Neurobehavioral function and low-level exposure to brominated flame retardants in adolescents: a cross-sectional study

Two novel in vitro assays to screen chemicals for their capacity to inhibit thyroid hormone transmembrane transporter proteins OATP1C1 and OAT4

Early brain development depends on adequate transport of thyroid hormones (THs) from the maternal circulation to the fetus. To reach the fetal brain, THs have to cross several physiological barriers, including the placenta, blood-brain-barrier and blood-cerebrospinal fluid-barrier. Transport across these barriers is facilitated by thyroid hormone transmembrane transporters (THTMTs). Some endocrine disrupting chemicals (EDCs) can interfere with the transport of THs by THTMTs. To screen chemicals for their capacity to disrupt THTMT facilitated TH transport, in vitro screening assays are required. In this study, we developed assays for two THTMTs, organic anion transporter polypeptide 1C1 (OATP1C1) and organic anion transporter 4 (OAT4), both known to play a role in the transport of THs across barriers. We used overexpressing cell models for both OATP1C1 and OAT4, which showed an increased uptake of radiolabeled T4 compared to control cell lines. Using these models, we screened various reference and environmental chemicals for their ability to inhibit T4 uptake by OATP1C1 and OAT4. Tetrabromobisphenol A (TBBPA) was identified as an OATP1C1 inhibitor, more potent than any of the reference chemicals tested. Additionally perfluorooctanesulfonic acid (PFOS), perfluoroctanic acid (PFOA), pentachlorophenol and quercetin were identified as OATP1C1 inhibitors in a similar range of potency to the reference chemicals tested. Bromosulfophthalein, TBBPA, PFOA and PFOS were identified as potent OAT4 inhibitors. These results demonstrate that EDCs commonly found in our environment can disrupt TH transport by THTMTs, and contribute to the identification of molecular mechanisms underlying TH system disruption chemicals.

Association between brominated flame retardants and risk of endocrine-related cancer: A systematic review and meta-analysis

BACKGROUND

The incidence of endocrine-related cancer, which includes tumors in major endocrine glands such as the breast, thyroid, pituitary, and prostate, has been increasing year by year. Various studies have indicated that brominated flame retardants (BFRs) are neurotoxic, endocrine-toxic, reproductive-toxic, and even carcinogenic. However, the epidemiological relationship between BFR exposure and endocrine-related cancer risk remains unclear.

METHODS

We searched the PubMed, Google Scholar, and Web of Science databases for articles evaluating the association between BFR exposure and endocrine-related cancer risk. The odds ratio (OR) and its corresponding 95% confidence interval (95% CI) were used to assess the association. Statistical heterogeneity among studies was assessed with the Q-test and I2 statistics. Begg's test was performed to evaluate the publication bias.

RESULTS

We collected 15 studies, including 6 nested case-control and 9 case-control studies, with 3468 cases and 4187 controls. These studies assessed the risk of breast cancer, thyroid cancer, and endocrine-related cancers in relation to BFR levels. Our findings indicate a significant association between BFR exposure in adipose tissue and an increased risk of breast cancer. However, this association was not observed for thyroid cancer. Generally, BFR exposure appears to elevate the risk of endocrine-related cancers, with a notable increase in risk linked to higher levels of BDE-28, a specific polybrominated diphenyl ether congener.

CONCLUSIONS

In conclusion, although this meta-analysis has several limitations, our results suggest that BFR exposure is a significant risk factor for breast cancer, and low-brominated BDE-28 exposure could significantly increase the risk of endocrine-related cancers. Further research is essential to clarify the potential causal relationships between BFRs and endocrine-related cancers, and their carcinogenic mechanisms.

Prenatal exposure to mixtures of per- and polyfluoroalkyl substances and organochlorines affects cognition in adolescence independent of postnatal exposure

BACKGROUND

Studies on cognitive and neurodevelopmental outcomes have shown inconsistent results regarding the association with prenatal exposure to perfluoroalkyl substance (PFAS) and organochlorines. Assessment of mixture effects of correlated chemical exposures that persist in later life may contribute to the unbiased evaluation and understanding of dose-response associations in real-life exposures.

METHODS

For a subset of the 4th Flemish Environment and Health Study (FLEHS), concentrations of four PFAS and six organochlorines were measured in respectively 99 and 153-160 cord plasma samples and 15 years later in adolescents' peripheral serum by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Sustained and selective attention were measured at 14-15 years with the Continuous Performance Test (CPT) and Stroop Test as indicators of potential neurodevelopmental deficits. Quantile g-computation was applied to assess the joint associations between prenatal exposure to separate and combined groups of PFAS and organochlorines and performance in the CPT and Stroop Test at adolescence. Subsequently, individual effects of each chemical compound were analyzed in mixed effects models with two sets of covariates. Analytical data at birth and at the time of cognitive assessment allowed for off-setting postnatal exposure.

RESULTS

In mixtures analysis, a simultaneous one-quantile increase in the natural log-transformed values of PFAS and organochlorines combined was associated with a decrease in the mean reaction time (RT) and the reaction time variability (RTV) in the CPT (β = -15.54, 95% CI:-29.64, -1.45, and β = -7.82, 95% CI: -14.97, -0.67 respectively) and for the mixture of PFAS alone with RT (β = -11.94, 95% CI: -23.29, -0.60). In the single pollutant models, these results were confirmed for the association between perfluorohexanesulfonate (PFHxS) with RT (β = -17.95, 95% CI = -33.35, -2.69) and hexachlorobenzene with RTV in the CPT (β = -5.78, 95% CI: -10.39, -0.76). Furthermore, the participants with prenatal exposure above the limit of quantification for perfluorononanoic acid (PFNA) had a significantly shorter RT and RTV in the CPT (β = -23.38, 95% CI: -41.55, -5.94, and β = -9.54, 95% CI: -19.75, -0.43, respectively).

CONCLUSION

Higher prenatal exposure to a PFAS mixture and a mixture of PFAS and organochlorines combined was associated with better sustained and selective attention during adolescence. The associations seemed to be driven by PFHxS and were not linked to exposure levels at the time of assessment.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

Short-term tetrabromobisphenol A exposure promotes fibrosis of human uterine fibroid cells in a 3D culture system through TGF-beta signaling

Tetrabromobisphenol A (TBBPA), a derivative of BPA, is a ubiquitous environmental contaminant with weak estrogenic properties. In women, uterine fibroids are highly prevalent estrogen‐responsive tumors often with excessive accumulation of extracellular matrix (ECM) and may be the target of environmental estrogens. We have found that BPA has profibrotic effects in vitro, in addition to previous reports of the in vivo fibrotic effects of BPA in mouse uterus. However, the role of TBBPA in fibrosis is unclear. To investigate the effects of TBBPA on uterine fibrosis, we developed a 3D human uterine leiomyoma (ht‐UtLM) spheroid culture model. Cell proliferation was evaluated in 3D ht‐UtLM spheroids following TBBPA (10⁻⁶–200 µM) administration at 48 h. Fibrosis was assessed using a Masson's Trichrome stain and light microscopy at 7 days of TBBPA (10⁻³ µM) treatment. Differential expression of ECM and fibrosis genes were determined using RT² Profiler™ PCR arrays. Network and pathway analyses were conducted using Ingenuity Pathway Analysis. The activation of pathway proteins was analyzed by a transforming growth factor‐beta (TGFB) protein array. We found that TBBPA increased cell proliferation and promoted fibrosis in 3D ht‐UtLM spheroids with increased deposition of collagens. TBBPA upregulated the expression of profibrotic genes and corresponding proteins associated with the TGFB pathway. TBBPA activated TGFB signaling through phosphorylation of TGFBR1 and downstream effectors—small mothers against decapentaplegic ‐2 and ‐3 proteins (SMAD2 and SMAD3). The 3D ht‐UtLM spheroid model is an effective system for studying environmental agents on human uterine fibrosis. TBBPA can promote fibrosis in uterine fibroid through TGFB/SMAD signaling.

