Prenatal exposure to organohalogens, including brominated flame retardants, influences motor, cognitive, and behavioral performance at school age

BACKGROUND

Organohalogen compounds (OHCs) are known to have neurotoxic effects on the developing brain.

OBJECTIVE

We investigated the influence of prenatal exposure to OHCs, including brominated flame retardants, on motor, cognitive, and behavioral outcome in healthy children of school age.

METHODS

This study was part of the prospective Groningen infant COMPARE (Comparison of Exposure-Effect Pathways to Improve the Assessment of Human Health Risks of Complex Environmental Mixtures of Organohalogens) study. It included 62 children in whose mothers the following compounds had been determined in the 35th week of pregnancy: 2,2'-bis-(4 chlorophenyl)-1,1'-dichloroethene, pentachlorophenol (PCP), polychlorinated biphenyl congener 153 (PCB-153), 4-hydroxy-2,3,3',4',5-pentachlorobiphenyl (4OH-CB-107), 4OH-CB-146, 4OH-CB-187, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), BDE-99, BDE-100, BDE-153, BDE-154, and hexabromocyclododecane. Thyroid hormones were determined in umbilical cord blood. When the children were 5-6 years of age, we assessed their neuropsychological functioning: motor performance (coordination, fine motor skills), cognition (intelligence, visual perception, visuomotor integration, inhibitory control, verbal memory, and attention), and behavior.

RESULTS

Brominated flame retardants correlated with worse fine manipulative abilities, worse attention, better coordination, better visual perception, and better behavior. Chlorinated OHCs correlated with less choreiform dyskinesia. Hydroxylated polychlorinated biphenyls correlated with worse fine manipulative abilities, better attention, and better visual perception. The wood protective agent (PCP) correlated with worse coordination, less sensory integrity, worse attention, and worse visuomotor integration.

CONCLUSIONS

Our results demonstrate for the first time that transplacental transfer of polybrominated flame retardants is associated with the development of children at school age. Because of the widespread use of these compounds, especially in the United States, where concentrations in the environment are four times higher than in Europe, these results cause serious concern.

Proteomic studies in zebrafish liver cells exposed to the brominated flame retardants HBCD and TBBPA

Proteomic effect screening in zebrafish liver cells was performed to generate hypotheses regarding single and mixed exposure to the BFRs HBCD and TBBPA. Responses at sublethal exposure were analysed by two-dimensional gel electrophoresis followed by MALDI-TOF and FT-ICR protein identification. Mixing of HBCD and TBBPA at sublethal doses of individual substances seemed to increase toxicity. Proteomic analyses revealed distinct exposure-specific and overlapping responses suggesting novel mechanisms with regard to HBCD and TBBPA exposure. While distinct HBCD responses were related to decreased protein metabolism, TBBPA revealed effects related to protein folding and NADPH production. Overlapping responses suggest increased gluconeogenesis (GAPDH and aldolase) while distinct mixture effects suggest a pronounced NADPH production and changes in proteins related to cell cycle control (prohibitin and crk-like oncogene). We conclude that mixtures containing HBCD and TBBPA may result in unexpected effects highlighting proteomics as a sensitive tool for detecting and hypothesis generation of mixture effects.

A cohort study of the association between secondary sex ratio and parental exposure to polybrominated biphenyl (PBB) and polychlorinated biphenyl (PCB)

BACKGROUND

Polybrominated biphenyl (PBB), a brominated flame retardant, was accidently mixed into animal feed in Michigan (1973-1974) resulting in human exposure through consumption of contaminated meat, milk and eggs. Beginning in 1976 individuals who consumed contaminated products were enrolled in the Michigan Long-Term PBB Study. This cohort presents a unique opportunity to study the association between parental exposures to PBB and offspring sex ratio.

METHODS

We identified offspring of female PBB cohort participants (born 1975-1988) and obtained electronic birth records for those born in the state of Michigan. We linked this information to parental serum PBB and PCB concentrations collected at enrollment into the cohort. We modeled the odds of a male birth with generalized estimating equations accounting for the non-independence of siblings born to the same parents. We explored potential confounders: parental age and education at offspring's birth, parental body mass index at cohort enrollment, birth order, gestational age and year of offspring's birth.

