Electrolytic debromination of PBDEs in DE-83 technical decabromodiphenyl ether

Electrochemical debromination of the commercial decabromodiphenyl ether flame retardant DE-83 in partly aqueous tetrahydrofuran (THF) solution gave lower brominated congeners by sequential loss of bromine atoms. Hydrodebromination was most facile for the most heavily brominated congeners. It involves initial electron transfer and proton transfer from water, rather than hydrogen atom abstraction from THF, as shown by experiments with deuterated water. The product distribution from electrolysis involves preferential loss of bromine meta- and para- to the ether linkage, comparable with the products of metabolism of BDE-209 in various organisms. Significantly, the environmentally relevant congeners BDE-47, BDE-99, and BDE-154 were not major products of debromination of BDE-209 by the electron transfer mechanism.     

Photocatalytic debromination of preloaded decabromodiphenyl ether on the TiO(2) surface in aqueous system

There have been serious concerns about polybromodiphenyl ethers (PBDEs) in the environment because of their global distribution and bioaccumulation. Owing to strong hydrophobicity of PBDEs, the regular photocatalytic system, in which the substrate is solvated in the bulk solution, is not applicable to the removal of the PBDEs in water. In this work, the photocatalytic reduction degradation of decabromodiphenyl ether (BDE209), the most-used PBDEs, was investigated in aqueous system, by pre-adsorbing it on the surface of photocatalyst. It was found that the preloaded BDE209 underwent efficient reductive debromination in aqueous system under irradiation with wavelength larger than 360 nm in the presence of electron donors such as methanol. Our experiments further show that such a preloaded system exhibits different characteristics from that in the organic solution. The meta-debrominated intermediate is predominant in the present system, while the ortho-debrominated one is the main nona-BDE products in the organic solution. In addition, different from other photocatalytic system, the pH has little effect on the photocatalytic reaction. We propose that these differences are originated from the formation of overlayer of hydrophobic BDE209 to limit the motion of BDE209 and the access of water and H⁺/OH⁻ to the TiO₂ surface.     

An exposure study with polybrominated diphenyl ethers (PBDEs) in female European starlings (Sturnus vulgaris): toxicokinetics and reproductive effects

We exposed female European starlings to a pentabromodiphenyl ether (Penta-BDE) mixture through subcutaneous implants, and examined levels and profiles of polybrominated diphenyl ethers (PBDEs) together with reproductive effects. Sum PBDE levels increased significantly in the serum of the exposed females from 218 ± 43 to 23,400 ± 2035 pg/ml. Sum PBDE concentrations in the eggs of the exposed group ranged from 130 ± 12 to 220 ± 37 ng/g wet weight (ww). The profile in serum after egg laying was very similar to that in eggs. There were no detectable levels of HO-PBDEs in both serum and eggs. Fewer females of the exposed group initiated egg laying compared to the control group, although the difference was not significant. In addition, egg weight and volume were significantly higher in the exposed group. These results suggest that, at the investigated exposure levels (150 μg sum PBDEs/bird), PBDEs may have a negative effect on reproductive performance.     

Aerobic biotransformation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa

Aerobic biodegradation of decabromodiphenyl ether (PBDE-209) by Pseudomonas aeruginosa under the influence of co-metabolic substrates and heavy metal cadmium ion was studied, The results showed that certain amount of co-metabolic substrates, such as glucose, sucrose, lactose, starch, and beef extract, would promote the biodegradation of PBDE-209, among which glucose most favorably accelerated PBDE-209 degradation by about 36% within 5 d. The highest degradation efficiency was reached at the ratio of PBDE-209 and glucose 1:5 while excessive carbon source would actually hamper the degradation efficiency. Exploration of influences of cadmium ion on PBDE-209 biodegradation indicated that degradation efficiency was stimulated at low concentrations of Cd²⁺ (0.5–2 mg L⁻¹) while inhibited at higher levels (5–10 mg L⁻¹), inferring that the heavy metals of different concentrations possessed mixed reactions on PBDE-209 bioremoval. Bromine ion was produced during the biotransformation process and its concentration had a good negative correlation with the residues of PBDE-209. Two nonabromodiphenyl ethers (PBDE-208, PBDE-207), four octabromodiphenyl ethers (PBDE-203, PBDE-202, PBDE-197, PBDE-196) and one heptabromodiphenyl ethers (PBDE-183) were formed with the decomposition of PBDE-209, demonstrating that the main aerobic transformation mechanism of PBDE-209 was debromination.     