Gestational exposure to polybrominated diphenyl ethers and social skills and problem behaviors in adolescents: The HOME study

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are persistent environmental pollutants used as flame retardants. Gestational PBDE exposure has been associated with a variety of behavior problems in children, but little is known about its impact into adolescence, particularly on social skills, which are important for achieving social competence, establishing identity, and forming lasting relationships.

OBJECTIVE

We investigated associations between gestational exposure to PBDEs and social skills and problem behaviors in early adolescence in a longitudinal pregnancy and birth cohort in Cincinnati, Ohio (recruited 2003-2006).

METHODS

We measured maternal serum concentrations of five PBDE congeners during gestation. At age 12, we measured social skills and problem behaviors scores for 243 adolescents using self- and caregiver-report on the Social Skills Improvement System (SSiS). We used multivariable linear regression models to estimate associations between maternal PBDE concentrations and SSiS scores, controlling for potential covariates. We report associations for the five congeners and a summary exposure variable (∑5BDE: the sum of BDE- 28, 47, 99, 100, and 153, n = 197).

RESULTS

We found sex-specific associations of ∑5BDE concentrations with adolescent-reported Problem Behaviors (∑5BDE × sex pint = 0.02) and caregiver-reported Social Skills (∑5BDE × sex pint = 0.02). In sex-stratified models, log10 transformed data revealed increased maternal ∑5BDE concentration among males was associated with decreased caregiver-reported Social Skills composite score (β = -10.2, 95% CI: -19.5, -1.0), increased adolescent-reported Problem Behaviors composite score (β = 12.1, 95% CI: 5.4, 18.8), and increased caregiver-reported Problem Behaviors composite score (β = 6.2, 95% CI: 0.7, 11.7). Further analysis on SSiS subscales revealed similar patterns in significant associations among males. There were no statistically significant associations in stratified models among females despite higher ∑5BDE exposure (Female GM=40.15 ng/g lipid, GSE=1.10; Male GM=35.30 ng/g lipid, GSE=1.09).

DISCUSSION

We found gestational PBDE exposure in males was associated with poorer behavioral outcomes, extending previous findings among this cohort into early adolescence.

Role of endocrine disrupting chemicals in children's neurodevelopment

Environmental stressors, like endocrine disrupting chemicals (EDC), are considered important contributors to the increased rates of neurodevelopmental dysfunctions. Considering the cumulative research on adverse neurodevelopmental effects associated with prenatal exposure to EDC, the purpose of this study was to review the available limited literature about the effects of postnatal exposure to EDC on child neurodevelopment and behaviour. Despite widespread children's exposure to EDC, there are a limited number of epidemiological studies on the association of this exposure with neurodevelopmental disorders, in particular in the postnatal period. The available research suggests that postnatal EDC exposure is related to adverse neurobehavioral outcomes in children; however the underlying mechanisms of action remain unclear. Timing of exposure is a key factor determining potential neurodevelopmental consequences, hence studying the impact of multiple EDC co-exposure in different vulnerable life periods could guide the identification of sensitive subpopulations. Most of the reviewed studies did not take into account sex differences in the EDC effects on children neurodevelopment. We believe that the inclusion of sex in the study design should be considered as the role of EDC on children neurodevelopment are likely sex-specific and should be taken into consideration when determining susceptibility and potential mechanisms of action.

Application of dual carbon-bromine stable isotope analysis to characterize anaerobic micro-degradation mechanisms of PBDEs in wetland bottom-water

Polybrominated diphenyl ethers (PBDEs), one kind of persistent organic pollutants, were widely detected in coastal wetlands. Microbial reductive debromination is one of the most important attenuation processes for PBDEs in anaerobic environment, whereas the underlying reaction mechanisms remain elusive. Dual-element stable isotope analysis was recently recognized to distinguish different reaction mechanism for degradation of organic pollutants. In this study, the dual carbon-bromine isotope effects associated with the anaerobic microbial degradation were first investigated to characterize the reaction mechanisms for BDE-47 and BDE-153. Presence of lower brominated congeners indicated stepwise debromination as the main degradation pathway, with the preferential removal of bromine in para position > meta/ortho position. The pronounced isotope fractionation was observed for both carbon and bromine, with similar carbon (ε_C) and bromine isotope enrichment factor (ε_Br) between BDE-47 (ε_C = -5.98‰, ε_Br = -2.44‰) and BDE-153 (ε_C = -5.57‰, ε_Br = -2.06‰) during the microbial degradation. Compared to ε_C and ε_Br, the correlation of carbon and isotope effects (Λ_C/Br = Δδ⁸¹Br/Δδ¹³C) was almost the same between BDE-47 (0.436) and BDE-153 (0.435), indicating the similar reaction mechanism. The calculated carbon and bromine apparent kinetic isotope effects (AKIE_C and AKIE_Br) were 1.0773 and 1.0098 for BDE-47 and 1.0716 and 1.0125 for BDE-153, within range reported for degradation of halogenated compounds following nucleophilic substitution. Combination analysis of degradation products, Λ_C/Br and AKIE, all the results pointed to that the anaerobic reductive debromination of BDE-47 and BDE-153 followed the nucleophilic aromatic substitution, with the addition of cofactor to the benzene ring concomitant with dissociation of carbon-bromine bond via the inner-sphere electron transfer, and the cleavage of C-Br bond was the rate-determining step. This study contributed to the development of dual carbon-bromine isotope analysis as a robust approach to probe the fate of PBDEs in contaminated sites.

Cell-Type-Specific High Throughput Toxicity Testing in Human Midbrain Organoids

Toxicity testing is a crucial step in the development and approval of chemical compounds for human contact and consumption. However, existing model systems often fall short in their prediction of human toxicity in vivo because they may not sufficiently recapitulate human physiology. The complexity of three-dimensional (3D) human organ-like cell culture systems ("organoids") can generate potentially more relevant models of human physiology and disease, including toxicity predictions. However, so far, the inherent biological heterogeneity and cumbersome generation and analysis of organoids has rendered efficient, unbiased, high throughput evaluation of toxic effects in these systems challenging. Recent advances in both standardization and quantitative fluorescent imaging enabled us to dissect the toxicities of compound exposure to separate cellular subpopulations within human organoids at the single-cell level in a framework that is compatible with high throughput approaches. Screening a library of 84 compounds in standardized human automated midbrain organoids (AMOs) generated from two independent cell lines correctly recognized known nigrostriatal toxicants. This approach further identified the flame retardant 3,3',5,5'-tetrabromobisphenol A (TBBPA) as a selective toxicant for dopaminergic neurons in the context of human midbrain-like tissues for the first time. Results were verified with high reproducibility in more detailed dose-response experiments. Further, we demonstrate higher sensitivity in 3D AMOs than in 2D cultures to the known neurotoxic effects of the pesticide lindane. Overall, the automated nature of our workflow is freely scalable and demonstrates the feasibility of quantitatively assessing cell-type-specific toxicity in human organoids in vitro.