RESULTS

The overall proportion of male offspring among 865 live births to cohort mothers was 0.542. This was higher than the national male proportion of 0.514 (binomial test: p = 0.10). When both parents were in the cohort (n = 300), we found increased odds of a male birth with combined parents' enrollment PBB exposure > or = the median concentrations (3 microg/L for mothers; 6 microg/L for fathers) compared to combined parents' PBB exposure < the median concentrations (AOR = 1.43, 95% CI: 0.89-2.29), although this did not reach statistical significance. In addition, there was a suggestion of increased odds of a male birth for combined parents' enrollment PCB exposure > or = the median concentrations (6 microg/L for mothers; 8 microg/L for fathers) compared to combined parents' enrollment PCB exposure < the median concentrations (AOR = 1.53, 95% CI: 0.93-2.52).

CONCLUSION

This study adds to the body of literature on secondary sex ratio and exposure to environmental contaminants. In this population, combined parental exposure to PBBs or PCBs increased the odds of a male birth. Further research is needed to corroborate these findings and shed light on the biological mechanisms by which these types of chemicals may influence the secondary sex ratio.

The hydroxyl radical generation and oxidative stress for the earthworm Eisenia fetida exposed to tetrabromobisphenol A

Biochemical effects of tetrabromobisphenol A (TBBPA) on the earthworm Eisenia fetida, including superoxide dismutase, catalase, glutathione-S-transferase, reduced glutathione, oxidized glutathione, GSH/GSSG ratio and malondialdehyde (MDA) level, were measured to assess ecological toxicity of TBBPA. With OECD standard filter-paper contact test method, earthworms were exposed to TBBPA of a range of concentrations (0.00, 0.01, 0.05, 0.1, 0.5 and 1.0 mg L(-1)). According to the electron paramagnetic resonance spectrum, reactive oxygen species (ROS) generated in the earthworm was identified as the hydroxyl radical ((*)OH) which was significantly induced at all TBBPA concentrations. With the increasing of TBBPA concentration, the antioxidant enzymes, glutathione and MDA levels varied significantly. The results showed that TBBPA exerts its toxic effects on E. fetida by inducing the generation of ROS and resulting in oxidative damage. The results show that the (*)OH production leads to oxidative stress in the tissues of the earthworm E. fetida.

Assessing the toxicity of TBBPA and HBCD by zebrafish embryo toxicity assay and biomarker analysis

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are two of the most widely used brominated flame retardants (BFRs). The biological toxicity effect of TBBPA and HBCD was studied by means of zebrafish embryo toxicity assays in combination with three biomarkers, including superoxide dismutase (SOD), lipid peroxidation, (LPO), and heat shock protein (Hsp70). The standard zebrafish embryo assay showed that high concentrations of TBBPA (> or =0.75 mg/L) can cause lethality or malformation. For HBCD within the concentration range (0.002-10 mg/L), no endpoint was observed. Furthermore, SOD activities of zebrafish embryos exposed to TBBPA were increased with the increasing concentrations. SOD activities in the group treated by HBCD showed an increase followed by a decline. Regardless of TBBPA or HBCD, LPO were increased along with the increase of the concentration. The change pattern of Hsp70 levels was the same with LPO. All these results showed that TBBPA and HBCD could cause oxidative stress and Hsp70 overexpression, inducing acute toxicity to zebrafish embryo in a short-term exposure. The study also indicates that the zebrafish embryo assay in combination with the biomarkers is effective in aquatic environmental toxicology and risk assessment.

Nephrotoxic potential and toxicokinetics of tetrabromobisphenol A in rat for risk assessment

Tetrabromobisphenol A (TBBPA), one of the most widely used global brominated flame retardants, is used to improve fire safety of laminates in electrical and electronic equipment. To investigate the nephrotoxic potential of TBBPA and its toxicokinetic profile in rats, single-dose and daily 14-d repeated-dose toxicity studies at 200, 500, or 1000 mg/kg were performed. Several biochemical parameters were analyzed to evaluate nephrotoxicity of TBBPA. High-dose 1000 mg/kg TBBPA significantly elevated renal thiobarbituric acid-reactive substance (TBARS) levels, and superoxide dismutase (SOD) activity was increased at all 3 doses administered. This was associated with no change in the activity of catalase (CAT). Our results suggest that acute 1-d high-dose administration of TBBPA produced transient renal changes at 5 h. Subsequently, TBBPA in serum, urine, and kidney was determined by liquid chromatography-mass spectroscopy (LC/MS). Toxicokinetic studies indicated that TBBPA shows relatively a short half-life (7-9 h) and was eliminated almost completely in feces by 2 d. Based on the results from the 14-d repeated-dose study, TBBPA did not accumulate in the rat, and was eliminated in feces. The present results suggested that TBBPA may not be toxic to kidney, as the chemical is not bioavailable and is not present in renal tissue.

