Polybrominated Diphenyl Ethers Metabolites Research Articles

Toxicity of persistent organic pollutants: a theoretical study

ContextPolychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two families of persistent organic pollutants that are dangerous as they remain in the atmosphere for long periods and are toxic for humans and animals. They are found all over the world, including the penguins of Antarctica. One of the mechanisms that explains the toxicity of these compounds is related to oxidative stress. The main idea of this theoretical research is to use conceptual density functional theory as a theory of chemical reactivity to analyze the oxidative stress that PCBs and PBDEs can produce. The electron transfer properties as well as the interaction with DNA nitrogenous bases of nine PCBs and ten PBDEs found in Antarctic penguins are investigated. From this study, it can be concluded that compounds with more chlorine or bromine atoms are more oxidizing and produce more oxidative stress. These molecules also interact directly with the nitrogenous bases of DNA, forming hydrogen bonds, and this may be an explanation for the toxicity. Since quinone-type metabolites of PCBs and PBDEs can cause neurotoxicity, examples of quinones are also investigated. Condensed Fukui functions are included to analyze local reactivity. These results are important as the reactivity of these compounds helps to explain the toxicity of PCBs and PBDEs.MethodsAll DFT computations were performed using Gaussian16 at M06-2x/6–311 + g(2d,p) level of theory without symmetry constraints. Electro-donating (ω-) and electro-accepting (ω +) powers were used as global response functions and condensed Fukui functions as local parameters of reactivity.

Polybrominated diphenyl ethers and bromophenols in paired serum, hair, and urine samples of e-waste dismantlers: Insights into hair as an indicator of endogenous exposure

Polybrominated diphenyl ethers (PBDEs) are important pollutants during dismantling activities of electronic waste (e-waste) in China due to its large production and usage. Bromophenols (BPs), which are a kind of flame retardants and diphenyl ether bond cleavage metabolites of PBDEs, are often neglected in the assessment of human exposure to e-waste. Herein, 22 PBDEs and 19 BPs were determined in paired serum, hair, and urine samples collected from workers and residents of a typical e-waste dismantling site in southern China. Both PBDE and BP congeners were more frequently detected in hair than serum and urine samples. The medians of ΣPBDEs and ΣBPs were 350 and 547 ng/g dw in hair internal (hair-In) of occupational population, respectively, which were significantly higher than non-occupational population. However, a non-significant difference was found in levels of ΣPBDEs and ΣBPs in serum and urine between occupational and non-occupational populations, suggesting that hair analysis could easily differentiate between the exposure intensities of PBDEs and BPs to populations than serum and urine analyses. Moreover, levels of BPs in hair-In were 1–2 orders of magnitude higher than those in hair external (hair-Ex), while a non-significant difference was found in the levels of PBDEs. This result indicated that BPs might have originated from endogenous contribution. Notably, as the predominant congeners, the level of 2,4,6-tribromophenol (2,4,6-TBP) in hair-In was 3–8 times higher than that of BDE-209, while level of 2,4,6-TBP in hair-Ex was 1–3 times lower than that of BDE-209. Furthermore, in vivo experiments performed on Sprague–Dawley rats following a 28-day oral treatment with BDE-209 and 2,4,6-TBP verified that endogenous accumulation of 2,4,6-TBP in hair could be attributed to the metabolism of BDE-209 and exposure to 2,4,6-TBP. In conclusion, compared with PBDEs, biomonitoring phenolic compounds or metabolites with hair could better reflect human endogenous exposure.

