Developmental exposure to a commercial PBDE mixture, DE-71: neurobehavioral, hormonal, and reproductive effects

Hepatic microsomal metabolism of BDE-47 and BDE-99 by lesser snow geese and Japanese quail

In the present study, we investigated the oxidative biotransformation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) by liver microsomes from wild lesser snow geese (Chen caerulescens caerulescens) and domesticated Japanese quail (Coturnix japonica). Formation of hydroxy-metabolites was analyzed using an ultra-high performance liquid chromatography-tandem mass spectrometry-based method. Incubation of BDE-47 with avian liver microsomes produced sixteen hydroxy-metabolites, eight of which were identified using authentic standards. The major metabolites formed by liver microsomes from individual lesser snow geese were 4-hydroxy-2,2',3,4'-tetrabromodiphenyl ether (4-OH-BDE-42), 3-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (3-OH-BDE-47), and 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether (4'-OH-BDE-49). By comparison, 4-OH-BDE-42 and 4'-OH-BDE-49, but not 3-OH-BDE-47, were major metabolites of Japanese quail liver microsomes. Unidentified metabolites included monohydroxy- and dihydroxy-tetrabromodiphenyl ethers. Incubation of BDE-99 with avian liver microsomes produced seventeen hydroxy-metabolites, twelve of which were identified using authentic standards. The major metabolites formed by lesser snow goose liver microsomes were 2,4,5-tribromophenol, 3-OH-BDE-47, 4'-OH-BDE-49, 4-hydroxy-2,2',3,4',5-pentabromodiphenyl ether (4-OH-BDE-90), and 5'-hydroxy-2,2',4,4',5-pentabromodiphenyl ether (5'-OH-BDE-99). By comparison, the major metabolites produced by liver microsomes from Japanese quail included 6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (6-OH-BDE-47) and 2-hydroxy-2',3,4,4',5-pentabromodiphenyl ether (2-OH-BDE-123), but not 3-OH-BDE-47. Unidentified metabolites consisted of monohydroxy-pentabromodiphenyl ethers, monohydroxy-tetrabromodiphenyl ethers and dihydroxy-tetrabromodiphenyl ethers. Another difference between the two species was that formation rates of BDE-47 and BDE-99 metabolites were greater with liver microsomes from male than female Japanese quail, but a sex difference was not observed with lesser snow geese.

Perinatal exposure to organohalogen pollutants decreases vasopressin content and its mRNA expression in magnocellular neuroendocrine cells activated by osmotic stress in adult rats

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that produce neurotoxicity and neuroendocrine disruption. They affect the vasopressinergic system but their disruptive mechanisms are not well understood. Our group reported that rats perinatally exposed to Aroclor-1254 (A1254) and DE-71 (commercial mixtures of PCBs and PBDEs) decrease somatodendritic vasopressin (AVP) release while increasing plasma AVP responses to osmotic activation, potentially emptying AVP reserves required for body-water balance. The aim of this research was to evaluate the effects of perinatal exposure to A1254 or DE-71 (30mgkg/day) on AVP transcription and protein content in the paraventricular and supraoptic hypothalamic nuclei, of male and female rats, by in situ hybridization and immunohistochemistry. cFOS mRNA expression was evaluated in order to determine neuroendocrine cells activation due to osmotic stimulation. Animal groups were: vehicle (control); exposed to either A1254 or DE-71; both, control and exposed, subjected to osmotic challenge. The results confirmed a physiological increase in AVP-immunoreactivity (AVP-IR) and gene expression in response to osmotic challenge as reported elsewhere. In contrast, the exposed groups did not show this response to osmotic activation, they showed significant reduction in AVP-IR neurons, and AVP mRNA expression as compared to the hyperosmotic controls. cFOS mRNA expression increased in A1254 dehydrated groups, suggesting that the AVP-IR decrease was not due to a lack of the response to the osmotic activation. Therefore, A1254 may interfere with the activation of AVP mRNA transcript levels and protein, causing a central dysfunction of vasopressinergic system.

The flame retardant DE-71 (a mixture of polybrominated diphenyl ethers) inhibits human differentiated thyroid cell function in vitro

BACKGROUND

Normal thyroid function is essential for general growth and metabolism, but can be affected by endocrine disrupting chemicals (EDCs). Polybrominated diphenyl ethers (PBDEs) have been used worldwide to reduce flammability in different materials and are suspected to be EDCs. The production of the commercial Penta- and OctaBDE mixtures is banned, but DecaBDEs and existing products may leak PBDEs into the environment. Our aim was to investigate the effect of the PentaBDE mixture DE-71 on human thyroid cells in vitro.

MATERIALS AND METHODS

Primary human thyroid cells were obtained as paraadenomatous tissue and cultured in monolayers. The influence of DE-71 on cyclic adenosine monophosphate (cAMP) and thyroglobulin (Tg) production was examined in the culture medium by competitive radioimmunoassay and enzyme-linked immunosorbent assay, respectively. Real-time quantitative PCR analysis of thyroid-specific genes was performed on the exposed cell cultures. PBDE concentrations were determined in cellular and supernatant fractions of the cultures.

RESULTS

DE-71 inhibited Tg-release from TSH-stimulated thyrocytes. At 50 mg/L DE-71, mean Tg production was reduced by 71.9% (range: 8.5-98.7%), and cAMP by 95.1% (range: 91.5-98.8%) compared to controls). Expression of mRNA encoding Tg, TPO and TSHr were significantly inhibited (p<0.0001, p = 0.0079, and p = 0.0002, respectively). The majority of DE-71 added was found in the cell fraction. No cytotoxicity was found.

CONCLUSIONS

DE-71 inhibited differentiated thyroid cell functions in a two phase response manner and a concentration-dependent inhibition of Tg and cAMP production, respectively, as well as expression of mRNA encoding Tg, TPO and TSHr. Our findings suggest an inhibiting effect of PBDEs on thyroid cells.

Gestational and Lactational Exposure to an Environmentally-Relevant Mixture of Brominated Flame Retardants: Effects on Neurodevelopment and Metabolism

BACKGROUND

Developmental exposure to brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD), has been associated with impaired neurodevelopment and some symptoms of metabolic syndrome. However, there are inconsistencies in studies reporting neurodevelopmental effects with studies of pure substances more likely to report effects than studies of technical products. In addition, the influence of early BFR exposures on later development of metabolic disease-like symptoms has not been investigated. This study examined the effects of perinatal exposure to an environmentally relevant mixture of BFRs based on relative levels observed in house dust, on several markers of neurodevelopment and metabolism in offspring.

METHODS

Sprague-Dawley female rats were fed a diet estimated to deliver daily doses of 0, 0.06, 20, or 60 mg/kg of a mixture of PBDEs and HBCDD from before mating to weaning. Offspring were weaned to control diet and subjected to neurobehavioral and metabolic assessments.

RESULTS

Exposure to BFRs decreased vertical movement in at postnatal day (PND) 32 and increased time to emerge to a lighted area on PND 105 in offspring of both sexes. Although early life exposure to the BFR mixture did not impact measures of glucose or insulin action, male offspring had significantly decreased fat pad weights at PND 46. Total cholesterol was increased in male and female offspring exposed to the highest dose at PND 21.