Update of the risk assessment of hexabromocyclododecanes (HBCDDs) in food

The European Commission asked EFSA to update its 2011 risk assessment on hexabromocyclododecanes (HBCDDs) in food. HBCDDs, predominantly mixtures of the stereoisomers α-, β- and γ-HBCDD, were widely used additive flame retardants. Concern has been raised because of the occurrence of HBCDDs in the environment, food and in humans. Main targets for toxicity are neurodevelopment, the liver, thyroid hormone homeostasis and the reproductive and immune systems. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour in mice can be considered the critical effects. Based on effects on spontaneous behaviour in mice, the Panel identified a lowest observed adverse effect level (LOAEL) of 0.9 mg/kg body weight (bw) as the Reference Point, corresponding to a body burden of 0.75 mg/kg bw. The chronic intake that would lead to the same body burden in humans was calculated to be 2.35 μg/kg bw per day. The derivation of a health-based guidance value (HBGV) was not considered appropriate. Instead, the margin of exposure (MOE) approach was applied to assess possible health concerns. Over 6,000 analytical results for HBCDDs in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary LB exposure to HBCDDs were fish meat, eggs, livestock meat and poultry. The CONTAM Panel concluded that the resulting MOE values support the conclusion that current dietary exposure to HBCDDs across European countries does not raise a health concern. An exception is breastfed infants with high milk consumption, for which the lowest MOE values may raise a health concern.

Changes in thyroid hormone related proteins and gene expression induced by polychlorinated biphenyls and halogen flame retardants exposure of children in a Chinese e-waste recycling area

Polychlorinated biphenyls (PCBs) and halogen flame retardants (HFRs) are major pollutants in e-waste recycling area. High internal exposure levels of PCBs and HFRs are harmful to human thyroid hormone (TH) equilibrium. To examine their disrupting effects on TH, we conducted a study on children (n = 114) of an e-waste recycling and a control area in South China. Concentrations of PCBs, HFRs, and TH levels were determined in serum samples. TH related proteins and their corresponding gene were also monitored as markers of such disruption. Levels of these chemicals in the exposed group were much greater than those in the control group. Results of the linear regression and generalized additive model indicated the presence of close relationships between the internal exposure levels and the responses of TH related proteins, gene expression. More extensive exposure concentrations of these chemicals led to higher expression of iodothyronine deiodinase I and decreased the concentrations of thyroid-stimulating hormone, expression of TH receptor α, indicating the exertion of discrepant and even contrary influences on equilibrium of TH, and a compensation of these mechanisms may kept the homeostasis of TH. These results for children warrant further investigation on the health risks of PCBs and HFRs exposure in e-waste area.

Tetrabromobisphenol A (TBBPA): A controversial environmental pollutant

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and is extensively used in electronic equipment, furniture, plastics, and textiles. It is frequently detected in water, soil, air, and organisms, including humans, and has raised concerns in the scientific community regarding its potential adverse health effects. Human exposure to TBBPA is mainly via diet, respiration, and skin contact. Various in vivo and in vitro studies based on animal and cell models have demonstrated that TBBPA can induce multifaceted effects in cells and animals, and potentially exert hepatic, renal, neural, cardiac, and reproductive toxicities. Nevertheless, other reports have claimed that TBBPA might be a safe chemical. In this review, we re-evaluated most of the published TBBPA toxicological assessments with the goal of reaching a conclusion about its potential toxicity. We concluded that, although low TBBPA exposure levels and rapid metabolism in humans may signify that TBBPA is a safe chemical for the general population, particular attention should be paid to the potential effects of TBBPA on early developmental stages.

Rno-miR-224-5p contributes to 2,2',4,4'-tetrabromodiphenyl ether-induced low triiodothyronine in rats by targeting deiodinases

Hypothyroidism is commonly associated with substantial adverse impacts on human health, and polybrominated diphenyl ether (PBDE), a kind of classic thyroid hormone disruptor, was speculated to be a potential environmental factor, but its effect on thyroxine metabolism has received little attention. In the present study, we investigated the role and mechanism of rno-miR-224-5p in deiodinase-mediated thyroxine metabolism in rats treated with 2,2',4,4'-tetrabromodiphenyl ether (BDE47), a predominant PBDE congener in humans. BDE47 decreased plasma triiodothyronine (T3) and thyroxine (T4) and increased reverse T3 (rT3) in the rats, and the expression of type 1 deiodinase (DIO1) and type 3 deiodinase (DIO3) increased in both the rats and H4-II-E cells. Rno-miR-224-5p was predicted to target dio1 instead of dio3, according to the TargetScan, miRmap.org and microRNA.org databases. Experiments showed that the rno-miR-224-5p level was decreased by BDE47 in a dose-dependent manner and confirmed that rno-miR-224-5p downregulated both DIO1 and DIO3 in the H4-II-E cells and in the rats, as determined using mimics and an inhibitor of rno-miR-224-5p. Furthermore, DIO1 was observed to be a direct functional target of rno-miR-224-5p, whereas DIO3 was indirectly regulated by rno-miR-224-5p via the phosphorylation of the MAPK/ERK (but not p38 or JNK) pathway. Reportedly, DIO1 and DIO3 act principally as inner-ring deiodinases and are responsible for the conversion of T4 to rT3, but not to T3, and the final clearance of thyroxine (mainly in the form of T2). Our results demonstrated that BDE47 induced low levels of T3 conversion through DIO1 and DIO3, which were regulated by rno-miR-224-5p. The findings suggest a novel additional mechanism of PBDE-induced thyroxine metabolism disorder that differs from that of PBDEs as environmental thyroid disruptors.

Absence of neurotoxicity and lack of neurobehavioral consequences due to exposure to tetrabromobisphenol A (TBBPA) exposure in humans, animals and zebrafish

Tetrabromobisphenol A (2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol, CAS no. 79-94-7) (TBBPA) is an effective brominated flame retardant present in many consumer products whose effectiveness is attributable to its ability to retard flames and consequently save human lives. Toxicokinetic studies revealed that TBBPA when absorbed via the gastrointestinal tract is rapidly metabolized to glucuronide or sulfate metabolites which are rapidly eliminated by the kidney. TBBPA does not accumulate in the body and there is no evidence that the parent compound is present in the brain. Although this brominated flame retardant was detected in human breast milk and serum, there was no evidence that TBBPA reached the brain in in vivo animal studies as reflected by the absence of neuropathological, neurotoxic, or behavioral alterations indicating that the central nervous system is not a target tissue. These animal investigations were further supported by use of the larval/embryo observations that TBBPA did not produce behavioral changes in a larval/embryo zebrafish a model of chemical-induced neurotoxicity. Although some protein expressions were increased, deceased or not affected in the blood-brain barrier indicating no evidence that TBBPA entered the brain, the changes were contradictory, or gender related, and behavior was not affected supporting that this compound was not neurotoxic. Taken together, TBBPA does not appear to target the brain and is not considered as a neurotoxicant.