Molecular targets of TBBPA in zebrafish analysed through integration of genomic and proteomic approaches

Tetrabromobisphenol-A (TBBPA) is nowadays one of the most frequently used brominated flame retardants (BFRs) and can be considered as a high production volume chemical. Over the last decade, numerous reports of increasing concentrations of BFRs in the environment and humans have been published. However, the toxicological knowledge on TBBPA, and more specifically its molecular mode of action, is rather fragmentary. In this study two populations of adult zebrafish (Danio rerio) were exposed for 14 days to 0.75 microM and 1.5 microM TBBPA. Subsequently, we employed a combined transcriptomic and proteomic approach to evaluate the molecular effects of TBBPA in zebrafish liver. Oligonucleotide microarrays were used to study the effects on gene expression levels. These results were validated through real-time PCR. The proteome of the liver was analysed by means of differential in-gel electrophoresis (DiGE), an innovative application of traditional 2D-PAGE. Combination of the extracted datasets allowed reassembling of individual molecular responses into a comprehensive overview of affected molecular pathways. Interpretation of the results depicted an interference of thyroid and Vitamin A homeostasis in the exposed zebrafish, TBBPA also elicited responses indicating onset of oxidative stress and general stress responses. Additionally, numerous differentially expressed transcripts could be associated with defence mechanisms or corresponded to metabolizing enzymes. Furthermore, cellular metabolism was clearly affected, illustrated as disturbance of e.g. lipid, carbohydrate, and organic acid metabolic processes. Summarizing, these results enabled us to hypothesize several working mechanisms of TBBPA and demonstrated the potential of a combined genome and proteome approach to generate detailed mechanistic toxicological information.

Effects of tetrabromobisphenol A as an emerging pollutant on wheat (Triticum aestivum) at biochemical levels

Biochemical responses of wheat (Triticum aestivum) to the stress of tetrabromobisphenol A (TBBPA) as an emerging pollutant were examined. The results indicated that reduction of the chlorophyll (CHL) content in wheat leaves could be observed. However, the changes in the CHL content with the increasing TBBPA concentration from 50 to 5000 mg kg(-1) were insignificant (p>0.05). Increased malondialdehyde levels were detected in wheat leaves after both 7-d and 12-d exposures. The changes in the activity of superoxide dismutases (SOD), peroxidases (POD) and catalases (CAT) in wheat leaves irregularly fluctuated with time as the TBBPA concentration increased. However, significant (p<0.05) decrease in the activity of POD and CAT treated with 500 and 5000 mg kg(-1) TBBPA could be observed. Our data also showed that the plant has the capacity to tolerate the oxidative stress, but the capacity would be lost with prolonged exposure and increasing TBBPA concentration. There were no dose-response effects in the changes between the activity of antioxidant enzymes (SOD, POD and CAT) and the concentration of TBBPA. The decrease in the activity of POD and CAT could be considered as good biomarkers of serious stress by TBBPA in soil environment.

Hormone disruption by PBDEs in adult male sport fish consumers

BACKGROUND

Persistent pollutants, such as polychlorinated biphenyls (PCBs), affect endocrine function. Human exposure to polybrominated diphenyl ethers (PBDEs), which are similar in structure to PCBs, has increased recently, but health effects have not been well studied.

OBJECTIVES

Our goal in this study was to determine whether PBDE body burdens are related to thyroid and steroid hormone levels, thyroid antibodies, and thyroid disease in a cohort of frequent and infrequent adult male sport fish consumers.

METHODS

We tested serum from 405 adult males for PBDE congeners, PCB congeners, testosterone, sex-hormone-binding globulin (SHBG), SHBG-bound testosterone, thyroglobulin antibodies, and the thyroid hormones thyroxine (T(4)), triiodothyronine (T(3)), thyroid-stimulating hormone (TSH), and T(4)-binding globulin (TBG). We collected data on demographics, fish consumption, medical diseases, and medication use.

