Endocrine effects of hexabromocyclododecane (HBCD) in a one-generation reproduction study in Wistar rats

Exposure of Female Rats to an Environmentally Relevant Mixture of Brominated Flame Retardants Targets the Ovary, Affecting Folliculogenesis and Steroidogenesis

Brominated flame retardants (BFRs) are incorporated into various consumer products to prevent flame propagation. These compounds leach into the domestic environment, resulting in chronic exposure and contamination. Pregnancy failure is associated with high levels of BFRs in human follicular fluid, raising serious questions regarding their impact on female reproductive health. The goal of this study is to elucidate the effects of an environmentally relevant BFR mixture on female rat ovarian functions (i.e., folliculogenesis and steroidogenesis). A BFR dietary mixture formulated to mimic the relative BFR congener levels in North American house dust was administered to adult female Sprague-Dawley rats from 2 to 3 wk before mating until Gestational Day 20; these diets were designed to deliver nominal doses of 0, 0.06, 20, or 60 mg/kg/day of the BFR mixture. Exposure to BFRs triggered an approximately 50% increase in the numbers of preantral and antral follicles and an enlargement of the antral follicles in the ovaries of the dams. A significant reduction in the expression of catalase, an antioxidant enzyme, and downregulation of the expression of insulin-like factor 3 (Insl3) and 17alpha-hydroxylase (Cyp17a1) were observed in the ovary. In addition, BFR exposure affected steroidogenesis; we observed a significant decrease in circulating 17-hydroxypregnenolone and an increase in testosterone concentrations in BFR-exposed dams. Thus, BFRs target ovarian function in the rat, adversely affecting both folliculogenesis and steroidogenesis.

Trends of polybrominated diphenyl ethers and hexabromocyclododecane in eggs of Canadian Arctic seabirds reflect changing use patterns

Due to the substantial use and release of polybrominated diphenyl ether (PBDE) flame retardants in North America, PBDE concentrations in North American marine biota are among the highest in the world. In this study, we compared PBDE concentrations and congener patterns in eggs of five seabird species (thick-billed murres, northern fulmars, black guillemots, glaucous gulls, black-legged kittiwakes) breeding at a colony in the Canadian Arctic in 1993, 2008 and 2013. Temporal trends of PBDEs (1975-2014) and another flame retardant, hexabromocyclododecane (HBCD) (2003-2014), were also examined in eggs of two seabird species, the thick-billed murre and northern fulmar. BDE-47 generally dominated the BDE congener profiles in eggs of all five species. Glaucous gulls had the highest concentrations of both ΣPBDE and BDE-47, and northern fulmars, the lowest. ΣPBDE concentrations increased exponentially in eggs of both thick-billed murres and northern fulmars from 1975 to 2003 with doubling times of 9.1 years in the murres and 7.2 years in the fulmars. From 2003 to 2008/09, ΣPBDE decreased rapidly in the murres and fulmars to concentrations not significantly different from those recorded in 1975 and 1987 for each species. After 2008/09, ΣPBDE concentrations plateaued. BDE-47 followed a similar temporal trend to that of ΣPBDE concentrations. These concentration trends were consistent with the phase-out of the penta- and octa-BDE products from the North American market in the mid-2000s. There was an overall decline in concentrations of HBCD in murre eggs from 2003 to 2014, whereas concentrations in the fulmar eggs increased from 2003 to 2006 followed by a decline to 2014. The ratio of HBCD to BDE-47 suggests that northern fulmars showed more of a European contaminant signature, and thick-billed murres, more of a North American signature.

HBCD and PCBs enhance the cell migration and invasion of HepG2 via the PI3 K/Akt pathway

Exposure to hexabromocyclododecane (HBCD) and polychlorinated biphenyls (PCBs) has been proved to result in diversified toxicity, including cancerogenesis.

Human health risk associated with brominated flame-retardants (BFRs)

The purposes of this review are to assess the human exposure and human and experimental evidence for adverse effects of brominated flame-retardants (BFRs) with specific focus on intake from seafood. The leakage of BFRs from consumer products leads to exposure of humans from fetal life to adulthood. Fish and fish products contain the highest levels of BFRs and dominate the dietary intake of frequent fish eaters in Europe, while meat, followed by seafood and dairy products accounted for the highest US dietary intake. House dust is also reported as an important source of exposure for children as well as adults. The levels of BFRs in the general North American populations are higher than those in Europe and Japan and the highest levels are detected in infants and toddlers. The daily intake via breast milk exceeds the RfD in 10% of US infants. BFRs including PBDEs, HBCDs and TBBP-A have induced endocrine-, reproductive- and behavior effects in laboratory animals. Furthermore, recent human epidemiological data demonstrated association between exposure to BFRs and similar adverse effects as observed in animal studies. Fish including farmed fish and crude fish oil for human consumption may contain substantial levels of BFRs and infants and toddlers consuming these products on a daily basis may exceed the tolerable daily intake suggesting that fish and fish oil alone represent a risk to human health. This intake comes in addition to exposure from other sources (breast milk, other food, house dust). Because potential harmful concentrations of BFRs and other toxicants occur in fish and fish products, research on a wider range of products is warranted, to assess health hazard related to the contamination of fish and fish products for human consumption.

HBCDD-induced sustained reduction in mitochondrial membrane potential, ATP and steroidogenesis in peripubertal rat Leydig cells

Hexabromocyclododecane (HBCDD), a brominated flame retardant added to various consumer products, is a ubiquitous environmental contaminant. We have previously shown that 6-hour exposure to HBCDD disturbs basal and human chorionic gonadotropin (hCG)-induced steroidogenesis in rat Leydig cells. Reduction in mitochondrial membrane potential (ΔΨm) and cAMP production was also observed. Here, we further expanded research on the effect of HBCDD on Leydig cells by using a prolonged exposure scenario. Cells were incubated in the presence of HBCDD during 24h and then treated with HBCDD+hCG for additional 2h. Results showed that HBCDD caused a sustained reduction in ATP level after 24h of exposure, which persisted after additional 2-hour treatment with HBCDD+hCG. cAMP and androgen accumulations measured after 2h of HBCDD+hCG treatment were also inhibited. Real-time PCR analysis showed significant inhibition in the expression of genes for steroidogenic enzymes, luteinizing hormone receptor, regulatory and transport proteins, and several transcription factors under both treatment conditions. Western blot analysis revealed a decreased level of 30kDa steroidogenic acute regulatory protein (StAR) after HBCDD+hCG treatment. In addition, HBCDD decreased the conversion of 22-OH cholesterol to pregnenolone and androstenedione to testosterone, indicating loss of the activity of cytochrome P450C11A1 (CYP11A1) and 17β-hydroxysteroid dehydrogenase (HSD17β). Cell survival was not affected, as confirmed by cytotoxicity and trypan blue tests or DNA fragmentation analysis. In summary, our data showed that HBCDD inhibits ATP supply, most likely through a decrease in ΔΨm, and targets multiple sites in the steroidogenic pathway in Leydig cells.

