Decabromodiphenyl ether (BDE-209) enters the food web of the River Po and is metabolically debrominated in resident cyprinid fishes

Decabromodiphenyl ether (BDE-209), the primary constituent of a widely used flame retardant formulation, is present at relatively high levels in sediments and macroinvertebrates of the River Po. Since it was demonstrated that BDE-209 can be biotransformed to smaller and more toxic polybrominated dipheyl ethers (PBDEs), the main objective of this study was to assess whether the large quantities of BDE-209 present in the River Po are bioavailable to the higher levels of the food web and are biotransformed in feral fishes. To this aim, 23 cyprinids, mainly common carp, were analysed for the hepatic contents of PBDEs. Contrary to sediments and invertebrates of the same area, no fish sample contained detectable levels of BDE-209. All fishes contained typical PBDE representatives, e.g. BDE-47, BDE-99, BDE-100, BDE-153 and BDE-154, but more importantly they contained three congeners, i.e. BDE-179, BDE-188 and BDE-202, which are not present in any technical formulations and are known products of BDE-209 debromination in fish. The age of carps had no effects on the bioaccumulation of PBDEs. Conversely, the contents of PCBs, which also were determined in the same fish samples, showed a positive correlation with age. Both groups of chemicals displayed a tendency to a higher contamination in male fish. This study shows that BDE-209 enters the food web of the River Po contributing to the load of lower brominated PBDEs and thus to the load of chemical stressors threatening the aquatic life of the major Italian watercourse.

Trophic level determines levels of brominated flame-retardants in coastal herring gulls

Liver concentrations of eight polybrominated diphenyl ethers (ΣPBDEs: sum of brominated diphenyl ethers [BDE]-28, -47, -99, -100, -153, -154, -183, and -209) ranged from 135 to 985 ngg(-1) lipid weight (lw) in coastal herring gulls (Larus argentatus) from the marine Hvaler Archipelago (The Glomma River Estuary), Norway. Hexabromocyclododecane (HBCD) concentrations ranged from 10 to 698 ngg(-1)lw. High range in δ(13)C indicates that gulls were subject to a diversity of carbon sources, likely reflecting their mixed feeding on terrestrial and marine organisms, or diversity of autochthonous and allochthonous (watershed) energy sources at the bases of their marine/estuarial food chains. Inverse relationships of HBCD, and to somewhat lesser extent of BDE-209, with δ(13)C values suggest higher abundance of these compounds in the land-derived energy-sources of the gulls. Inverse relationships of BDE-99, BDE-183 and BDE-209 with δ(15)N suggest that trophic relationships affect bioaccumulation of these compounds in the herring gulls, with greater bioaccumulation from lower trophic level prey species. This may be because these PBDE congeners are subject of debromination in higher trophic levels prey species of the gulls (e.g., teleost fish). Levels of BDE-209 (up to 95 ng/g lipid) of these herring gulls from 1998 were in the higher range reported in European birds, and not matched by other reports in North Sea seabirds. The present study suggests that the currently used brominated flame-retardants (BFRs), BDE-209 and HBCD relate to changing nutrient allocation in the herring gulls, and represent a risk to seabirds exploiting near-shore and estuary ecosystems.

Accumulation and debromination of decabromodiphenyl ether (BDE-209) in juvenile fathead minnows (Pimephales promelas) induces thyroid disruption and liver alterations

Polybrominated diphenyl ether (PBDE) flame retardants are known to affect thyroid hormone (TH) regulation. The TH-regulating deiodinases have been implicated in these impacts; however, PBDE effects on the fish thyroid system are largely unknown. Moreover, the liver as a potential target of PBDE toxicity has not been explored in young fish. This study measured decabromodiphenyl ether (BDE-209) effects on TH regulation by measuring deiodinase activity in juvenile fathead minnows (Pimephales promelas). Dietary accumulations and debromination of BDE-209 were also measured, and the morphology of thyroid and liver tissues was examined. Juvenile fathead minnows (28 days old) received a 28-day dietary treatment of BDE-209 at 9.8 ± 0.16 μg/g of food at 5% of their body weight per day followed by a 14-day depuration period in which they were fed clean food. Chemical analysis revealed that BDE-209 accumulated in tissues and was metabolized to reductive products ranging from penta- to octaBDEs with 2,2',4,4',5,6'-hexabromodiphenyl ether (BDE-154) being the most accumulative metabolite. By day 28 of the exposure, rates of outer and inner ring deiodination (ORD and IRD, respectively) of thyroxine (T4) were each reduced by ∼74% among treatments. Effects on T4-ORD and T4-IRD remained significant even after the 14-day depuration period. Histological examination of treated fish showed significantly increased thyroid follicular epithelial cell heights and vacuolated hepatocyte nuclei. Enlarged biliary passageways may be the cause of the distinctive liver phenotype observed, although further testing is needed. Altogether, these results suggest that juvenile fish may be uniquely susceptible to thyroid disruptors like PBDEs.