Behavior of decabromodiphenyl ether (BDE-209) in soil: effects of rhizosphere and mycorrhizal colonization of ryegrass roots

A rhizobox experiment was conducted to investigate degradation of decabromodiphenyl ether (BDE-209) in the rhizosphere of ryegrass and the influence of root colonization with an arbuscular mycorrhizal (AM) fungus. BDE-209 dissipation in soil varied with its proximity to the roots and was enhanced by AM inoculation. A negative correlation (P < 0.001, R² = 0.66) was found between the residual BDE-209 concentration in soil and soil microbial biomass estimated as the total phospholipid fatty acids, suggesting a contribution of microbial degradation to BDE-209 dissipation. Twelve and twenty-four lower brominated PBDEs were detected in soil and plant samples, respectively, with a higher proportion of di- through hepta-BDE congeners in the plant tissues than in the soils, indicating the occurrence of BDE-209 debromination in the soil-plant system. AM inoculation increased the levels of lower brominated PBDEs in ryegrass. These results provide important information about the behavior of BDE-209 in the soil-plant system.     

Effect of Tween 80 and beta-cyclodextrin on degradation of decabromodiphenyl ether (BDE-209) by White rot fungi

The environmental safety of decabromodiphenyl ether (BDE-209), a widely used flame retardant, has been the topic of controversial discussions during the past several years. Degradation of BDE-209 into lower brominated diphenyl ether congeners, exhibiting a higher bioaccumulation potential, has been a critical issue. White rot fungi are known to degrade a wide variety of recalcitrant pollutants. In this work, white rot fungi were used to degrade BDE-209 in liquid culture medium, and the effects of Tween 80 and beta-cyclodextrin on BDE-209 degradation by white rot fungi were evaluated. On the basis of these results, it appears that BDE-209 could be degraded by white rot fungi, and Tween 80 and beta-cyclodextrin can both increase the biodegradation. The best result in Tween 80 experiments was obtained at a Tween 80 concentration of 500mgl(-1) within 10d, which showed 96.5% (w/w) BDE-209 transformed. Tween 80 at a high concentration will restrain the fungal growth and the degradation of BDE-209. However, beta-cyclodextrin had positive effects both on the BDE-209 degradation and the fungal growth.     

An international survey of decabromodiphenyl ethane (deBDethane) and decabromodiphenyl ether (decaBDE) in sewage sludge samples

Decabromodiphenyl ethane (deBDethane) is an additive flame retardant marketed as a replacement for decabromodiphenyl ether (decaBDE). The structures of the two chemicals are similar, and hence deBDethane may also become an environmental contaminant of concern. Environmental data on deBDethane are scarce. Since sewage sludge is an early indicator of leakage of these chemicals into the environment, an international survey of deBDethane and decaBDE levels in sludge was conducted. Samples were collected from 42 WWTPs in 12 different countries and analyzed with GC/LRMS. DeBDethane was present in sludge from all countries and may therefore be a worldwide concern. The levels of deBDethane in sludge samples from the Ruhr area of Germany were the highest so far reported in the literature (216 ng g⁻¹ d.wt.). The [deBDethane]/[decaBDE] quotient for the whole data set ranged from 0.0018 to 0.83. High ratios were found in and around Germany where deBDethane imports are known to have been high and substitution of decaBDE with deBDethane is likely to have occurred. Low ratios were found in the USA and the UK, countries that have traditionally been large users of decaBDE. An estimate of the flux of deBDEthane from the technosphere via WWTPs to the environment within the European Union gave 1.7 ± 0.34 mg annually per person. The corresponding value for decaBDE was 41 ± 22 mg annually per person.     

An international survey of decabromodiphenyl ethane (deBDethane) and decabromodiphenyl ether (decaBDE) in sewage sludge samples

Decabromodiphenyl ethane (deBDethane) is an additive flame retardant marketed as a replacement for decabromodiphenyl ether (decaBDE). The structures of the two chemicals are similar, and hence deBDethane may also become an environmental contaminant of concern. Environmental data on deBDethane are scarce. Since sewage sludge is an early indicator of leakage of these chemicals into the environment, an international survey of deBDethane and decaBDE levels in sludge was conducted. Samples were collected from 42 WWTPs in 12 different countries and analyzed with GC/LRMS. DeBDethane was present in sludge from all countries and may therefore be a worldwide concern. The levels of deBDethane in sludge samples from the Ruhr area of Germany were the highest so far reported in the literature (216 ng g⁻¹ d.wt.). The [deBDethane]/[decaBDE] quotient for the whole data set ranged from 0.0018 to 0.83. High ratios were found in and around Germany where deBDethane imports are known to have been high and substitution of decaBDE with deBDethane is likely to have occurred. Low ratios were found in the USA and the UK, countries that have traditionally been large users of decaBDE. An estimate of the flux of deBDEthane from the technosphere via WWTPs to the environment within the European Union gave 1.7 ± 0.34 mg annually per person. The corresponding value for decaBDE was 41 ± 22 mg annually per person.     