Nucleophilic and redox properties of polybrominated diphenyl ether derived-quinone/hydroquinone metabolites are responsible for their neurotoxicity

Polybrominated diphenyl ethers (PBDEs) are a category of brominated flame retardants, which were widely used in industrial products since the 1970 s. Our previous studies indicated quinone-type metabolites of PBDEs (PBDE-Qs) cause neurotoxicity, however, their inherent toxicological mechanism remains unclear. Here, we first synthesized PBDE-Qs and corresponding reduced hydroquinone homologous (PBDE-HQs) with different pattern of bromine substitution. Their nucleophilic and redox properties were investigated. PBDE-Qs react with reduced glutathione (GSH) via Michael addition and bromine displacement reaction, whilst PBDE-HQs lack the ability of reacting with GSH. Of note, the displacement reaction only occurs with bromine on the quinone ring of PBDE-Qs but not phenyl ring. Next, electron paramagnetic resonance (EPR) analysis revealed the generation of SQ•−, along with their downstream hydroxyl radical (HO•) and methyl radical (•CH3) through a PBDE quinone/semiquinone/hydroquinone (Q/SQ•−/HQ) futile cycle. In addition, a structure-dependent cytotoxicity pattern was found, the exposure of PBDE-Q/HQ with bromine substitution on the quinone ring resulted in higher level of apoptosis and autophagy in BV2 cells. In conclusion, this work clearly demonstrated that the nucleophilic and redox properties of PBDE-Qs/HQs are responsible for their neurotoxicity, and this finding provide better understanding of neurotoxicity of PBDEs.

Bioaccumulation and Trophic Transfer of Polybrominated Diphenyl Ethers and Their Hydroxylated and Methoxylated Analogues in Polar Marine Food Webs.

Arctic and Antarctic marine ecosystems, which are important components of global biodiversity, have been severely threatened by environmental pollutants in recent decades. In this study, polybrominated diphenyl ethers (PBDEs) and their hydroxylated and methoxylated analogues (OH-PBDEs and MeO-PBDEs) were analyzed in seawater, sediment, and marine organisms (algae, invertebrates, and fishes) collected surrounding the Arctic Yellow River Station (n = 83) and the Antarctic Great Wall Station (n = 72). PBDEs and the analogues were detectable in all polar marine matrices, except MeO-PBDEs in seawater. The concentrations of ∑PBDEs, ∑MeO-PBDEs, and ∑OH-PBDEs in the marine organisms were in the range of 0.33-16 ng/g lipid weight (lw), n.d.-2.6 ng/g lw, and 0.12-2.3 ng/g lw in the Arctic and 0.06-31 ng/g lw, n.d.-5.8 ng/g lw, and 0.17-35 ng/g lw in Antarctica, respectively. Biota-sediment bioaccumulation factor (BSAF, g TOC/g lipid) values of MeO-PBDEs (0.002-0.14) and OH-PBDEs (0.004-0.18) were lower than the BSAF values of PBDEs (0.85-12). Trophic magnification was found for ∑MeO-PBDEs, whereas trophic dilution was observed for ∑OH-PBDEs in both regions. This is one of very few investigations on trophic transfer of PBDE metabolites in the Antarctic and Arctic regions and will further strengthen concerns about the ecological risk of PBDE metabolites in remote areas.

Certain ortho-hydroxylated brominated ethers are promiscuous kinase inhibitors that impair neuronal signaling and neurodevelopmental processes

The developing nervous system is remarkably sensitive to environmental signals, including disruptive toxins, such as polybrominated diphenyl ethers (PBDEs). PBDEs are an environmentally pervasive class of brominated flame retardants whose neurodevelopmental toxicity mechanisms remain largely unclear. Using dissociated cortical neurons from embryonic Rattus norvegicus, we found here that chronic exposure to 6-OH-BDE-47, one of the most prevalent hydroxylated PBDE metabolites, suppresses both spontaneous and evoked neuronal electrical activity. On the basis of our previous work on mitogen-activated protein kinase (MAPK)/extracellular signal-related kinase (ERK) (MEK) biology and our observation that 6-OH-BDE-47 is structurally similar to kinase inhibitors, we hypothesized that certain hydroxylated PBDEs mediate neurotoxicity, at least in part, by impairing the MEK-ERK axis of MAPK signal transduction. We tested this hypothesis on three experimental platforms: 1) in silico, where modeling ligand-protein docking suggested that 6-OH-BDE-47 is a promiscuous ATP-competitive kinase inhibitor; 2) in vitro in dissociated neurons, where 6-OH-BDE-47 and another specific hydroxylated BDE metabolite similarly impaired phosphorylation of MEK/ERK1/2 and activity-induced transcription of a neuronal immediate early gene; and 3) in vivo in Drosophila melanogaster, where developmental exposures to 6-OH-BDE-47 and a MAPK inhibitor resulted in offspring displaying similarly increased frequency of mushroom-body β-lobe midline crossing, a metric of axonal guidance. Taken together, our results support that certain ortho-hydroxylated PBDE metabolites are promiscuous kinase inhibitors and can cause disruptions of critical neurodevelopmental processes, including neuronal electrical activity, pre-synaptic functions, MEK-ERK signaling, and axonal guidance.