Pre- and Postnatal Polybrominated Diphenyl Ether Concentrations in Relation to Thyroid Parameters Measured During Early Childhood

Background: Penta-brominated diphenyl ethers (PentaBDEs) are endocrine-disrupting chemicals that structurally resemble thyroid hormones and were widely used as flame retardants in household consumer products from 1975 to 2004. Polybrominated diphenyl ethers (PBDEs) cross the placenta, and evidence suggests that for many children, body burdens may peak during the toddler years. This study aimed to understand the impact of exposure timing by examining both pre- and postnatal exposure to BDE-47, the predominant penta-brominated diphenyl ether congener detected in humans, in relation to thyroid hormone parameters measured during early childhood. Methods: The Columbia Center for Children's Environmental Health Mothers and Newborns Study is a prospective birth cohort of African American and Dominican maternal-child pairs. Pregnant women were recruited from two prenatal clinics in Northern Manhattan and the South Bronx between 1998 and 2006. Participants included 158 children with (i) plasma PBDE concentrations measured at birth and in the toddler years (age 2-3 years), and (ii) serum thyroid parameters measured at three and/or five years of age. Outcomes included concentrations of serum thyrotropin, free thyroxine, and total thyroxine. Results: Children with high exposure to BDE-47 during the prenatal period (-17% [confidence interval -29 to -2]) or toddler age (-19% [confidence interval -31 to -5]) had significantly lower geometric mean thyrotropin levels compared to children with low BDE-47 exposure throughout early life. Associations with thyroxine were also inverse; however, they did not reach statistical significance at the p = 0.05 level. Sex-stratified models suggest associations with postnatal exposure may be stronger among boys compared to girls. Conclusions: The thyroid regulatory system may be sensitive to BDE-47 during pre- and postnatal periods.

Reductive Debromination of Polybrominated Diphenyl Ethers: Dependence on Br Number of the Br-Rich Phenyl Ring

Reductive debromination has been widely studied for the degradation of polybrominated diphenyl ethers (PBDEs), although the reaction mechanisms are not so clear. In the present study, the photocatalytic degradation and debromination of ten PBDEs were carried out with CuO/TiO₂ nanocomposites as the photocatalyst under an anaerobic condition. The pseudo-first-order rate constants were obtained for the photocatalytic debromination of PBDEs, and their relative rate constants ( k_R) were evaluated against k_R= 1 for BDE209. Unlike the generally accepted summary that k_R is dependent on the total Br number ( N) of PBDEs, k_R is found to depend on the Br number on a phenyl ring with more Br atoms than the other one. In other words, a phenyl ring substituted by more Br is more reactive for the reductive debromination. The calculated LUMO energies ( E_LUMO) of all PBDEs are well correlated to the more reactive phenyl ring with more Br, compared with the N of two phenyl rings. The result was explained by LUMO localization on the Br-rich phenyl ring, suggesting that the reductive debromination occurs on the phenyl ring.

Factors influencing risk assessments of brominated flame-retardants; evidence based on seafood from the North East Atlantic Ocean

Brominated flame-retardants (BFRs) such as polybrominated diphenyl ethers (PBDE) and hexabromocyclododecane (HBCD) are considered hazardous to human health. Due to their persistence, they are still present in the environment and in biota and seafood is major contributor of BFRs to human exposure. Here, we used data from >9700 samples of wild and farmed fish, fish feed and fish feed ingredients collected from the North Atlantic between 2006 and 2016 aiming to investigate factors influencing the risk assessments of BFRs. Due to most representative number of analyses, PBDEs were the main focus of investigation. Mean ∑PBDE in fillet samples ranged from below quantification in Atlantic cod fillet to 2.0 μg kg^-1 in Atlantic halibut. The main congener contributing to the ∑PBDE in all species was BDE 47. Factors affecting the level of BFR in seafood were multifaceted, and the levels were within species mainly determined by fish age, geographical origin and time of sampling. BDE 47, 99, 153 and HBCD were selected for margin of exposure (MOE) evaluation. When other sources of BFR than seafood were excluded, our risk assessment showed low risk at the current dietary intake of seafood. However, the dietary intake of BDE 99 may be of concern for toddlers when all sources are considered. The choice of fish species, dietary studies, choice of statistics, as well as exposure from other sources than seafood, were all factors that influenced the final MOE of BFRs. We propose the use of regression on order statistics as a tool for risk assessment, to illustrate means and spreads in large surveillance datasets to avoid the issue of measurements below the limit of quantification. A harmonized, updated evaluation of the risk associated with exposure to BFRs from diet, air and dust is warranted, where the fish species most commonly consumed also is taken into consideration.

Polybrominated diphenyl ether (PBDE) exposures and thyroid hormones in children at age 3 years

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) reduce serum thyroid hormone concentrations in animal studies, but few studies have examined the impact of early-life PBDE exposures on thyroid hormone disruption in childhood.

METHODS

We used data from 162 mother-child pairs from the Health Outcomes and Measures of the Environment Study (2003-2006, Cincinnati, OH). We measured PBDEs in maternal serum at 16 ± 3 weeks gestation and in child serum at 1-3 years. Thyroid hormones were measured in serum at 3 years. We used multiple informant models to investigate associations between prenatal and early-life PBDE exposures and thyroid hormone levels at age 3 years.

RESULTS

Prenatal PBDEs were associated with decreased thyroid stimulating hormone (TSH) levels at age 3 years. A 10-fold increase in prenatal ∑PBDEs (BDE-28, -47, -99, -100, and -153) was associated with a 27.6% decrease (95% CI -40.8%, -11.3%) in TSH. A ten-fold increase in prenatal ∑PBDEs was associated with a 0.25 pg/mL (0.07, 0.43) increase in free triiodothyronine (FT3). Child sex modified associations between prenatal PBDEs and thyroid hormones, with significant decrements in TSH among females and decreased free T4 (FT4) in males. Prenatal ∑PBDEs were not associated with TT4, FT4, or total T3.

CONCLUSIONS

These findings suggest an inverse relationship between prenatal ∑PBDEs and TSH at 3 years. Associations may be sexually dimorphic, with an inverse relationship between prenatal BDE-47 and -99 and TSH in females and null associations among males.

Association between serum polybrominated diphenyl ethers, new flame retardants and thyroid hormone levels for school students near a petrochemical complex, South China

As surrogates of polybrominated diphenyl ethers (PBDEs), new flame retardants (NFRs) include a series of chlorinated and brominated flame retardants. Though the NFRs are thought to induce similar thyroid hormone (TH) disrupting effects as PBDEs, few studies have focused on them. Given the increasing levels of NFRs in the environment, more in depth investigation of the potential TH disrupting effects of NFRs is warranted. This research involved a health survey to collect data and examine the associations between PBDEs, NFRs and TH. 174 school students lived near a petrochemical complex in South China participated in the survey, completing questionnaires and providing blood samples. Thirteen congeners of PBDEs, eight species of NFRs, TH and thyroid-stimulating hormone (TSH) were measured. The median levels of ΣPBDE (sum of thirteen congeners of PBDEs) and ΣNFR (sum of eight species of NFRs) for students were 140 and 240 ng g^-1 lipid, respectively. Nonmonotonic relationships were observed between quartile levels of PBDEs, NFRs and corresponding TH. In contrast to ΣPBDE that was positively associated with triidothyrine (T₃) level, ΣNFR was not statistically associated with TH. ΣPBDE + NFR (sum of thirteen congeners of PBDEs and eight species of NFRs) was significantly associated with T₃ level.