Neurotoxicity of brominated flame retardants: (in)direct effects of parent and hydroxylated polybrominated diphenyl ethers on the (developing) nervous system

BACKGROUND/OBJECTIVE

Polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH-) or methoxylated forms have been detected in humans. Because this raises concern about adverse effects on the developing brain, we reviewed the scientific literature on these mechanisms.

DATA SYNTHESIS

Many rodent studies reported behavioral changes after developmental, neonatal, or adult exposure to PBDEs, and other studies documented subtle structural and functional alterations in brains of PBDE-exposed animals. Functional effects have been observed on synaptic plasticity and the glutamate-nitric oxide-cyclic guanosine monophosphate pathway. In the brain, changes have been observed in the expression of genes and proteins involved in synapse and axon formation, neuronal morphology, cell migration, synaptic plasticity, ion channels, and vesicular neurotransmitter release. Cellular and molecular mechanisms include effects on neuronal viability 
(via apoptosis and oxidative stress), neuronal differentiation and migration, neurotransmitter release/uptake, neurotransmitter receptors and ion channels, calcium (Ca²⁺) homeostasis, and intracellular signaling pathways.

DISCUSSION

Bioactivation of PBDEs by hydroxylation has been observed for several endocrine end points. This has also been observed for mechanisms related to neurodevelopment, including binding to thyroid hormone receptors and transport proteins, disruption of Ca²⁺ homeostasis, and modulation of GABA and nicotinic acetylcholine receptor function.

CONCLUSIONS

The increased hazard for developmental neurotoxicity by hydroxylated (OH-)PBDEs compared with their parent congeners via direct neurotoxicity and thyroid disruption clearly warrants further investigation into a) the role of oxidative metabolism in producing active metabolites of PBDEs and their impact on brain development; b) concentrations of parent and OH-PBDEs in the brain; and c) interactions between different environmental contaminants during exposure to mixtures, which may increase neurotoxicity.

Toxicokinetics of tetrabromoethylcyclohexane (TBECH) in juvenile brown trout (Salmo trutta) and effects on plasma sex hormones

Technical 1,2-dibromo-4-(1,2 dibromoethyl)cyclohexane or tetrabromoethylcyclohexane (TBECH) used primarily as an additive flame retardant in polystyrene foams, contains two diastereoisomers, α- and β- present in equimolar amounts. At temperatures in excess of 125°C, isomerization to two other isoforms, δ- and γ- is possible. The recent detection of TBECH in the environment and studies suggesting that isomers are androgenic prompted us to examine the toxicokinetics and biochemical effects of one of the isomers, β-, in a controlled laboratory environment. Juvenile brown trout (Salmo trutta) were exposed to three different amounts of the β-isomer (low, medium and high) via the food followed by a period in which they were exposed to unfortified food. A fourth group of fish was exposed to unfortified food for the duration of the experiment. On days 0, 7, 14, 21, 35, 49, 56, 63, 77, 91, 105, and 133, eight fish from each treatment group were euthanized and liver, plasma, lower jaw (i.e., thyroid tissue) and gonad were collected and the remaining tissue ('whole-fish') was retained. β-Isomer content was measured in whole-fish and in liver while estradiol (E2), 11-ketotestosterone (11-KT) and testosterone (T) were measured in plasma. Based on liver and gonad somatic indices, no apparent effects on liver or gonad development in fish from any of the treatment groups were observed. The bioaccumulation of β-isomer was similar in fish from all treatment groups with steady-state occurring before the end of the uptake phase. Depuration of the β-isomer from fish obeyed first order kinetics and there were no statistically significant differences in the depuration half life (t(1/2)) among the treatment groups: 22.5 ± 10.4 (low), 13.5 ± 5.9 (med) and 13.8 ± 2.2 (high) days. Steady-state biomagnification factors were much smaller than 1 for fish in all treatment groups. Debrominated metabolites were not detected in composite liver or whole-fish extracts and there was no evidence of isomerization of the β-isomer to other isoforms in vivo. While there were occasional differences among treatment groups in circulating plasma E2, T and 11-KT levels there was no clear, temporal trend or dose-response.