Polybrominated Diphenyl Ethers Quinone Induces NCOA4-Mediated Ferritinophagy through Selectively Autophagic Degradation of Ferritin.

Polybrominated diphenyl ethers (PBDEs) have been detected ubiquitously in biological and environmental samples. Growing epidemiological data suggested the obvious correlation of PBDEs exposure with adverse health outcomes toward human beings, but exact molecular mechanism(s) are limited. Especially, the toxicological information regarding PBDEs metabolites is missing. Thereafter, this study intends to explore unidentified cell death modalities caused by PBDEs reactive quinone-type metabolite, PBDEQ. We found that PBDEQ induces autophagy in an ROS-dependent manner. Interestingly, the results indicated that PBDEQ degraded ferritin and activated a selective autophagy (termed as ferritinophagy) by using NCOA4 as its cargo receptor. These processes may further promote the release of iron and ROS. These results suggested the incidence of ferritinophagy induced by PBDEQ, which may contribute to PBDE exposure-caused diseases and dysfunctions.

Species and habitat-dependent accumulation and biomagnification of brominated flame retardants and PBDE metabolites.

The occurrence, species- and habitat-dependent distribution of brominated flame retardants (BFRs) and PBDE metabolites comprising 27 polybrominated diphenyl ethers (PBDEs), 3 hexabromocyclododecanes (HBCDs), tetrabromobisphenol A (TBBPA), 17 methoxylated (MeO-) BDEs, and 8 hydroxylated (OH-) BDEs were determined in marine environments (sediment and seawater) and 20 biota species in food web in the southern part of Korea. The concentration of HBCDs was statistically higher in both pelagic (5.73-60.1 ng/g lipid weight [lw]) and demersal fish (2.45-31.3 ng/g lw), whereas a higher level of OH-BDEs was observed in benthic invertebrates (2.48-40.7 ng/g lw), suggesting different composition of BFRs and PBDE metabolites between species. The concentrations of TBBPA and MeO-BDEs were significantly higher in pelagic fish (1.31-11.3, 6.15-61.5 ng/g lw) than in demersal fish (not detected [N.D.]-4.45, 0.956-8.52 ng/g lw) and benthic invertebrates (N.D.-8.11, 0.182-4.65 ng/g lw), reflecting a dependence on habitat. Additionally, analogue distribution of PBDEs in pelagic fish was similar to that in seawater, whereas the distribution in demersal fish and benthic invertebrates was similar to the distribution in sediment. The bioconcentration factor (BCF) and trophic magnification factor (TMF) of α-HBCD, some of PBDEs, and 6-MeO-BDE47 were up to 5000 and 1, respectively, suggesting strong bioaccumulation and biomagnification.

Association between persistent endocrine-disrupting chemicals (PBDEs, OH-PBDEs, PCBs, and PFASs) and biomarkers of inflammation and cellular aging during pregnancy and postpartum