RESULTS

The median sum of PBDEs was 38 ng/g lipid. In 308 men without thyroid disease or diabetes, PBDEs were positively related to measures of T(4) and reverse T(3) and inversely related to total T(3) and TSH. PBDEs were positively related to the percentage of T(4) bound to albumin, and inversely related to the percentage of T(4) bound to TBG. Associations of BDE congeners with hormones varied. BDE-47 was positively associated with testosterone levels. Participants with PBDEs over the 95th percentile were more likely to have thyroglobulin antibodies, although high PBDE exposure was not associated with thyroid disease. PBDE effects were independent of PCB exposure and sport fish consumption.

CONCLUSIONS

PBDE exposure, at levels comparable with those of the general U.S. population, was associated with increased thyroglobulin antibodies and increased T(4) in adult males.

Critical factors in assessing exposure to PBDEs via house dust

Assessment of indoor exposure to polybrominated diphenyl ethers (PBDEs) requires a critical examination of methods that may influence exposure estimates and comparisons between studies. We measured PBDEs in residential dust collected from 20 homes in Boston, MA, to examine 5 key questions: 1) Does the choice of dust exposure metric-e.g., concentration (ng/g) or dust loading (ng/m2)-affect analysis and results? 2) To what degree do dust concentrations change over time? 3) Do dust concentrations vary between rooms? 4) Is the home vacuum bag an acceptable surrogate for researcher-collected dust? 5) Are air and dust concentrations correlated for the same room? We used linear mixed-effects models to analyze the data while accounting for within-home and within-room correlations. We found that PBDE dust concentration and surface loading were highly correlated (r=0.86-0.95, p<0.001). Average dust concentrations did not significantly differ over an 8-month period, possibly because home furnishings changed little over this time. We observed significant differences between rooms in the same home: PBDE concentrations in the main living area were 97% higher than the bedroom for decaBDE (p=0.02) and 72% higher for pentaBDE (p=0.05). Home vacuum bag dust concentrations were significantly lower than researcher-collected dust and not strongly correlated. Air (vapor and particulate phase) and dust concentrations were correlated for pentaBDE (p=0.62, p<0.01), but not for decaBDE (p=0.25). In addition, potential markers of BDE 209 debromination (BDE 202 and the BDE197:BDE201 ratio) were also observed in household dust samples. One vacuum bag sample contained the highest concentrations of BDE 209 (527,000 ng/g) and total PBDEs (544,000 ng/g) that have been reported in house dust.

Birth delivery mode modifies the associations between prenatal polychlorinated biphenyl (PCB) and polybrominated diphenyl ether (PBDE) and neonatal thyroid hormone levels

BACKGROUND

Developing infants may be especially sensitive to hormone disruption from chemicals including polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs).

OBJECTIVE

We investigated relationships between cord serum levels of PCBs and PBDEs and thyroid hormones measured in cord blood serum and neonatal blood spots.

METHODS

We measured PCBs and PBDEs, thyrotropin (TSH), thyroxine (T4) and free T4 (FT4) in cord blood serum from 297 infants who were delivered at the Johns Hopkins Hospital in 2004-2005. We abstracted results of total T4 (TT4) measured in blood spots collected in the hospital and at neonatal visits. We used delivery mode (augmented vaginal deliveries and nonelective cesarean deliveries) as a surrogate for intrapartum stress, which is known to alter cord blood thyroid hormones.

RESULTS

In the full study population, no compounds were associated with a change in average TSH, FT4, or TT4. BDE-100 was associated with increased odds of low cord TT4, BDE-153 with increased odds of low cord TT4 and FT4, and no compounds were associated with increased odds of high TSH. For infants born by spontaneous, vaginal, unassisted deliveries, PCBs were associated with lower cord TT4 and FT4 and lower TT4 measured in neonatal blood spots. PBDEs showed consistent but mainly nonsignificant negative associations with TT4 and FT4 measurements.

CONCLUSIONS

Prenatal PCB and PBDE exposures were associated with reduced TT4 and FT4 levels among infants born by spontaneous, unassisted vaginal delivery. Intrapartum stress associated with delivery mode may mask hormonal effects of PCBs and PBDEs.