Extent and mechanisms of brominated flame retardant emissions from waste soft furnishings and fabrics: A critical review

Use of brominated flame retardants (BFRs) in soft furnishings has occurred for over thirty years with the phase out of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD) only relatively recently begun. As products treated with BFRs reach the end of their lifecycle they enter the waste stream, thereby constituting an important and increasing reservoir of these chemicals. This review highlights the dearth of data on the extent and potential mechanisms of BFR emissions from waste soft furnishings. However, insights into what may occur are provided by scrutiny of the larger (though still incomplete) database related to BFR emissions from electronic waste (e-waste). In many countries, municipal landfills have historically been the primary disposal method of waste consumer products and therefore represent a substantial reservoir of BFRs. Published data for BFR emissions to both air and water from landfill and other waste disposal routes are collated, presented and reviewed. Reported concentrations of PBDEs in landfill leachate range considerably from <1ngL(-1) to 133,000ngΣPBDEL(-1). In addition to direct migration of BFRs from waste materials; there is evidence that some higher brominated flame retardants are able to undergo degradation and debromination during waste treatment, that in some instances may lead to the formation of more toxic and bioavailable compounds. We propose that waste soft furnishings be treated with the same concern as e-waste, given its potential as a reservoir and source of environmental contamination with BFRs.

Prenatal exposure to the brominated flame retardant hexabromocyclododecane (HBCD) impairs measures of sustained attention and increases age-related morbidity in the Long-Evans rat

Hexabromocyclododecane (HBCD) is a brominated flame retardant that is widely-used in foam building materials and to a lesser extent, furniture and electronic equipment. After decades of use, HBCD and its metabolites have become globally-distributed environmental contaminants that can be measured in the atmosphere, water bodies, wildlife, food staples and human breastmilk. Emerging evidence suggests that HBCD can affect early brain development and produce behavioral consequences for exposed organisms. The current study examined some of the developmental and lifelong neurobehavioral effects of prenatal HBCD exposure in a rat model. Pregnant rats were gavaged with 0, 3, 10, or 30mg/kg HBCD from gestation day 1 to parturition. A functional observation battery was used to assess sensorimotor behaviors in neonates. Locomotor and operant responding under random ratio and Go/no-go schedules of food reinforcement were examined in cohorts of young adult and aged rats. HBCD exposure was associated with increased reactivity to a tailpinch in neonates, decreased forelimb grip strength in juveniles, and impaired sustained attention indicated by Go/no-go responding in aged rats. In addition, HBCD exposure was associated with a significant increase in morbidity in the aged cohort. One health complication, a progressive loss of hindleg function, was observed only in the aged, 3mg/kg HBCD animals. These effects suggest that HBCD is a developmental neurotoxicant that can produce long-term behavioral impairments that emerge at different points in the lifespan following prenatal exposure.

Gestational and lactational exposure to the polychlorinated biphenyl mixture Aroclor 1254 modulates retinoid homeostasis in rat offspring

Polychlorinated biphenyls (PCBs) induce a broad spectrum of biochemical and toxic effects in mammals including alterations of the vital retinoid (vitamin A) system. The aim of this study was to characterize alterations of tissue retinoid levels in rat offspring and their dams following gestational and lactational exposure to the PCB mixture Aroclor 1254 (A1254) and to assess the interrelationship of these changes with other established sensitive biochemical and toxicological endpoints. Sprague-Dawley rat dams were exposed orally to 0 or 15 mg/kg body weight/day of A1254 from gestational day 1 to postnatal day (PND) 23. Livers, kidneys and serum were collected from the offspring on PNDs 35, 77 and 350. Tissue and serum retinoid levels, hepatic cytochrome P450 (CYP) enzymes and serum thyroid hormones were analyzed. A multivariate regression between A1254 treatment, hepatic retinoid levels, hepatic CYP enzymes activities, thyroid hormone levels and body/liver weights was performed using an orthogonal partial least-squares (PLS) analysis. The contribution of dioxin-like (DL) components of A1254 to the observed effects was also estimated using the toxic equivalency (TEQ) concept. In both male and female offspring short-term alterations in tissue retinoid levels occurred at PND35, i.e. decreased levels of hepatic retinol and retinoic acid (RA) metabolite 9-cis-4-oxo-13,14-dihydro-RA with concurrent increases in hepatic and renal all-trans-RA levels. Long-term changes consisted of decreased hepatic retinyl palmitate and increased renal retinol levels that were apparent until PND350. Retinoid system alterations were associated with altered CYP enzyme activities and serum thyroid hormone levels as well as body and liver weights in both offspring and dams. The estimated DL activity was within an order of magnitude of the theoretical TEQ for different endpoints, indicating significant involvement of DL congeners in the observed effects. This study shows that tissue retinoid levels are affected both short- and long-term by developmental A1254 exposure and are associated with alterations of other established endpoints of toxicological concern.

Actions of endocrine-disrupting chemicals on stem/progenitor cells during development and disease

Development and fate of the stem cell are regulated by extrinsic signals from the environment. Endocrine-disrupting chemicals which perturb hormonal signaling in utero and during early childhood may cause deregulation of multiple developmental processes, ranging from breakdown of stem cell niche architecture, developmental reprograming and altered stem cell fate to impaired organ and gonad development and sexual differentiation. Therefore, study of the environmental effects on stem cell integrity and normal development is a new and emerging focus for developmental biologists and cell toxicologists. When combined with new human and mouse stem cell-based models, stem cell differentiation dynamics can be studied in more biologically relevant ways. In this study, we review the current status of our understanding of the molecular mechanisms by which endocrine disruptors alter embryonic stem cell and adult stem/progenitor cell fate, organ development, cancer stem cell activity, and tumorigenesis.

Antioxidant responses in clam Venerupis philippinarum exposed to environmental pollutant hexabromocyclododecane

The objective of this study was to assess the potential toxic effects of hexabromocyclododecane (HBCD) on tissues of clam Venerupis philippinarum using parameters of antioxidant defenses and oxidative stress. Antioxidant biomarkers including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), superoxide dismutase (SOD), and glutathione (GSH), as well as DNA damage and lipid peroxidation (LPO) in gills and digestive glands of V. philippinarum, were analyzed after a 1-, 3-, 6-, 10-, and 15-day exposure to seawater containing HBCD at environmentally related concentrations, respectively. The results showed that the activity of most antioxidant enzymes increased, and different trends were detected with exposure time extending. The oxidative stress could be obviously caused in the gills and digestive glands under the experimental conditions. This could provide useful information for toxic risk assessment of environmental pollutant HBCD.

Enantioselective biotransformation of hexabromocyclododecane by in vitro rat and trout hepatic sub-cellular fractions

α-, β-, and γ-Hexabromocyclododecanes (HBCDs) were subjected to in vitro biotransformation experiments with rat and trout liver S9 fractions for different incubation times (10, 30, and 60 min) at 2 concentration levels (1 and 10 μM). The metabolic degradation of target HBCDs followed first order kinetics. Whereas β-HBCD undergoes rapid biotransformation (t0.5 = 6.4 and 38.1 min in rat and trout, respectively), α-HBCD appears the most resistant to metabolic degradation (t0.5 = 17.1 and 134.9 min). The biotransformation rate in trout was slower than in rat. Investigation of HBCD degradation profiles revealed the presence of at least 3 pentabromocyclododecene (PBCD) and 2 tetrabromocyclododecadiene (TBCD) isomers indicating reductive debromination as a metabolic pathway for HBCDs. Both mono- and di- hydroxyl metabolites were identified for parent HBCDs, while only mono hydroxyl metabolites were detected for PBCDs and TBCDs. Interestingly, δ-HBCD was detected only in trout S9 fraction assays indicating metabolic interconversion of test HBCD diastereomers during biotransformation in trout. Finally, enantioselective analysis showed significant enrichment of the (-)-α-HBCD enantiomer (EF = 0.321 and 0.419 after 60 min incubation in rat and trout, respectively). The greater enrichment of (-)-α-HBCD in rat than in trout underlines the species-specific differences in HBCD metabolism and the need for caution when extending similar results from animal studies to humans.