BackgroundEndocrine-disrupting chemicals (EDCs) can target immune and metabolic pathways. However, few epidemiologic studies have examined the influence of EDCs on measures of inflammation and cellular aging during pregnancy and postpartum. ObjectiveWe investigated associations between prenatal exposures to polybrominated diphenyl ethers (PBDEs), hydroxylated PBDE metabolites (OH-PBDEs), polychlorinated biphenyls (PCBs), and per- and polyfluorochemicals (PFASs) with repeated biomarker measurements of inflammation and cellular aging in women during pregnancy and the postpartum period. MethodologyOverweight or obese pregnant women were recruited from the San Francisco Bay area (n = 103) during their first or second trimester of pregnancy. Blood samples were collected from participants at baseline (median 16 weeks gestation) and at three and nine months postpartum. Serum concentrations of PBDEs, OH-PBDEs, PCBs, and PFASs were measured at baseline. Inflammation biomarkers (interleukin 6 [IL-6], interleukin 10 [IL-10], and tumor necrosis factor [TNF-α]) and leukocyte telomere length (LTL), a biomarker of cellular aging, were measured at all three time points. Associations between serum chemical concentrations and repeated measures of IL-6, IL-10, TNF-α, and LTL were examined using linear mixed models. We also examined the potential for effect modification by time (visit) and obesity. ResultsIn adjusted models, we observed positive relationships between PBDEs and pro-inflammatory cytokines (IL-6 and TNF-α). A doubling in ∑PBDEs was associated with a 15.26% (95% CI 1.24, 31.22) and 3.74% (95% CI −0.19, 7.82) increase in IL-6 and TNF-α, respectively. Positive associations were also observed for PFASs and IL-6. A two-fold increase in ∑PFASs was associated with a 20.87% (95% CI 3.46, 41.22) increase in IL-6. 5-OHBDE-47 was inversely associated with anti-inflammatory cytokine IL-10. Some EDC-outcome associations, including those of PBDEs with TNF-α, were stronger during pregnancy (compared to three or nine months postpartum) and among obese (compared to overweight) women (p-interaction <0.05). ConclusionsThese findings suggest that exposure to specific EDCs is associated with increased inflammation among women during pregnancy and the postpartum period. Future studies should replicate these findings in additional study populations and examine the implications of these associations for maternal and child health.

Neurobehavioral effects of two metabolites of BDE-47 (6-OH-BDE-47 and 6-MeO-BDE-47) on zebrafish larvae

Two metabolites, OH-BDEs and MeO-BDEs, of polybrominated diphenyl ethers (PBDEs) were ubiquitously detected in animal tissues and environmental samples, drawing a widely public concern to their toxicity. The comparison of toxicity between PBDEs and their metabolites has been a focus in recent years, however, comparisons seldom involve neurobehavioral toxicity of PBDEs metabolites in published works. In this study, zebrafish larvae were exposed to 6-OH-BDE-47 and 6-MeO-BDE-47 and their neurobehavioral traits (including locomotion, path angle, and social activity) were recorded using the instrument Zebrabox; meanwhile, light illumination was used as stimuli in the test duration. The results showed larvae were more active in dark periods than light periods, and preferred turning right (+) to left (−). Effects of the two metabolites varied in different behavioral indicators. They induced different effects on path angle but did not reverse the left-right asymmetry. 6-OH-BDE-47 did not induce the effects on larval locomotion and social activity, but mainly decreased average and routine turn numbers; 6-MeO-BDE-47 promoted larvae responsive turns but inhibited social activity. This study offered new experimental means to the neurobehavioral toxicity of various PBDE metabolites. Further studies may focus on the toxic mechanisms of specific neurobehavioral traits.

Polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDE metabolites (OH-PBDEs) in maternal and fetal tissues, and associations with fetal cytochrome P450 gene expression