CONCLUSIONS

These results suggest that gestational and lactational exposure to an environmentally relevant BFR mixture may induce changes in neurodevelopment and lipid metabolism in offspring. Birth Defects Research 109:497-512, 2017.© 2017 The Authors Birth Defects Research Published by Wiley Periodicals, Inc.

BDE-99 impairs differentiation of human and mouse NPCs into the oligodendroglial lineage by species-specific modes of action

Polybrominated diphenyl ethers (PBDEs) are bioaccumulating flame retardants causing developmental neurotoxicity (DNT) in humans and rodents. Their DNT effects are suspected to involve thyroid hormone (TH) signaling disruption. Here, we tested the hypothesis whether disturbance of neural progenitor cell (NPC) differentiation into the oligodendrocyte lineage (O4⁺ cells) by BDE-99 involves disruption of TH action in human and mouse (h,m)NPCs. Therefore, we quantified differentiation of NPCs into O4⁺ cells and measured their maturation via expression of myelin-associated genes (hMBP, mMog) in presence and absence of TH and/or BDE-99. T3 promoted O4⁺ cell differentiation in mouse, but not hNPCs, and induced hMBP/mMog gene expression in both species. BDE-99 reduced generation of human and mouse O4⁺ cells, but there is no indication for BDE-99 interfering with cellular TH signaling during O4⁺ cell formation. BDE-99 reduced hMBP expression due to oligodendrocyte reduction, but concentrations that did not affect the number of mouse O4⁺ cells inhibited TH-induced mMog transcription by a yet unknown mechanism. In addition, ascorbic acid antagonized only the BDE-99-dependent loss of human, not mouse, O4⁺ cells by a mechanism probably independent of reactive oxygen species. These data point to species-specific modes of action of BDE-99 on h/mNPC development into the oligodendrocyte lineage.

Association of prenatal and childhood PBDE exposure with timing of puberty in boys and girls

BACKGROUND

Polybrominated diphenyl ether (PBDE) flame retardants are endocrine-disrupting chemicals that exhibit estrogenic and androgenic properties and may affect pubertal timing.

METHODS

Study subjects were participants between 1999 and 2013 in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a longitudinal cohort study of predominantly Mexican origin families in Northern California. We measured serum concentrations of four PBDEs (BDE-47, -99, -100, -153) in blood collected from mothers during pregnancy (N=263) and their children at age 9years (N=522). We determined timing of pubertal onset in 309 boys and 314 girls using clinical Tanner staging every 9months between 9 and 13years of age, and timing of menarche by self-report. We used Poisson regression for relative risk (RR) of earlier puberty and parametric survival analysis for time ratios (TR) of pubertal milestones.

RESULTS

Prenatal concentrations of all 4 congeners and ƩPBDEs were associated with later menarche in girls (RR_{earlier menarche}=0.5, 95% confidence interval (CI): 0.3, 0.9 for ƩPBDEs) but earlier pubic hair development in boys (RR_{earlier pubarche}=2.0, 95% CI: 1.3, 3.3 for ƩPBDEs). No associations were seen between prenatal exposure and girls' breast or pubic hair development or boys' genital development. Childhood PBDE exposure was not associated with any measure of pubertal timing, except for an association of BDE-153 with later menarche.

CONCLUSIONS

We found that prenatal PBDE exposure was associated with later menarche in girls but earlier pubarche in boys, suggesting opposite pubertal effects in girls and boys.

PBDE-209 exposure damages learning and memory ability in rats potentially through increased autophagy and apoptosis in the hippocampus neuron

This study is to investigate the neurotoxicity of PBDE-209 during pregnancy through autophagy and apoptosis in the fetal hippocampus neuron. The autophagy protein levels of LC3-II and Beclin-1 were significantly higher in hippocampus tissue and neuron, while P62 protein were lower. Apoptosis protein Cleaved Caspase-3 and Cleaved PARP was significantly higher in PBDE dose groups and BCL-2 levels in high PBDE dose groups were significantly lower. During the Morris water maze task, the escape latency times of high PBDE dose groups were significantly longer. PBDE-209-induced autophagy leads to neurons death and inhibition of autophagy reduce PBDE-209-induced apoptotic cell death. These results suggest that exposure of the PBDE-209 during pregnancy increases hippocampal autophagy, decrease neuron viability, and it partly effect apoptosis induced by PBDE-209. All that may contribute to the decline of learning and memory ability in the offspring.

Prenatal and postnatal polybrominated diphenyl ether exposure and visual spatial abilities in children

Polybrominated diphenyl ethers (PBDEs) are associated with impaired visual spatial abilities in toxicological studies, but no epidemiologic study has investigated PBDEs and visual spatial abilities in children. The Health Outcomes and Measures of the Environment Study, a prospective birth cohort (2003-2006, Cincinnati, OH), was used to examine prenatal and childhood PBDEs and visual spatial abilities in 199 children. PBDEs were measured at 16±3 weeks gestation and at 1, 2, 3, 5, and 8 years using gas chromatography/isotope dilution high-resolution mass spectrometry. We used the Virtual Morris Water Maze to measure visual spatial abilities at 8 years. In covariate-adjusted models, 10-fold increases in BDE-47, -99, and -100 at 5 years were associated with shorter completion times by 5.2s (95% Confidence Interval [CI] -9.3, -1.1), 4.5s (95% CI -8.1, -0.9), and 4.7s (95% CI -9.0, -0.3), respectively. However, children with higher BDE-153 at 3 years had longer completion times (β=5.4s, 95% CI -0.3, 11.1). Prenatal PBDEs were associated with improved visual spatial memory retention, with children spending a higher percentage of their search path in the correct quadrant. Child sex modified some associations between PBDEs and visual spatial learning. Longer path lengths were observed among males with increased BDE-47 at 2 and 3 years, while females had shorter paths. In conclusion, prenatal and postnatal BDE-28, -47, -99, and -100 at 5 and 8 years were associated with improved visual spatial abilities, whereas a pattern of impairments in visual spatial learning was noted with early childhood BDE-153 concentrations.

Profiling of Selected Functional Metabolites in the Central Nervous System of Marine Medaka (Oryzias melastigma) for Environmental Neurotoxicological Assessments

The simultaneous profiling of 43 functional metabolites in the brain of the small model vertebrate organism, marine medaka (Oryzais melastigma), has been accomplished via dansyl chloride derivatization and LC-MS/MS quantification. This technique was applied to examine effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), one of the most abundant polybrominated diphenyl ether flame retardants in the natural environment, on the central nervous system (CNS) of vertebrates. The model teleosts were fed with bioencapsulated Artemia nauplii for up to 21 days. Multivariate statistical analysis has demonstrated that levels of numerous classical neurotransmitters and their metabolites in the CNS of the fish were perturbed even at the early phase of dietary exposure. Subsequent metabolic pathway analysis further implied potential impairment of the arginine and proline metabolism; glycine, serine and threonine metabolism; D-glutamine and D-glutamate metabolism; alanine, aspartate, and glutamate metabolism; valine, leucine, and isoleucine biosynthesis, and the cysteine and methionine metabolism in the brain of the test organism. Our results demonstrate that targeted profiling of functional metabolites in the CNS may shed light on how the various neurological pathways of vertebrates, including humans, are affected by toxicant/stress exposure.