Time-of-flight secondary ion mass spectrometry imaging demonstrates the specific localization of deca-bromo-diphenyl-ether residues in the ovaries and adrenal glands of exposed rats

Deca-bromo-diphenyl ether (DBDE) is one of the most efficient brominated flame retardant (BFR) available on the market. We recently demonstrated that when administered to female rat by oral route, DBDE is efficiently absorbed, with the highest residual concentrations found in two endocrine glands, namely the adrenal glands and the ovaries. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging, a technique usually used for the study of endogenous compounds, was applied for the first time to a persistent organic pollutant, allowing to detect and to precisely localize DBDE residues in these two target tissues. The detection of the bromide ion ((81)Br isotope) by TOF-SIMS mass spectrometry imaging allowed us to demonstrate a marked cortical tropism of DBDE residues for the adrenal glands in female rats dosed per os 2 mg·kg(-1) DBDE, daily, over 96 h. In ovaries, DBDE residues were found to be concentrated in spots corresponding to part of the corpora lutea. Hepatic residues of DBDE were found to be homogeneously distributed. Due to the intrinsic toxicity of DBDE, its accumulation in the adrenal glands and the ovaries may be connected to the mechanisms of actions by which DBDE could trigger endocrine disruption in mammals.

Occurrence of anthropogenic and naturally-produced organohalogenated compounds in tissues of Black Sea harbour porpoises

Harbour porpoises are one of the three cetacean species inhabiting the Black Sea. This is the first study to report on polybrominated diphenyl ethers (PBDEs) and naturally-produced compounds, methoxylated PBDEs (MeO-PBDEs) and polybrominated hexahydroxanthene derivatives (PBHDs), in tissues (kidney, brain, blubber, liver, muscle) of male harbour porpoises (11 adults, 9 juveniles) from the Black Sea. Lipid-normalized concentrations decreased from muscle>blubber>liver>kidney>brain for the sum of polychlorinated biphenyls (PCBs) and for the sum of PBDEs. Among the naturally-produced compounds, levels of PBHDs were higher than of MeO-PBDEs, with tri-BHD and 6-MeO-BDE 47 being the dominant compounds for both groups, respectively. Concentrations of naturally-produced compounds decreased from blubber to brain, similarly to the sum of DDT and metabolites (DDXs). Concentrations of DDXs were highest, followed by PCBs, HCB, PBHDs, PBDEs and MeO-PBDEs. Levels of PCBs and PBDEs in blubber were lower than concentrations reported for harbour porpoises from the North Sea, while concentrations of DDXs were higher.

Characterizing the in vitro hepatic biotransformation of the flame retardant BDE 99 by common carp

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardant chemicals known to biomagnify in aquatic foodwebs. However, significant biotransformation of some congeners via reductive dehalogenation has been observed during in vivo and in vitro laboratory exposures, particularly in fish models. Little information is available on the enzyme systems responsible for catalyzing this metabolic pathway in fish. This study was undertaken to characterize the biotransformation of one primary BDE congener, 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), using in vitro techniques. Hepatic sub-cellular fractions were first prepared from individual adult common carp (Cyprinus carpio) to examine metabolism in both microsomal and cytosolic sub-cellular fractions. Debromination rates (i.e. BDE-99 biotransformation to BDE-47) were generally higher in the microsomal fraction than in the cytosolic fraction, and some intra-species variability was observed. Further experiments were conducted to determine the biotransformation kinetics and the influence of specific co-factors, inhibitors and competitive substrates on metabolism using pooled carp liver microsomes. The apparent K(m) and V(max) values were 19.4microM and 1120pmolesh(-1)mgprotein(-1), respectively. Iodoacetate (IaC) and the two thyroid hormones, reverse triodothyronine (rT3) and thyroxine (T4), significantly inhibited the debromination of BDE-99 in microsomal sub-cellular fractions with IC(50) values of 2.2microM, 0.83microM, and >1.0microM, respectively. These results support our hypothesis that deiodinase enzymes may be catalyzing the metabolism of PBDEs in fish liver tissues. Further studies are needed to evaluate metabolic activity in other species and tissues that contain these enzymes.