BackgroundHuman fetal exposures to polybrominated diphenyl ethers (PBDEs) and their metabolites (OH-PBDEs) are unique from adults, and in combination with a different metabolic profile, may make fetal development more sensitive to adverse health outcomes from these exposures. However, we lack data to characterize human fetal PBDE exposures and the metabolic factors that can influence these exposures. ObjectiveWe examined differences between 2nd trimester maternal and fetal exposures to PBDEs and OH-PBDEs. We also characterized fetal cytochrome P450 (CYP) mRNA expression and its associations with PBDE exposures. MethodsWe collected paired samples of maternal serum and fetal liver (n=86) with a subset having matched placenta (n=50). We measured PBDEs, OH-PBDEs, and mRNA expression of CYP genes (e.g. CYP1A1, -2E1, -2J2, -2C9) in all samples. As a sensitivity analysis, we measured PBDEs and OH-PBDEs in umbilical cord serum from a subset (n=22). ResultsBDE-47 was detected in ≥96% of all tissues. Unadjusted ∑PBDEs concentrations were highest in fetal liver (geometric mean (GM)=0.72ng/g), whereas lipid-adjusted concentrations were highest in cord serum (111.12ng/g lipid). In both cases, fetal concentrations were approximately two times higher than maternal serum levels (GM=0.33ng/g or 48.75ng/g lipid). ΣOH-PBDEs were highest in maternal and cord sera and 20–200 times lower than PBDE concentrations. In regression models, maternal BDE-47 explained more of the model variance of liver than of placenta BDE-47 concentrations (adjusted R2=0.79 vs 0.48, respectively). In adjusted logistic regression models, ∑PBDEs were positively associated with expression of CYP2E1 and -2J2 (placenta), and -1A1 (liver) (p<0.05). ConclusionOur findings suggest that under normal conditions of mid-gestation, the human fetus is directly exposed to concentrations of PBDEs that may be higher than previously estimated based on maternal serum and that these exposures are associated with the expression of mRNAs coding for CYP enzymes. These results will help frame and interpret findings from studies that use maternal or cord blood as proxy measures of fetal exposures, and will inform the molecular pathways by which PBDEs affect human health.

Polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDE metabolites (OH-PBDEs): A six-year temporal trend in Northern California pregnant women

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants. Technical mixtures PentaBDE and OctaBDE were phased out in 2004 through voluntary and regulatory actions with DecaBDE remaining in limited use until 2013. Biomonitoring studies have shown widespread presence of PBDEs in the US and worldwide population. While some studies suggest that human serum concentrations are declining over time, it is unclear whether this trend will continue. Our objective was to examine temporal trends of PentaBDEs and their hydroxylated metabolites (OH-PBDEs) between 2008 and 2014 in populations of ethnically diverse, pregnant women residing in Northern California (n = 111). Serum samples were collected and analyzed by high resolution mass spectrometry for five PentaBDE congeners and two OH-PBDEs. We found widespread exposures in participants from all three time points (2008/09, 2011/12, 2014). Temporal patterns varied substantially by congener. BDE-47, -99 and the OH-PBDEs decreased between 2008/09-2011/12 but plateaued between 2011/12-2014. In contrast, BDE-100 decreased across all years, BDE-153 decreased in the latter years, and BDE-28 decreased initially and then increased. These findings indicate that while policies to remove PBDEs from the marketplace have successfully lead to declines in exposures to some PBDE congeners, human exposures to these legacy pollutants could plateau and remain ubiquitous in human populations.

Suspect screening of maternal serum to identify new environmental chemical biomonitoring targets using liquid chromatography-quadrupole time-of-flight mass spectrometry.

The use and advantages of high-resolution mass spectrometry as a discovery tool for environmental chemical monitoring has been demonstrated for environmental samples but not for biological samples. We developed a method using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) for discovery of previously unmeasured environmental chemicals in human serum. Using non-targeted data acquisition (full scan MS analysis) we were able to screen for environmental organic acids (EOAs) in 20 serum samples from second trimester pregnant women. We define EOAs as environmental organic compounds with at least one dissociable proton which are utilized in commerce. EOAs include environmental phenols, phthalate metabolites, perfluorinated compounds (PFCs), phenolic metabolites of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs), and acidic pesticides and/or predicted acidic pesticide metabolites. Our validated method used solid phase extraction, reversed phase chromatography in a C18 column with gradient elution, electrospray ionization in negative polarity, and automated MS/MS data acquisition to maximize true positive rates. We identified “suspect EOAs” using Agilent MassHunter Qualitative Analysis software to match chemical formulas it generated from each sample run with molecular formulas in our unique database of 693 EOAs assembled from multiple environmental literature sources. We found potential matches for 282 (41%) of the EOAs in our database. Sixty-five of these suspect EOAs were detected in at least 75% of the samples, only 19 of these compounds are currently biomonitored in NHANES. We confirmed two of three suspect EOAs by LC-QTOF/MS using a targeted method developed through liquid chromatography-tandem mass spectrometry, reporting the first confirmation of benzophenone-1 and bisphenol S in pregnant women’s sera. Our suspect screening workflow provides an approach to comprehensively scan environmental chemical exposures in humans. This can provide a better source of exposure information to help improve exposure and risk evaluation of industrial chemicals.