Lactational Exposure to Polybrominated Diphenyl Ethers and Its Relation to Early Childhood Anthropometric Measurements

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants that may influence growth and development.

OBJECTIVE

We investigated the association between exposure to PBDEs via breast milk and anthropometric measurements in early childhood.

METHODS

The Pregnancy Infection and Nutrition (PIN) Babies studies followed a cohort of North Carolina pregnant women and their children through 36 months of age. Breast milk samples obtained at 3 months postpartum were analyzed for PBDEs. We collected height and weight records from well-baby doctor visits and also measured children during study visits (n = 246 children with > 1,400 anthropometric measurements). We assessed the relationship between breast milk concentrations of five PBDE congeners-BDEs 28, 47, 99, 100, and 153-and child's weight-for-age, height-for-age, and weight-for-height z-scores (WAZ, HAZ, and WHZ, respectively), adjusting for age; maternal age, race, prepregnancy BMI; parity; smoking during pregnancy; and breastfeeding, and stratifying by sex.

RESULTS

Overall, PBDE exposures via breast milk were not associated with early-life anthropometric measures in the PIN Babies cohort. When stratified by sex, PBDEs in milk were inversely associated with WHZ for boys; however, associations did not follow a consistent pattern across the concentration gradient and were imprecisely estimated. Among girls, PBDEs tended to be associated with increased WHZ except for BDE-153, which was inversely associated with WHZ, though all estimates were imprecisely estimated.

CONCLUSIONS

We observed little evidence of associations between early-life PBDE exposures via breast milk and anthropometric measurements overall; however, our results prompt the need for sex-specific investigations in larger cohorts.

CITATION

Hoffman K, Mendez M, Siega-Riz AM, Herring AH, Sjödin A, Daniels JL. 2016. Lactational exposure to polybrominated diphenyl ethers and its relation to early childhood anthropometric measurements. Environ Health Perspect 124:1656-1661; http://dx.doi.org/10.1289/EHP201.

Editor's Highlight: Comparative Toxicity of Organophosphate Flame Retardants and Polybrominated Diphenyl Ethers to Caenorhabditis elegans

With the phasing-out of the polybrominated diphenyl ether (PBDE) flame retardants due to concerns regarding their potential developmental toxicity, the use of replacement compounds such as organophosphate flame retardants (OPFRs) has increased. Limited toxicity data are currently available to estimate the potential adverse health effects of the OPFRs. The toxicological effects of 4 brominated flame retardants, including 3 PBDEs and 3,3',5,5'-tetrabromobisphenol A, were compared with 6 aromatic OPFRs and 2 aliphatic OPFRs. The effects of these chemicals were determined using 3 biological endpoints in the nematode Caenorhabditis elegans (feeding, larval development, and reproduction). Because C. elegans development was previously reported to be sensitive to mitochondrial function, results were compared with those from an in vitro mitochondrial membrane permeabilization (MMP) assay. Overall 11 of the 12 flame retardants were active in 1 or more C. elegans biological endpoints, with only tris(2-chloroethyl) phosphate inactive across all endpoints including the in vitro MMP assay. For 2 of the C. elegans endpoints, at least 1 OPFR had similar toxicity to the PBDEs: triphenyl phosphate (TPHP) inhibited larval development at levels comparable to the 3 PBDEs; whereas TPHP and isopropylated phenol phosphate (IPP) affected C. elegans reproduction at levels similar to the PBDE commercial mixture, DE-71. The PBDEs reduced C. elegans feeding at lower concentrations than any OPFR. In addition, 9 of the 11 chemicals that inhibited C. elegans larval development also caused significant mitochondrial toxicity. These results suggest that some of the replacement aromatic OPFRs may have levels of toxicity comparable to PBDEs.

Exposure to endocrine disrupting chemicals and neurodevelopmental alterations

The developing brain is remarkably malleable as neural circuits are formed and these circuits are strongly dependent on hormones for their development. For those reasons, the brain is very vulnerable to the effects of endocrine-disrupting chemicals (EDCs) during critical periods of development. This review focuses on three ubiquitous endocrine disruptors that are known to disrupt the thyroid function and are associated with neurobehavioral deficits: polychlorinated biphenyls, polybrominated diphenyl ethers, and bisphenol A. The human and rodent data suggesting effects of those EDCs on memory, cognition, and social behavior are discussed. Their mechanisms of action go beyond relative hypothyroidism with effects on neurotransmitter release and calcium signaling.

Polybrominated Diphenyl Ether Exposure and Thyroid Function Tests in North American Adults

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are flame-retardant chemicals that are added to many consumer products. Multiple animal studies have shown PBDEs to be thyroid hormone (TH) disruptors. Epidemiologic evidence of PBDE exposure associated with TH disruption has been inconclusive.

OBJECTIVES

We used repeated measures to estimate associations between serum PBDE concentrations and THs in a North American adult cohort.

METHODS

From 2010 to 2011, we collected ≤ 3 serum samples at approximately 6-month intervals from 52 healthy adult office workers from Boston, Massachusetts, for analysis of PBDE congeners and THs.

RESULTS

The geometric mean sum concentrations of the most prevalent PBDE congeners (BDE-28, BDE-47, BDE-99, BDE-100, and BDE-153) were 22 ng/g lipid in winter 2010, 23 ng/g lipid in summer 2010, and 19 ng/g lipid in winter 2011. BDE-47 was the predominant congener. Based on a multivariable mixed regression model, we estimated that on average, a 1-ng/g serum increase in BDE-47 was associated with a 2.6-μg/dL decrease in total thyroxine (T4) (95% CI: -4.7, -0.35). Total T4 was inversely associated with each PBDE congener. Serum concentrations of PBDEs were not strongly associated with total triiodothyronine (T3), free T4, or thyroid-stimulating hormone (TSH).

CONCLUSION

These results are consistent with those from animal studies showing that exposure to PBDEs is associated with a decrease in serum T4. Because the other TH concentrations did not appear to be associated with BDE exposures, our findings do not indicate effects on the pituitary-thyroid axis. Taken together, our findings suggest that PBDE exposure might decrease the binding of T4 to serum T4 binding proteins.

CITATION

Makey CM, McClean MD, Braverman LE, Pearce EN, He XM, Sjödin A, Weinberg JM, Webster TF. 2016. Polybrominated diphenyl ether exposure and thyroid function tests in North American adults. Environ Health Perspect 124:420-425; http://dx.doi.org/10.1289/ehp.1509755.