Dietary exposure of American kestrels (Falco sparverius) to decabromodiphenyl ether (BDE-209) flame retardant: uptake, distribution, debromination and cytochrome P450 enzyme induction

Accumulation and evidence of debromination of the flame retardant 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) have been reported for biota, including raptorial birds, based on PBDE congener residues in tissues and eggs. However, in vivo studies with BDE-209-exposed birds are rare and unknown for a raptorial species. In the present study, males (n=22) of raptorial American kestrels (Falco sparverius) were exposed to 116,000ng of BDE-209 (high purity, >98%; in safflower oil) per day for 21days (~2,436,000ng total BDE-209 exposure over this uptake period), followed by a 25-day depuration period. Control males (n=11) received the safflower vehicle only. In the exposed birds, BDE-209 was quantifiable in all plasma (end of uptake and depuration period) as well as liver and fat (end of depuration only) samples. The mean (±SE) BDE-209 level in plasma was 1474±1145ng/g wet weight (ww) at the end of the uptake period, and was significantly (p<0.001) lower (88%) at 174±148ng/g ww after the 25day depuration period. This equates to a mean reduction rate of 52ng/g ww per day and a rough estimation of the BDE-209 half-life in plasma of approximately 14days. The mean (±SE) BDE-209 levels were 4668±6192ng/g ww in the fat, and 338±311ng/g ww in the liver, of exposed individuals, which were significantly (p≤0.001) greater than mean concentrations (25±20 in fat and 2.6±0.9ng/g ww in liver) in the control birds. In addition to BDE-209, lower brominated PBDE congeners, and mainly meta- and para-debromination products of BDE-209 were also quantified in plasma, liver and/or fat. We estimated based on the dose that at least 80% of the non-BDE-209 concentration in the kestrel tissues and plasma must be derived from BDE-209 debromination by the kestrels. Where quantifiable, lower brominated PBDE concentrations were significantly (0.023>p>0.001) higher in the exposed relative to the control bird samples (except for BDE-154 and -153 in fat). Additional PBDE congeners found in plasma included nona-BDEs (208, 207 and 206), followed by octa-BDEs (197, 196, 201 and 203), and in liver and/or fat, the hepta-BDEs 180 and 183 and BDE-153. Higher hepatic EROD activity (cytochrome P450 1A1 monooxygenase-mediation) in the exposed birds compared to control birds was strongly suggested to be PBDE-induced, and was consistent with BDE-209 and congener metabolism in the exposed kestrels. The mean EROD activity rate was 36.1pmol/min/mg protein relative to the (n=4) control birds whose activity was just above the detection limit (10.3pmol/min/mg protein). Overall, the results demonstrated that following diet exposure of kestrels to high purity BDE-209, uptake occurred as well as BDE-209 degradation via debromination to lower brominated PBDE congeners.

In utero and lactational exposure to a mixture of environmental contaminants detected in Canadian Arctic human populations alters retinoid levels in rat offspring with low margins of exposure

Arctic inhabitants are highly exposed to persistent organic pollutants (POP), which may produce adverse health effects. This study characterized alterations in tissue retinoid (vitamin A) levels in rat offspring and their dams following in utero and lactational exposure to the Northern Contaminant Mixture (NCM), a mixture of 27 contaminants including polychlorinated biphenyls (PCB), organochlorine (OC) pesticides, and methylmercury (MeHg), present in maternal blood of the Canadian Arctic Inuit population. Further, effect levels for retinoid system alterations and other endpoints were compared to the Arctic Inuit population exposure and their interrelationships were assessed. Sprague-Dawley rat dams were dosed with NCM from gestational day 1 to postnatal day (PND) 23. Livers, kidneys and serum were obtained from offspring on PND35, PND77, and PND350 and their dams on PND30 for analysis of tissue retinoid levels, hepatic cytochrome P-450 (CYP) enzymes, and serum thyroid hormones. Benchmark doses were established for all endpoints, and a partial least-squares regression analysis was performed for NCM treatment, hepatic retinoid levels, CYP enzyme induction, and thyroid hormone levels, as well as body and liver weights. Hepatic retinoid levels were sensitive endpoints, with the most pronounced effects at PND35 though still apparent at PND350. The effects on tissue retinoid levels and changes in CYP enzyme activities, body and liver weights, and thyroid hormone levels were associated and likely driven by dioxin-like compounds in the mixture. Low margins of exposure were observed for all retinoid endpoints at PND35. These findings are important for health risk assessment of Canadian Arctic populations and further support the use of retinoid system analyses in testing of endocrine-system-modulating compounds.

Brominated flame-retardants in Sub-Saharan Africa: burdens in inland and coastal sediments in the eThekwini metropolitan municipality, South Africa

Brominated flame-retardant (BFR) additives are present in many polymeric consumer products at percent levels. High environmental concentrations have been observed near cities and polymer, textile, and electronics manufacturing centers. Most studies have focused on European, North American, and Asian locales. Releases are likely rising most dramatically in countries with weak environmental and human health regulation and enforcement, demand for electrical and electronic equipment (EEE) is escalating, and importation of waste EEE occurs. Several African countries meet these criteria, but little data are available on burdens or sources. To better understand the extent of BFR environmental dissemination in a southern African urban community, inland and coastal sediments were collected in the eThekwini metropolitan municipality, South Africa, and analyzed for polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB), 2-ethylhexyl 2,3,4,5-tretabromophalate (TBPH), 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE), and decabromodiphenyl ethane (DBDPE). BFRs were detected in all samples (n = 45). Concentration data are presented on total organic carbon (TOC) normalized basis. ΣBFR ranged from 114 to 47 100 ng g(-1). Decabromodiphenyl ether was detected in 93% of samples (mean concentration 3208 ng g(-1)) followed by TBB at 91% (mean conc. 545 ng g(-1)). Durban Bay is strongly influenced by urban runoff and tidal hydrology, and sediments therein exhibited ΣPBDE concentrations ranging from 1850 to 25 400 ng g(-1) (median conc. 3240 ng g(-1)). These levels rival those in the heavily impacted Pearl River Delta, China. BFRs likely enter the South African environment during manufacture of BFR-containing products, during and following product use (i.e., after disposal and as a result of materials recycling activities), and from nonpoint sources such as atmospheric fallout and urban runoff. These results underline the need to investigate further the environmental burdens and risks associated with BFRs in developing countries.

The fate of β-hexabromocyclododecane in female C57BL/6 mice

1,2,5,6,9,10-Hexabromocyclododecane (HBCD) is a high production volume cycloaliphatic used as an additive flame retardant primarily in polystyrene foam building materials. HBCD mixtures contain three major stereoisomers, alpha (α), beta (β), and gamma (γ), at a typical ratio of 1.2:0.6:8.2. The toxicokinetic properties of the α and γ isomers differ. For instance, α-HBCD has greater bioavailability and potential for accumulation in mice than γ-HBCD. The present study reports comparative kinetics data for β-HBCD needed to support toxicological evaluations of HBCD mixtures. Results indicated that a single oral dose of 3mg/kg of [(14)C]-labeled β-HBCD was absorbed rapidly (≥ 85% total dose) in the female C57BL/6 mouse. The C max for β-HBCD-derived radioactivity in tissues, except adipose, was observed 3h following gavage. Approximately 90% of the administered dose was excreted in urine and feces within 24h, primarily as β-HBCD-derived metabolites. A portion of the dose (circa 9%) was excreted in feces as γ-HBCD. Oral administration of 30 or 100mg/kg of β-HBCD resulted initially in slower rates of [(14)C] elimination; however, cumulative excretion data were similar across the dosing range 4 days postdosing. Residual concentrations of [(14)C] in tissues were highest in adipose and liver. β-HBCD-derived radioactivity accumulated in most tissues following four consecutive daily oral doses of 3mg/kg. The extent of metabolism and excretion of β-HBCD in female C57BL/6 mice was similar to that for γ-HBCD. The potential for accumulation of β-HBCD-derived material in most tissues appeared to be less than for α-HBCD.

Acute effects of hexabromocyclododecane on Leydig cell cyclic nucleotide signaling and steroidogenesis in vitro

Hexabromocyclododecane (HBCDD), an additive brominated flame retardant routinely added to various consumer products, was reported to have toxic effects upon biota, including endocrine disruption. In this study, the potential toxicity of HBCDD was tested in peripubertal rat Leydig cells in vitro during 6h exposure. HBCDD inhibited human chorionic gonadotropin- and forskolin-supported cAMP accumulation and steroidogenesis. It also inhibited basal cAMP production, but elevated basal steroidogenesis. The expression of several cAMP-dependent genes, including steroidogenic acute regulatory protein, cholesterol side chain cleavage enzyme, and 3β-hydroxysteroid dehydrogenase, was also inhibited by HBCDD treatment. Nevertheless, this was not accompanied by a decrease in steroidogenic acute regulatory protein expression, as documented by western blot analysis, and activity of steroidogenic enzymes, as documented by unaffected steroidogenesis in the presence of permeable 22(R)-hydroxycholesterol. However, HBCDD caused significant decrease in mitochondrial membrane potential in untreated and human chorionic gonadotropin-treated cells. This indicates that HBCDD acute toxicity in Leydig cells reflects changes in mitochondrial membrane potential-dependent cAMP production and basal and cAMP-regulated cholesterol transport. This in turn facilitates basal but inhibits cAMP-dependent steroidogenesis. Acute effects of HBCDD treatment on transcription are also indicative of its sustained effects on Leydig cell function.

The cytological effects of HBCDs on human hepatocyte L02 and the potential molecular mechanism

The concentration of hexabromocyclododecanes (HBCDs) in the environment media and organism samples are gradually rising with the increase of HBCDs usage. This study is designed to investigate the cytological effects of HBCDs on human hepatocyte L02 and explore the potential molecular mechanism. The results of CCK-8 assay showed that high concentration of HBCDs (>20 μM) significantly suppressed cell survival, while comparatively lower dose of HBCDs (10(-13)-10(-7)M) slightly stimulated cell proliferation (P < 0.05). In the mean time, high concentration HBCDs markedly induced cell apoptosis and DNA damage, accompanying with increase of intracellular Ca(2+)level and decrease of mitochondrial membrane potential (P < 0.05). ROS level induced by low concentration of HBCDs was comparatively lower than that by high concentration of HBCDs. In addition, low concentration HBCDs exposure (10(-13)-10(-7)M) resulted in up-regulation of PCNA protein expression level in a time-dependent manner. However, high concentration HBCDs exposure led to increase of Apaf-1 expression level. In conclusion, loss of mitochondrial membrane potential and activation of Apaf-1 mediated pathway involve the L02 cell apoptosis induced by high concentration HBCDs exposure. However, low concentration HBCDs exposure could stimulate cell proliferation of L02 cells, which might be associated with enhancement of PCNA expression.

The flame retardant β-1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane: fate, fertility, and reproductive success in American kestrels (Falco sparverius)

Captive American kestrels (Falco sparverius) were exposed via diet during reproduction to an environmentally relevant concentration of β-1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (β-TBECH). The β-TBECH isomer was injected into the food source at a daily dosing concentration of 0.239 ng/g kestrel/day (22 pairs); control birds were exposed via diet to the safflower oil vehicle only (24 pairs). Eight pairs in each group were exposed for four weeks and sacrificed for tissue analysis; the remaining pairs completed their breeding cycle, with exposure ceasing at the end of incubation (82 days). α- and β-TBECH appeared to be rapidly metabolized and/or eliminated from fat, liver, and plasma; both isomers and potential hydroxylated metabolites of β-TBECH (plasma) were undetected. Notwithstanding, compared to controls, pairs exposed to β-TBECH laid fewer eggs (p = 0.019) and laid lighter eggs (successful eggs: p = 0.009). Exposed pairs also demonstrated poorer egg fertility (p = 0.035) although testis mass and histology were similar among males. Reductions in egg production and fertility resulted in decreased hatchling success (p = 0.023). The β-TBECH-exposed pairs also produced fewer males overall (p = 0.009), which occurred concurrently with increased estradiols maternally deposited in eggs (p = 0.039). These findings demonstrate that β-TBECH may be detrimental for breeding in wild birds receiving similar exposure levels.

Policy relevant results from an expert elicitation on the human health risks of decabromodiphenyl ether (decaBDE) and hexabromocyclododecane (HBCD)

AIM

Apply a recently developed expert elicitation procedure to evaluate the state of the current knowledge of the two brominated flame retardants (BFRs) most commonly used today; decabromo-diphenyl ether (decaBDE) and hexabromocyclododecane (HBCD) and their potential impact on human health in order to support policy considerations. This expert elicitation was organized by the HENVINET (Health and Environment Network) Consortium.

METHOD

The HENVINET expert elicitation procedure that was used in the evaluations of decaBDE and HBCD is a rapid assessment tool aimed at highlighting areas of agreement and areas of disagreement on knowledge-related key issues for environment and health policy decision making.

RESULTS

The outcome of the expert consultation on BFRs was concrete expert advice for policy makers with specific priorities for further action made clear for both stakeholders and policy makers. The experts were not in agreement whether or not the knowledge currently available on decaBDE or HBCD is sufficient to justify policy actions, but most experts considered that enough data already exists to support a ban or restriction on the use of these compounds. All experts agreed on the necessity of more research on the compounds. Priority issues for further research were, among others:• more studies on the extent of human exposure to the compounds.• more studies on the fate and concentration in the human body of the compounds.

In situ accumulation of HBCD, PBDEs, and several alternative flame-retardants in the bivalve (Corbicula fluminea) and gastropod (Elimia proxima)

Alternative brominated flame-retardants (BFRs), 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB), 2-ethylhexyl 2,3,4,5-tetrabromophthalate (TBPH), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) and decabromodiphenyl ethane (DBDPE), are now being detected in the environment. However, contaminant bioavailability is influenced by the organisms' ecology (i.e., route of uptake) and in situ environmental factors. We observed that the filter-feeding bivalve (Corbicula fluminea) and grazing gastropod (Elimia proxima), collected downstream from a textile manufacturing outfall, exhibited TBB, TBPH, and BTBPE concentrations from 152 to 2230 ng g(-1) lipid weight (lw). These species also contained additional BFRs. Maximum levels of total hexabromocyclododecane diastereomers (∑HBCDs) in these species were 363,000 and 151,000 ng g(-1) lw, and those of polybrominated diphenyl ethers (∑PBDEs) were 64,900 and 47,200 ng g(-1) lw, respectively. These concentrations are among the highest reported to date worldwide. While BDE-209 was once thought to be nonbioavailable and resistant to degradation, it was the dominant BFR present and likely debromination products were detected. Contributions of α- and β-HBCD were higher in tissues than sediments, consistent with γ-HBCD bioisomerization. Mollusk bioaccumulation factors were similar between HBCD and PBDEs with 4 to 6 bromines, but factors for TBB, TBPH, and BTBPE were lower. Despite different feeding strategies, the bivalves and gastropods exhibited similar BFR water and sediment accumulation factors.

Effects of chronic exposure to an environmentally relevant mixture of brominated flame retardants on the reproductive and thyroid system in adult male rats

Brominated flame retardants (BFRs) are incorporated into a wide variety of consumer products, are readily released into home and work environments, and are present in house dust. Studies using animal models have revealed that exposure to polybrominated diphenyl ethers (PBDEs) may impair adult male reproductive function and thyroid hormone physiology. Such studies have generally characterized the outcome of acute or chronic exposure to a single BFR technical mixture or congener but not the impact of environmentally relevant BFR mixtures. We tested whether exposure to the BFRs found in house dust would have an adverse impact on the adult male rat reproductive system and thyroid function. Adult male Sprague Dawley rats were exposed to a complex BFR mixture composed of three commercial brominated diphenyl ethers (52.1% DE-71, 0.4% DE-79, and 44.2% decaBDE-209) and hexabromocyclododecane (3.3%), formulated to mimic the relative congener levels in house dust. BFRs were delivered in the diet at target doses of 0, 0.02, 0.2, 2, or 20 mg/kg/day for 70 days. Compared with controls, males exposed to the highest dose of BFRs displayed a significant increase in the weights of the kidneys and liver, which was accompanied by induction of CYP1A and CYP2B P450 hepatic drug–metabolizing enzymes. BFR exposure did not affect reproductive organ weights, serum testosterone levels, testicular function, or sperm DNA integrity. The highest dose caused thyroid toxicity as indicated by decreased serum thyroxine (T4) and hypertrophy of the thyroid gland epithelium. At lower doses, the thickness of the thyroid gland epithelium was reduced, but no changes in hormone levels (T4 and thyroid-stimulating hormone) were observed. Thus, exposure to BFRs affected liver and thyroid physiology but not male reproductive parameters.

Tri-decabrominated diphenyl ethers and hexabromocyclododecane in indoor air and dust from Stockholm microenvironments 1: levels and profiles

Indoor air (gas and particle phase) and dust samples were collected from 10 houses, 44 apartments, 10 day care centers, 10 offices, 17 new cars and two car dealership halls from Stockholm, Sweden, and analyzed for polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). Median ΣPBDE concentrations in air were 330, 58, 4000, 14000 and 510 pg/m(3) in houses, apartments, day care centers, offices and cars, respectively. Median ΣPBDE concentrations in dust were 510, 1400, 1200, 1200 and 1400 ng/g in houses, apartments, day care centers, offices and cars, respectively. HBCD was detected in most dust samples (median range, 45-340 ng/g) but only in a few air samples (median range, <1.6-2.0 pg/m(3)). For all microenvironments, the brominated flame retardant (BFR) found in highest concentration in air was ΣDecaBDE, primarily BDE-209, followed by ΣPentaBDE, and in dust, ΣDecaBDE, followed by HBCD (offices, day care centers, cars) or ΣPentaBDE (houses, apartments). Positive correlations were found between matched air and dust samples for ΣPentaBDE, but not for ΣDecaBDE.

Diet exposure to technical hexabromocyclododecane (HBCD) affects testes and circulating testosterone and thyroxine levels in American kestrels (Falco sparverius)

Hexabromocyclododecane (HBCD) is a high-production-volume, brominated flame-retardant that is used in items such as polystyrene foams. HBCD has been detected in the environment, wildlife tissues and in humans globally with some of the highest recorded levels in predatory birds. This study examined the effects of exposure to environmentally relevant levels of HBCD on the reproductive physiology of captive male American kestrels (Falco sparverius), a predatory bird. Two sets of males were used: one group not housed with females (unpaired: nc=12, nHBCD=10) and the second group housed with females (breeding: nc=10, nHBCD=20). All treatment birds were exposed to 0.51 μg HBCD/g kestrel/day technical HBCD, and controls to safflower oil only, injected into their food during seasonal testicular development. Unpaired males were exposed for 3 weeks and euthanized for testicular analysis. Breeding males were exposed for 3 weeks prior to pairing and throughout the courtship period. The HBCD-exposed unpaired males had heavier testes (p≤0.017) and a trend towards more seminiferous tubules containing elongated spermatids (p=0.052). There was also a moderate increase in plasma testosterone concentrations (p=0.056) compared to controls. In breeding males, testosterone levels increased during courtship to culminate in higher levels than controls by the time the first egg was laid (p=0.010) and circulating free and total T4 was reduced throughout. The number of sperm cells reaching the perivitelline layer of the first egg for breeding males did not differ between the two groups. This study is the first report that HBCD exposure at environmentally relevant levels alters reproductive physiology in male birds and suggests that birds may be more sensitive to HBCD than mammals.

Hexabromocyclododecane: current understanding of chemistry, environmental fate and toxicology and implications for global management

Hexabromocyclododecane (HBCD) is a globally produced brominated flame retardant (BFR) used primarily as an additive FR in polystyrene and textile products and has been the subject of intensified research, monitoring and regulatory interest over the past decade. HBCD is currently being evaluated under the Stockholm Convention on Persistent Organic Pollutants. HBCD is hydrophobic (i.e., has low water solubility) and thus partitions to organic phases in the aquatic environment (e.g., lipids, suspended solids). It is ubiquitous in the global environment with monitoring data generally exhibiting the expected relationship between proximity to known sources and levels; however, temporal trends are not consistent. Estimated degradation half-lives, together with data in abiotic compartments and long-range transport potential indicate HBCD may be sufficiently persistent and distributed to be of global concern. The detection of HBCD in biota in the Arctic and in source regions and available bioaccumulation data also support the case for regulatory scrutiny. Toxicity testing has detected reproductive, developmental and behavioral effects in animals where exposures are sufficient. Recent toxicological advances include a better mechanistic understanding of how HBCD can interfere with the hypothalamic-pituitary-thyroid axis, affect normal development, and impact the central nervous system; however, levels in biota in remote locations are below known effects thresholds. For many regulatory criteria, there are substantial uncertainties that reduce confidence in evaluations and thereby confound management decision-making based on currently available information.

Levels of brominated flame retardants and other pesistent organic pollutants in breast milk samples from Limpopo Province, South Africa

The non-occupational exposure to brominated flame retardants, and other persistent organic pollutants (POPs) was studied by collecting human breast milk samples from mothers residing in Thohoyandou area, a rural district in the Limpopo Province, northern part of South Africa (SA). Of all collected samples to be analysed (n=28), those with large enough milk volumes, (n=14) were quantified for polybrominated diphenyl ethers (PBDEs) (9 congeners: BDE-28, 47, 66, 99, 100, 138, 153, 154, and 183) and hexabromocyclododecane (HBCD) on a GC equipped with dual capillary columns and dual electron-capture detectors (ECD). The levels of PBDE congeners (median sumBDE 1.3 ng/g of lipids) and of HBCD were not far from levels generally found in European studies, and this study may be the first report on the presence of PBDEs and HBCD in SA breast milk. On a congener basis, the finding of comparably high BDE-183 levels suggests a specific PBDE usage, or contamination situation in SA. Apart from BFRs, the high DDT levels found in the breast milk from this area (median and maximum sumDDT levels of about 4600 and over 20,000 ng/g of lipids, respectively; n=28) have earlier been reported. In addition, other POPs (PCBs, HCB and HCHs) were found in SA breast milk, at relatively low levels. To conclude, measurable levels of PBDEs and HBCD, and a specific BDE congener pattern, were found in breast milk from the Limpopo province, SA. A number of other POPs, including DDTs in high levels, were also present.

Relative importance of lean mass and fat mass on bone mineral density in a group of Lebanese postmenopausal women

The aim of this study was to determine the relative importance of lean mass and fat mass on bone mineral density (BMD) in a group of Lebanese postmenopausal women. One hundred ten Lebanese postmenopausal women (aged 65-84 yr) participated in this study. Age and years since menopause were recorded. Body weight and height were measured and body mass index (BMI) was calculated. Body composition (lean mass, fat mass, and fat mass percentage) was assessed by dual-energy X-ray absorptiometry (DXA). Bone mineral content (BMC) of the whole body (WB) and BMD of the WB, the lumbar spine (L1-L4), the total hip (TH), the femoral neck (FN), the ultra distal (UD) Radius, and the 1/3 Radius were measured by DXA. The expressions WB BMC/height and WB BMD/height were also used. Weight, BMI, fat mass, and lean mass were positively correlated to WB BMC, WB BMC/height, WB BMD/height, and to WB, L1-L4, TH, FN, UD Radius, and 1/3 Radius BMD. However, using multiple linear regression analyses, fat mass was more strongly correlated to BMC and to BMD values than lean mass after controlling for years since menopause. This study suggests that fat mass is a stronger determinant of BMC and BMD than lean mass in Lebanese postmenopausal women.

Temporal trends of polybrominated diphenyl ethers and hexabromocyclododecane in Swedish Peregrine Falcon (Falco peregrinus peregrinus) eggs

A temporal trend study of brominated flame retardants in eggs from peregrine falcon (Falco peregrinus peregrinus), a terrestrial bird of prey, is presented. Eggs collected between 1974 and 2007 were analyzed for the major constituents of the Penta-, Octa- and Decabromodiphenyl ether technical products (BDE-47, -99, -100, -153, -183 and -209), and hexabromocyclododecane (HBCD). Concentrations of BDE-99, -100, -153, -183, -209 and HBCD increased from 1974 to 2000. After the early 2000s, BDE-99, -100, -153 and -183 concentrations decreased, whereas BDE-209 and HBCD concentrations continued to increase. No temporal trend was detected for BDE-47. Rates of increase also differed, with BDE-99 and -100 increasing 3-fold between the 1980s and mid-1990s, and BDE-153 and -183 increasing approximately 10-fold during the same period. The average yearly increase was 15% and 11% for BDE-209 and HBCD, respectively, based on log-linear regression trends. There is a change in BDE congener patterns over time, with a shift from the predominance of BDE-99 and -47 until the late 1980s, to BDE-153 becoming the predominant congener later on. BFR temporal trends in Swedish peregrine falcon eggs reflect European BFR usage patterns.

Biomonitoring-based risk assessment for hexabromocyclododecane (HBCD)

Hexabromocyclododecane (HBCD) is a brominated flame retardant compound that has been the subject of recent interest and risk assessment efforts due to its detection in a variety of environmental media and in human biological matrices. Because the exposure pathways for HBCD may be varied and exposure estimation uncertain, biomonitoring for HBCD in humans shows promise as a means of reflecting integrated human exposures to HBCD with lower uncertainty than through estimation of external exposures via multiple pathways. Data from numerous biomonitoring studies of HBCD over the past decade indicate that the central tendency of lipid-adjusted serum and human milk concentrations is approximately 1ng/g lipid, with upper bound levels of approximately 20 ng/g lipid. Recent risk assessment evaluations from Health Canada and the European Union have identified points of departure of 10 and 20mg/kg day, respectively, from rat repeated dose studies. The corresponding measured or estimated lipid-adjusted tissue concentrations in the laboratory animals at these points of departure range from 120,000 to 190,000 ng/g lipid. In comparison to these concentrations, the biomonitored human serum and milk concentrations indicate margins of exposure (MOEs) of 6000 to more than 100,000, which are greatly in excess of target MOE values. The use of internal dose measures (both from measurements of tissue concentrations in animal toxicology studies and from human biomonitoring studies) provides risk managers with highly relevant exposure information that is less uncertain than estimated external doses.

Brominated flame retardants in dust from UK cars--within-vehicle spatial variability, evidence for degradation and exposure implications

Polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), and tetrabromobiphenol-A (TBBP-A) were measured in a preliminary study of dust from passenger cabins and trunks of 14 UK cars. Concentrations in cabin dust of HBCDs, TBBP-A, and BDEs 47, 85, 99, 100, 153, 154, 183, 196, 197, 202, 203, 206, 207, 208, and 209 exceeded significantly (p<0.05) those in trunk dust. Sampling cabin dust thus appears to provide a more accurate indicator of human exposure via car dust ingestion than trunk dust. Elevated cabin concentrations are consistent with greater in-cabin use of BFRs. In five cars, while no significant differences (p>0.05) in concentrations of HBCDs and most PBDEs were detected in dust sampled from four different seating areas; concentrations of TBBP-A and of PBDEs 154, 206, 207, 208, and 209 were significantly higher (p<0.05) in dust sampled in the front seats. Possible photodebromination of BDE-209 was indicated by significantly higher (p<0.05) concentrations of BDE-202 in cabin dust. In-vehicle exposure via dust ingestion to PBDEs, HBCDs and TBBP-A exceeded that via inhalation. Comparison with overall exposure via diet, dust ingestion, and inhalation shows while in-vehicle exposure is a minor contributor to overall exposure to BDE-99, ΣHBCDs, and TBBP-A, it is a significant pathway for BDE-209.

Perinatal exposure to environmental contaminants detected in Canadian Arctic human populations changes bone geometry and biomechanical properties in rat offspring

Arctic inhabitants consume large proportions of fish and marine mammals, and are therefore continuously exposed to levels of environmental toxicants, which may produce adverse health effects. Fetuses and newborns are the most vulnerable groups. The aim of this study was to evaluate changes in bone geometry, mineral density, and biomechanical properties during development following perinatal exposure to a mixture of environmental contaminants corresponding to maternal blood levels in Canadian Arctic human populations. Sprague-Dawley rat dams were dosed with a Northern Contaminant Mixture (NCM) from gestational day 1 to postnatal day (PND) 23. NCM contains 27 contaminants comprising polychlorinated biphenyls, organochlorine pesticides, and methylmercury. Femurs were collected on PND 35, 77 and 350, and diaphysis was analyzed by peripheral quantitative computed tomography and three-point bending test, while femoral neck was assessed in an axial loading experiment. Dose-response modeling was performed to establish the benchmark dose (BMD) for the analyzed bone parameters. Exposure to the high dose of NMC resulted in short and thin femur with reduced mechanical strength in offspring at PND35. BMD of femur length, cortical area, and stiffness were 3.2, 1.6, and 0.8 mg/kg bw/d, respectively. At PND77 femur was still thin, but at PND350 no treatment-related bone differences were detected. This study provides new insights on environmental contaminants present in the maternal blood of Canadian Arctic populations, showing that perinatal exposure induces bone alterations in the young offspring. These findings could be significant from a health risk assessment point of view.

Halogenated flame retardants: do the fire safety benefits justify the risks?

Since the 1970s, an increasing number of regulations have expanded the use of brominated and chlorinated flame retardants. Many of these chemicals are now recognized as global contaminants and are associated with adverse health effects in animals and humans, including endocrine and thyroid disruption, immunotoxicity, reproductive toxicity, cancer, and adverse effects on fetal and child development and neurologic function. Some flame retardants such as polybrominated diphenyl ethers (PBDEs) have been banned or voluntarily phased out by manufacturers because of their environmental persistence and toxicity, only to be replaced by other organohalogens of unknown toxicity. Despite restrictions on further production in some countries, consumer products previously treated with banned retardants are still in use and continue to release toxic chemicals into the environment, and the worldwide use of organohalogen retardants continues to increase. This paper examines major uses and known toxic effects of commonly-used organohalogen flame retardants, replacements for those that have been phased out, their combustion by-products, and their effectiveness at reducing fire hazard. Policy and other solutions to maintain fire safety while reducing toxicity are suggested. The major conclusions are: (1) Flammability regulations can cause greater adverse environmental and health impacts than fire safety benefits. (2) The current options for end-of-life disposal of products treated with organohalogens retardants are problematic. (3) Life-cycle analyses evaluating benefits and risks should consider the health and environmental effects of the chemicals, as well as their fire safety impacts. (4) Most fire deaths and most fire injuries result from inhaling carbon monoxide, irritant gases, and soot. The incorporation of organohalogens can increase the yield of these toxic by-products during combustion. (5) Fire-safe cigarettes, fire-safe candles, child-resistant lighters, sprinklers, and smoke detectors can prevent fires without the potential adverse effects of flame retardant chemicals. (6) Alternatives to organohalogen flame retardant chemicals include using less flammable materials, design changes, and safer chemicals. To date, before evaluating their health and environmental impacts, many flame retardant chemicals have been produced and used, resulting in high levels of human exposure. As a growing literature continues to find adverse impacts from such chemicals, a more systematic approach to their regulation is needed. Before implementing new flammability standards, decision-makers should evaluate the potential fire safety benefit versus the health and environmental impacts of the chemicals, materials, or technologies likely to be used to meet the standard. Reducing the use of toxic or untested flame retardant chemicals in consumer products can protect human and animal health and the global environment without compromising fire safety.

Brominated flame retardants and perfluorinated compounds in indoor dust from homes and offices in Flanders, Belgium

The increasing time spent indoors combined with the abundant usage of diverse indoor chemicals led to concerns involving the impact of these compounds on human health. The current study focused on two groups of important indoor contaminants i.e. Brominated flame retardants (BFRs) and Perfluorinated compounds (PFCs). Concentrations of both compound classes have been measured in Flemish indoor dust samples from homes and offices. ΣPolybrominated diphenyl ethers (PBDEs) (BDE 47, 99, 100, 154, 153, 197, 196 and 203) and BDE 209 in homes ranged between 4-1214 ng g(-1)dw (median 35) and <5-5295 ng g(-1)dw (median 313), respectively. Hexabromocyclododecane (ΣHBCD) levels ranged from 5 to 4,2692 ng g(-1)dw (median 130), with α-HBCD being the major isomer (mean 59%). In addition, tetrabromobisphenol A (TBBPA) ranged between <3 and 419 ng g(-1)dw (median 12). For all BFRs, median levels in office dust were up to an order of magnitude higher than in home dust. ΣPFCs (sum of perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA)) concentrations in homes ranged from 0.2 to 336 ng g(-1) (median 3.0 ng g(-1)). Levels in office dust were higher (p<0.01) than in house dust with ΣPFCs ranging between 2.2 and 647 ng g(-1) (median 10 ng g(-1)) and median (PFOA) and perfluorooctane sulfonate values of 2.9 and 2.2 ng g(-1), respectively. The congener pattern was dominated by PFOA, followed by PFOS. Calculated human exposure was below the reference dose values set by the US-EPA for BDE 209, HBCD and below the provisional tolerable daily intakes proposed by European Food Safety Authority for PFOS and PFOA.

Effects of metals on the transformation of hexabromocyclododecane (HBCD) in solvents: implications for solvent-based recycling of brominated flame retardants

The management of electronic wastes (e-wastes) has become a global issue as it may release large quantities of hazardous materials such as heavy metals and brominated flame retardants (BFRs) to the environment. Solvent-based recycling is a newly developed, efficient and environmentally beneficial technology for the removal or recovery of BFRs from e-wastes. However, little is known about the behavior of BFRs in the solvents and to what extent they may be affected by co-existing heavy metals. This study quantified the rates of transformation of hexabromocyclododecane (HBCD), a widely used BFR, in the presence of different solvents (i.e. acetone, methanol or toluene) and metals (i.e. Ni, Cu, Zn, Fe or Al). Our experimental results showed that less than 20% of HBCD was transformed in all pure solvent systems within 24h at 50 degrees C. The presence of Ni greatly increased the transformation of HBCD (45-99%) in these solvent systems, whereas other metals had little or no effect on extraction process. The kinetics study showed that transformation of HBCD in Ni-containing systems followed pseudo-first-order kinetics and that the highest transformation rate constant (1.2+/-0.1h(-1)) of HBCD was recorded in the Ni+acetone system. The formation of HBr and pentabromocyclododecene in the acetone+Ni system suggested that transformation of HBCD proceeded via dehydrobromination. Collectively, these results indicated that acetone should not be applied in the recycling or extraction of HBCD from Ni-rich e-wastes, as debromination of HBCD may occur during these processes, even at mild extraction temperatures.

Brominated flame retardants and perfluorinated chemicals, two groups of persistent contaminants in Belgian human blood and milk

We assessed the exposure of the Flemish population to brominated flame retardants (BFRs) and perfluorinated compounds (PFCs) by analysis of pooled cord blood, adolescent and adult serum, and human milk. Levels of polybrominated diphenyl ethers (PBDEs) in blood (range 1.6-6.5 ng/g lipid weight, lw) and milk (range 2.0-6.4 ng/g lw) agreed with European data. Hexabromocyclododecane ranged between <2.1-5.7 ng/g lw in milk. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) dominated in blood and ranged between 1 and 171 ng/mL and <0.9-9.5 ng/mL, respectively. Total PFC levels in milk ranged between <0.5-29 ng/mL. A significant increase in PBDE concentrations was detected from newborns (median 2.1) to the adolescents and adults (medians 3.8 and 4.6 ng/g lw, respectively). An identical trend was observed for PFOS, but not for PFOA. We estimated that newborn exposure to BFRs and PFCs occurs predominantly post-natally, whereas placental transfer has a minor impact on the body burden.

Dust from U.K. primary school classrooms and daycare centers: the significance of dust as a pathway of exposure of young U.K. children to brominated flame retardants and polychlorinated biphenyls

Polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), tetrabromobisphenol-A (TBBP-A), and polychlorinated biphenyls (PCBs) were measured in floor dust from U.K. child daycare center and primary school classrooms (n = 43, 36 for PCBs). Concentrations of HBCDs exceeded significantly (p < 0.05) those reported previously for U.K. houses and offices, while those of TBBP-A exceeded significantly those in U.K. cars and offices. PCB concentrations were statistically indistinguishable from those in U.K. house dust but lower than in U.S. classroom dust, while BDEs 47, 99, 100, 153, 196, 197, 203, and 209 in classrooms were significantly below concentrations in U.K. cars. Exposure of young U.K. children via classroom dust exceeds that of U.K. adults via office dust for all contaminants monitored. Overall dust exposure of young U.K. children was estimated including car, classroom, and house dust. Exposure to TBBP-A was well below a U.K. health-based limit value (HBLV). Though no HBLVs exist for non-dioxin-like PCBs and HBCDs; dust exposure to PCBs fell well below U.K. dietary and inhalation exposure. Contrastingly, a high-end estimate of HBCD dust exposure exceeded U.K. dietary exposure substantially. Moreover, high-end estimates of dust exposure to BDE-99 and BDE-209 (4.3 and 13000 ng/kg bw/day, respectively) exceeded HBLVs of 0.23-0.30 and 7000 ng/kg bw/day respectively.

Exposure of the Flemish population to brominated flame retardants: model and risk assessment

Human exposure to brominated flame retardants (BFRs) varies widely throughout the world as it depends on country-related usage, production and legislation of these chemicals. US and UK exposure assessments show very diverse levels and patterns which in turn, are likely to differ from those in background exposed countries such as Belgium, where levels tend to be about an order of magnitude lower. The current study assessed human exposure to BFRs through the indoor and outdoor environment (e.g. dust, soil, and air) and food for all age groups in Flanders, Belgium. Most relevant food groups were identified based on a national food consumption survey and food items with Flemish origin were collected. Dust samples were collected using a standardized protocol in 43 homes and 10 offices throughout Flanders. Food, human milk and dust samples were analysed for their polybrominated diphenylethers (PBDE) and hexabromocyclodecane (HBCD) content using GC/MS and LC/MS-MS. An exposure model was developed including all analysed data, complemented with literature data. The model covered human exposure of infants, children and adults through human milk, food, dust/soil ingestion and air inhalation. Total human exposure was compared to the existing toxicological criteria and previous exposure estimates. In general, the exposure levels through human milk are consistent with those of a background exposed European population, whereas dust and food intake are at the low end of what has been reported in previous European intake assessments. Total average intake of SigmaHBCD and SigmaBDE(5) at 50th percentile (P50) levels by newborns equals 3.1 and 12.0ng/kg body weight (bw) day, respectively. This intake increases to 15.2 and 20.9ng/kgbwday for SigmaHBCD and SigmaBDE(5), for higher exposed newborns (95th percentile=P95 levels). Due to the limited database on health-based limit values for PBDEs and HBCD, it is difficult to assess the immediate health concern for any of the age groups, although the higher intake of newborns indicates the need for ongoing monitoring. For median exposed individuals, the average SigmaHBCD intake peaked at the age 3 to 6years with an intake of 6.59ng/kgbwday and declines to approximately 1ng/kgbwday at later age. SigmaBDE(5) intake exhibited a different profile compared to SigmaHBCD with maximal levels for newborns and a decline to approximately 0.7ng/kgbwday at adulthood.

Indoor contamination with hexabromocyclododecanes, polybrominated diphenyl ethers, and perfluoroalkyl compounds: an important exposure pathway for people?

This review underlines the importance of indoor contamination as a pathway of human exposure to hexabromocyclododecanes (HBCDs), polybrominated diphenyl ethers (PBDEs), and perfluoroalkyl compounds (PFCs). There is ample evidence of substantial contamination of indoor dust with these chemicals and that their concentrations in indoor air exceed substantially those outdoors. Studies examining the relationship between body burden and exposure via indoor dust are inconsistent; while some indicate a link between body burdens and PBDE and HBCD exposure via dust ingestion, others find no correlation. Likewise, while concentrations in indoor dust and human tissues are both highly skewed, this does not necessarily imply causality. Evidence suggests exposure via dust ingestion is higher for toddlers than adults. Research priorities include identifying means of reducing indoor concentrations and indoor monitoring methods that provide the most "biologically-relevant" measures of exposure as well as monitoring a wider range of microenvironment categories. Other gaps include studies to improve understanding of the following: emission rates and mechanisms via which these contaminants migrate from products into indoor air and dust; relationships between indoor exposures and human body burdens; relevant physicochemical properties; the gastrointestinal uptake by humans of these chemicals from indoor dust; and human dust ingestion rates.

Accumulation and disposition of hexabromocyclododecane (HBCD) in juvenile rainbow trout (Oncorhynchus mykiss)

The brominated flame retardant hexabromocyclododecane (HBCD) has been reported in environmental samples worldwide. The three diastereomers, alpha-, beta- and gamma-HBCD, behave differently in aquatic food webs; likely depending on different factors influencing assimilation efficiency and metabolism. In the present study, two oral exposure experiments with rainbow trout were performed to assess the role of selective uptake on diastereomer-specific accumulation and disposition of HBCD to liver, brain and muscle. In both experiments, juvenile rainbow trout (Oncorhynchus mykiss) were administrated a technical HBCD-mixture in commercial feed (10mgkg(-1)), followed by up to 21 days of food deprivation. Already 6h after exposure, the HBCD accumulation was significant, and the concentrations peaked 4-8 days after the exposure. The relative change in HBCD pattern during the accumulation process (0-8 days), suggested that there was a diastereomer-selective uptake of alpha- and beta-HBCD in the rainbow trout. During the initial 48h, considerable amounts of all three diastereomers were distributed to liver, brain and muscle. A 70% reduction in SigmaHBCD levels after 21 days, indicated elimination of HBCD from brain and liver, but no clear elimination from the muscle was observed. Differences in HBCD pattern between organs at the end of the experiment support a proposal of an organ-specific diastereomer accumulation.