Novel Chemicals Identified in Pregnant Women in Northern California

Introduction: In utero exposure to multiple environmental chemicals can adversely impact health throughout the lifespan. Developing analytical techniques to rapidly characterize exposure to the full spectrum environmental chemicals present in the human body is an integral component of an “exposome” approach. Therefore we apply a new method using liquid chromatography-quadrupole time-of-flight mass spectrometry to perform a general suspects screen for the presence and co-occurrence of ~700 Environmental Organic Acids (EOAs): organic industrial chemicals with at least one dissociable proton, including phenolic compounds such as Bisphenol A; phthalate metabolites; phenolic metabolites of polybrominated diphenyl ethers and polychlorinated biphenyls; perfluorinated compounds; and phenolic and acidic pesticides and/or their predicted acidic and phenolic metabolites. Methods: We analyzed samples from 19 pregnant women in their 2nd trimester receiving care at San Francisco General Hospital, using the Agilent QTOF/MS 6550 instrument to identify ‘suspect EOAs.’ Results: We detected, on average, 100 (SD: 23) suspect EOAs in each woman (range: 56-126), including universal exposure to nine novel suspect EOAs – five phenols (e.g., 2,4-Dihydroxyphenone) and four phenolic pesticides and/or their phenolic metabolites (e.g., Dinoterb) – and two previously biomonitored suspect EOAs ((Mono-n-butyl phthalate (MnBP) and Perfluoroundecanoic acid (PFUA)). Some suspect EOAs that we detected in all participants who smoked last year were detected in only 60% of their counterparts. We detected in all Black participants ~17 suspect EOAs that had &lt;60% detection frequency in White and Latina participants. Conclusion: Non-targeted analysis provides a viable method to screen for a broad spectrum of chemicals and help identify ubiquitously present and thus priority chemicals for targeted method development.

Occurrence, removal and release characteristics of dissolved brominated flame retardants and their potential metabolites in various kinds of wastewater

The dissolved phase compound and congener specific distribution characteristics of three widely used brominated flame retardants (BFRs) comprising 27 polybrominated diphenyl ethers (PBDEs), 12 hydroxylated and methoxylated metabolites (OH- and MeO-BDEs), 3 hexabromocyclododecanes (HBCDs) and tetrabromobisphenol A (TBBPA) were investigated in influents and effluents of various kinds of wastewater treatment plants (WWTPs), with varying source of wastewater and type of treatment, and nearby rivers in Korea. The concentration of total BFRs were the highest in industrial WWTPs nearby large industrial complexes specialized in heavy chemicals. The distribution of BFRs was differed according to composition of wastewater, with predominance of TBBPA in WWTPs with higher portion of inflowing industrial wastewater. Among HBCD diastereomers, γ-HBCD was dominant in industrial wastewater as consistent to the previous reports, however, similar contribution of α- and γ-HBCD was found in sewage and human wastewater. Through treatment process, PBDEs were the most effectively removed with a mean removal efficiency of 68.3%. HBCDs and TBBPA had removal efficiencies of 41.3% and 48.7%, respectively. The lowest removal efficiency (10.3%) was observed for PBDE metabolites and their concentration in effluent of human wastewater was even increased at maximum 1.9 fold compared with influent, implying the possibility of transformation during treatment. The estimated dissolved phase daily load of PBDEs was highest in sewage while that of TBBPA was highest in industrial wastewater.

Isomer Separation of Polybrominated Diphenyl Ether Metabolites using nanoESI-TIMS-MS.