Developmental exposure to decabromodiphenyl ether (PBDE 209): effects on thyroid hormone and hepatic enzyme activity in male mouse offspring

Decabrominated diphenyl ether (PBDE 209) is the second most used brominated flame retardant (BFRs). Many studies have shown that some of the BFRs act as endocrine disruptors via alterations in thyroid hormone homeostasis and affect development. Little is known about the effect of prenatal exposure to PBDE 209 on the development in male offspring. Using a CD-1 mouse model, we attempt to estimate the possible effect of in utero exposure to PBDE 209 on thyroid hormone and hepatic enzymes activities in male offspring. Pregnant mice were administered different doses of PBDE 209 (10, 500, and 1500 mg/kg/day) or corn oil for controls per gavage from gestational days 0-17. In adult male offspring whose mothers had been treated with 1500 mg/kg of PBD 209, hepatic enzyme activity of S9 7-ethoxyresorufin O-deethylase (EROD) was weak but significantly increased (54%). However, no significant changes were observed in S9 4-nitrophenol uridinediphosphate-glucuronosyltransferase (UDPGT) in any of the treatment groups. Serum triiodothyronine (T3) was found to have decreased significantly (ca. 21% both 10 mg/kg and 1500 mg/kg) in offspring, but not thyroxine (T4). Histopathological examination revealed that prenatal exposure of PBDE 209 might be related with cell swelling of hepatocytes in male offspring and there were mild changes in the thyroid glands in 1500 mg/kg group. These data demonstrate that PBDE 209 is likely an endocrine disrupter in male mice following exposure during development. Further studies using environmentally relevant doses are needed for hazard identification.     

Mass balance of decabromodiphenyl ethane and decabromodiphenyl ether in a WWTP

The additive flame retardant decabromodiphenyl ethane (deBDethane) has been identified in the environment, but little is known about its environmental behaviour. It is structurally similar to decabromodiphenyl ether (decaBDE), making it conceivable that it may also become an environmental contaminant of concern. In this study a mass balance of deBDethane and decaBDE was undertaken in a modern WWTP in Stockholm serving 7.05x10(5) inhabitants. Flow proportional samples of plant influent and effluent as well as daily grab samples of digested sludge were collected during two 7-day periods. All samples were analyzed with GC/HRMS using isotope labelled internal standards. The mean mass flows of deBDethane and decaBDE to the WWTP were 6.0 g per day and 55 g per day, respectively. Of this, less than 1% of both BFRs left the WWTP via the effluent, while the bulk was sequestered into the digested sludge, where the mean concentrations of deBDethane and decaBDE were 81 and 800 ng g(-1)d.wt., respectively. It is concluded that the transfer efficiency of deBDethane from the technosphere to the environment via WWTPs is similar to that of decaBDE.     

Absorption of decabromodiphenyl ether and other organohalogen chemicals by grey seals (Halichoerus grypus)

An input-output balance study was performed for polybrominated diphenyl ethers, polychlorinated biphenyls and some organochlorine pesticides on three captive, juvenile grey seals (Halichoerus grypus). The animals were fed a diet of herring for six months, during the last three months of which this study was performed. A supplement of decabromodiphenyl ether was included in the diet during the second month of the study. Consistently high absorption (>89%) was observed for all of the chemicals studied, whereas work on other animals has generally shown high (>80%) net absorption at log K(OW) < approximately 6, dropping towards higher log K(OW), and very low absorption of decabromodiphenyl ether. The half-life of decabromodiphenyl ether in blood was estimated to be between 8.5 and 13 days. Measurable concentrations of decabromodiphenyl ether were detected in seal blubber at the end of the study, indicating that this chemical can be stored in adipose and may bioaccumulate. Current understanding of the mechanism of absorption of organohalogen chemicals and the potential for accumulation of decabromodiphenyl ether will need reassessing in the light of these results.     

