Brominated flame retardants: a novel class of developmental neurotoxicants in our environment?

Exposure to mixtures of organohalogen contaminants and associative interactions with thyroid hormones in East Greenland polar bears (Ursus maritimus)

We investigated the multivariate relationships between adipose tissue residue levels of 48 individual organohalogen contaminants (OHCs) and circulating thyroid hormone (TH) levels in polar bears (Ursus maritimus) from East Greenland (1999-2001, n=62), using projection to latent structure (PLS) regression for four groupings of polar bears; subadults (SubA), adult females with cubs (AdF_N), adult females without cubs (AdF_S) and adult males (AdM). In the resulting significant PLS models for SubA, AdF_N and AdF_S, some OHCs were especially important in explaining variations in circulating TH levels: polybrominated diphenylether (PBDE)-99, PBDE-100, PBDE-153, polychlorinated biphenyl (PCB)-52, PCB-118, cis-nonachlor, trans-nonachlor, trichlorobenzene (TCB) and pentachlorobenzene (QCB), and both negative and positive relationships with THs were found. In addition, the models revealed that DDTs had a positive influence on total 3,5,3'-triiodothyronine (TT3) in AdF_S, and that a group of 17 higher chlorinated ortho-PCBs had a positive influence on total 3,5,3',5'-tetraiodothyronine (thyroxine, TT4) in AdF_N. TH levels in AdM seemed less influenced by OHCs because of non-significant PLS models. TH levels were also influenced by biological factors such as age, sex, body size, lipid content of adipose tissue and sampling date. When controlling for biological variables, the major relationships from the PLS models for SubA, AdF_N and AdF_S were found significant in partial correlations. The most important OHCs that influenced TH levels in the significant PLS models may potentially act through similar mechanisms on the hypothalamic-pituitary-thyroid (HPT) axis, suggesting that both combined effects by dose and response addition and perhaps synergistic potentiation may be a possibility in these polar bears. Statistical associations are not evidence per se of biological cause-effect relationships. Still, the results of the present study indicate that OHCs may affect circulating TH levels in East Greenland polar bears, adding to the "weight of evidence" suggesting that OHCs might interfere with thyroid homeostasis in polar bears.

Polybrominated diphenyl ethers in three commercially important fish from the northwestern Arabian Gulf: occurrence, concentration, and profiles

Polybrominated diphenyl ethers (PBDEs) were measured in three species of fish (yellowfin seabream [Acanthopagrus latus, a predatory fish]; Klunzinger's mullet [Liza klunzingeri, a pelagic fish]; and large-scaled tonguesole [Cynoglossus arel, a demersal fish]) collected from two sites in the northwestern part of the Arabian Gulf, a marginal sea of the tropical Indo-Pacific Ocean. Concentrations of ΣPBDEs ranged from 11 to 57 ng g(-1) lipid weight (lw) for mullet, 5.0-38 ng g(-1) lw for tonguesole, and 2.8-48 ng g(-1) lw for seabream in Kuwait Bay, whereas in the open gulf, concentrations ranged from 6.0 to 160 lw for mullet, 8.3-190 lw for tonguesole, and 7.1-62 for lw for seabream. The congener composition in all species from both sites was dominated by BDEs 47, 99, and 100, which together constituted approximately 90% of the congeners detected. Although no statistically significant intersite differences were found, ΣPBDEs concentrations in mullet were significantly higher than those in seabream (p = 0.01). However, no significant differences existed between mullet and tonguesole (p = 0.28) or between tonguesole and seabream (p = 0.06). ΣPBDE concentrations were negatively correlated with fish mass for all species; however, the correlations were statistically insignificant, suggesting a growth dilution effect.

Neurobehavioral and physiological effects of low doses of polybrominated diphenyl ether (PBDE)-99 in male adult rats

Polybrominated diphenyl ethers (PBDEs) are flame retardants. Because of their high lipophilicity and persistence, PBDEs bioaccumulate in all abiotic and biological matrices. The aim of this study was to investigate the long-term neurobehavioral and physiological effects of exposure to environmental doses of PBDE-99 in adult rats. Rats received a daily administration of PBDE-99 for 90 days by oral gavage at 0.15, 1.5 and 15μg/kg, doses which are relevant of human exposure. Before and after the 90 days of exposure, behavioral tests including the open-field and the elevated plus-maze tests for locomotor activity and anxiety, and the Morris water maze for spatial learning were conducted. Physiological measures such as body weight, food and water consumption, organs weight, hepatic enzymes levels and PBDE-99 concentration in adipose tissue were also evaluated at the end of exposure. There was no effect on body weight, food and water consumption, organs weight, hepatic enzymes levels despite rising PBDE-99 concentration in adipose tissue with the doses tested. Moreover, there was no effect on locomotor activity and exploration, and spatial learning. Deleterious effects of PBDE-99 at high doses have often been highlighted in many studies after an acute dose whereas exposure during 90 days at realistic doses would have no significant effect in adult rats.

Perinatal exposure to low-dose DE-71 increases serum thyroid hormones and gonadal osteopontin gene expression

Polybrominated diphenyl ethers (PBDEs) are flame retardants that have been widely used in manufacturing. They are major household and environmental contaminants that bioaccumulate. Humans are exposed primarily through dust inhalation and dietary ingestion of animal products. In animal studies, high doses of penta-brominated diphenyl ethers (penta-BDEs) in the mg/kg body weight (BW) range negatively impact brain development, behavior, memory, circulating thyroid hormone concentrations, the reproductive system and bone development. We investigated the effects of ingestion of a relatively low dose of the penta-BDE mixture DE-71 by pregnant and lactating rats on reproductive and thyroid parameters of the F1 offspring. F0 mothers received 60 μg/kg BW of DE-71 or vehicle daily by gavage from Day 1.5 of pregnancy through lactation (except the day of parturition). F1 pups were sacrificed at 21 d of age or outbred at approximately 80 d of age. Bred F1 females were sacrificed at Day 14.5 of pregnancy or at five months of age. Bred F1 males were sacrificed at five months of age. DE-71 treatment of the mothers affected the F1 females as evidenced by lower body weights at 80 d and five months of age, elevated serum T3 and T4 concentrations at Day 14.5 of pregnancy and increased thyroid gland weight and ovarian osteopontin mRNA at five months of age. Perinatal DE-71 exposure also increased testicular osteopontin mRNA in 21-day-old F1 males. Utilizing a granulosa cell in vitro model, we demonstrated that DE-71 activated the rat osteopontin gene promoter. Our results are the first to demonstrate that PBDEs increase rodent circulating T3 and T4 concentrations and gonadal osteopontin mRNA, and activate the osteopontin gene promoter. These changes may have clinical implications as others have shown associations between human exposure to PBDEs and subclinical hyperthyroidism, and overexpression of ovarian osteopontin has been associated with ovarian cancer.