Occurrence of polybrominated diphenyl ethers in floor and elevated surface house dust from Shanghai, China

House dust is the main source of human exposure to flame retardants by ingestion. This study investigated the occurrence of polybrominated diphenyl ethers (PBDEs) in indoor dust from 22 houses in Shanghai, China. House dust was separately collected from the floor and elevated furnishings surface (mostly between 0.5 and 2 m height) for comparison. The concentrations of ∑₂₂ PBDEs ranged from 19.4 to 3280 ng/g (with a geometric mean of 203 ng/g) and from 55.1 to 792 ng/g (with a geometric mean of 166 ng/g) in floor dust (FD) and elevated surface dust (ESD), respectively. BDE-209 was the predominant congener, accounting for about 73.1% of total PBDE burdens. In terms of congener profiles, the comparison of FD and ESD revealed no significant differences except for the ratio of BDE-47/BDE-99. ESD samples displayed a ratio of BDE-47/BDE-99 very similar to commercial penta-BDE products DE-71 while the ratio in FD was exceptionally higher. Significant correlation was found between concentrations of commercial penta-BDE compositions in FD and ESD (p < 0.05). Except for some occasional values, PBDE levels in house dust exhibited temporal stability. Human exposure to PBDEs via dust ingestion was estimated. The highest daily intake of PBDEs was for toddlers by using 95th percentile concentrations of PBDEs via high dust ingestion in FD (23.07 ng/kg bw/day). About 20-fold difference in exposure estimates between toddlers and adults supports that toddlers are facing greater risk from indoor floor dust. Expectedly, this study highlighted the point that residents in Shanghai were exposed to low doses of PBDEs in house dust.

Methods of Responsibly Managing End-of-Life Foams and Plastics Containing Flame Retardants: Part I

Flame retardants (FRs) are added to foams and plastics to comply with flammability standards and test requirements in products for household and industrial uses. When these regulations were implemented, potential health and environmental impacts of FR use were not fully recognized or understood. Extensive research in the past decades reveal that exposure to halogenated FRs, such as those used widely in furniture foam, is associated with and/or causally related to numerous health effects in animals and humans. While many of the toxic FRs have been eliminated and replaced by other FRs, existing products containing toxic or potentially toxic chemical FRs will remain in use for decades, and new products containing these and similar chemicals will permeate the environment. When such products reach the end of their useful life, proper disposal methods are needed to avoid health and ecological risks. To minimize continued human and environmental exposures to hazardous FR chemicals from discarded products, waste management technologies and processes must be improved. This review discusses a wide range of issues associated with all aspects of the use and responsible disposal of wastes containing FRs, and identifies basic and applied research needs in the areas of responsible collection, pretreatment, processing, and management of these wastes.

Thyroid-disrupting chemicals and brain development: an update

This review covers recent findings on the main categories of thyroid hormone-disrupting chemicals and their effects on brain development. We draw mostly on epidemiological and experimental data published in the last decade. For each chemical class considered, we deal with not only the thyroid hormone-disrupting effects but also briefly mention the main mechanisms by which the same chemicals could modify estrogen and/or androgen signalling, thereby exacerbating adverse effects on endocrine-dependent developmental programmes. Further, we emphasize recent data showing how maternal thyroid hormone signalling during early pregnancy affects not only offspring IQ, but also neurodevelopmental disease risk. These recent findings add to established knowledge on the crucial importance of iodine and thyroid hormone for optimal brain development. We propose that prenatal exposure to mixtures of thyroid hormone-disrupting chemicals provides a plausible biological mechanism contributing to current increases in the incidence of neurodevelopmental disease and IQ loss.

Childhood polybrominated diphenyl ether (PBDE) exposure and executive function in children in the HOME Study

Prenatal exposure to polybrominated diphenyl ethers (PBDEs) have been reported to impair executive function in children, but little is known whether childhood PBDE exposures play a role. Using the Health Outcomes and Measures of the Environment (HOME) Study, a prospective birth cohort in the greater Cincinnati area, we investigated the association between repeated measures of PBDEs during childhood and executive function at 8 years in 208 children and whether effect modification by child sex was present. We used child serum collected at 1, 2, 3, 5, and 8 years to measure PBDEs. The Behavior Rating Inventory of Executive Function was completed by parents to assess executive function at 8 years. We used multiple informant models to examine childhood PBDEs during several exposure windows. Null associations were observed between early childhood PBDEs and executive function. However, we observed significant adverse associations between a 10-fold increase in concurrent concentrations of BDE-28 (β=4.6, 95% CI 0.5, 8.7) and BDE-153 (β=4.8, 95% CI 0.8, 8.8) with behavioral regulation. In addition, PBDEs at 8 years were significantly associated with poorer emotional and impulse control. No associations were noted between childhood PBDEs and metacognition or global executive function. However, child sex significantly modified the associations, with significantly poorer executive function among males with higher concurrent BDE-153, and null associations in females. Our study findings suggest that concurrent PBDE exposures during childhood may be associated with poorer executive function, specifically behavior regulation. Males may also be more sensitive to adverse associations of concurrent PBDEs on executive function.

Dynamics of persistent organic pollutants in obese adolescents during weight loss

We have investigated the dynamics of various persistent organic pollutants (POPs) in the serum of 94 obese adolescents (34 boys and 60 girls: age range 11-19years) before (0M) and after 5months (5M) of undergoing weight loss treatment. Six groups of POPs, such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlordane compounds (CHLs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDEs), were detected in all samples in the decreasing order of median levels: DDTs>PCBs>HCB>HCHs>CHLs>PBDEs. Levels and patterns of POPs between boys and girls at two time-points were similar. DDTs (0M/5M; median: 31/42ng/g lw) and PCBs (0M/5M; median: 17/28ng/g lw) were the major POPs. PCB 153 (0M/5M; 33/34% of the sum PCBs) was the most dominant PCB congener, followed by PCB 138 (0M/5M; 31/31%) and PCB 180 (0M/5M; 13/12%), respectively. The most important PBDE congeners were BDE 47 and 153, although total PBDE levels were low and ranged between 0.63 and 0.88ng/g lw. In general, levels of POPs in the obese adolescents were lower than previously reported in Belgian adolescents and adults. Due to weight loss, serum levels (except PBDEs) increased significantly thereafter combined with a body weight decrease (from 4 to 42kg). Serum concentrations increased by 1-3.5% per kilogram weight loss and 1-2.5% per BMI z-score loss for most POPs. To our knowledge, this is the first report on the dynamics of POPs in obese adolescents during weight loss. Lipid-soluble contaminants were released from adipose tissue into the blood leading to redistribution into the body. Whether the increase in the internal exposure to POPs may adversely influence health remains to be determined.

Biomonitoring of Danish school children and mothers including biomarkers of PBDE and glyphosate

BACKGROUND

The Danish part of the large European Human biomonitoring pilot project Demonstration of a study to Coordinate and Perform Human biomonitoring on a European Scale (DEMOCOPHES) investigated the urine, hair and blood concentrations of 66 different environmental chemicals in a group of 145 Danish school children aged 6-11 years and their mothers from rural and urban areas in autumn 2011. Some - but not all - results were published; however, the concurrence of the chemicals has not been assessed.