In this paper, high-resolution nano-electrospray ionization-trapped ion mobility spectrometry coupled to mass spectrometry (nESI-TIMS-MS) is used for the study of hydroxylated polybrominated diphenyl ether (OH-PBDE) metabolites. In particular, experimental ion-neutral collision cross sections (CCS) were measured for five structural OH-PBDE isomers using TIMS-MS. Candidate structures were proposed for each IMS band observed in good agreement with the experimental CCS measurements (5% error). The analytical power of TIMS-MS to baseline and partially separate structural isomers of OH-BDE in binary and ternary mixtures is shown for single charge species with a mobility resolving power of RIMS ~ 400. This work provides the proof of concept for the analysis of low concentration OH-PBDE in environmental samples based on accurate collision cross section and mass measurements without the need for derivatization and pre-fractionation protocols, thus significantly reducing the cost and analysis time.

Determination of urinary bromophenols (BrPs) as potential biomarkers for human exposure to polybrominated diphenyl ethers (PBDEs) using gas chromatography-tandem mass spectrometry (GC-MS/MS).

Bromophenols (BrPs), as the metabolites of PBDEs, would be the potential exposure markers for human biomonitoring (HB) of PBDEs in urine. An analytical method using solid-phrase extraction (SPE) and gas chromatography coupled to tandem mass spectrometer (GC-MS/MS) was developed and validated for simultaneous determination of nineteen BrPs in human urine. The method detection limits (MDLs) were below 23pgmL(-1), with recovery ranged from 63% to 133% and inter-day repeatability ranged from 3% to 11% for the majority of target analytes. This method was applied in a pilot study and 2-Bromophenol (2-BrP), 4-Bromophenol (4-BrP), 2,4-Dibromophenol (2,4-DBP) and 2,4,6-Tribromophenol (2,4,6-TBP) as the predominant analytes were detected in human urine samples collected from the general population. Among the four detected analytes, 2-BrP and 4-BrP as the mono-brominated BrP congeners were firstly reported. To our knowledge, it is the first study covering all BrP congeners (from mono-brominated to penta-brominated, totally 19 congeners) in human urine. Therefore, this study is very useful for profiling urinary BrPs and discovering potential relationship between urinary BrPs and human internal exposure to PBDEs. The mechanism of fragmentation pathway of silanized BrPs was firstly illustrated in this study.

Structure prediction of methyoxy-polybrominated diphenyl ethers (MeO-PBDEs) through GC–MS analysis of their corresponding PBDEs

It is hard to quantify the trace pollutants in the environment without the corresponding reference standards. Structure identifications of unknown organic pollutants are thus of great importance in environmental analysis. As for polybrominated diphenyl ethers (PBDE) with one substituent of methoxyl group, there are 837 congeners, but only 32 standards are commercially available. In this work, an effective method based on gas chromatography coupled with mass spectrometry (GC–MS) was proposed to predict the potential structures of methoxylated polybrominated diphenyl ethers (MeO-PBDEs). The mass fragmentation pattern using SIM mode not only provided the useful information on the substitution position of methoxyl group, the number of Br atoms, but also guaranteed the high sensitivity for trace analysis. Br distribution patterns of the unknown MeO-PBDEs were revealed by a linear regression model with dummy variables which described the retention time relationship between MeO-PBDEs and the corresponding PBDEs on different types of GC columns. This method was successfully used to identify three new MeO-PBDEs metabolites of BDE-28 as 4-MeO-BDE-22, 4′-MeO-BDE-25 and 4-MeO-BDE-31 in the pumpkins. Therefore, the newly developed structure prediction model based on GC–MS behavior is helpful in the evaluation of unknown PBDE metabolites in the environment.

Developmental toxicity of the PBDE metabolite 6-OH-BDE-47 in zebrafish and the potential role of thyroid receptor β