Bioaccumulation and behavioral effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) in perinatally exposed mice

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants that have become pervasive environmental contaminants and may contribute to adverse health outcomes. We evaluated in mice the developmental neurotoxicity of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), one of the most abundant PBDE congeners detected in animal and human tissues. Female C57BL/6J mice were exposed to daily doses of 0, 0.03, 0.1 or 1mg/kg beginning 4 weeks prior to conception, continuing through gestation and lactation, and ending at weaning on postnatal day (PND) 21. Levels of BDE-47 in blood, brain, liver and adipose tissues of dams were markedly increased after 4 weeks of exposure, around the time of mating, and continued to increase through the time of parturition. Blood levels of BDE-47 in the dosed dams were within the range reported in humans. BDE-47 tissue levels in the dams decreased between parturition and weaning, possibly reflecting mobilization during lactation. Brain BDE-47 levels in the offspring at PND 1 approached those of the dams at parturition. Perinatal exposure to BDE-47 resulted in significant dose dependent growth retardation, slower motor performance in several behavioral tests, and mice exposed to 1mg/kg/day BDE-47 showed altered performance in the Morris water maze. There were no differences between groups in the numbers of pyramidal neurons in hippocampus CA1. These results document accumulation of BDE-47 in several organ systems following exposure to low-levels of BDE-47, and provide evidence that such exposure is associated with early behavioral deficits in exposed neonates.

Disruption of thyroid hormone receptor-mediated transcription and thyroid hormone-induced Purkinje cell dendrite arborization by polybrominated diphenyl ethers

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants and are becoming a ubiquitous environmental contaminant. Adverse effects in the developing brain are of great health concern.

OBJECTIVE

We investigated the effect of PBDEs/hydroxylated PBDEs (OH-PBDEs) on thyroid hormone (TH) receptor (TR)-mediated transcription and on TH-induced dendrite arborization of cerebellar Purkinje cells.

METHODS

We examined the effect of PBDEs/OH-PBDEs on TR action using a transient transfection-based reporter gene assay. TR-cofactor binding was studied by the mammalian two-hybrid assay, and TR-DNA [TH response element (TRE)] binding was examined by the liquid chemiluminescent DNA pull-down assay. Chimeric receptors generated from TR and glucocorticoid receptor (GR) were used to identify the functional domain of TR responsible for PBDE action. The change in dendrite arborization of the Purkinje cell in primary culture of newborn rat cerebellum was also examined.

RESULTS

Several PBDE congeners suppressed TR-mediated transcription. The magnitude of suppression correlated with that of TR-TRE dissociation. PBDEs suppressed transcription of chimeric receptors containing the TR DNA binding domain (TR-DBD). We observed no such suppression with chimeras containing GR-DBD. In the cerebellar culture, PBDE significantly suppressed TH-induced Purkinje cell dendrite arborization.

CONCLUSIONS

Several PBDE congeners may disrupt the TH system by partial dissociation of TR from TRE acting through TR-DBD and, consequently, may disrupt normal brain development.

Long-term effects of environmentally relevant doses of 2,2',4,4',5,5' hexachlorobiphenyl (PCB153) on neurobehavioural development, health and spontaneous behaviour in maternally exposed mice

Background

Polychlorinated biphenyls (PCBs) are widespread in the environment, human food and breast milk. Seafood is known to contain nutrients beneficial for the normal development and function of the brain, but also contaminants such as PCBs which are neurotoxic. Exposure to non-coplanar PCBs during brain development can disrupt spontaneous behaviour in mice and lead to hyperactive behaviour. Humans are chronically exposed to the highest relative levels of organochlorines in early childhood during brain development, though usually at doses which do not give clinical symptoms of toxicity. This study aimed to elucidate the developmental and behavioural effects of 2,2',4,4',5,5' hexachlorobiphenyl (PCB153) in mice, mimicking human exposure during gestation and lactation.

Methods

Environmentally relevant doses of PCB153 were added to the experimental diets. Feed concentrations were approximately 0.5, 6.5, and 1500 μg PCB153/kg feed, representing a realistic and a worst case scenario of frequent consumption of contaminated fish. The study also investigated the effects of maternal nutrition, i.e. a standard rodent diet versus a high inclusion of salmon. Mice pups were examined for physical- and reflex development, sensorimotor function and spontaneous behaviour from five days after birth until weaning. A selection of pups were followed until 16 weeks of age and tested for open field behaviour and the acoustic startle response (ASR) with prepulse inhibition (PPI). Blood thyroid hormones and liver enzymes, blood lipids and PCB153 content in fat were examined at 16 weeks. Statistical analyses modelled the three way interactions of diet, PCB exposure and litter size on behaviour, using generalized linear models (GLM) and linear mixed effect models (LME). The litter was used as a random variable. Non-parametric tests were used for pair wise comparisons of biochemical analyses.

Results

Litter size consistently influenced pup development and behaviour. Few lasting PCB153 related changes were observed, but results indicated effects on synchronization of physical development. Perinatal PCB153 exposure appeared to reduce habituation and cause aggression in males, though not statistically significant.

Conclusions

Litter size and maternal diet influenced physical development and function more than PCB153 in perinatally exposed mouse pups and supports the developmental importance of maternal care and the social environment.

High concentrations of polybrominated diphenylethers (PBDEs) in breast adipose tissue of California women

We measured major PBDEs and PCBs in breast adipose tissues of California women participating in a breast cancer study in the late 1990s. Samples were analyzed using gas chromatography with electron impact ionization and tandem mass spectrometry detection. The congener profile observed was: BDE47>BDE99>BDE153>BDE100>BDE154 and PCB153>PCB180>PCB138>PCB118. Whereas high correlations were observed within each chemical class, very weak correlations appeared between classes, pointing to different exposure pathways. Weak negative associations were observed for PBDE congeners and age. Our PBDE data are among the highest reported, exceeding data from the National Health and Nutrition Examination Survey and consistent with the high use of PBDEs in California. These data may be helpful in establishing a baseline for PBDE body burdens to gauge changes over time as a result of restrictions in the use of PBDE formulations.

Understanding the mismatch between the demands of risk assessment and practice of scientists--the case of Deca-BDE

This review describes how a mismatch between the knowledge produced by scientists and the evidence demanded by regulators has emerged, and how society has struggled to find definitive answers to questions of safety, for an important flame retardant chemical in current use - Deca-BDE. This has involved two key disciplines: analytical chemistry and toxicology. Within the chemistry, a lack of standardized methodologies among scientists has resulted in a persistent yet largely undeclared failure to replicate results within the discipline. Within the toxicology, the quest for innovative, curiosity-driven research by university scientists in preference to using validated standard protocols, designed to promote consistency within the risk assessment process, has prompted questions about the credibility and relevance of scientific findings. Yet scientific laboratories have compelling reasons to do things the way they do in the cause of producing new knowledge, pointing to a sustained gap between the aims and practices of research scientists and those of risk management. A more rigorous scientific process that treats different elements of input data as discrete pieces of evidence is needed to ensure that science rather than politics will always define chemical safety.

Cytotoxic effects and oxidative stress response of six PBDE metabolites on human L02 cells

In the present study, the cytotoxic effects and toxicological mechanism of six polybrominated diphenyl ethers (PBDEs) metabolites (3-OH-BDE47, 3-MeO-BDE47, 5-OH-BDE47, 5-MeO-BDE47, 6-OH-BDE85 and 6-MeO-BDE85) on L02 cells were explored by investigating the cell viability, apoptosis, lactic dehydrogenase (LDH) leakage, and oxidative stress response. The results showed that these metabolites could inhibit cell proliferation and induce apoptosis, among which 6-OH-BDE85 had the highest efficiency. LDH leakage test also showed that 6-OH-BDE85 had the strongest ability to cause LDH release. The reactive oxygen species (ROS) levels in 6-OH-BDE85- and 3-OH-BDE47-treated groups were significantly elevated in a dose-dependent manner. After treatment for 24 h, four BDE47 metabolites (3-OH-BDE47, 3-MeO-BDE47, 5-OH-BDE47, and 5-MeO-BDE47) induced an increase in superoxide dismutase (SOD) activity and decrease in glutathione (GSH) level, whereas 6-OH-BDE85 led to a decrease in both SOD activity and GSH level. These effects disappeared after continued culturing for another 24 h. In conclusion, these PBDE metabolites, especially 6-OH-BDE85, showed cytotoxicity on L02 cells, which was at least partially related to the oxidative stress level.