Qualitative determination of 10,10'-oxybisphenoxarsine and decabromodiphenyl ether in plastics

Plastics destined for facilities holding aquatic fauna, such as aquaculture and aquatic toxicology laboratories, were studied. The plastics were extracted with dichloromethane. The fungicide 10,10'-oxybisphenoxarsine (OBPA) was detected by silver nitrate after cleanup on a silica cartridge and TLC in petroleum ether-diethyl ether-acetic acid 80:20:1. The flame retardant decabromodiphenyl ether (DBDPO) was crystallized from dichloromethane and confirmed by IR spectrum. A UV-spectrophotometric method is suggested for the estimation of the leaching potential of additives from plastics.     

Comparative effects of oral exposure to 2, 4, 6-tribromophenol and decabromodiphenyl ether in Nile tilapia

Environmental Science and Pollution Research - Flame retardants are compounds added to a high diversity of polymers used in electronics and furniture to decrease the risk of combustion....     

Sources, distribution and behaviour of methyl tert-butyl ether (MTBE) in the Tamar Estuary, UK

Negligible information is currently available concerning levels of the fuel additive methyl tert-butyl ether (MTBE) in European estuaries or coastal environments. MTBE was measured at selected potentially contaminated harbours and marinas, and throughout an axial transect of the Tamar Estuary, UK. Headspace solid-phase microextraction was used in combination with GC-MS for its determination. MTBE was detected in water samples from all stations at concentrations ranging from a few ng/l to a maximum of 194 ng/l (in a semi-enclosed harbour). Elevated levels were generally associated with motor vehicle and boating activities. The Tamar road and rail bridges provided a major input to the lower estuary, downstream of which conservative mixing appeared depressed, probably through volatilisation and possibly through salting-out. The selected analytical system (using a Carboxen/PDMS fiber) proved both rapid and highly sensitive (with a detection limit of 6 ng/l). During method development, salinity was shown to have a major influence in controlling the extraction efficiency and it was found necessary to adjust salinity in all samples (to 75% saturation) prior to extraction. From these tests, we (for the first time) estimated the Setschenow ("salting-out") constant of MTBE to be 0.11 l/mol.     

A technical mixture of 2,2',4,4'-tetrabromo diphenyl ether (BDE47) and brominated furans triggers aryl hydrocarbon receptor (AhR) mediated gene expression and toxicity

Polybrominated diphenyl ethers (PBDE) are found as ubiquitous contaminants in the environment, e.g., in sediments and biota as well as in human blood samples and mother's milk. PBDEs are neuro- and developmental toxins, disturb the endocrine system and some are even carcinogenic. Structural similarities of PBDEs with dioxin-like compounds, e.g., 2,3,7,8-tetrachloro-dibenzodioxin (TCDD), have raised concern about a possible "dioxin-like" action of PBDEs. TCDD exerts its toxicity via binding to and activation of the aryl hydrocarbon receptor (AhR). AhR ligands are in contrast to PBDEs usually coplanar compounds. Thus, PBDEs are not likely to be strong AhR agonists. The aim of this study was to analyze the effects of the most abundant PBDE congener, 2,2',4,4'-tetrabromo diphenyl ether (BDE47), on AhR activity and signaling. Initially, we measured cytochrome P450 1A1 (Cyp1A1) induction as a readout for AhR activation by BDE47. Low grade purified BDE47 increased CYP1A1 levels in transformed and primary rat hepatocytes and human hepatoma cells. Chemical analysis of the BDE47 sample identified trace contaminations with brominated furans such as 2,3,7,8-tetrabromo dibenzodioxin (TBDF), which most likely were responsible for the observed activation of AhR. Subsequently, the BDE47 mixture was studied for its effect on AhR mediated toxicity and global gene expression. Indeed, in rat hepatoma cells and in zebrafish embryos the BDE47 mixture provoked changes in gene expression and toxicity similar to known AhR agonists. In addition to the dioxin-like actions, the BDE47 sample enhanced Cyp2B and Cyp3A expression suggesting that commercial PBDE mixtures, which also often contain brominated furans, may disturb cellular homeostasis at multiple levels.     

Accumulation and distribution of polycyclic aromatic hydrocarbons in rice (Oryza sativa)

Various tissues of rice plants were sampled from a PAH contaminated site in Tianjin, China at different growth stages of the ripening period and analyzed for PAHs. PAHs were much higher in roots than in the exposed tissues. Grains and internodes accumulated much smaller amounts of PAHs than leaves, hulls or ear axes. No specific gradient trends along roots, stem, ear axes, and grains were observed, suggesting that systematic translocation among them is unlikely. Over the ripening period, PAH concentrations were increased in rice roots and decreased in most above-ground tissues. Significant correlations between PAH and lipid contents can only be observed during full mature stage. The spectra of individual PAH compounds in rice organs including roots were similar to those in air, rather than those in soil. There was also a significant correlation between bioconcentration factor (BCF, plant over air) and octanol/air partitioning coefficient (Koa).     