Contaminant pattern and bioaccumulation of legacy and emerging organhalogen pollutants in the aquatic biota from an e-waste recycling region in South China

Legacy pollutants, polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane and its metabolites (DDTs), and some emerging organhalogen pollutants, such as polybrominated diphenyl ethers (PBDEs), hexabromobenzene (HBB), pentabromotoluene (PBT), 2,3,4,5,6-pentabromoethyl benzene (PBEB), 1,2-bis (2,4,6-tribromophenoxy) ethane (BTBPE), and dechlorane plus (DP), were detected in an aquatic food chain (invertebrates and fish) from an e-waste recycling region in South China. Polychlorinated biphenyls, DDTs, PBDEs, and HBB were detected in more than 90% of the samples, with respective concentrations ranging from not detected (ND)-32,000 ng/g lipid weight, ND-850 ng/g lipid weight, 8 to 1,300 ng/g lipid weight, and 0.28 to 240 ng/g lipid weight. Pentabromotoluene, PBEB, BTBPE, and DP were also quantifiable in collected samples with a concentration range of ND-40 ng/g lipid weight. The elevated levels of PCBs and PBDEs in the organisms, compared with those in non-e-waste regions in South China, suggest that these two kinds of pollutants derived mainly from e-waste recycling practices. Hexabromobenzene was significantly correlated with PBDEs, implying that HBB come from the release of e-waste along with PBDEs and/or the pyrolysis of BDE209. Most of the compounds whose trophic magnification factor (TMF) could be calculated were found to biomagnify (TMF > 1). Hexabromobenzene was also found, for the first time, to biomagnify in the present food web, with a TMF of 2.1.

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.

Accumulation and DNA damage in fathead minnows (Pimephales promelas) exposed to 2 brominated flame-retardant mixtures, Firemaster 550 and Firemaster BZ-54

Firemaster 550 and Firemaster BZ-54 are two brominated formulations that are in use as replacements for polybrominated diphenyl ether (PBDE) flame retardants. Two major components of these mixtures are 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB) and 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH). Both have been measured in environmental matrices; however, scant toxicological information exists. The present study aimed to determine if these brominated flame-retardant formulations are bioavailable and adversely affect DNA integrity in fish. Fathead minnows (Pimephales promelas) were orally exposed to either FM 550, FM BZ54, or the nonbrominated form of TBPH, di-(2-ethylhexyl) phthalate (DEHP) for 56 d and depurated (e.g., fed clean food) for 22 d. At several time points, liver and blood cells were collected and assessed for DNA damage. Homogenized fish tissues were extracted and analyzed on day 0 and day 56 to determine the residue of TBB and TBPH and the appearance of any metabolites using gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS). Significant increases (p < 0.05) in DNA strand breaks from liver cells (but not blood cells) were observed during the exposure period compared with controls, although during depuration these levels returned to control. Both parent compounds, TBB and TBPH, were detected in tissues at approximately 1% of daily dosage along with brominated metabolites. The present study provides evidence for accumulation, metabolism, and genotoxicity of these new formulation flame retardants in fish and highlights the potential adverse effects of TBB- and TBPH-formulated fire retardants to aquatic species.

Desorption and bioavailability of spiked pentabromo diphenyl ether and tetrachlorodibenzo(p)dioxin in contaminated sediments