METHODS

The measured concentrations of polybrominated diphenyl ethers (PBDEs) and glyphosate is assessed to complete the investigation of all 66 chemicals in DEMOCOPHES. The concentrations of PBDEs were measured in plasma samples of 143 mothers and 116 children. Glyphosate was measured in a subsample of 27 urine samples. Previously assessed chemicals were polychlorinated biphenyls (PCBs), and polyfluoroalkyl substances (PFASs) analyzed in blood samples, mercury analyzed in hair, and phthalate metabolites, parabens, phenols, cadmium, paracetamol and cotinine analyzed in urine samples. Differences in concentrations between mothers and children were assessed, and the associations between the concentrations of the different environmental chemicals. investigated by correlation analysis.

RESULTS

PBDE47 was found in relatively high levels compared with previous Danish results in both mothers and children, with a significantly higher level in the children compared to their mothers. Glyphosate in concentrations around 1 ng/mL was detected in all 27 samples. The analyzed environmental exposures seem to follow a pattern where chemicals within the same classes are strongly correlated and where children and mothers are exposed to the same chemicals.

CONCLUSION

The correlations between the measured environmental chemicals indicate that a specific exposure pattern may exist, where people who are highly exposed to one class of environmental chemicals also may be highly exposed to certain other classes. As some of the compounds were measured in higher levels in children compared to mothers, increased focus also on the exposure in young children is recommended. For more detailed investigation of specific exposure sources more studies with increased power and detailed questionnaires should be developed.

Prenatal and postnatal polybrominated diphenyl ether (PBDE) exposure and measures of inattention and impulsivity in children

Exposure to polybrominated diphenyl ethers (PBDEs) during fetal development may be associated with deficits in attention and impulse control. However, studies examining postnatal PBDE exposures and inattention and impulsivity have been inconsistent. Using data from 214 children in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort with enrollment from 2003 to 2006 in the Greater Cincinnati Area, we investigated the relationship of both prenatal and postnatal PBDE exposures with attention and impulse control. Serum PBDEs were measured at 16±3weeks of gestation and during childhood at 1, 2, 3, 5, and 8years. We assessed children's attention and impulse control using the Conners' Continuous Performance Test-Second Edition (CPT-II) at 8years. We used multiple informant models to estimate associations of repeated PBDE measures with inattention and impulsivity. There was a pattern of associations between PBDEs and poorer performance on CPT-II measures of attention. For BDE-153, adverse associations extended to exposures at preschool and kindergarten ages; ten-fold increases in exposure were associated with higher omission errors (BDE-153 at 3years: β=4.0 [95% CI: -2.4, 10.5]; at 5years: β=4.6 [95% CI: -2.8, 12.0]; at 8years: β=4.1 [95% CI: -3.4, 11.5]). Longer hit reaction times, indicated by the exponential part of the hit reaction curve, were also observed with 10-fold increases in BDE-153 during the prenatal period and throughout childhood (Prenatal: β=15.0 milliseconds (ms) [95% CI: -15.8, 45.8]; 5years: β=20.6ms [95% CI: -20.8, 61.9]; 8years: β=28.6ms [95% CI: -12.1, 69.4]). Significant impairment in discriminability, as indicated by detectability (d'), between targets and non-targets was also noted with 5 and 8-year PBDE concentrations. Associations between PBDEs and inattention significantly differed by child sex, with males performing more poorly than females with regard to omission errors and measures of reaction times. Collectively, these results do not strongly support that PBDEs are associated with poorer impulse and attention control among 8year old children. However, there may be a possible relationship between prenatal and concurrent PBDEs and inattention, which requires additional research.

Serum Metabolomic Profiles in Neonatal Mice following Oral Brominated Flame Retardant Exposures to Hexabromocyclododecane (HBCD) Alpha, Gamma, and Commercial Mixture

BACKGROUND

Hexabromocyclododecane (HBCD) is a high production volume brominated flame retardant added to building insulation foams, electronics, and textiles. HBCD is a commercial mixture (CM-HBCD) composed of three main stereoisomers: α-HBCD (10%), β-HBCD (10%), and γ-HBCD (80%). A shift from the dominant stereoisomer γ-HBCD to α-HBCD is detected in humans and wildlife.

OBJECTIVES

Considering CM-HBCD has been implicated in neurodevelopment and endocrine disruption, with expected metabolism perturbations, we performed metabolomics on mice serum obtained during a window-of-developmental neurotoxicity to draw correlations between early-life exposures and developmental outcomes and to predict health risks.

METHODS

Six female C57BL/6 mice at postnatal day (PND) 10 were administered a single gavage dose of α-, γ-, or CM-HBCD at 3, 10, and 30 mg/kg. Nuclear magnetic resonance metabolomics was used to analyze 60 μL serum aliquots of blood collected 4 days post-oral exposure.

RESULTS

Infantile mice exposed to α-, γ-, or CM-HBCD demonstrated differences in endogenous metabolites by treatment and dose groups, including metabolites involved in glycolysis, gluconeogenesis, lipid metabolism, citric acid cycle, and neurodevelopment. Ketone bodies, 3-hydroxybutyrate, and acetoacetate, were nonstatistically elevated, when compared with mean control levels, in all treatment and dose groups, while glucose, pyruvate, and alanine varied. Acetoacetate was significantly increased in the 10 mg/kg α-HBCD and was nonsignificantly decreased with CM-HBCD. A third ketone body, acetone, was significantly lower in the 30 mg/kg α-HBCD group with significant increases in pyruvate at the same treatment and dose group. Metabolites significant in differentiating treatment and dose groups were also identified, including decreases in amino acids glutamate (excitatory neurotransmitter in learning and memory) and phenylalanine (neurotransmitter precursor) after α-HBCD and γ-HBCD exposure, respectively.

CONCLUSIONS

We demonstrated that 4 days following a single neonatal oral exposure to α-, γ-, and CM-HBCD resulted in different serum metabolomic profiles, indicating stereoisomer- and mixture-specific effects and possible mechanisms of action.

Impairment in the mesohippocampal dopamine circuit following exposure to the brominated flame retardant, HBCDD

Many chemicals have been used to increase the safety of consumer products by reducing their flammability and risk for ignition. Recent focus on brominated flame retardants, such as polybrominated diphenyl ethers (PBDEs) has shown them to contribute to neurobehavioral deficits in children, including learning and memory. As the manufacture and use of PBDEs have been reduced, replacement chemicals, such as hexabromocyclododecane (HBCDD) have been substituted. Our current study evaluated the neurotoxicity of HBCDD, concentrating on dopaminergic innervation to the hippocampus. Using an in vivo model, we exposed male mice to HBCDD and then assessed alterations to the dopamine synapse 6 weeks later. These exposures elicited significant reductions in presynaptic dopaminergic proteins, including TH, COMT, MAO-B, DAT, VMAT2, and alpha-synuclein. In contrast, postsynaptic dopamine receptors were not impaired. These findings suggest that the mesohippocampal dopamine circuit is vulnerable to HBCDD and the dopamine terminal may be a selective target for alteration.

Correlation between Atmospheric Boundary Layer Height and Polybrominated Diphenyl Ether Concentrations in Air

In this study, we aim to determine the correlation between the height of the atmospheric boundary layer (ABL) and the concentrations of polybrominated diphenyl ether (PBDE) congeners, in an effort to improve comprehension of the atmospheric behavior of PBDEs. We used the PBDE data in air (n = 298), which were measured by the Japan Ministry of Environment (JMOE) at 50 sites across Japan during the period 2009-2012. The height of the ABL, which directly affects the PBDE concentrations in the near-surface air, was estimated by employing data retrieved from the Japanese global reanalysis (JRA-55) database, using the parcel and Richardson number method. The ABL has shown a strong inverse relationship with BDE-47 and BDE-99 (p < 0.01). In contrast, there was less correlation between BDE-209 and the ABL (p = 0.258). These differing behaviors could be explained by differences in particle size distribution of PBDEs, where BDE-47 and BDE-99 are associated with gas phases and fine particles and BDE-209 is associated with coarse particles. To our knowledge, this paper represents the first large-scale analysis of correlations between the ABL and the concentrations of PBDEs in the air.