Thermal formation of polybrominated dibenzofurans and dioxins from decabromodiphenyl ether flame retardant: Influence of antimony(III) oxide and the polymer matrix

While pure decabromodiphenyl ether forms highly brominated PBDF in combustion at 700°C in yields of ca. 7000 ppm the yield is significantly increased up to 16 percent in the polymeric matrix and the presence of antimony(III) oxide. Combustion of the ternary mixture results in a decrease of the temperature maximum to 500°C; the ratio of isomers is changed to lower brominated PBDF with the tetrabromo compounds as most abundant products.     

Disruption of thyroid hormone-mediated Xenopus laevis tadpole tail tip regression by hexabromocyclododecane (HBCD) and 2,2',3,3',4,4',5,5',6-nona brominated diphenyl ether (BDE206)

Thyroid hormone regulates amphibian metamorphosis, including the transformation of a tadpole into a froglet and regression of the tail. Xenopus laevis tadpole tail tips in organ culture (ex vivo) undergo regression when exposed to 3,3',5-triiodo-l-thyronine (T(3)) and interference by chemicals with this process was utilized as a bioassay to detect thyroid hormone disruption. In the present study the bioassay was further validated by investigating its response to compound induced T(3)-antagonism and - potentiation. Tadpole tail tips were exposed to two brominated flame retardants (BFRs) in presence or absence of T(3) at its EC(50) (20 nM). T(3)-induced tail tip regression was antagonized by 2,2',3,3',4,4',5,5',6-nona brominated diphenyl ether (BDE206) and potentiated by hexabromocyclododecane (HBCD) in a concentration dependent manner, which was consistent with results obtained with a in vitro T(3)-dependent proliferation bioassay termed the T-screen. Neither compound induced any effect in the absence of T(3). The results indicate that studying possible hormone disrupting effects of agonistic, antagonistic or potentiating compounds should include combined exposure with the natural hormone at around its EC(50) concentration. The results obtained with the tail tip exposures were in accordance with the T-screen predictions, and occurred at BFR-concentrations that were only 5-50 times those of T(3). The bioassay proved to be suitable not only for detecting T(3)-agonism, but also for antagonism and potentiation.     

Accumulation of anticoagulant rodenticides in a non-target insectivore, the European hedgehog (Erinaceus europaeus)

Studies on exposure of non-targets to anticoagulant rodenticides have largely focussed on predatory birds and mammals; insectivores have rarely been studied. We investigated the exposure of 120 European hedgehogs (Erinaceus europaeus) from throughout Britain to first- and second-generation anticoagulant rodenticides (FGARs and SGARs) using high performance liquid chromatography coupled with fluorescence detection (HPLC) and liquid-chromatography mass spectrometry (LCMS). The proportion of hedgehogs with liver SGAR concentrations detected by HPLC was 3-13% per compound, 23% overall. LCMS identified much higher prevalence for difenacoum and bromadiolone, mainly because of greater ability to detect low-level contamination. The overall proportion of hedgehogs with LCMS-detected residues was 57.5% (SGARs alone) and 66.7% (FGARs and SGARs combined); 27 (22.5%) hedgehogs contained >1 rodenticide. Exposure of insectivores and predators to anticoagulant rodenticides appears to be similar. The greater sensitivity of LCMS suggests that hitherto exposure of non-targets is likely to have been under-estimated using HPLC techniques.     

Accumulation and fraction distribution of Ni(II) in activated sludge treating Ni-laden wastewater

The accumulation and fraction distribution of Ni(II) in sludge was determined, and their effect on the performance of sequencing batch reactor (SBR) systems was evaluated at laboratory scale. The results showed that the removal efficiencies of substrates decreased significantly with increasing feeding concentration of Ni(II) into SBRs. The concentration of Ni(II) fed into the SBRs was significantly positively correlated with the Ni(II) contents accumulated in the sludge, while it was negatively correlated with the biomass in the SBRs. The accumulated Ni(II) in the sludge was distributed mainly in the available fraction, accounting for 75.8–90.0 % of the total Ni(II) content. The accumulated content of Ni(II) in each sludge fraction could be predicted satisfactorily by the feeding Ni(II) concentrations in the solutions. As compared with the total contents and other chemical fractions, Ni(II) in the oxidizable fraction in sludge exhibited more important inhibition effects on sludge microorganisms in the SBRs.