trend=0.02 and 0.04, respectively). Working memory scores seemed to be lower in children with higher BDE99 concentrations in dust (p trend=0.10). No association was observed with cord blood levels of BDE209. Our findings are in agreement with those of four previous studies suggesting adverse cognitive outcomes among children associated with early-life exposure to penta-BDE mixtures, and provide new evidence for the potential neurotoxicity of BDE209. Several countries are in the process of banning the use of PBDE mixtures as flame-retardants. However, these compounds are likely to remain present in the environment for a long time to come.

Probing the debromination of the flame retardant decabromodiphenyl ether in sediments of a boreal lake

After decades of use of polybrominated diphenyl ethers (PBDEs) as flame retardants, a large reservoir of these toxins has accumulated in ecosystems worldwide. The present study used an innovative approach to examine whether the fully brominated PBDE decabromodiphenyl ether (decaBDE) degrades to more toxic congeners in aquatic environments. The authors incubated intact sediment microcosms with high-purity [(13)C]decaBDE in a remote boreal lake to assess its debromination under ambient conditions. Although the addition of [(13)C]decaBDE increased total PBDE concentrations in sediment more than 10-fold, the relative amount of [(13)C]decaBDE in sediment did not change significantly over a 1-mo incubation. However, observation of small quantities of lower-brominated [(13)C]BDEs lent support to the hypothesis that decaBDE is slowly debrominated. The authors observed a significant increase in octaBDEs and nonaBDEs in profundal, but not littoral, sediment over 30 d. A second experiment in which sediment was incubated under different light and oxygen regimes yielded a surprising result-oxygen significantly stimulated the formation of octaBDEs and nonaBDEs. The authors also conducted a large-scale in situ enclosure experiment in which they followed the fate of experimentally added decaBDE in sediment over 26 mo, but that study yielded little evidence of decaBDE debromination. Overall, the authors suggest that the debromination of decaBDE occurs very slowly, if at all, in natural sediment of boreal lakes, in contrast to the rapid degradation kinetics reported by most laboratory-based studies, which are usually conducted by dissolving decaBDE in organic solvents. The findings reinforce the need for field studies on contaminant fate to inform environmental policy decisions.