Levels of polybrominated diphenyl ethers in house dust in Central Poland

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants in numerous products, from which they are emitted to the environment, including house dust. House dust is a source of human exposure to these compounds by ingestion. The aim of this article was to determine the levels of selected PBDEs in the house dust and indicate their potential sources of origin. PBDE congeners: BDE-47, BDE-99, BDE-153 and BDE-209, were analyzed in 129 samples. The geometric mean levels (and 95% CIs) of the aforementioned congeners amounted to 3.8 (3.1-4.7) ng/g, 4.5 (3.5-5.6) ng/g, 2.2 (2.1-2.4) ng/g and 345 (269-442) ng/g respectively. BDE-209 was the dominant congener in the majority of tested samples. We found a statistically significant correlation between the concentrations of BDE-47 and the computer operating time per day (r_s - 0.18) and the living area (r_s - 0.20). Statistically significant higher levels of BDE-99 were found in homes where the floor was not replaced during the last 2 years.

Assessing Pediatric Nurses' Knowledge About Chemical Flame Retardants

Chemical flame retardants are routinely applied to children's products and are harmful to their health. Pediatric nurses are in a key position to provide education to caregivers on methods to decrease their children's exposure to these harmful chemicals. However, a critical barrier is the absence of any program to educate nurses about chemical flame retardants. In order to overcome this barrier, we must first assess their knowledge. This article provides key highlights every pediatric nurse should know about chemical flame retardants and reports the results of a knowledge assessment study.

PURPOSE

The purpose of this study was to (1) assess pediatric nurses' knowledge of chemical flame retardants, (2) determine what topic areas of chemical flame retardants pediatric nurses lack knowledge in, and (3) determine the best method to educate nurses about chemical flame retardants.

DESIGN AND METHODS

A single sample cross-sectional questionnaire design was used. A total sample of 417 advanced practice registered nurses and registered nurses completed an online survey about chemical flame retardants.

RESULTS

Pediatric nurses' knowledge of chemical flame retardants was low (M=13.4 out of 51). Articles, webinars, and e-mails were the primary preferred methods for education on the subject identified as a result of the survey.

CONCLUSIONS

Pediatric nurses have a large knowledge deficit related to chemical flame retardants. The data collected from this study will help structure future educational formats for pediatric nurses on chemical flame retardants to increase their knowledge.

Evaluation of tetrabromobisphenol A effects on human glucocorticoid and androgen receptors: A comparison of results from human- with yeast-based in vitro assays

The incidence of immune-related diseases increased over the last years in industrialized countries, suggesting a contribution of environmental factors. Impaired glucocorticoid action has been associated with immune disorders. Thus, there is an increasing interest to identify chemicals disrupting glucocorticoid action. The widely used flame retardant tetrabromobisphenol A (TBBPA) was reported earlier to potently inhibit glucocorticoid receptor (GR) and moderately androgen receptor (AR) activity in yeast-based reporter gene assays. To further characterize possible GR disrupting effects of TBBPA, transactivation experiments using a human HEK-293 cell-based reporter gene assay and cell-free receptor binding experiments were performed in the present study. Both, transactivation and GR binding experiments failed to detect any activity of TBBPA on GR function. Molecular docking calculations supported this observation. Additionally, the current study could confirm the antiandrogenic activity of TBBPA seen in the yeast assay, although the effect was an order of magnitude less pronounced in the HEK-293 cell-based system. In conclusion, TBBPA does not directly affect GR function and, considering its rapid metabolism and low concentrations found in humans, it is unlikely to cause adverse effects by acting through AR. This study emphasizes the use of cell-free assays in combination with cell-based assays for the in vitro evaluation of endocrine disrupting chemicals.

Serum polybrominated diphenyl ether concentrations and thyroid function in young children

Thyroid hormones are essential for proper neurodevelopment in early life. There is evidence that exposure to polybrominated diphenyl ethers (PBDEs) affects thyroid function, but previous studies have been inconsistent, and no studies among children have been conducted in the United States where PBDE levels are particularly high. Serum levels of seven PBDE congeners and thyroid hormones and other thyroid parameters were measured in 80 children aged 1-5 years from the southeastern United States between 2011 and 2012. Parents of the children completed questionnaires with details on demographics and behaviors. Multivariate linear regression models were used to estimate the associations between serum PBDE levels, expressed as quartiles and as log-transformed continuous variables, and markers of thyroid function. BDE-47, 99, 100 and 153 were detected in >60% of samples, and were summed (∑PBDE). PBDE congeners and ∑PBDE were positively associated with thyroid-stimulating hormone (TSH). A log-unit increase in ∑PBDE was associated with a 22.1% increase in TSH (95% CI: 2.0%, 47.7%). Compared with children in the lowest quartile of ∑PBDE exposure, children in higher quartiles had greater TSH concentrations as modeled on the log-scale (second quartile: β=0.32, 95% confidence interval (CI): -0.09, 0.74; third quartile: β=0.44, 95% CI: 0.04, 0.85; and fourth quartile: β=0.49, 95% CI: 0.09, 0.89). There was also a tendency toward lower total T4 and higher free T3 with increasing PBDE exposure. Results suggest that exposure to PBDEs during childhood subclinically disrupts thyroid hormone function, with impacts in the direction of hypothyroidism.

Hexabromocyclododecane (HBCD) induced changes in the liver proteome of eu- and hypothyroid female rats

Hexabromocyclododecane (HBCD) is a brominated flame retardant known for its low acute toxicity as observed in animal experiments. However, HBCD exposure can affect liver functioning and thyroid hormone (TH) status. As exact mechanisms are unknown and only limited toxicological data exists, a gel-based proteomic approach was undertaken. In a eu- and hypothyroid female rat model, rats were exposed to 3 and 30 mg/kg bw/day HBCD for 7 days via their diet, and exposure was related to a range of canonical endpoints (hormone status, body weight) available for these animals. Alterations in the liver proteome under HBCD exposure were determined in comparison with patterns of control animals, for both thyroid states. This revealed significantly changed abundance of proteins involved in metabolic processes (gluconeogenesis/glycolysis, amino acid metabolism, lipid metabolism), but also in oxidative stress responses, in both euthyroid and hypothyroid rats. The results provide a more detailed picture on the mechanisms involved in these alterations, e.g. at the protein level changes of the proposed influence of HBCD on the lipid metabolism. Present results show that proteomic approaches can provide further mechanistic insights in toxicological studies.

Human exposure to endocrine disrupting chemicals and fertility: A case-control study in male subfertility patients

BACKGROUND

Dioxins, PCBs, chlorinated pesticides, brominated flame retardants, bisphenol A, triclosan, perfluorinated compounds and phthalates are known as endocrine disrupting chemicals (EDCs).

OBJECTIVES

The aim of our study was to investigate whether higher exposure to EDCs is associated with increased subfertility in men.