Nitric oxide signaling as a common target of organohalogens and other neuroendocrine disruptors

Organohalogen compounds such as polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDE) are global environmental pollutants and highly persistent, bioaccumulative chemicals that produce adverse effects in humans and wildlife. Because of the widespread use of these organohalogens in household items and consumer products, indoor contamination is a significant source of human exposure, especially for children. One significant concern with regard to health effects associated with exposure to organohalogens is endocrine disruption. Toxicological studies on organohalogen pollutants primarily focused on sex steroid and thyroid hormone actions, and findings have largely shaped the way one envisions their disruptive effects occurring. Organohalogens exert additional effects on other systems including other complex endocrine systems that may be disregulated at various levels of organization. Over the last 20 years evidence has mounted in favor of a critical role of nitric oxide (NO) in numerous functions ranging from neuroendocrine functions to learning and memory. With its participation in multiple systems and action at several levels of integration, NO signaling has a pervasive influence on nervous and endocrine functions. Like blockers of NO synthesis, PCBs and PBDEs produce multifaceted effects on physiological systems. Based on this unique set of converging information it is proposed that organohalogen actions occur, in part, by hijacking processes associated with this ubiquitous bioactive molecule. The current review examines the emerging evidence for NO involvement in selected organohalogen actions and includes recent progress from our laboratory that adds to our current understanding of the actions of organohalogens within hypothalamic neuroendocrine circuits. The thyroid, vasopressin, and reproductive systems as well as processes associated with long-term potentiation were selected as sample targets of organohalogens that rely on regulation by NO. Information is provided about other toxicants with demonstrated interference of NO signaling. Our focus on the convergence between NO system and organohalogen toxicity offers a novel approach to understanding endocrine and neuroendocrine disruption that is particularly problematic for developing organisms. This new working model is proposed as a way to encourage future study in elucidating common mechanisms of action that are selected with a better operational understanding of the systems affected.

Is decabromodiphenyl ether (BDE-209) a developmental neurotoxicant?

Polybrominated diphenyl ether (PBDE) flame retardants have become ubiquitous environmental pollutants. The relatively higher body burden in toddlers and children has raised concern for their potential developmental neurotoxicity, which has been suggested by animal studies, in vitro experiments, and recent human epidemiological evidence. While lower brominated PBDEs have been banned in several countries, the fully brominated decaBDE (BDE-209) is still utilized, though manufacturers will discontinue production in the U.S.A. in 2013. The recent decision by the U.S. Environmental Protection Agency to base the reference dose (RfD) for BDE-209 on a developmental neurotoxicity study has generated some controversy. Because of its bulky configuration, BDE-209 is poorly absorbed and does not easily penetrate the cell wall. Its acute and chronic toxicities are relatively low, with the liver and the thyroid as the primary targets, though there is some evidence of carcinogenicity. A few animal studies have indicated that BDE-209 may cause developmental neurotoxicity, affecting motor and cognitive domains, as seen for other PBDEs. Limited in vivo and in vitro studies have also evidenced effects of BDE-209 on thyroid hormone homeostasis and direct effects on nervous cells, again similar to what found with other lower brominated PBDEs. In contrast, a recent developmental neurotoxicity study, carried out according to international guidelines, has provided no evidence of adverse effects on neurodevelopment, and this should be considered in a future re-evaluation of BDE-209. While estimated exposure to BDE-209 in children is believed to be several orders of magnitude below the most conservative RfD proposed by the USEPA, questions remain on the extent and relevance of BDE-209 metabolism to lower brominated PBDEs in the environment and in humans.

Levels of brominated flame retardants and methoxylated polybrominated diphenyl ethers in eggs of white-tailed sea eagles breeding in different regions of Sweden

Forty-four unhatched eggs from white-tailed sea eagle (Haliaeetus albicilla), collected in four regions in Sweden in 1992-2005, were analysed for contents of polybrominated diphenyl ethers (PBDEs), polybrominated biphenyl (PBB), hexabromocyclododecane (HBCD) and naturally occurring methoxylated polybrominated diphenyl ethers (MeO-PBDEs). Two freshwater areas-Lapland in the arctic zone (LAP) and inland lakes in central and southern Sweden (INL), and two brackish marine areas in the Baltic Sea-the south Bothnian Sea (SB) and the Baltic Proper (BP)-were chosen for comparison of the concentrations and congener distributions in white-tailed sea eagles with different diet and migratory patterns. The geometric mean (GM) concentrations (ng/g lipid weight (l.w.)) of ∑(5)PBDE (BDE-47, -99, -100, -153, and -154) were 720 (LAP), 1500 (INL), 4 100 (SB) and 4 300 (BP), whereas BDE-209 was not detectable in any of the samples. The GM concentrations for HBCD content in LAP, INL, SB and BP were 60, 90, 150 and 140ng/g l.w., respectively, whereas the corresponding values for BB-153 were 20, 30, 100 and 120ng/g l.w. In general, the eggs from all four regions demonstrated similar patterns of PBDE congeners, with concentrations in descending order of BDE-47, -100, -99, -153 and -154. The ∑(3)-MeO-BDEs (6-MeO-BDE47, 2'-MeO-BDE68, 5-Cl-6-MeO-BDE47) for these same regions (as above) were 80, 40, 340 and 240ng/g l.w., respectively. ∑(3)-MeO-BDEs for LAP and INL (freshwaters) were significantly different, whereas those for SB and BP were not. The presence of MeO-PBDEs in all of the inland samples indicates that there is an as-yet-unidentified source of these compounds in the freshwater ecosystem. Between the two more contaminated subpopulations from the Baltic Sea coast, SB showed significantly lower productivity than BP, but no correlation was found between productivity and PBDE, PBB and HBCD at the concentrations found in this study.

Toxic effect of PBDE-47 on thyroid development, learning, and memory, and the interaction between PBDE-47 and PCB153 that enhances toxicity in rats

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are widespread environmental contaminants. There are potential interactive effects between PBDEs and PCBs, as these compounds share similar structures. The developmental neurotoxicity of 2, 2', 4, 4'-tetrabromodiphenyl ether (PBDE-47) and the interaction of PBDE-47 with 2, 2', 4, 4', 5, 5'-hexachlorobipheny (PCB153) were investigated herein, as the dominant congener forms of PBDEs and PCBs, respectively. SD rats were exposed to a single oral dose of PBDE-47 (1, 5, and 10 μg/g) and/or PCB153 (5 μg/g) on post-natal day (PND) 10. Concentrations of PBDE-47, triiodothyronine (T(3)), thyroxine (T(4)), and thyroid-stimulating hormone (TSH) in serum; organ-to-body weight ratios; as well as long-term learning and memory were measured in 2-month-old rats. The present study found that some doses of PBDE-47 decreased the organ-to-body weight ratios of the thyroid and uterus, decreased the concentration of T(4) in serum, and increased the organ-to-body weight ratio of the ovaries (p < 0.05). PCB153 could increase the action of PBDE-47 during combined exposure, but this interaction was not found between PBDE-47 and PCB153. In a Morris water maze experiment, the latency periods were significantly prolonged and time ratios were obviously depressed in all PBDE-47-treated groups compared to the control (p < 0.05); furthermore, significant interactions between PBDE-47 and PCB153 were observed (p < 0.05). In conclusion, PBDE-47 may depress thyroid development as well as the long-term learning and memory capabilities in adult rats exposed to PBDE-47 on PND 10. PCB153 can interact with PBDE-47, resulting in an increase in developmental neurotoxicity.

Impact of non-occupational exposure to polybrominated diphenyl ethers on menstruation characteristics of reproductive-age females

Polybrominated diphenyl ethers (PBDEs) have documented effects on thyroid functions and rodent behavior in vivo. Epidemiological studies, however, have revealed only limited information about associations between PBDE exposure and menstruation characteristics. Our goal was to examine whether high breast milk PBDE levels in reproductive-age females lead to interference with menstruation characteristics. We analyzed 15 PBDE congeners in 46 breast milk samples. Fifteen PBDE congeners (BDE-15, 28, 47, 49, 99, 100, 153, 154, 183, 196, 197, 203, 207, 208, and 209) were analyzed using a gas chromatograph equipped with a high resolution mass spectrometer. The mean sum of PBDEs (SigmaPBDEs) in breast milk was 3.42 ng/g lipid. Women's age at menarche was not correlated with breast milk PBDE levels. Increased BDE-208 and 209 levels were significantly associated with the prolonged length of average and the longest menstrual cycle independent of age, pre-pregnant BMI, and parity. Higher concentrations of SigmaPBDEs and the higher brominated PBDEs from BDE-183 to 209, except 197, were significantly linked to women whose menstruation periods were still coming irregularly at the sampling time. Age-adjusted odds ratios (ORs) of BDE-153, 183, 207, 208, and SigmaPBDEs were significantly higher in women with length of average menstrual cycle >32 days, compared to the control. Women whose menstruation periods still came irregularly when they were 18 years old had higher age-adjusted ORs of BDE-207, 208, 209, and SigmaPBDEs than those whose periods came regularly at the same age. Although SigmaPBDEs and certain higher brominated PBDEs appear to have potential to prolong length of average menstrual cycle and delay the age when menstruation periods begin coming regularly, these findings are not conclusive because our sample size is small and more scientific evidence is needed.

Dietary intake of persistent organic pollutants and potential health risks via consumption of global aquatic products

The concentration levels of typical persistent organic pollutants such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) including dioxin-like PCBs (DL-PCBs) and non-dioxin-like PCBs, organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) in global aquatic products from major producing countries were summarized. Daily intakes of these compounds via consumption of various aquatic products for global consumers were also estimated based on available literature data. Risk assessment based upon existing criteria for OCPs and PBDEs shows that there is minimal risk to global consumers from consumption of aquatic products, with the exception of products from specific regions located around known heavy-point sources. Exposure to dioxins through consumption of aquatic products, excluding marine fish, is also in the range of the acceptable level, lower than 4 pg World Health Organization toxic equivalent (WHO-TEQ)/kg bw/d; however, dioxin intake via marine fish may cause hazards to human health, especially for Europeans. Regarding PCBs, there is cancer risk for global consumers via consumption of aquatic products, especially marine fish, based on cancer and noncancer hazard ratio assessment. Generally, European consumers have higher exposure levels of PCDD/Fs and DL-PCBs, while Americans and Asians have relatively higher exposure levels of OCPs and PCBs. In contrast, all global populations are found to have lower exposure levels of PBDEs, which may be attributed to its relatively shorter history of use compared with PCBs and OCPs. Finally, the estimated total amounts of PCBs, OCPs, and PBDEs stored in global aquatic products constitute only a small portion of the total amount that has been used, and the majority obviously occurs in other environmental media or even remains in commercial products.

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.

Experimental and theoretical study on molecular structure and FT-IR, Raman, NMR spectra of 4,4'-dibromodiphenyl ether

In this work, both experimental and theoretical study on the FT-IR and Raman spectra as well as (1)H NMR and (13)C NMR chemical shifts of 4,4'-dibromodiphenyl ether have been carried out. The optimized geometry was obtained by using both HF and density functional B3LYP method with the 6-31G(d) and 6-311+G(d, p) basis sets. The calculated bond lengths and dihedral angles for both methods on 6-31G(d) level show the best agreement with the experimental data, while the dihedral angles of C(1')-O-C(1)-C(6) and C(1')-O-C(1)-C(2), critical geometry parameters for conformers in the ground state, indicates significant deviation of HF results from the experimental information. The harmonic vibration frequencies and intensities in IR and Raman spectra and chemical shifts of the molecule were calculated on the B3LYP/6-31G(d) and B3LYP/6-311+G(d, p) levels. The scaled theoretical vibration frequencies present good agreement with the experimental values. The larger basis set makes no significant improvement in the accuracy of the vibration frequencies. Besides, chemical shifts of hydrogen and carbon computed on B3LYP/6-31G(d) level agree well with the observations.

Effects of decabrominated diphenyl ether (PBDE 209) on voltage-gated sodium channels in primary cultured rat hippocampal neurons

Polybrominated diphenyl ethers (PBDEs) are widely used as flame-retardant additives. But the application of PBDEs has been challenged due to their toxicity, especially neurotoxicity. In this study, we investigated the effects of decabrominated diphenyl ether (PBDE 209), the major PBDEs product, on voltage-gated sodium channels (VGSCs) in primary cultured rat hippocampal neurons. Employing the whole-cell patch-clamp technique, we found that PBDE 209 could irreversibly decrease voltage-gated sodium channel currents (I(Na)) in a very low dose and in a concentration-dependent manner. We had systematically explored the effects of PBDE 209 on I(Na) and found that PBDE 209 could shift the activation and inactivation of I(Na) toward hyperpolarizing direction, slow down the recovery from inactivation of I(Na), and decrease the fraction of activated sodium channels. These results suggested that PBDE 209 could affect VGSCs, which may lead to changes in electrical activities and contribute to neurotoxicological damages. We also showed that ascorbic acid, as an antioxidant, was able to mitigate the inhibitory effects of PBDE 209 on VGSCs, which suggested that PBDE 209 might inhibit I(Na) through peroxidation. Our findings provide new insights into the mechanism for the neurological symptoms caused by PBDE 209.

Brominated flame retardants in the Arctic environment--trends and new candidates

Polybrominated diphenyl ethers (PBDEs) containing two to 10 bromines are ubiquitous in the Arctic, in both abiotic and biotic samples. Hexabromocyclododecane (HBCD) is also ubiquitous in the Arctic, with the gamma-HBCD isomer predominating in air, the alpha-HBCD isomer predominating in biota and similar concentrations of alpha-, beta- and gamma-HBCD found in marine sediments. Other brominated flame retardants (BFRs) found in some Arctic samples are polybrominated biphenyls (PBBs), tetrabromobisphenol A (TBBPA), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), hexabromobenzene (HxBBz), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH). Temporal trends of tetra- to heptaBDEs and HBCD show increasing concentrations or a tendency to levelling off depending on the matrix (air, sediment, biota) and location, but no uniform picture for the Arctic emerges. BDE-209 concentrations are increasing in air. PBDEs and HBCD spatial trends in seabirds and marine mammals are similar to those seen previously for polychlorinated biphenyls (PCBs), with highest concentrations found in organisms from East Greenland and Svalbard. These trends indicate western Europe and eastern North America as important source regions of these compounds via long range atmospheric transport and ocean currents. Latitudinal trends showed lower concentrations and fluxes of PBDEs at higher latitudes. The tetra-hexaBDEs and alpha-HBCD biomagnify in Arctic food webs. Results for BDE-209 are more conflicting, showing either only low or no biomagnification potential. PBDE and HBCD concentrations are lower in terrestrial organisms and higher in marine top predators such as some killer whale populations in Alaska and glaucous gulls from the Barents Sea area. Higher concentrations are seen near populated areas indicating local sources. Findings of BTBPE, HxBBz, PBEB, PBT and TBECH in seabirds and/or marine mammals indicate that these compounds reach the Arctic, most probably by long range atmospheric transport and accumulate in higher trophic level organisms and that increasing use as PBDE replacements will lead to increasing concentrations.

Effects of environmental pollutants on the reproduction and welfare of ruminants

Anthropogenic pollutants comprise a wide range of synthetic organic compounds and heavy metals, which are dispersed throughout the environment, usually at low concentrations. Exposure of ruminants, as for all other animals, is unavoidable and while the levels of exposure to most chemicals are usually too low to induce any physiological effects, combinations of pollutants can act additively or synergistically to perturb multiple physiological systems at all ages but particularly in the developing foetus. In sheep, organs affected by pollutant exposure include the ovary, testis, hypothalamus and pituitary gland and bone. Reported effects of exposure include changes in organ weight and gross structure, histology and gene and protein expression but these changes are not reflected in changes in reproductive performance under the conditions tested. These results illustrate the complexity of the effects of endocrine disrupting compounds on the reproductive axis, which make it difficult to extrapolate between, or even within, species. Effects of pollutant exposure on the thyroid gland, immune, cardiovascular and obesogenic systems have not been shown explicitly, in ruminants, but work on other species suggests that these systems can also be perturbed. It is concluded that exposure to a mixture of anthropogenic pollutants has significant effects on a wide variety of physiological systems, including the reproductive system. Although this physiological insult has not yet been shown to lead to a reduction in ruminant gross performance, there are already reports indicating that anthropogenic pollutant exposure can compromise several physiological systems and may pose a significant threat to both reproductive performance and welfare in the longer term. At present, many potential mechanisms of action for individual chemicals have been identified but knowledge of factors affecting the rate of tissue exposure and of the effects of combinations of chemicals on physiological systems is poor. Nevertheless, both are vital for the identification of risks to animal productivity and welfare.

Spatial variations in the levels and isomeric patterns of PBDEs and HBCDs in the European eel in Flanders

Pooled yellow eel (Anguilla anguilla L.) samples, consisting of 3-10 eels, from 50 locations collected in the period 2000-2006 were used to assess the pollution with PBDEs and HBCDs in Flemish waters (Belgium). Results from this monitoring network are presented and the spatial aspect throughout Flanders is included, linking POP levels to the industrial characteristics of the different sampling locations. The following PBDE congeners were measured using GC/MS: 28, 47, 49, 66, 85, 99, 100, 153, 154, 183 and 209. Concentrations of summation sigmaPBDE ranged between 10 and 5811 ng/g lipid weight (lw) with a median value of 81 ng/glw. BDE 47 dominated the PBDE profile in the majority of the eel samples, except for six samples, in which BDE 209 was the dominating congener. These latter samples are probably associated with recent exposure to the Deca-BDE mixture. Three HBCD diastereoisomers (alpha-, beta- and gamma-HBCD) were measured using LC/MS-MS. summation sigmaHBCDs ranged between 16 and 4397 ng/glw, with a median value of 73 ng/glw. alpha-HBCD was the dominant isomer in all eel samples. Sediment concentrations of PBDEs were available from four locations and were used to compare the PBDE profile with those in eel. An important shift in the profile was observed, especially for BDE 209. While BDE 209 was only found in 12 eel samples, it was the dominant congener in all sediment samples. This could be due to its metabolisation or degradation in biota combined with the poor uptake of BDE 209 from sediments and its very low water solubility. No HBCDs were detected in any of the sediment samples. No significant correlation could be found between concentrations of PBDEs in eel and sediment from the same location. Comparison with previous studies shows that PBDE and HBCD levels in Flemish eels have decreased rapidly between 2000 and 2006 at particular sites, but alarming concentrations can still be found at industrialized hot spots. This finding is reflected in the human exposure to PBDEs and HBCDs through eel consumption. For average consumers (2.9 geel/day), intakes ranged between 3 and 2295 ng/day for summation sigmaPBDEs (with a median value of 16 ng/day) and between 3 and 1110 ng/day for summation sigmaHBCDs (with a median value of 18 ng/day), respectively. Additionally, human intakes were calculated for recreational fishermen, eating up to 12 g or 86 geel/day. Intakes of those risk groups were higher in comparison with average consumers and were above reference doses described in literature which may induce adverse effects.

Polybrominated diphenyl ethers and synthetic musks in umbilical cord serum, maternal serum, and breast milk from Seoul, South Korea

Fetal and maternal exposure levels of two emerging pollutants, polybrominated diephenyl ethers (PBDEs) and synthetic musks, were measured in Korean general population to assess prenatal and postnatal exposures in infants. For this purpose, paired samples of breast milk, maternal and cord blood were collected from 20 Korean women in 2007. In comparison to data from other countries and previous data from Korea, relatively higher and gradually increasing concentrations for PBDEs were found in Korean breast milk (< LOQ to 590 ng g(-1) lipid wt; median=90 ng g(-1)). Differences in PBDEs and musk concentrations were found among age groups and parity levels. PBDEs concentrations in breast milk were lower in the younger mothers and/or the mothers with multiple parities, while these trends were not found for musks. Compared with PBDEs, concentrations of musks were significantly lower in breast milk than in serum and a little correlation in concentrations among the three human biological matrices were observed. The differences in the profiles of musks relative to PBDEs were due to different clearance rates between these two compounds. The average hazard quotients (HQs) for daily intake of PBDEs by infants via lactation were 0.62, 0.42, and 0.19 for BDE-47, BDE-99, and BDE-153, respectively.

PBDE concentrations in women's serum and fecundability

BACKGROUND

Exposure to polybrominated diphenyl ether (PBDE) flame retardants is widespread, with 97% of Americans having detectable levels. Although PBDEs have been associated with reproductive and hormonal effects in animals, no human studies have examined their association with fertility.

OBJECTIVES

This study was designed to determine whether maternal concentrations of PBDEs in serum collected during pregnancy are associated with time to pregnancy and menstrual cycle characteristics.

METHODS

Pregnant women (n = 223) living in a low-income, predominantly Mexican-immigrant community in California were interviewed to determine how many months they took to become pregnant. Blood samples were collected and analyzed for PBDEs. PBDE concentrations were lipid adjusted and log10 transformed. Analyses were limited to PBDE congeners detected in > 75% of the population (BDEs 47, 99, 100, 153). Cox proportional hazards models modified for discrete time were used to obtain fecundability odds ratios (fORs) for the association of PBDEs and time to pregnancy.

RESULTS

We detected all four congeners in > 97% of women. Increasing levels of BDEs 47, 99, 100, 153 and the sum of these four congeners were all associated with longer time to pregnancy. We observed significantly reduced fORs for BDE-100 [adjusted fOR = 0.6; 95% confidence interval (CI), 0.4-0.9], BDE-153 (adjusted fOR = 0.5; 95% CI, 0.3-0.8), and the sum of the four congeners (adjusted fOR = 0.7; 95% CI, 0.5-1.0). PBDEs were not associated with menstrual cycle characteristics.

CONCLUSIONS

We found significant decreases in fecundability associated with PBDE exposure in women. Future studies are needed to replicate and confirm this finding.

Effects of repeated exposure to decabrominated diphenyl ether (BDE-209) on mice nervous system and its self repair

Decabrominated diphenyl ether (BDE-209) is widely used as brominated flame retardants (BFRs). In order to investigate its direct neurotoxic effects on mice and its self repair, mice were repeatedly exposured to BDE-209. Different concentrations of BDE-209 (0, 0.1, 40, 80 and 160mg/kgbw/d) were administered daily to CD-1 Swiss mice by gavage for 15, 30 and 60 days. Body and brain weights were recorded after the exposure. And the self repair was studied. Levels of acetylcholinesterase (TchE), superoxide dismutase (SOD) and malonic dialdehyde (MDA) in brain were analyzed. Experimental results suggested that the nervous system was permanently damaged by BDE-209 through the cholinergic system enzyme.

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

Developmental effects of polybrominated diphenyl ethers (PBDEs) have been suspected due to their structural similarities to polychlorinated biphenyls (PCBs). This study evaluated neurobehavioral, hormonal, and reproductive effects in rat offspring perinatally exposed to a widely used pentabrominated commercial mixture, DE-71. Pregnant Long-Evans rats were exposed to 0, 1.7, 10.2, or 30.6 mg/kg/day DE-71 in corn oil by oral gavage from gestational day 6 to weaning. DE-71 did not alter maternal or male offspring body weights. However, female offspring were smaller compared with controls from postnatal days (PNDs) 35-60. Although several neurobehavioral endpoints were assessed, the only statistically significant behavioral finding was a dose-by-age interaction in the number of rears in an open-field test. Developmental exposure to DE-71 caused severe hypothyroxinemia in the dams and early postnatal offspring. DE-71 also affected anogenital distance and preputial separation in male pups. Body weight gain over time, reproductive tissue weights, and serum testosterone concentrations at PND 60 were not altered. Mammary gland development of female offspring was significantly affected at PND 21. Congener-specific analysis of PBDEs indicated accumulation in all tissues examined. Highest PBDE concentrations were found in fat including milk, whereas blood had the lowest concentrations on a wet weight basis. PBDE concentrations were comparable among various brain regions. Thus, perinatal exposure to DE-71 leads to accumulation of PBDE congeners in various tissues crossing blood-placenta and blood-brain barriers, causing subtle changes in some parameters of neurobehavior and dramatic changes in circulating thyroid hormone levels, as well as changes in both male and female reproductive endpoints. Some of these effects are similar to those seen with PCBs, and the persistence of these changes requires further investigation.

Bromination pattern of hydroxylated metabolites of BDE-47 affects their potency to release calcium from intracellular stores in PC12 cells

BACKGROUND

Brominated flame retardants, including the widely used polybrominated diphenyl ethers (PBDEs), have been detected in humans, raising concern about possible neurotoxicity. Recent research demonstrated that the hydroxylated metabolite 6-OH-BDE-47 increases neurotransmitter release by releasing calcium ions (Ca2+) from intracellular stores at much lower concentrations than its environmentally relevant parent congener BDE-47. Recently, several other hydroxylated BDE-47 metabolites, besides 6-OH-BDE-47, have been detected in human serum and cord blood.

OBJECTIVE AND METHODS

To investigate the neurotoxic potential of other environmentally relevant PBDEs and their metabolites, we examined and compared the acute effects of BDE-47, BDE-49, BDE-99, BDE-100, BDE-153, and several metabolites of BDE-47-6-OH-BDE-47 (and its methoxylated analog 6-MeO-BDE-47), 6 -OH-BDE-49, 5-OH-BDE-47, 3-OH-BDE-47, and 4 -OH-BDE-49--on intracellular Ca2+ concentration ([Ca2+]i), measured using the Ca2+-responsive dye Fura-2 in neuroendocrine pheochromocytoma (PC12) cells.

RESULTS

In contrast to the parent PBDEs and 6-MeO-BDE-47, all hydroxylated metabolites induced Ca2+ release from intracellular stores, although with different lowest observed effect concentrations (LOECs). The major intracellular Ca2+ sources were either endoplasmic reticulum (ER; 5-OH-BDE-47 and 6 -OH-BDE-49) or both ER and mitochondria (6-OH-BDE-47, 3-OH-BDE-47, and 4 -OH-BDE-49). When investigating fluctuations in [Ca2+]i, which is a more subtle end point, we observed lower LOECs for 6-OH-BDE-47 and 4 -OH-BDE-49, as well as for BDE-47.

CONCLUSIONS

The present findings demonstrate that hydroxylated metabolites of BDE-47 cause disturbance of the [Ca2+]i. Importantly, shielding of the OH group on both sides with bromine atoms and/or the ether bond to the other phenyl ring lowers the potency of hydroxylated PBDE metabolites.

Bioavailability of decabromodiphenyl ether to the marine polychaete Nereis virens

The flame retardant decabromodiphenyl ether (BDE 209) accumulates in humans and terrestrial food webs, but few studies have reported the accumulation of BDE 209 in aquatic biota. To investigate the mechanisms controlling the bioavailability of BDE 209, a 28-d bioaccumulation experiment was conducted in which the marine polychaete worm Nereis virens was exposed to a decabromodiphenyl ether (deca-BDE) commercial mixture (>85% BDE 209) in spiked sediments, in spiked food, or in field sediments. Bioaccumulation from spiked substrate with maximum bioavailability demonstrated that BDE 209 accumulates in this species. Bioavailability depends on the exposure conditions, however, because BDE 209 in field sediments did not accumulate (<0.3 ng/g wet weight; 28-d biota-sediment accumulation factors [BSAFs] <0.001). When exposed to deca-BDE in spiked sediments also containing lower brominated congeners (a penta-BDE mixture), bioaccumulation of BDE 209 was 30 times lower than when exposed to deca-BDE alone. Selective accumulation of the lower brominated congeners supports their prevalence in higher trophic level species. The mechanisms responsible for limited accumulation of BDE 209 may involve characteristics of the sediment matrix and low transfer efficiency in the digestive fluid.

Flow cytometric analysis of BDE 47 mediated injury to rainbow trout gill epithelial cells

The polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants whose residues are increasing in fish, wildlife and human tissues. However, relatively little is known regarding the mechanisms of cell injury caused by PBDE congeners in fish. In the present study, we employed flow cytometry-based analyses to understand the onset and mechanisms of cell injury in rainbow trout gill cells (RTgill-W1 cells) exposed to 2,2',4,4'-tetrabromodiphenyl ether (BDE 47). Substantial optimization and validation for flow cytometry protocols were required during assay development for the trout gill cell line. Exposure to micromolar concentrations of BDE 47 elicited a significant loss in RTgill-W1 cell viability that was accompanied by a decrease in NAD(P)H autofluorescence, a marker associated with disruption of cellular redox status. This loss in NAD(P)H content was accompanied by a decrease in nonyl acridine orange fluorescence, indicating mitochondrial membrane lipid peroxidation. Furthermore, low doses of BDE 47 altered cellular forward angle light scatter (FS, a measure of cell diameter or size) and side light scatter properties (SS, a measure of cellular internal complexity), consistent with the early stages of apoptosis. These changes were more pronounced at higher BDE 47 concentrations, which led to an increase in the percentage of cells undergoing frank apoptosis as evidenced by sub-G1 DNA content. Apoptosis was also observed at a relatively low dose (3.2muM) of BDE 47 if cells were exposed for an extended period of time (24h). Collectively, the results of these studies indicate that exposure of rainbow trout gill cells to BDE47 is associated with the induction of apoptosis likely originating from disruption of cellular redox status and mitochondrial oxidative injury. The current report extends observations in other species demonstrating that oxidative stress is an important mechanism of BDE 47 mediated cellular toxicity, and supports the use of oxidative stress-associated biomarkers in assessing the sublethal effects of PBDEs and their replacements in fish. The application of flow cytometry endpoints using fish cell lines should facilitate study of the mechanisms of chemical injury in aquatic species.

Partitioning of polybrominated diphenyl ethers (PBDEs) in serum and milk from the same mothers

We and others have previously described partitioning of chemicals, including polychlorinated-p-dioxins, dibenzofurans, and biphenyls in different types of human tissues and fluids, including blood and milk. Additionally, we previously reported the blood to milk partitioning of polybrominated diphenyl ethers (PBDEs) in a group of 11 women. Partitioning is of importance in understanding the toxicokinetics of these compounds and also in clinical medicine in improving estimates of levels in different matrices including blood and milk. In this study we extend these findings, describing the levels of PBDEs detected in the serum and milk of 29 women from Texas. The median sum of the levels of the four most detected congeners (BDE 47, 99, 100, and 153) in serum was 27.8 ng g(-1) lipid (range 6.7-501.6 ng g(-1) lipid). In milk, the median sum of the levels of the same congeners was 39.7 ng g(-1) lipid (range 12.9-580.3 ng g(-1) lipid). The levels detected in breast milk in this study are similar to those we reported in 2003, where a median total PBDE level of 34 ng g(-1) lipid was reported. When congener specific blood to milk partitioning ratios were calculated for BDEs 47, 99, 100, and 153, the relatively small tetrabrominated congener, BDE 47, was found in higher concentrations in milk compared to blood, while the higher molecular weight hexabrominated congener, BDE 153, was found in approximately equal quantities in blood and milk, on a lipid normalized basis. The reason for the differential partitioning of PBDE congeners in milk and blood could be due to variation in toxicokinetics, specifically distribution based on molecular size or molecular weight.

PCBs and PBDEs in wild Chinook salmon (Oncorhynchus tshawytscha) in the Northern Patagonia, Chile

This paper documents the accumulation and emerging levels of Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) found in the tissues of the migrating salmon species Oncorhynchus tshawytscha (Chinook salmon) in the Chilean Patagonia area. Even though salmon are not native to the southern hemisphere, reports indicate that Chinook salmon in the last few years have performed natural free-living style cycling, returning to rivers in the southern Patagonia area. Our study seeks to determine the presence and levels of PCB's and PBDE's in wild Chinook salmon in the northern part of the Chilean Patagonia, analyzing their relation with physiological parameters. Fish were sampled at the end of their entire life cycle when they returned to two principal rivers in the Aysen region in southern Chile. A number of fish (12) were sacrificed in situ and muscle samples were taken for PCBs measurements (sum 44 congeners) by gas chromatography electron capture detector (GC-ECD) and a number of PBDEs congeners, by gas chromatography mass spectrometry with negative chemical ionization detection (GC-MS NCI). Observed levels and patterns were characterized by concentrations of these POPs for PCBs ranging between 78 and 25.5 ng g(-1) wet weight and for PBDEs ranging between 272 and 1046 pg g(-1) wet weight, respectively. These ranges are among same levels reported in this same species in the northern hemisphere.

Cytotoxicity and apoptosis induction on RTG-2 cells of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabrominated diphenyl ether (BDE-209)

Recently, the environmental residues of polybrominated diphenyl ethers (PBDEs) have markedly increased. In particular, the levels of certain PBDE congeners in fish have raised concern regarding potential risks associated with dietary PBDEs exposures. However, little is known regarding PBDE-mediated cell injury in relevant in vitro fish cell models. In this study, the cytotoxic effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and decabrominated diphenyl ether (BDE-209) on RTG-2 cells were investigated. RTG-2 cells were incubated with different concentrations of BDE-47 and BDE-209 (1-100 microM) for 72 h, and a set of bioassays were conducted to measure: cell viability (evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and neutral red (NR) uptake), lactate dehydrogenase (LDH) leakage, reactive oxygen species (ROS) formation and cell apoptosis. The results showed that BDE-47 and BDE-209 inhibited the cells viability, increased LDH leakage, and induced cell apoptosis in time and concentration-dependent manner. All significant effects were observed at concentrations of 12.5 microM and above for BDE-47 and 25 microM and above for BDE-209 (P<0.05). At the concentration of 100 microM BDE-47 and BDE-209, the cell viability of the exposed cells dropped to about 40% and 50% of the control, and the apoptotic rates were 52.6% and 34.6%, respectively. After 12h exposure, a concentration-dependent increases of BDE-47 and BDE-209 (12.5-100 microM) in ROS formation were observed. Collectively, the results of cell viability, LDH leakage, cell apoptosis and ROS formation demonstrated that the toxic mechanism of PBDEs on RTG-2 might be mediated by oxidative stress.

The potential of selected brominated flame retardants to affect neurological development

Various brominated flame retardants (BFR), including polybrominated diphenyl ether (PBDE) congeners, hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), are commonly used in household items and electronics and have been detected in the environment and/or the bodily fluids of people, including children. Some studies in animals suggest that exposure to PBDE congeners, HBCD, or TBBPA during the perinatal period may affect locomotor activity and/or memory and learning. Epidemiological studies showing similar effects in humans, however, are lacking. To assess whether an association exists between perinatal exposure and development of consistent neurobehavioral alterations, published animal studies investigating perinatal exposure to PBDE congeners, HBCD, or TBBPA with specific neurobehavioral evaluations-particularly, assessments of motor activity-were reviewed for consistency of results. Our analysis shows that although the majority of studies suggest that perinatal exposure affects motor activity, the effects observed were not consistent. This lack of consistency includes the type of motor activity (locomotion, rearing, or total activity) affected, the direction (increase or decrease) and pattern of change associated with exposure, the existence of a dose response, the permanency of findings, and the possibility of gender differences in response. Interestingly, Good Laboratory Practices (GLP)-compliant studies that followed U.S. Environmental Protection Agency (EPA)/Organization for Economic Cooperation and Development (OECD) guidelines for developmental neurotoxicity testing found no adverse effects associated with exposure to PBDE209, HBCD, or TBBPA at doses that were orders of magnitude higher and administered over longer durations than those used in the other studies examined herein. The lack of consistency across studies precludes establishment of a causal relationship between perinatal exposure to these substances and alterations in motor activity.

Individual characteristics associated with PBDE levels in U.S. human milk samples

BACKGROUND

Reported polybrominated diphenyl ether (PBDE) concentrations in human samples in the United States have been higher than in Europe and Asia. Little is known about factors that contribute to individual variability in body burden.

OBJECTIVE

In this large study we measured PBDE concentrations in human milk from the United States during 2004-2006. We assessed characteristics associated with concentrations in milk and change in milk concentration between 3 and 12 months postpartum.

METHODS

We analyzed 303 milk samples obtained 3 months postpartum for PBDEs. A second sample was analyzed for 83 women still lactating 12 months postpartum. PBDE concentrations in milk and variability by individual characteristics such as age, parity, and prepregnancy body mass index (BMI) were evaluated using generalized linear models.

RESULTS

PBDE congeners BDEs 28, 47, 99, 100, and 153 were detected in > 70% of samples. BDE-47 concentrations were the highest, ranging from below the limit of detection to 1,430 ng/g lipid, with a median of 28 ng/g lipid. Concentrations of most individual PBDE congeners and the sum of BDEs 28, 47, 99, 100, and 153 (SigmaPBDE) were lower among mothers > 34 years of age compared with those 25-29 years of age and higher among mothers with high compared with normal BMI, after adjustment for other covariates. Parity was not associated with PBDE concentration. The change in SigmaPBDE concentration in milk between 3 and 12 months postpartum was highly variable (median increase, 14%; interquartile range, -26% to 50%).

CONCLUSIONS

PBDEs were detected in nearly all human milk samples, varying by maternal weight and age and over the course of breast-feeding.

Calcium-related processes involved in the inhibition of depolarization-evoked calcium increase by hydroxylated PBDEs in PC12 cells

In vitro studies indicated that hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have an increased toxic potential compared to their parent congeners. An example is the OH-PBDE-induced increase of basal intracellular Ca(2+) concentration ([Ca(2+)](i)) by release of Ca(2+) from endoplasmic reticulum (ER) and mitochondria and/or influx of extracellular Ca(2+). ER and mitochondria regulate Ca(2+) homeostasis in close association with voltage-gated Ca(2+) channels (VGCCs). Therefore, effects of (OH-)PBDEs on the depolarization-evoked (100 mM K(+)) net increase in [Ca(2+)](i) (depolarization-evoked [Ca(2+)](i)) were measured in neuroendocrine pheochromocytoma cells using the Ca(2+)-responsive dye Fura-2. OH-PBDEs dose dependently inhibited depolarization-evoked [Ca(2+)](i). This inhibition was potentiated by a preceding increase in basal [Ca(2+)](i). Especially at higher concentrations of OH-PBDEs (5-20 microM), large increases in basal [Ca(2+)](i) strongly inhibited depolarization-evoked [Ca(2+)](i). The inhibition appeared more sensitive to increases in basal [Ca(2+)](i) by Ca(2+) release from intracellular stores (by 3-OH-BDE-47 or 6'-OH-BDE-49) compared to those by influx of extracellular Ca(2+) (by 6-OH-BDE-47 or 5-OH-BDE-47). The expected [Ca(2+)](i) difference close to the membrane suggests involvement of Ca(2+)-dependent regulatory processes close to VGCCs. When coapplied with depolarization, some OH-PBDEs induced also moderate direct inhibition of depolarization-evoked [Ca(2+)](i). Polybrominated diphenyl ethers and methoxylated BDE-47 affected neither basal nor depolarization-evoked [Ca(2+)](i), except for BDE-47, which moderately increased fluctuations in basal [Ca(2+)](i) and depolarization-evoked [Ca(2+)](i). These findings demonstrate that OH-PBDEs inhibit depolarization-evoked [Ca(2+)](i) depending on preceding basal [Ca(2+)](i). Related environmental pollutants that affect Ca(2+) homeostasis (e.g., polychlorinated biphenyls) may thus also inhibit depolarization-evoked [Ca(2+)](i), justifying further investigation of possible mixture effects of environmental pollutants on Ca(2+) homeostasis.

Comparative cytotoxicity and intracellular accumulation of five polybrominated diphenyl ether congeners in mouse cerebellar granule neurons

Polybrominated diphenyl ethers (PBDEs), a group of flame retardants comprising 209 congeners, have become widespread environmental pollutants. High levels of PBDEs have been detected in human tissues, particularly in North America, and body burden is especially high in infants and toddlers because of exposure through breast milk and house dust. Increasing evidence, provided by animal studies, suggests that PBDEs are developmental neurotoxicants, although the underlying mechanisms are still unknown. Various PBDEs have been reported to cause oxidative stress and to induce apoptotic cell death in several cell types. In the present study, we investigated the comparative neurotoxicity in mouse cerebellar granule neurons of five brominated diphenyl ether (BDE) congeners, chosen among the most commonly found at the highest levels in human tissues. All BDE congener tested (BDE-47, BDE-99, BDE-100, BDE-153, and BDE-209) decreased cell viability and induced apoptotic cell death, which was prevented by antioxidants. They also caused oxidative stress, as indicated by an increase in reactive oxygen species and in lipid peroxidation. For all end points measured, the potency ranking of the congeners was BDE-100 > BDE-47 > BDE-99 > BDE-153 >> BDE-209. Measurement of BDE congener levels in neurons after exposure to different concentrations showed a significant accumulation in cells, which followed the same relative ranking. The findings suggest that all BDE congeners tested exhibit the same general mode of action (induction of oxidative stress-mediated apoptosis) and that the ability of each isomer to elicit such effects is dependent upon their accumulation in neurons, particularly in the microsomal fraction and the mitochondria.

Behavioral changes in aging but not young mice after neonatal exposure to the polybrominated flame retardant decaBDE

BACKGROUND

After several decades of commercial use, the flame-retardant chemicals polybrominated diphenyl ethers (PBDEs) and their metabolites are pervasive environmental contaminants and are detected in the human body. Decabrominated diphenyl ether (decaBDE) is currently the only PBDE in production in the United States.

OBJECTIVES

Little is known about the health effects of decaBDE. In the present study we examined the effects of neonatal decaBDE exposure on behavior in mice at two ages.

METHODS

Neonatal male and female C57BL6/J mice were exposed to a daily oral dose of 0, 6, or 20 mg/kg decaBDE from postnatal days 2 through 15. Two age groups were examined: a cohort that began training during young adulthood and an aging cohort of littermates that began training at 16 months of age. Both cohorts were tested on a series of operant procedures that included a fixed-ratio 1 schedule of reinforcement, a fixed-interval (FI) 2-min schedule, and a light-dark visual discrimination.

RESULTS

We observed minimal effects on the light-dark discrimination in the young cohort, with no effects on the other tasks. The performance of the aging cohort was significantly affected by decaBDE. On the FI schedule, decaBDE exposure increased the overall response rate. On the light-dark discrimination, older treated mice learned the task more slowly, made fewer errors on the first-response choice of a trial but more perseverative errors after an initial error, and had lower latencies to respond compared with controls. Effects were observed in both dose groups and sexes on various measures.

CONCLUSIONS

These findings suggest that neonatal decaBDE exposure produces effects on behavioral tasks in older but not younger animals. The behavioral mechanisms responsible for the pattern of observed effects may include increased impulsivity, although further research is required.