Comparison of toxicity of congener-153 of PCB, PBB, and PBDE to Daphnia magna

Acute and reproductive toxicity tests were performed to assess the effects of two polybrominated flame retardants, polybrominated biphenyl (PBB)-153, polybrominated diphenyl ether (PBDE)-153, and polychlorinated biphenyl (PCB)-153 on Daphnia magna. According to the 24-h acute toxicity test, up to concentration of 210 microg/L, these chemicals were not toxic to Daphnia. In the reproductive tests, we used concentrations of 12.5, 25, 50, and 100 microg/L. At the concentrations of 50 and 100 microg/L, the Daphnia started to die after the second test day, and there were no Daphnia alive on the fourth test day. The testing was continued using the concentrations of 12.5 and 25 microg/L. The reproductive tests were then repeated using only concentrations of 12.5 and 25 microg/L. The results, based on the weight per volume (w/v) concentrations, showed that of the three compounds we tested PCB-153 had the most severe effects on the Daphnia reproduction. PBDE-153 was the least toxic, although in this group, too, offspring production was significantly lower and mortality significantly higher than those in the control group. Also, it was observed that PCB-153 accumulated into the parent Daphnia nearly three times more actively than the two other chemicals we tested. These chemicals, although having very similar structures, seem to affect differently the reproduction of Daphnia. They also seem to accumulate differently into Daphnia. Thus, further research data are needed to understand the mechanisms responsible for the effects caused by these kinds of chemicals and to assess their risks accurately.

Hydroxylated metabolites of the polybrominated diphenyl ether mixture DE-71 are weak estrogen receptor-alpha ligands

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are widely found in the environment and are suspected endocrine disruptors. We previously identified six hydroxylated metabolites of PBDE (OH-PBDEs) in treated mice.

OBJECTIVE

We tested the hypothesis that OH-PBDEs would interact with and alter activity of estrogen receptor-alpha (ER-alpha).

METHODS

We tested estrogenicity using two assays: 3H-estradiol (3H-E2) displacement from recombinant ER-alpha and induction of reporter gene (ERE-luciferase) in cultured cells. We incubated the PBDE mixture DE-71 with rat liver microsomes and tested the resultant metabolite mixture for estrogenic activity. We also determined relative estrogenic potential of individual hydroxylated PBDE congeners.

RESULTS

Reporter gene activity was increased by DE-71 that had been subjected to microsomal metabolism. DE-71 did not displace E2 from ER-alpha, but all six of the OH-PBDE metabolites did. para-Hydroxylated metabolites displayed a 10- to 30-fold higher affinity for ER-alpha compared with ortho-hydroxylated PBDEs, and one produced a maximal effect 30% higher than that produced by E2. Coadministration of E2 and DE-71, or certain of its metabolites, yielded reporter activity greater than either chemical alone. Two ortho-OH-PBDEs were antiestrogenic in the reporter assay.

CONCLUSIONS

The observations--that the DE-71 mixture did not displace 3H-E2 from ER-alpha while the hydroxylated metabolites did-suggest that the weak estrogenic effects of DE-71 are due to metabolic activation of individual congeners. However, the behavior of DE-71 and its metabolites, when co-administered with E2, suggest a secondary, undetermined mechanism from classical ER-alpha activation.

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.

New insights into the endocrine disrupting effects of brominated flame retardants

The objective of this review is to provide an overview of recent studies demonstrating the endocrine disrupting (ED) effects of brominated flame retardants (BFRs), while highlighting interesting data presented at the recent international BFR workshop in Amsterdam in April, 2007. A review written in 2002 was used as a starting point and about 60 publications published since 2003 were reviewed. New insights into the in vivo effects of BFRs on thyroid hormone, estrogen and androgen pathways in both mammalian and non-mammalian models are provided, and novel (in vitro) findings on the mechanisms underlying ED effects are highlighted. Special attention is also given to reports on neurotoxicological effects at relatively low doses of BFRs, although an endocrine-related mechanism is disputable. Convincing evidence has been published showing that BFRs and importantly, BFR metabolites, have the potential to disrupt endocrine systems at multiple target sites. While some studies suggest a wide margin of safety between effect concentrations in rodent models and levels encountered in humans and the environment, other studies demonstrate that exposure to low doses relevant for humans and wildlife at critical time points in development can result in profound effects on both endocrine pathways and (neuro)development.