The relationship between desorption kinetics and bioavailability of sediment-associated 2,2',4,4,5' pentabromo diphenyl ether [(14)C] (BDE-99) and 2,3,7,8 tetrachlorodibenzo(p)dioxin [(3)H] (TCDD) was examined in the contaminated sediments. The desorption kinetics were measured in a sediment-water suspension using Tenax extraction, and bioaccumulation was examined by exposing Lumbriculus variegatus (Oligochaeta) to BDE-99 and TCDD spiked sediment in a 14-day kinetic study. Both chemicals had a high affinity to the finest particle size fraction (<20 microm) and the large, very slowly desorbing fraction (58-75%). The biota-sediment accumulation factors ranged between 1.9 and 4.4 for BDE-99 and between 1.4 and 2.8 for TCDD. The chemical outflux from the rapidly desorbing fraction and influx into organisms shows the connection between desorption and bioavailability. Despite this, normalization to the rapidly desorbing fraction was unable to reduce differences in bioavailability estimates between the chemicals. Thus, it is evident that chemical extraction in the mixed system (Tenax tubes) does not fully describe the bioavailable fraction that worms face in stagnant sediments in a similar way for all chemicals. However, when all desorbing domains were included in the calculation, the difference between the chemicals disappears. Desorbing fractions were also able to reduce variability in the biota-sediment accumulation factors between the tested sediments when organic carbon-based sediment chemical concentrations were modified by the desorbing fractions.

Bioaccumulation of polybrominated diphenyl ethers and hexabromocyclododecane in the northwest Atlantic marine food web

Seven species of teleost fishes comprising major prey of northwest Atlantic harbor seals were analyzed for polybrominated diphenyl ethers (PBDEs). PBDE concentrations in whole fish samples (n=87) were compared with those measured previously in harbor seal blubber to evaluate the transfer of PBDEs from prey to predator. Hexabromocyclododecane (HBCD) concentrations were measured in three fish species to provide an initial estimation of HBCD contamination in this ecosystem. HBCD was detected in 87% of the fish samples at concentrations ranging from 2.4 to 38.1 ng/g, lw (overall mean 17.2+/-10.2 ng/g, lw). SigmaPBDE concentrations in fish ranged from 17.9 to 94 ng/g, lw (overall mean 62+/-34 ng/g, lw). SigmaPBDE concentrations in the harbor seals were two orders of magnitude higher than levels in the fish. Biomagnification factors (BMFs) from fish to seals averaged from 17 to 76, indicating that tetra- to hexa-BDEs are highly biomagnified in this marine food web. BDE-47 was the dominant congener in all samples, suggesting exposure to the penta-BDE mixture. The presence of higher brominated congeners including BDE-209 at measurable levels in fish and seal tissue, along with the very high biomagnification of BDE-153, as well as -155, and -154, suggests recent exposure to the octa- and deca-BDE formulations in this US coastal marine food web, as well as the additional contribution of BDE-209 debromination in fish to the loading of persistent PBDEs in the seals. This is the first study to report the occurrence of BDE-209 and other higher BDEs in commercially important marine fishes from the northwest Atlantic.

Uptake and biotransformation of structurally diverse brominated flame retardants in zebrafish (Danio rerio) after dietary exposure

Zebrafish (Danio rerio) were fed a diet containing a mixture of 11 structurally diverse brominated flame retardants (BFRs) at nominal concentrations of either 1 or 100 nmol/g for up to 42 d, followed by an elimination period of 14 d. Uptake rates and elimination constants for five of the BFRs were calculated from measurements of their concentrations in the male fish during the exposure and elimination phases. Observed uptake efficiencies were highest for 2,4,4'-tribromodiphenyl ether (BDE 28) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) and were lowest for decabromodiphenyl ether (BDE 209). Estimated half-lives for TBECH and 2,4,6-tribromophenol were short (<2 d). Four BFR metabolites were identified in the fish: 2,2',3,4',5',6-Hexabromodiphenyl ether (BDE 149), 2,2',4,4',5,6'-hexabromodiphenyl ether (BDE 154), 2,4,6-tribromoanisole, and 1,2,4,5-hexabromobenzene. These metabolites were still present in the zebrafish after the 14-d elimination period. No relationship between the BFR concentrations in the zebrafish and their log octanol-water partition coefficient (Kow) values was found. Generally, low tendencies to bioaccumulate were observed for perbrominated and hydroxylated compounds. The observed accumulation of BFR metabolites in fish, however, shows that low concentration of a BFR does not provide, in isolation, a sound indication that the BFR poses low risks.