6-hydroxy-2,2′,4,4′-tetrabromodiphenyl ether (6-OH-BDE-47) is both a polybrominated diphenyl ether (PBDE) flame retardant metabolite and a marine natural product. It has been identified both as a neurotoxicant in cell-based studies and as a developmental toxicant in zebrafish. However, hydroxylated PBDE metabolites are also considered thyroid hormone disruptors due to their structural similarity to endogenous thyroid hormones. The purpose of this study was to evaluate the effects of 6-OH-BDE-47 on a developmental pathway regulated by thyroid hormones in zebrafish. Morphological measurements of development (head trunk angle, otic vesicle length, and eye pigmentation) were recorded in embryos at 30h post fertilization (hpf) and detailed craniofacial morphology was examined in 4 day old larvae using cartilage staining. Exposure to 6-OH-BDE-47 resulted in severe developmental delays. A 100nM concentration resulted in a 26% decrease in head trunk angle, a 54% increase in otic vesicle length, and a 42% decrease in eye pigmentation. Similarly, altered developmental morphology was observed following thyroid receptor β morpholino knockdown, exposure to the thyroid hormone triiodothyronine (T3) or to thyroid disrupting chemicals (TDC; iopanoic acid and propylthiouracil). The threshold for lower jaw deformities and craniofacial cartilage malformations was at doses greater than 50nM. Of interest, these developmental delays and effects were rescued by microinjection of TRβ mRNA during the 1–2 cell stage. These data indicate that OH-BDEs can adversely affect early life development of zebrafish and suggest they may be impacting thyroid hormone regulation in vivo through downregulation of the thyroid hormone receptor.

Higher PBDE serum concentrations may be associated with feline hyperthyroidism in Swedish cats.

Serum from 82 individual cats was analyzed for decabromobiphenyl (BB-209), polybrominated diphenyl ethers (PBDEs), hydroxylated PBDEs (OH-PBDEs), and 2,4,6-TBP in order to study differences in body burden between healthy and sick cats diagnosed with Feline Hyperthyroidism (FH). Within the study group, 60 of these cats had a euthyroid (n = 23) or hyperthyroid (n = 37) status, all of which were used in the comparison. This study shows that hyperthyroid compared to euthyroid cats have higher serum concentrations for some of the investigated PBDEs (BDE-99, BDE-153, and BDE-183) and CB-153 on a fat weight basis. Further, it is intriguing, and beyond explanation, why the flame retardant BB-209 (discontinued in 2000) is present in all of the cat serum samples in concentrations similar to BDE-209. Median BDE-47/-99 ratios are 0.47 and 0.32 for healthy and euthyroid cats, respectively, which differs significantly from Swedes, where the ratio is 3.5. Another important finding is the occurrence of very low levels or the absence of hydroxylated PBDE metabolites in the cats. In addition, the major OH-PBDE, 6-OH-BDE47, is likely of natural origin, probably ingested via cat food. The statistics indicate an association between elevated PBDE concentrations in the cats and FH.

Levels of PBDEs in plasma of juvenile starlings (Sturnus vulgaris) from British Columbia, Canada and assessment of PBDE metabolism by avian liver microsomes

In this study, the levels of polybrominated diphenyl ethers (PBDEs), HO-PBDEs, and bromophenols were monitored in starling chick plasma samples collected in Delta (British Columbia, Canada) close to the Vancouver municipal landfill and in Glen Valley, a rural area in British Columbia. The in vitro formation of hydroxylated metabolites of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) and 2,2′,4,4′,5-pentabromodiphenyl ether (BDE-99) was also investigated using starling chick liver microsomes. Total PBDE plasma levels were approximately 60 times higher in starling chicks from Delta than from Glen Valley, suggesting that the Delta site is a major source of PBDEs for the local population of starlings and that PBDEs previously measured in starling eggs are bioavailable to chicks. In both locations, BDE-47 and BDE-99 were the two major congeners present at similar concentrations, suggesting contamination with the Penta-BDE mixture. Among the several possible hydroxylated metabolites of PBDEs monitored in starling plasma, only 2,4,5-tribromophenol was detected and its levels did not exceed 18±7pg/mL. Also, several hydroxylated metabolites of BDE-47 and BDE-99 were formed by starling chick liver microsomes, but in low amounts. Therefore, our data consistently suggest that oxidative metabolism of PBDEs in starling chicks proceeds at low rate in vivo and in vitro. In conclusion, the landfill located in Delta is a relevant source of bioavailable PBDEs for the local starling population. Because of the limited ability of starling chicks to metabolize PBDEs, these compounds are likely to bioaccumulate in starlings over time. The possible toxicological implications of PBDEs bioaccumulation in starlings are currently unknown and require further research.