Assessment of polybrominated diphenyl ether exposures and health risks associated with consumption of southern Mississippi catfish

Despite the growing public interest in polybrominated diphenyl ethers (PBDEs), there are relatively few studies in the published literature which characterize and quantify human intake of these compounds. In this study, PBDE concentrations were measured in southern Mississippi catfish to determine background levels, daily intake, and risk associated with the consumption of these chemicals from a primary food source for residents in this region of the United States. A total of 33 wild catfish samples were collected from five sites, and 28 farm-raised catfish samples were purchased, all of which were from locations in southern Mississippi. All samples were analyzed for 43 PBDEs (mono- through deca-congeners) using high-resolution gas chromatography-mass spectrometry. Both PBDE concentrations (sigmaPBDE ranged from 0.3 to 23.3 ng/g wet weight) and congener profiles varied by fish type and location; however, BDE congeners 47, 99, 100, 153, and 154 were the dominant contributors in all samples. The estimated daily intake of PBDEs associated with consumption of the catfish ranged from 0.03 to 1.80 ng/kg-day. Evaluation of the cancer risk for BDE 209 and the noncancer hazard for BDE congeners 47, 99, 153, and 209 indicated that health risks/hazards due to fish consumption in adults are substantially lower than risk levels generally considered to be at the U.S. EPA minimum concern level.

Global contamination of coplanar polybrominated/chlorinated biphenyls (Co-PXBs) in the market fishes from Japan

Polybrominated chlorinated biphenyls (PXBs, X=Br, Cl) are a group of environmental contaminants that have not been studied previously. The introduction of the second halogen to the biphenyl backbone increases the number of possible congeners to more than 9000. Only a limited number of PXBs are commercially available. In order to determine the occurrence of these compounds in environmental matrices, an isotope dilution HRGC/HRMS method for determination of five co-planar polybrominated/chlorinated biphenyls (Co-PXBs) in biota was developed. The method detection limit for these compounds ranged between 0.05 and 0.5 pg/g for 4'-monobromo-3,3',4,5-tetrachlorobiphenyl and 3',4',5'-tribromo-3,4-dichlorobiphenyl, respectively. Concentrations of five co-planar polybrominated and chlorinated biphenyls in eighteen different fish fillets from Japanese markets ranged between 4 and 46 pg/g wet weight for mink whale and young yellow-tail fish. These values are substantially lower than those reported for Co-PCBs; however, it should be noted that due to the unavailability of standards, identification and quantification of all the isomers was not possible.

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in 0+ juvenile cyprinids and sediments of the Po River

PBDE and PCB content has been determined in 0+ bleak (Cyprinus alburnus), nase (Chondrostoma soetta), gudgeon (Cyprinus gobio), chub (Cyprinus cephalus), and barbel (Barbus sp.) as well as in bed sediments sampled from the River Po upstream and downstream of the confluence of a tributary draining a highly industrialized and urbanized subbasin. Both groups of chemicals were present at higher levels in fish and sediments downstream from the confluence. In addition, whole-body concentrations of PBDEs and PCBs were different among species despite the young specimen age. The fact that PBDEs and PCBs were higher in benthivorous versus planktivorous fish, as well as in carnivorous versus herbivorous species, suggests that feeding behavior is a major controlling factor that may help differentiate the accumulation levels of 0+ juveniles. Of the five species, the pelagic/planktivorous cyprinid bleak (C. alburnus) showed the lowest concentrations (111 ng PBDE/g lipid weight [l.w.], 2016 ng PCB/g l.w.), whereas the benthic dweller and feeder barbel (Barbus sp.) had the highest concentrations of both groups of chemicals (259 ng PBDE/g l.w., 4785 ng PCB/g l.w.). The rank order of species contamination was essentially stable upstream and downstream from the tributary, and the congener contribution of PBDEs was also similar. In general, BDE-47 was the dominant congener, followed by BDE-100, -154, -153, and -28. BDE-209 dominated the PBDE congener profiles of sediments but was not found in any fish sample. Conversely, an unidentified hexa-BDE congener, which was not detected in sediments, was found in all fish species. The levels of PBDEs and PCBs determined in adult goby (Padogobius martensii), a small demersal predator also examined in the same river stretches, provided additional useful insights with which to interpret results.

Microbial O-methylation of the flame retardant tetrabromobisphenol-A

We demonstrated the O-methylation of tetrabromobisphenol-A (TBBPA) [4,4'-isopropylidenebis (2,6-dibromophenol)] to its mono- and dimethyl ether derivatives by microorganisms present in different sediments. A most probable number assay of a marsh sediment suggested that up to 10% of the total aerobic heterotrophs may be capable of O-methylation. Although TBBPA dimethyl ether is not produced in industry, it has been detected in terrestrial and aquatic sediments. Our study supports the hypothesis that TBBPA dimethyl ether is a product of microbial O-methylation. The O-methylation of TBBPA, as well as its analog, tetrachlorobisphenol-A (TCBPA), was also demonstrated in cultures of two chlorophenol-metabolizing bacteria, Mycobacterium fortuitum CG-2 and Mycobacterium chlorophenolicum PCP-1. These strains also mediated the O-methylation of 2,6-dibromophenol and 2,6-dichlorophenol, analogs of TBBPA and TCBPA, to their corresponding anisoles, but 2,6-fluorophenol was not transformed. Due to the addition of hydrophobic methyl groups, O-methylated derivatives are more lipophilic, increasing the probability of bioaccumulation in the food chain. Future research regarding the toxicological effects of the O-methylated derivatives of TBBPA is recommended and will further elucidate potential risks to environmental and human health.

The case of Deborah Rice: who is the Environmental Protection Agency protecting?

Why did the EPA dismiss a highly respected neurotoxicologist as chair of its external review panel on the fire retardant deca? Pioneering lead researcher Herbert Needleman, MD, argues that the answer has little to do with science.

Comparative oxygen radical formation and toxicity of BDE 47 in rainbow trout cell lines

The polybrominated diphenyl ethers (PBDEs) constitute a class of flame retardants whose residues have markedly increased in fish and human tissues during the last decade. In particular, the levels of certain PBDE congeners in salmon have raised concern regarding potential risks associated with dietary PBDE exposures. However, little is known regarding PBDE-mediated cell injury in relevant in vitro cell models. We conducted a comparative study of oxyradical production and cell injury in rainbow trout gill (RTgill-W1) and trout liver cells (RTL-W1) exposed to 2,2',4,4'-tetrabromodiphenyl ether (BDE 47), a predominant BDE residue found in fish tissues such as salmonids. Exposure to low micromolar concentrations of BDE 47 elicited a significant loss in RTgill-W1 and RTL-W1 cell viability as measured by alamarBlue assay. The dose-response of BDE toxicity differed among the two cell lines, with the RTL-W1 liver cells showing greater resistance to toxicity at lower BDE 47 doses, but a more dramatic loss of viability relative to gill cells when challenged with higher (50 microM) doses. The sensitivity of the trout liver cells at higher BDE 47 exposures was reflected by a higher basal production of oxygen radical production by 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence that was markedly enhanced in the presence of BDE 47, suggesting an overwhelming of trout liver cell antioxidant defense pathways. Collectively, our data indicate that RTgill-W1 and RTL-W1 liver cells are sensitive to BDE 47-mediated cell injury through a mechanism that may involve oxidative stress. Our data also provide an in vitro basis for potential tissue differences in BDE 47-mediated cell injury.

Effect of parental exposure to trenbolone and the brominated flame retardant BDE-47 on fertility in rainbow trout (Oncorhynchus mykiss)

We exposed sexually maturing male rainbow trout (Oncorhynchus mykiss) to BDE-47 (a polybrominated diphenyl ether) and female rainbow trout to trenbolone (an anabolic steroid). Male trout were orally exposed for 17 days to 55 microg/kg/day BDE-47 and female trout continuously exposed for 60-77 days to a measured trenbolone water concentration of 35 ng/L. After the exposure, eggs and semen were collected and in vitro fertilization trials performed using a sperm:egg ratio of 300,000:1. In the BDE-47 study, eggs from control females were fertilized with semen from exposed males, while in the trenbolone study, eggs from exposed females were fertilized with semen from control males. All treatments were evaluated at two-three early developmental time-points representing first cleavage (0.5 day), embryonic keel (9 days), and eyed stages (19 days), respectively. The results indicated that BDE-47 exposure did not alter fertility as embryonic survival was similar between control and exposed groups. Trenbolone exposure also did not alter embryo survival. However, in the embryos fertilized with eggs from trenbolone exposed females, a noticeable delay in developmental progress was observed. On day 19 when eye development is normally complete, the majority of the embryos either lacked eyes or displayed under-developed eyes, in contrast to control embryos. This finding suggests steroidal androgen exposure in sexually maturing female rainbow trout can impact developmental timing of F1 offspring.