Evaluation of hepatic biotransformation of polybrominated diphenyl ethers in the polar bear (Ursus maritimus)

Polar bears are at the top of the Arctic marine food chain and are subject to exposure and bioaccumulation of environmental chemicals of concern such as polybrominated diphenyl ethers (PBDEs), which were widely used as flame retardants. The aim of the present study was to evaluate the in vitro oxidative metabolism of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and 2,2',4,4',5-pentabrominated diphenyl ether (BDE-99) by polar bear liver microsomes. The identification and quantification of the hydroxy-brominated diphenyl ethers formed were assessed using an ultra-high performance liquid chromatography-tandem mass spectrometry-based method. Incubation of BDE-47 with archived individual liver microsomes, prepared from fifteen polar bears from northern Canada, produced a total of eleven hydroxylated metabolites, eight of which were identified using authentic standards. The major metabolites were 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether and 5'-hydroxy-2,2',4,4'-tetrabromodiphenyl ether. Incubation of BDE-99 with polar bear liver microsomes produced a total of eleven hydroxylated metabolites, seven of which were identified using authentic standards. The major metabolites were 2,4,5-tribromophenol and 4-hydroxy-2,2',3,4',5-pentabromodiphenyl ether. Among the CYP specific antibodies tested, anti-rat CYP2B was found to be the most active in inhibiting the formation of hydroxylated metabolites of both BDE-47 and BDE-99, indicating that CYP2B was the major CYP enzyme involved in the oxidative biotransformation of these two congeners. Our study shows that polar bears are capable of forming multiple hydroxylated metabolites of BDE-47 and BDE-99 in vitro and demonstrates the role of CYP2B in the biotransformation and possibly in the toxicity of BDE-47 and BDE-99 in polar bears.

Role of glutamate receptors in tetrabrominated diphenyl ether (BDE-47) neurotoxicity in mouse cerebellar granule neurons

The polybrominated diphenyl ether (PBDE) flame retardants are developmental neurotoxicants, as evidenced by numerous in vitro, animal and human studies. PBDEs can alter the homeostasis of thyroid hormone and directly interact with brain cells. Induction of oxidative stress, leading to DNA damage and apoptotic cell death is a prominent mechanism of PBDE neurotoxicity, though other mechanisms have also been suggested. In the present study we investigated the potential role played by glutamate receptors in the in vitro neurotoxicity of the tetrabromodiphenyl ether BDE-47, one of the most abundant PBDE congeners. Toxicity of BDE-47 in mouse cerebellar neurons was diminished by antagonists of glutamate ionotropic receptors, but not by antagonists of glutamate metabotropic receptors. Antagonists of NMDA and AMPA/Kainate receptors also inhibited BDE-47-induced oxidative stress and increases in intracellular calcium. The calcium chelator BAPTA-AM also inhibited BDE-47 cytotoxicity and oxidative stress. BDE-47 caused a rapid increase of extracellular glutamate levels, which was not antagonized by any of the compounds tested. The results suggest that BDE-47, by still unknown mechanisms, increases extracellular glutamate which in turn activates ionotropic glutamate receptors leading to increased calcium levels, oxidative stress, and ultimately cell death.

Polybrominated diphenyl ethers (PBDEs) concentration in soil from San Luis Potosi, Mexico: levels and ecological and human health risk characterization

The aim of this study was to assess the levels of polybrominated diphenyl ethers (PBDEs) in soils from the city of San Luis Potosi in Mexico and perform an ecological and human health risk characterization. In order to confirm the presence of PBDEs, outdoor surface soil samples were collected and the concentrations of PBDEs in urban, industrial, agricultural, and brick kiln industry areas were determined. The mean total PBDEs levels obtained in the study sites were 25.0 ± 39.5 μg/kg (geometric mean ± standard deviation) in the brick kiln industry zone; 34.5 ± 36.0 μg/kg in the urban zone; 8.00 ± 7.10 μg/kg in the industrial zone and 16.6 ± 15.3 μg/kg in the agricultural zone. The ecological and human health risk characterization showed relatively low-hazard quotient values. However, the moderately high PBDEs levels found in soils highlight the necessity to establish a systematic monitoring process for PBDEs in environmental and biological samples.

Contaminants of Emerging Concern in Bats from the Northeastern United States

We analyzed bat carcasses (Myotis lucifugus, M. sodalis, M. septentrionalis, and Eptesicus fuscus) from the northeastern United States for contaminants of emerging concern (CECs) such as polybrominated diphenyl ethers (PBDEs), and pharmaceuticals and personal care products. The CECs detected most frequently in samples were PBDEs (100 %), salicylic acid (81 %), thiabendazole (50 %), and caffeine (23 %). Other compounds detected in at least 15 % of bat samples were digoxigenin, ibuprofen, warfarin, penicillin V, testosterone, and N,N-diethyl-meta-toluamide (DEET). The CECs present at the highest geometric mean wet weight concentrations in bat carcasses were bisphenol A (397 ng/g), ΣPDBE congeners 28, 47, 99, 100, 153, and 154 (83.5 ng/g), triclosan (71.3 n/g), caffeine (68.3 ng/g), salicylic acid (66.4 ng/g), warfarin (57.6 ng/g), sulfathiazole (55.8 ng/g), tris(1-chloro-2-propyl) phosphate (53.8 ng/g), and DEET (37.2 ng/g). Bats frequently forage in aquatic and terrestrial habitats that may be subjected to discharges from wastewater-treatment plants, agricultural operations, and other point and nonpoint sources of contaminants. This study shows that some CECs are accumulating in the tissue of bats. We propose that CECs detected in bats have the potential to affect a number of physiological systems in bats including hibernation, immune function, and response to white-nose syndrome, a fungal disease causing population-level impacts to bats.

Facilitation of adipocyte differentiation of 3T3-L1 cells by debrominated tetrabromobisphenol A compounds detected in Japanese breast milk

Tetrabromobisphenol A (TeBBPA) is widely used type of brominated flame retardant. In this study, we newly synthesized materials for the debrominated congeners, 2,2',6-tribromobisphenol A (TriBBPA), 2,2'-dibromobisphenol A (2,2'-DiBBPA), 2,6-dibromobisphenol A (2,6-DiBBPA), and 2-monobromobisphenol A (MoBBPA) and evaluated the actual extent of contamination with bisphenol A (BPA), TeBBPA and debrominated congeners in Japanese breast milk samples. TriBBPA was detected at higher levels than that of TeBBPA, while DiBBPA and MoBBPA were detected at lower levels than that of TeBBPA. This observation suggested that humans are exposed to debrominated congeners, which might cause adverse effects. Contamination of the congeners in breast milk was concern about risk infant health, having vulnerable defense system. As pilot study by in vitro experiment, we assessed the toxic potency of debrominated congeners by studying their effect on adipocyte differentiation in 3T3-L1 cells. We observed 2,6-DiBBPA, TriBBPA and TeBBPA elevated the lipid accumulation and adipocyte-specific protein 2 expression in a manner dependent on the number of substituted bromines. Moreover, PPARγ transcriptional activities increased in a dose-dependent manner in the presence of 2,6-DiBBPA and TriBBPA as well as TeBBPA. Our study clarified that TeBBPA and its debrominated congeners accumulated in breast milk and the debrominated congeners promoted adipocyte differentiation, showing that a comprehensive evaluation of the influences of these compounds including the debrominated congeners of TeBBPA on health in infants is necessary.

Polybrominated diphenyl ethers in thirteen shark species from offshore and coastal waters of Korea

Limited reports are available on polybrominated diphenyl ethers (PBDEs) in sharks. In this study, PBDEs were measured in dorsal muscles (n=105) from 13 shark species collected from offshore and coastal waters of Korea. The PBDE concentrations varied greatly not only among species but also within species of sharks. The major PBDE congeners detected in our samples were BDEs 47, 28, 99, 153, 100, and 154. Concentrations of PBDEs in sharks in this study were lower than those reported for previous studies. The high PBDE concentrations were found for aggressive shark species. Inter-species differences in the concentrations and accumulation profiles of PBDEs are explained by differences in feeding habits and sampling locations. Several contributing factors such as growth velocity, trophic level, and local contamination may affect the bioaccumulation of PBDEs in sharks. The present study provides baselines for the occurrence and accumulation status of PBDEs in various shark species.

Association between Several Persistent Organic Pollutants and Thyroid Hormone Levels in Cord Blood Serum and Bloodspot of the Newborn Infants of Korea

Current knowledge on adverse endocrine disruption effects of persistent organic pollutants (POPs) among newborn infants is limited and often controversial. To investigate the associations between prenatal exposure to major POPs and thyroid hormone levels among newborn infants, both cord serum or maternal serum concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) were compared with five thyroid hormones in cord serum of newborn infants as well as TSH in bloodspot collected at 2 day after birth (n=104). Since cord serum thyroid hormones could be affected by those of mothers, thyroid hormone concentrations of the matching mothers at delivery were adjusted. In cord serum, BDE-47, -99, and Σchlordane (CHD) showed significant positive associations with cord or bloodspot TSH. At the same time, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorbenzene (HCB) showed negative associations with total T3 and total T4 in cord serum, respectively. Maternal exposure to β-hexachlorhexane (β-HCH), ΣCHD, ΣDDT, or p,p'-DDE were also associated with neonatal thyroid hormones. Although the sample size is small and the thyroid hormone levels of the subjects were within the reference range, our observation supports thyroid disrupting potential of several POPs among newborn infants, at the levels occurring in the general population. Considering the importance of thyroid hormones during gestation and early life stages, health implication of thyroid hormone effects by low level POPs exposure deserves further follow up investigations.

Developmental exposure to a commercial PBDE mixture: effects on protein networks in the cerebellum and hippocampus of rats

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are structurally similar to polychlorinated biphenyls (PCBs) and have both central (learning and memory deficits) and peripheral (motor dysfunction) neurotoxic effects at concentrations/doses similar to those of PCBs. The cellular and molecular mechanisms for these neurotoxic effects are not fully understood; however, several studies have shown that PBDEs affect thyroid hormones, cause oxidative stress, and disrupt Ca2+-mediated signal transduction. Changes in these signal transduction pathways can lead to differential gene regulation with subsequent changes in protein expression, which can affect the development and function of the nervous system.

OBJECTIVE

In this study, we examined the protein expression profiles in the rat cerebellum and hippocampus following developmental exposure to a commercial PBDE mixture, DE-71.

METHODS

Pregnant Long-Evans rats were dosed perinatally with 0 or 30.6 mg/kg/day of DE-71 from gestation day 6 through sampling on postnatal day 14. Proteins from the cerebellum and hippocampus were extracted, expression differences were detected by two-dimensional difference gel electrophoresis, and proteins were identified by tandem mass spectrometry. Protein network interaction analysis was performed using Ingenuity® Pathway Analysis, and the proteins of interest were validated by Western blotting.

RESULTS

Four proteins were significantly differentially expressed in the cerebellum following DE-71 exposure, whereas 70 proteins were significantly differentially expressed in the hippocampus. Of these proteins, 4 from the cerebellum and 47 from the hippocampus, identifiable by mass spectrometry, were found to have roles in mitochondrial energy metabolism, oxidative stress, apoptosis, calcium signaling, and growth of the nervous system.

CONCLUSIONS

Results suggest that changes in energy metabolism and processes related to neuroplasticity and growth may be involved in the developmental neurotoxicity of PBDEs.

Multiple biomarkers of the cytotoxicity induced by BDE-47 in human embryonic kidney cells

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame-retardants in a variety of industrial products. Among these PBDEs, 2,2',4,4'-tetra-bromodiphenyl ether (BDE-47) is one of the most predominant congeners inducing multiple toxicities, including hepatotoxicity, neurotoxicity, cytotoxicity, genotoxicity, carcinogenecity and immunotoxicity in human body. In this study, the cytotoxicity of BDE-47 in human embryonic kidney cells (HEK293) was investigated by a set of bioassays, including cell proliferation, apoptosis, oxidative stress and metabolic responses as well as gene expressions related to apoptosis. Results showed that BDE-47 induced an inverted U-shaped curve of cell proliferation in HEK293 cells from 10(-6) to 10(-4) M. Cell apoptosis and ROS overproduction were detected at 10(-5) M of BDE-47 (p<0.05). In addition, the expressions of Bcl-2 family-encoding genes (Bad, Hrk and Bcl-2) increased significantly in 10(-4)M group (p<0.05). Metabolic responses indicated that BDE-47 mainly caused disturbance in energy metabolism marked by differentially altered ethanol, glutathione, creatine, aspartate, UDP-glucose and NAD(+). The increased lactate/alanine ratios indicated the higher reductive state induced by BDE-47 in all exposures confirmed by the overproduction of ROS.

Male reproductive disorders, diseases, and costs of exposure to endocrine-disrupting chemicals in the European Union

INTRODUCTION

Increasing evidence suggests that endocrine-disrupting chemicals (EDCs) contribute to male reproductive diseases and disorders.

PURPOSE

To estimate the incidence/prevalence of selected male reproductive disorders/diseases and associated economic costs that can be reasonably attributed to specific EDC exposures in the European Union (EU).

METHODS

An expert panel evaluated evidence for probability of causation using the Intergovernmental Panel on Climate Change weight-of-evidence characterization. Exposure-response relationships and reference levels were evaluated, and biomarker data were organized from carefully identified studies from the peer-reviewed literature to represent European exposure and approximate burden of disease as it occurred in 2010. The cost-of-illness estimation utilized multiple peer-reviewed sources.

RESULTS

The expert panel identified low epidemiological and strong toxicological evidence for male infertility attributable to phthalate exposure, with a 40-69% probability of causing 618,000 additional assisted reproductive technology procedures, costing €4.71 billion annually. Low epidemiological and strong toxicological evidence was also identified for cryptorchidism due to prenatal polybrominated diphenyl ether exposure, resulting in a 40-69% probability that 4615 cases result, at a cost of €130 million (sensitivity analysis, €117-130 million). A much more modest (0-19%) probability of causation in testicular cancer by polybrominated diphenyl ethers was identified due to very low epidemiological and weak toxicological evidence, with 6830 potential cases annually and costs of €848 million annually (sensitivity analysis, €313-848 million). The panel assigned 40-69% probability of lower T concentrations in 55- to 64-year-old men due to phthalate exposure, with 24 800 associated deaths annually and lost economic productivity of €7.96 billion.

CONCLUSIONS

EDCs may contribute substantially to male reproductive disorders and diseases, with nearly €15 billion annual associated costs in the EU. These estimates represent only a few EDCs for which there were sufficient epidemiological studies and those with the highest probability of causation. These public health costs should be considered as the EU contemplates regulatory action on EDCs.

Polybrominated diphenyl ethers in human placenta associated with neonatal physiological development at a typical e-waste recycling area in China

Our aim of this study was to characterize the exposure pattern of polybrominated diphenyl ethers(PBDEs) in human placenta and assess their potential effects on neonates. Placenta samples were obtained from a typical e-waste area in Guiyu and a reference area in Haojiang, China. The median ΣPBDE concentration was 32.25 ng/g lipid weight (lw) in placenta samples from Guiyu, and 5.13 ng/g lw from Haojiang. BDE-209 predominated in placenta samples, followed by BDE-28, -47, -99 -153, -183. Residence in Guiyu contributed the most to elevated PDBE levels. Neonatal physiological indices, including bodymass index (BMI), Apgar 1 score and head circumference, were reduced in Guiyu group. No significant difference was found in neonatal weight between the two groups, but neonatal body length in Guiyu was increased. Our data suggest prenatal exposure to PBDEs is high at the e-waste recycling area, and may lead to adverse physiological development in the fetus.

Hair as a biomarker of systemic exposure to polybrominated diphenyl ethers

The efficacy of using hair as a biomarker for exposure to polybrominated diphenyl ether (PBDE) flame retardants was assessed in humans and an animal model. Paired human hair and serum samples were obtained from adult men and women (n = 50). In parallel, hair, serum, liver, and fat were collected from adult male Sprague-Dawley rats exposed to increasing doses of the PBDE mixture found in house dust for 70 days via the diet. All samples were analyzed by GC-MS for eight common PBDEs: BDE-28, -47, -99, -100, -153, -154, -183, and -209. Paired human hair and serum samples had five congeners (BDE-28, -47, -99, -100, and -154) with significant individual correlations (0.345-0.566). In rat samples, BDE-28 and BDE-183 were frequently below the level of detection. Significant correlations were observed for BDE-47, -99, -100, -153, -154, and -209 in rat hair, serum, liver, and fat across doses, with r values ranging from 0.803 to 0.988; weaker correlations were observed between hair and other tissues when data from the lowest dose group or for BDE-209 were analyzed. Thus, human and rat hair PBDE measurements correlate strongly with those in alternative matrices, validating the use of hair as a noninvasive biomarker of long-term PBDE exposure.

Prenatal exposure to endocrine disrupting chemicals in relation to thyroid hormone levels in infants - a Dutch prospective cohort study

BACKGROUND

Endocrine disrupting chemicals (EDCs) present in the environment may disrupt thyroid hormones, which in early life are essential for brain development. Observational studies regarding this topic are still limited, however as the presence of chemicals in the environment is ubiquitous, further research is warranted. The objective of the current study was to assess the association between exposure markers of various EDCs and thyroxine (T4) levels in newborns in a mother-child cohort in the Netherlands.

METHODS

Exposure to dichlorodiphenyldichloroethylene (DDE), three di-2-ethylhexyl phthalate (DEHP) metabolites, hexachlorobenzene (HCB), polychlorinated biphenyl (PCB)-153, perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA) was determined in cord plasma or breast milk, and information on T4 levels in heel prick blood spots was obtained through the neonatal screening programme in the Netherlands. Linear regression models were composed to determine associations between each of the compounds and T4, which were stratified for gender and adjusted for a priori defined covariates.

RESULTS

Mean T4 level was 86.9 nmol/L (n = 83). Girls in the highest quartile of DDE and PFOA exposure showed an increased T4 level compared to the lowest quartile with both crude and fully adjusted models (DDE > 107.50 ng/L, +24.8 nmol/L, 95% CI 0.79, 48.75; PFOA > 1200 ng/L, +38.6 nmol/L, 95% CI 13.34, 63.83). In boys a lower T4 level was seen in the second quartile of exposure for both PFOS and PFOA, however after fully adjusting the models these associations were attenuated. No effects were observed for the other compounds.

CONCLUSION

DDE and perfluorinated alkyl acids may be associated with T4 in a sex-specific manner. These results should however be interpreted with caution, due to the relatively small study population. More research is warranted, as studies on the role of environmental contaminants in this area are still limited.

Emissions of polybrominated diphenyl ethers (PBDEs) in Zurich, Switzerland, determined by a combination of measurements and modeling

Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants but they are of concern and are currently being phased-out because of their environmentally hazardous properties and their potential to cause adverse health effects. We analyzed PBDEs in Zurich, Switzerland, and applied a multi-media environmental fate model to back-calculate the rate of PBDE emission to air. PBDE concentrations in ambient air were measured in summer 2010 and winter 2011 in the city center of Zurich. Concentrations were higher in summer (sum PBDEs 118-591 pg m(-3)) than in winter (sum PBDEs 17-151 pg m(-3)), and are on the upper end of concentrations reported in literature for urban sites with no point sources of PBDEs. The emissions derived from our measurements (summer: 53-165 μg capita(-1) d(-1), winter: 25-112 μg capita(-1) d(-1)) and extrapolated to annual emissions for Switzerland (114-406 kg a(-1)) lie in the middle of ranges reported on the basis of substance flow analyses and emission inventories. The difference between summer and winter emissions is small compared to the difference that would be expected from the temperature dependence of PBDE vapor pressure, which would be consistent with emissions occurring to a large extent from flame-proofed materials located indoors under nearly constant temperature conditions and/or emissions to air occurring by suspension of particles containing PBDEs. Compared to previous studies in Switzerland, concentrations and emissions of PBDEs appear to have increased during the last five years with an increasing contribution of decabromodiphenyl ether, despite the addition of PBDEs to national and international regulations.

Impact of endocrine-disrupting chemicals on thyroid function and brain development

Endocrine disrupting chemicals (EDCs) are synthetic or natural substances in the environment. EDCs have been shown to disrupt reproductive, developmental and other homeostatic systems by interfering with the synthesis, secretion, transport, metabolism and action of endogenous hormones including the thyroid hormone (TH) system. Since TH plays a critical role in brain development, the exposure to TH-system disrupting EDCs during development may have serious consequences. In this article, representative previous studies showing the effect of representative EDCs on the TH system are summarized. Then, the molecular mechanisms of action of polychlorinated biphenyls and polybrominated diphenyl ethers on the TH system are discussed further. Particularly, the effect of polychlorinated biphenyls and polybrominated diphenyl ethers on TH-mediated brain development is discussed. Our recent studies may provide a novel idea regarding the effect of EDCs on the TH system.

A mechanistic view of polybrominated diphenyl ether (PBDE) developmental neurotoxicity

Polybrominated diphenyl ethers (PBDEs), extensively used in the past few decades as flame retardants in a variety of consumer products, have become world-wide persistent environmental pollutants. Levels in North America are usually higher than those in Europe and Asia, and body burden is 3-to-9-fold higher in infants and toddlers than in adults. The latter has raised concern for potential developmental toxicity and neurotoxicity of PBDEs. Experimental studies in animals and epidemiological observations in humans suggest that PBDEs may be developmental neurotoxicants. Pre- and/or post-natal exposure to PBDEs may cause long-lasting behavioral abnormalities, particularly in the domains of motor activity and cognition. The mechanisms underlying the developmental neurotoxic effects of PBDEs are not known, though several hypotheses have been put forward. One general mode of action relates to the ability of PBDEs to impair thyroid hormone homeostasis, thus indirectly affecting the developing brain. An alternative or additional mode of action involves a direct effect of PBDEs on nervous system cells; PBDEs can cause oxidative stress-related damage (DNA damage, mitochondrial dysfunction, apoptosis), and interfere with signal transduction (particularly calcium signaling), and with neurotransmitter systems. Important issues such as bioavailability and metabolism of PBDEs, extrapolation of results to low level of exposures, and the potential effects of interactions among PBDE congeners and between PBDEs and other contaminants also need to be taken into account.

Development and utilization of camelid VHH antibodies from alpaca for 2,2',4,4'-tetrabrominated diphenyl ether detection

An antibody-based analytical method for the detection of a chemical flame retardant using antibody fragments isolated from an alpaca has been developed. One specific chemical flame retardant congener, 2,2′,4,4′-tetrabrominated diphenyl ether (BDE-47), is often the major poly-BDE (PBDE) congener present in human and environmental samples and that which is the most frequently detected. An alpaca was immunized with a surrogate of BDE-47 covalently attached to a carrier protein. The resulting mRNA coding for the variable domain of heavy-chain antibodies (VHH) were isolated, transcribed to cDNA, and cloned into a phagemid vector for phage display library construction. Selection of VHHs recognizing BDE-47 was achieved by panning under carefully modified conditions. The assay sensitivity for detecting BDE-47 was down to the part-per-billion (microgram per liter) level. Cross-reactivity analyses confirmed that this method was highly selective for BDE-47 and selected hydroxylated metabolites. When exposed to elevated temperatures, the camelid VHH antibodies retained more reactivity than a polyclonal antibody developed to the same target analyte. The use of this VHH antibody reagent immobilized onto a Au electrode for impedance biosensing demonstrates the increased versatility of VHH antibodies.

Developmental Exposure to Polybrominated Diphenyl Ethers and Neurodevelopment

Exposure to polybrominated diphenyl ethers (PBDE) during sensitive developmental windows can interfere with cognitive function and behavior, which are critical components of neurodevelopment. The association between developmental exposure to PBDEs and neurodevelopment has been extensively studied using animal models. In this review, we focus on the accumulating evidence in humans. Despite methodological, geographical, and temporal differences between studies, the majority of the epidemiologic evidence supports that early life exposure to PBDEs measured during pregnancy and/or during childhood is detrimental to child neurodevelopment in domains related to child behavior, cognition, and motor skills. While the precise mechanism of action of PBDEs on neurodevelopment is unknown, PBDE-induced neurotoxicity via thyroid hormone disruption and direct action of PBDEs on the developing brain have been proposed and tested. Additional studies are suggested to better understand how early life and/or childhood PBDE exposures, including exposure to specific PBDE congeners, impact neurodevelopmental indices.

Designing quantitative structure activity relationships to predict specific toxic endpoints for polybrominated diphenyl ethers in mammalian cells

Polybrominated diphenyl ethers (PBDEs) are known as effective flame retardants and have vast industrial application in products like plastics, building materials and textiles. They are found to be structurally similar to thyroid hormones that are responsible for regulating metabolism in the body. Structural similarity with the hormones poses a threat to human health because, once in the system, PBDEs have the potential to affect thyroid hormone transport and metabolism. This study was aimed at designing quantitative structure-activity relationship (QSAR) models for predicting toxic endpoints, namely cell viability and apoptosis, elicited by PBDEs in mammalian cells. Cell viability was evaluated quantitatively using a general cytotoxicity bioassay using Janus Green dye and apoptosis was evaluated using a caspase assay. This study has thus modelled the overall cytotoxic influence of PBDEs at an early and a late endpoint by the Genetic Function Approximation method. This research was a twofold process including running in vitro bioassays to collect data on the toxic endpoints and modeling the evaluated endpoints using QSARs. Cell viability and apoptosis responses for Hep G2 cells exposed to PBDEs were successfully modelled with an r(2) of 0.97 and 0.94, respectively.

A Mini-Review on Disposal of WEEE Plastics Containing PBDEs with a Special Focus on China

Polybrominated diphenyl ethers (PBDEs), especially pentaBDE and decaBDE have been extensively used as flame retardants in plastics of most electronic equipment. However, PBDE congeners have been found in the environment, in wildlife and in human body worldwide with evidences that they pose risks both to human health and to the entire ecosystem. China has become an important pentaBDE and decaBDE production country because of the increasing domestic demand due to rapid development of electronic industry in recent years. Although pentaBDE was phased out in 2004, decaBDE still remains in production and is used in electrical industry. Additionally, large amounts of plastics containing these pollutants from waste electrical and electronic equipment (WEEE) are generated in China each year and their disposal has been a vital environmental challenge. Machaniclal recycling, fedlock recycling and landfilling are three main means of disposal of WEEE plastics. This article reviews the production of PBDEs, the amounts of WEEE and the disposal of WEEE plastics worldwide, with a special focus on China. The state of the emission of PBDEs and highly toxic polybrominated dibenzo dioxins/furans in the process of disposal is summed up based on previous studies. This article recommends that mechanical recycling should be the main means of disposal of WEEE recycling with regards to the summaries, the current practices and the status in China.

Locomotor activity changes on zebrafish larvae with different 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) embryonic exposure modes

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants and are banned around the world as potent environmental contaminants. PBDE-47 is the most concerned PBDE with its environmental prevalence and various toxicity characteristics including neurotoxicity. In this paper, we studied larval zebrafish behavioral alterations caused by PBDE-47 neurotoxicity. The light-dark cycle stimulation was used to investigate the locomotor changes of zebrafish larvae at different ages (4-6 day post-fertilization, dpf) after PBDE-47 exposure (5, 50, 500 μg L(-1)). Three exposure modes, namely continuous exposure, early pulse exposure and interval exposure, were adopted to assess and compare the impacts of exposure modes on larval zebrafish locomotion. Our results showed that locomotor effects upon PBDE exposure depended on the specific exposure mode studied. In the early pulse exposure mode, the locomotion of zebrafish larvae did not change significantly at all PBDE-47 concentrations tested. In contrast, for both the continuous exposure and interval exposure modes, the highest dose of PBDE-47 (500 μg L(-1)) elicited pronounced hypoactivity at 5 dpf during dark periods except for the initial one. However, at 6 dpf, hypoactivity was only observed in the continuously exposed zebrafish larvae (to an even higher degree compared to 5 dpf), but not in the interval exposure treatment group. Our results suggested that the conventional, continuous exposure mode might not be enough to evaluate the toxicity of chemicals in the real environments.

Effects of decabromodiphenyl ether (BDE-209) on mRNA transcription of thyroid hormone pathway and spermatogenesis associated genes in Chinese rare minnow (Gobiocypris rarus)

Polybrominated diphenyl ethers (PBDEs) are widely used as flame retardants, which are ubiquitous environmental contaminant found in both abiotic and biotic environmental samples. Deca-BDE (BDE-209) is the principal component, which is currently used worldwide. In this study, the effect of BDE-209 on the mRNA levels of thyroid hormone (TH) related genes and spermatogenesis associated genes were determined from larvae and adult rare minnow (Gobiocypris rarus) exposed to concentrations 0.01, 0.1, 1, and 10 μg/L for 21 days. The results showed that the type II deiodinase (dio2) and sodium iodide symporter (nis) mRNA levels were significantly up-regulated in the larvae at 10 μg/L treatment. In adult, histopathological observations showed that liver of female fish were degenerated at 10 μg/L treatment, and inhibition of spermatogenesis were observed in testis of male fish. In addition, the thyroid hormone receptor α (trα), dio2, and nis mRNA levels in the liver of male and female fish were significantly up-regulated, whereas dio2 and nis mRNA levels were significantly down-regulated in the brain. These results indicate that exposure to BDE-209 could result in tissue-specific alternations of TH-related genes expression in adults. Moreover, the mRNA levels of the testis-specific apoptosis genes, the spermatogenesis-associated 4 (spata4) and spermatogenesis-associated 17 (spata17), were down-regulated at 10 μg/L treatment in testis of male fish. Our results suggest that BDE-209 may pose threat to normal thyroid and reproductive function in fish.

Flame retardant BDE-47 effectively activates nuclear receptor CAR in human primary hepatocytes

Polybrominated diphenyl ether BDE-47 (2,2',4,4'-tetrabromodiphenyl ether) is a thyroid hormone disruptor in mice; hepatic induction of various metabolic enzymes and transporters has been suggested as the mechanism for this disruption. Utilizing Car (-/-) and Pxr (-/-) mice as well as human primary hepatocytes, here we have demonstrated that BDE-47 activated both mouse and human nuclear receptor constitutive activated/androstane receptor (CAR). In mouse livers, CAR, not PXR, was responsible for Cyp2b10 mRNA induction by BDE-47. In human primary hepatocytes, BDE-47 was able to induce translocation of YFP-tagged human CAR from the cytoplasm to the nucleus andCYP2B6 and CYP3A4 mRNAs expressions. BDE-47 activated human CAR in a manner akin to the human CAR ligand CITCO (6-(4-Chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime) in luciferase-reporter assays using Huh-7 cells. In contrast, mouse CAR was not potently activated by BDE-47 in the same reporter assays. Furthermore, human pregnane X receptor (PXR) was effectively activated by BDE-47 while mouse PXR was weakly activated in luciferase-reporter assays. Our results indicate that BDE-47 induces CYP genes through activation of human CAR in addition to the previously identified pathway through human PXR.

Effects of perchlorate on BDE-47-induced alteration thyroid hormone and gene expression of in the hypothalamus-pituitary-thyroid axis in zebrafish larvae

To investigate the effects of perchlorate on thyroid hormone disturbances induced by 2,2',4',4-tetrabromodiphenyl ether (BDE-47) via thyroid hormone (TH)-mediated pathways, zebrafish embryos were exposed to a combination of BDE-47 and PER from the time of fertilisation to 14 d (dpf). The whole-body content of TH and the expression of genes and proteins related to the hypothalamic-pituitary-thyroid (HPT) axis were analysed. Co-exposure to BDE-47 and PER decreased the body weight and increased malformation rates relative to the effects of exposure to only BDE-47. Compared with the exposure to BDE-47 alone, the exposure to a combination of BDE-47 (10 μg/L) and PER (3.5 mg/L) significantly up-regulated the expression of genes involved in TH synthesis (NIS and Nkx2.1a) and significantly down-regulated the expression of genes related to the regulation of the HPT axis (CRH and TSHβ). The expression of TG at the gene and protein levels was significantly up-regulated, but the expression of TTR was significantly down-regulated in the co-exposures relative to BDE-47 treated alone. In addition, the larger reduction in the T4 level resulting from exposure to the mixture of BDE-47 and PER demonstrated that PER enhanced the thyroid-disruptive effects of BDE-47. These results help to elucidate the complicated chemical interactions and the molecular mechanism of action of these two TH disruptors.

Polybrominated diphenyl ethers (PBDEs) in breast milk of Korea in 2011: current contamination, time course variation, influencing factors and health risks

Breast milk is a valuable biological specimen to assess maternal and infant exposure to polybrominated diphenyl ethers (PBDEs). In this study, 208 breast milk samples were collected from 89 participants during lactation period, at <7, 15, 30, and 90 days postpartum, in four cities in Korea, and were determined for 19 PBDE congeners. The total PBDE concentrations (ΣPBDE) ranged from 0.23 to 68.4 (mean: 2.73) ng/g lipid weight, and were within the ranges reported for European and Asian countries. Within a month of lactation after delivery, no significant changes were found in the PBDE concentrations. The predominance of BDE 153 rather than BDE 47 was found in the most samples that BDE 153 was detected, and was likely to be associated with stepwise debromination of BDE 209. No associations were found between PBDE concentrations in breast milk and demographic parameters, except for ΣPBDE with maternal age and delivery mode. Certain types of diet such as corn, seafood and nut correlated significantly with PBDE levels in breast milk. The estimated daily intakes of ΣPBDE for breast-feeding infants were lower than the guidelines proposed by the US EPA, indicating limited health risk from PBDEs through breast feeding.

Simultaneous determination of polybrominated diphenyl ethers and polychlorinated biphenyls by gas chromatography-tandem mass spectrometry in human serum and plasma

Sensitive and reliable methods for simultaneous determination of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in limited volumes of human serum or plasma need to be further documented especially when they accumulate at low levels that are still capable of disrupting endocrine and immune functions, and affecting neurodevelopment and reproduction. The objective of this study was to develop and validate a sensitive and quantitative method that simultaneously quantifies PBDEs and PCBs in 0.5 ml of human serum or plasma. We optimized a solid-phase extraction (SPE) method and used silica particle purification for the extraction of PBDEs and PCBs. Two multiple reactions monitoring (MRM) transitions were optimized for each congener. The sum of the transitions was used for quantification, and their abundance ratios were used for identification. The combined method optimization techniques resulted in limits of detection from 3 to 145 pg/ml for 10 PBDEs and 1-12 pg/ml for 15 PCBs. Method was solidly validated by analyzing serum fortified with a certified PBDE and PCB standard mixture from the National Institute of Standards and Technology (NIST). The accuracy was 88-118% and day-to-day precision was within 19%. The method was successfully applied to quantify native concentrations of PBDE and PCB in commercially available human serum. The sensitivity and selectivity of the GC/EI-MS/MS analysis enables it to be the method of choice for investigations of exposures to PBDE and PCB congeners, especially when sample volume is limited.

Maternal and cord-blood thyroid hormone levels and exposure to polybrominated diphenyl ethers and polychlorinated biphenyls during early pregnancy

Thyroid hormones play a critical role in the growth of many organs, especially the brain. Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) interact with the thyroid pathway and may disturb neurodevelopment. This prospective study was designed to examine associations between maternal blood PBDEs and PCBs in early pregnancy and levels of thyroid hormones in maternal and umbilical-cord blood. Levels of low-brominated PBDEs, 3 PCB congeners, total and free thyroid hormones (triiodothyronine (T3) and thyroxine (T4)), thyroid-stimulating hormone, thyroid peroxidase antibodies, iodine, selenium, and mercury were measured in 380 pregnant women in the first trimester who were recruited at the University Hospital Center of Sherbrooke (Quebec, Canada) between September 2007 and December 2008. Thyroid hormone levels were also assessed at delivery and in cord blood (n = 260). Data were analyzed on both a volume basis and a lipid basis. At less than 20 weeks of pregnancy, no relationship was statistically significant in volume-based analysis. In lipid-based models, an inverse association between maternal PBDEs and total T3 and total T4 and a direct association with free T3 and free T4 were observed. At delivery, in both analyses, we observed negative associations between maternal total T4, free T3, cord-blood free T4, and PBDEs and between maternal free T3 and PCBs. Our results suggest that exposure to PBDEs and PCBs in pregnancy may interfere with thyroid hormone levels.