METHODS

We measured biomarkers of exposure in 163 men, recruited through four fertility clinics. According to WHO guidelines, we used a total motility count (TMC) of 20 million as cut-off value. We assigned patients to the case group when two semen samples - collected at least one week apart - had a TMC<20 and to the control group when both samples had a TMC≥20. To estimate the risk of subfertility and alteration in sex hormone concentrations we used multivariable-adjusted analysis, using logistic and linear regressions, respectively.

RESULTS

For an IQR increase in serum oxychlordane, the odds ratio for subfertility was 1.98 (95% CI: 1.07; 3.69). Furthermore, men with serum levels of BDE209 above the quantification limit had an odds of 7.22 (1.03; 50.6) for subfertility compared with those having values below the LOQ. Urinary levels of phthalates and triclosan were negatively associated with inhibin B and positively with LH. Urinary bisphenol A correlated negatively with testosterone levels.

CONCLUSIONS

Our study in men showed that internal body concentrations of endocrine disrupting chemicals are associated with an increased risk of subfertility together with alterations in hormone levels. The results emphasize the importance to reduce chemicals in the environment in order to safeguard male fertility.

Selective damage to dopaminergic transporters following exposure to the brominated flame retardant, HBCDD

Over the last several decades, the use of halogenated organic compounds has become the cause of environmental and human health concerns. Of particular notoriety has been the establishment of the neurotoxicity of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). The subsequent banning of PBDEs has led to greatly increased use of 1,2,5,6,9,10-hexabromocyclododecane (HBCDD, also known as HBCD) as a flame retardant in consumer products. The physiochemical similarities between HBCDD and PBDEs suggest that HBCDD may also be neurotoxic to the dopamine system, which is specifically damaged in Parkinson disease (PD). The purpose of this study was to assess the neurotoxicity of HBCDD on the nigrostriatal dopamine system using an in vitro and in vivo approach. We demonstrate that exposure to HBCDD (0-25 μM) for 24 h causes significant cell death in the SK-N-SH catecholaminergic cell line, as well as reductions in the growth and viability of TH+ primary cultured neurons at lower concentrations (0-10 μM) after 72 h of treatment. Assessment of the in vivo neurotoxicity of HBCDD (25 mg/kg for 30 days) resulted in significant reductions in the expression of the striatal dopamine transporter and vesicular monoamine transporter 2, both of which are integral in mediating dopamine homeostasis and neurotransmission in the dopamine circuit. However, no changes were seen in the expression of tyrosine hydroxylase in the dopamine terminal, or striatal levels of dopamine. To date, these are the first data to demonstrate that exposure to HBCDD disrupts the nigrostriatal dopamine system. Given these results and the ubiquitous nature of HBCDD in the environment, its possible role as an environmental risk factor for PD should be further investigated.

High exposure of California firefighters to polybrominated diphenyl ethers

Concern about persistent organic pollutants (POPs) in Californians prompted the state's biomonitoring program to conduct a study in firefighters, who are occupationally exposed to high levels of POPs. In this work we present serum concentrations of several classes of POPs (polybrominated diphenyl ethers [PBDEs], polychlorinated biphenyls [PCBs], and organochlorine pesticides [OCPs]) in 101 Southern California firefighters. Despite recently reported declining trends of PBDEs in Californians, high levels were measured in firefighters' serum (Σ5PBDEs: median = 59.1 ng/(g of lipid); range = 18.8-714 ng/(g of lipid)) in comparison to other populations in California during the same period. In addition, nearly one-third of subjects had particularly high serum levels of decabromodiphenyl ether (BDE-209), consistent with other recent results in firefighters; this pattern may be a marker of recent firefighting activity. In contrast, serum levels of PCBs and OCPs measured in firefighters' sera were not elevated compared to U.S. levels. Multivariable analysis indicated that lower levels of serum PBDEs were associated with turnout gear cleaning and storage practices after fires. Our study supports the hypothesis that firefighting activities are likely to increase exposure to PBDEs and that good housekeeping and personal hygiene practices may reduce exposure to these compounds.

Bisphenol A and risk management ethics

It is widely recognized that endocrine disrupting compounds, such as Bisphenol A, pose challenges for traditional paradigms in toxicology, insofar as these substances appear to have a wider range of low-dose effects than previously recognized. These compounds also pose challenges for ethics and policymaking. When a chemical does not have significant low-dose effects, regulators can allow it to be introduced into commerce or the environment, provided that procedures and rules are in place to keep exposures below an acceptable level. This option allows society to maximize the benefits from the use of the chemical while minimizing risks to human health or the environment, and it represents a compromise between competing values. When it is not possible to establish acceptable exposure levels for chemicals that pose significant health or environmental risks, the most reasonable options for risk management may be to enact either partial or complete bans on their use. These options create greater moral conflict than other risk management strategies, leaving policymakers difficult choices between competing values.

Neurobehavioral performance in adolescents is inversely associated with traffic exposure

On the basis of animal research and epidemiological studies in children and elderly there is a growing concern that traffic exposure may affect the brain. The aim of our study was to investigate the association between traffic exposure and neurobehavioral performance in adolescents. We examined 606 adolescents. To model the exposure, we constructed a traffic exposure factor based on a biomarker of benzene (urinary trans,trans-muconic acid) and the amount of contact with traffic preceding the neurobehavioral examination (using distance-weighted traffic density and time spent in traffic). We used a Bayesian structural equation model to investigate the association between traffic exposure and three neurobehavioral domains: sustained attention, short-term memory, and manual motor speed. A one standard deviation increase in traffic exposure was associated with a 0.26 standard deviation decrease in sustained attention (95% credible interval: -0.02 to -0.51), adjusting for gender, age, smoking, passive smoking, level of education of the mother, socioeconomic status, time of the day, and day of the week. The associations between traffic exposure and the other neurobehavioral domains studied had the same direction but did not reach the level of statistical significance. The results remained consistent in the sensitivity analysis excluding smokers and passive smokers. The inverse association between sustained attention and traffic exposure was independent of the blood lead level. Our study in adolescents supports the recent findings in children and elderly suggesting that traffic exposure adversely affects the neurobehavioral function.

Particle size distribution of halogenated flame retardants and implications for atmospheric deposition and transport

This study investigates the distribution of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and a group of novel flame retardants (NFRs) on atmospheric aerosols. Two high volume cascade impactors were used to collect particulate fractions of ambient air over a one year period at urban and rural sites. The majority of FRs were found on the finest aerosols (<0.95 μm). Concentrations of HBCD were higher than those of ΣPBDEs. Moreover, we noted seasonality and spatial differences in particle size distributions, yet a large portion of the observed differences were due to differences in particulate matter (PM) itself. When normalized by PM, the size distributions of the FRs exhibited much greater heterogeneity. Differences existed between the FR distributions by molecular weight, with the higher molecular weight FRs (e.g., BDE-209, Dechlorane Plus) distributed more uniformly across all particulate size fractions. The seasonal, spatial, and compound-specific differences are of crucial importance when estimating dry and wet deposition of FRs as smaller aerosols have longer atmospheric residence times. Estimated wet and dry deposition of four representative FRs (BDE-47, BDE-209, HBCD, and Dechlorane Plus) using size-segregated aerosol data resulted in lower deposition estimates than when bulk aerosol data were used. This has implications for estimates of long-range atmospheric transport and atmospheric residence times, as it suggests that without size-specific distributions, these parameters could be underestimated for FRs.