Environmental impact of flame retardants (persistence and biodegradability)

Flame-retardants (FR) are a group of anthropogenic environmental contaminants used at relatively high concentrations in many applications. Currently, the largest market group of FRs is the brominated flame retardants (BFRs). Many of the BFRs are considered toxic, persistent and bioaccumulative. Bioremediation of contaminated water, soil and sediments is a possible solution for the problem. However, the main problem with this approach is the lack of knowledge concerning appropriate microorganisms, biochemical pathways and operational conditions facilitating degradation of these chemicals at an acceptable rate. This paper reviews and discusses current knowledge and recent developments related to the environmental fate and impact of FRs in natural systems and in engineered treatment processes.

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

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

Overview of toxicological aspects of polybrominated diphenyl ethers: a flame-retardant additive in several consumer products

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their long half-life and widespread use as flame retardants in several consumer products, including plastics. In addition to other actions, these compounds are characterized as thyroid hormone disruptors. Thyroid hormones affect the function of nearly all tissues via their effects on cellular metabolism and the essential roles they play in differentiation and growth. Interference with thyroid hormone homeostasis by these environmental compounds, therefore, has the potential to impact development and every system in the body. Their presence in human breast milk is particularly troubling due to exposure of nursing children. The last trimester of pregnancy up to 2 years of age corresponds to a time of rapid neurodevelopment and represents a period of vulnerability to environmental insults. Rodent studies indicate that PBDEs may act as developmental neurotoxicants and effects on the reproductive system have been reported as well. Concerns exist regarding possible impacts of exposure, in particular ones which occur during development, on human health. This paper is part of a series of articles regarding contaminants in plastic and provides an overview regarding PBDEs, a class of flame-retardant additives to plastic. PBDEs possess a similar structure to the polychlorinated biphenyls (PCBs) previously used as lubricants in electrical generators and transformers until production was prohibited approximately 25 years ago. Parallels between the two compounds will be briefly made and in particular, as more epidemiological studies on PCBs are available than on PBDEs, a few examples concerning thyroid homeostasis, cognitive function and sexually dimorphic behavior in humans will be mentioned.

Bioavailability and half-life of decabromodiphenyl ether (BDE-209) in rat

1. The absorption of the flame retardant decabromodiphenyl ether (BDE-209) has been shown by its detection in human plasma, but reported experimental data on its determined in rat, and qualitative analyses by GC/MS of metabolites in plasma were performed. The relative amount of phenolic metabolites was determined in a rat plasma sample obtained after administration of radiolabelled BDE-209. 2. The bioavailability of parent BDE-209 was calculated to be about 26% in rat. The concentrations of phenolic radioactivity in plasma 3 and 7 days after dosing were four times higher than those of the neutral compounds, i.e. parent compound, indicating absorption in rat are inconsistent. The bioavailability and half-life were therefore that total absorption was higher than 26%. 3. Thirteen phenolic metabolites were determined in the plasma and the major phenolic metabolites were characterized as a hydroxy-octaBDE, a hydroxy-nonaBDE and a hydroxy-methoxy-hexaBDE (guaiacol-type). The exposure to the phenolic metabolites seemed higher than the parent compound, BDE-209. 4. The initial elimination phase in plasma t1/2alpha for BDE-209 was 2 h, implying a rapid distribution of BDE-209 to well-perfused tissues. The distribution volume at steady state was 1.4 l kg-1, implying a low tendency for distribution to adipose tissue. The terminal t1/2 for BDE-209 in the intravenously dosed rat was calculated as 2.5 days (58 h).

Bioaccumulation behaviour of polybrominated diphenyl ethers (PBDEs) in a Canadian Arctic marine food web

A comparative analysis of the bioaccumulation behaviour of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) was conducted involving simultaneous measurements of PBDE and PCB concentrations in organisms of a Canadian Arctic marine food web. Concentrations of individual PBDE congeners (BDE-28, -47, -99, -153, -154 and -183) in Arctic marine sediments (0.001-0.5 ng.g(-1) dry wt) and biota (0.1-30 ng.g(-1) wet wt) were low compared to those concentrations in biota from urbanized/industrial regions. While recalcitrant PCB congeners exhibited a high degree of biomagnification in this food web, PBDE congeners exhibited negligible biomagnification. Trophic magnification factors (TMFs) of PCBs ranged between 2.9 and 11, while TMFs of PBDEs ranged between 0.7 and 1.6. TMFs of several PBDE congeners (BDE-28, -66, -99, -100, -118, -153 and -154) were not statistically greater than 1, indicating a lack of food web magnification. BDE-47 was the only PBDE with a TMF (i.e. 1.6) statistically greater than 1, hence showing evidence of biomagnification in the food web. However, the TMF of BDE-47 (1.6) was substantially lower than TMFs of recalcitrant Cl(5)-Cl(7) PCBs (TMFs~9-11). Species-specific bioaccumulation factors (BAFs) of PBDEs in homeotherms were much smaller than those for PCBs. This further indicates the low degree or absence of biomagnification of PBDEs compared to PCBs in this food web. The field observations suggest PBDEs exhibit a relatively rapid rate of depuration though biotransformation in Arctic marine organisms, which is consistent with laboratory studies in fish and rats.

Polybrominated diphenyl ethers (PBDEs) in seal populations from eastern and western Canada: an assessment of the processes and factors controlling PBDE distribution in seals

Polybrominated diphenyl ether (PBDE) concentrations were measured in the blubber of five mother-pup pairs of grey seals (Halichoerus grypus) from Sable Island, Nova Scotia (NS) sampled in 1995 and in 20 harbour seals (Phoca vitulina) from British Columbia (BC) sampled in 1991-1992. Concentrations in maternal grey seals from Sable Island averaged 112+/-55.2 ng/g lipid (mean+/-s.d.) and were over twice the concentrations measured in their pups; higher brominated PBDEs showed a distinct decline in PBDEs transfer efficiency in mother-pup pairs as a function of increasing K(o/w). Hepta-BDEs and higher molecular weight (MW) congeners appear not to be transferred efficiently from the grey seals mother to pup during lactation on the basis of lipid/water partitioning (as indicated by ln K(o/w)) and this may be a consequence of molecular size (MW>600 Da) which may limit diffusion and partitioning. PBDE concentrations in blubber from harbour seals from the Strait of Georgia averaged 319+/-132 ng/g lipid (mean+/-s.d., n=13), while those from the more remote and less contaminated Quatsino Sd. averaged 27.8+/-11.8 ng/g (mean+/-s.d., n=7). Tri- to hexa-BDEs were appreciably enriched in Strait of Georgia harbour seals relative to those from Quatsino Sd, suggesting that the former were closer to PBDE sources. The main congeners identified in all samples were BDEs 47, 99, 100, 153 and 154. Data were compared to those in ringed seals sampled from Holman, North West Territories (NWT), in 1996. The Holman samples had a higher proportion of lower bromination congeners, and a lower proportion of higher bromination congeners, than did the Sable Island and BC seal samples, consistent with selection in favour of more volatile compounds during atmospheric transport to the Arctic.

Measurement of polybrominated diphenyl ethers on hand wipes: estimating exposure from hand-to-mouth contact

Estimates of exposure to the flame-retardant polybrominated diphenyl ethers (PBDEs) in dust are very poor due to limited knowledge about dust ingestion. This study was undertaken to determine if PBDEs could be measured on hand wipes, and if so, to determine the distribution of levels present on the skin surface area to provide preliminary exposure estimates from hand-to-mouth contact. Hand wipes were collected from 33 individuals residing in the United States using sterile gauze pads soaked in isopropyl alcohol. The total PBDE residue collected on the wipes ranged from 2.60 to 1982 ng, with a median value of 130 ng, or normalized to hand surface area, a concentration of 135 pg/cm2. The fully brominated congener, BDE 209, was also detected and ranged from < DL to 270 ng with a median value of 26 ng. Congener patterns observed on the wipes were similar to patterns observed in house dust samples, consisting of congeners associated with the PentaBDE and DecaBDE mixtures, suggesting that the source of PBDEs to the hands may be dust particles. However, PBDE hand residues may also be a result of direct contact with PBDE-laden products, leading to adsorption to the skin surface oils. Repeated wipe sampling from three individuals suggests that sigmaPBDE levels on the hand may be relatively consistent for some individuals but not for others. Furthermore, levels of sigmaPBDEs were greater on the bottom of the hands relative to the top of the hands. Using these values we have calculated potential human exposure from hand-to-mouth contact. The median exposure estimates for children and adults are 1380 and 154 ng/day, respectively, whereas the 95th percentile exposure estimates were 6090 and 677 ng/day, respectively. These estimates are greater than dietary intake rates and suggest hand-to-mouth contact may be a key exposure route for PBDEs.

Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality

Concentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition.