Developmental neurotoxicity of polybrominated diphenyl ether (PBDE) flame retardants

Recent advances and current challenges of new approach methodologies in developmental and adult neurotoxicity testing

Adult neurotoxicity (ANT) and developmental neurotoxicity (DNT) assessments aim to understand the adverse effects and underlying mechanisms of toxicants on the human nervous system. In recent years, there has been an increasing focus on the so-called new approach methodologies (NAMs). The Organization for Economic Co-operation and Development (OECD), together with European and American regulatory agencies, promote the use of validated alternative test systems, but to date, guidelines for regulatory DNT and ANT assessment rely primarily on classical animal testing. Alternative methods include both non-animal approaches and test systems on non-vertebrates (e.g., nematodes) or non-mammals (e.g., fish). Therefore, this review summarizes the recent advances of NAMs focusing on ANT and DNT and highlights the potential and current critical issues for the full implementation of these methods in the future. The status of the DNT in vitro battery (DNT IVB) is also reviewed as a first step of NAMs for the assessment of neurotoxicity in the regulatory context. Critical issues such as (i) the need for test batteries and method integration (from in silico and in vitro to in vivo alternatives, e.g., zebrafish, C. elegans) requiring interdisciplinarity to manage complexity, (ii) interlaboratory transferability, and (iii) the urgent need for method validation are discussed.

Degradation of the emerging brominated flame retardant tetrabromobisphenol S using organo-montmorillonite supported nanoscale zero-valent iron

The widespread occurrence of emerging brominated flame retardant tetrabromobisphenol S (TBBPS) has become a major environmental concern. In this study, a nanoscale zero-valent iron (nZVI) impregnated organic montmorillonite composite (nZVI-OMT) was successfully prepared and utilized to degrade TBBPS in aqueous solution. The results show that the nZVI-OMT composite was very stable and reusable as the nZVI was well dispersed on the organic montmorillonite. Organic montmorillonite clay layers provide a strong support, facilitate well dispersion of the nZVI chains, and accelerate the overall TBBPS transformation with a degradation rate constant 5.5 times higher than that of the original nZVI. Four major intermediates, including tribromobisphenol S (tri-BBPS), dibromobisphenol S (di-BBPS), bromobisphenol S (BBPS), and bisphenol S (BPS), were detected by high-resolution mass spectrometry (HRMS), indicating sequential reductive debromination of TBBPS mediated by nZVI-OMT. The effective elimination of acute ecotoxicity predicted by toxicity analysis also suggests that the debromination process is a safe and viable option for the treatment of TBBPS. Our results have shown for the first time that TBBPS can be rapidly degraded by an nZVI-OMT composite, expanding the potential use of clay-supported nZVI composites as an environmentally friendly material for wastewater treatment and groundwater remediation.

Prenatal exposure to polybrominated diphenyl ether (PBDE) and child neurodevelopment: The role of breastfeeding duration

BACKGROUND

Prenatal and early-life exposure to polybrominated diphenyl ethers (PBDEs) is associated with detrimental and irreversible neurodevelopmental health outcomes during childhood. Breastfeeding may be a child's largest sustained exposure to PBDE- potentially exacerbating their risk for adverse neurodevelopment outcomes. However, breastfeeding has also been associated with positive neurodevelopment. Our study investigates if breastfeeding mitigates or exacerbates the known adverse effects of prenatal exposure to PBDEs and child neurodevelopment.

METHODS

Participants included 321 mother-infant dyads from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), a longitudinal birth cohort in California. PBDE concentrations were measured in maternal serum blood samples collected during pregnancy or at delivery. Using generalized estimated equations (GEE), we estimated associations of PBDE concentrations with children's attention, executive function, and cognitive scores assessed longitudinally between 7 and 12 years of age, stratified by duration of exclusive and complementary breastfeeding.

RESULTS

We observed that higher maternal prenatal PBDE concentrations were associated with poorer executive function among children who were complementary breastfed for a shorter duration compared to children breastfed for a longer duration; preservative errors (β for 10-fold increase in complementary breastfeeding <7 months = -6.6; 95 % Confidence Interval (CI): -11.4, -1.8; β ≥ 7 months = -5.1; 95 % CI: -10.2, 0.1) and global executive composition (β for 10-fold increase <7 months = 4.3; 95 % CI: 0.4, 8.2; β for 10-fold increase ≥7 months = 0.6; 95 % CI: -2.8, 3.9).

CONCLUSIONS

Prolonged breastfeeding does not exacerbate but may mitigate some previously observed negative associations of prenatal PBDE exposure and child neurodevelopment.

Toxicity of persistent organic pollutants: a theoretical study

CONTEXT

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are two families of persistent organic pollutants that are dangerous as they remain in the atmosphere for long periods and are toxic for humans and animals. They are found all over the world, including the penguins of Antarctica. One of the mechanisms that explains the toxicity of these compounds is related to oxidative stress. The main idea of this theoretical research is to use conceptual density functional theory as a theory of chemical reactivity to analyze the oxidative stress that PCBs and PBDEs can produce. The electron transfer properties as well as the interaction with DNA nitrogenous bases of nine PCBs and ten PBDEs found in Antarctic penguins are investigated. From this study, it can be concluded that compounds with more chlorine or bromine atoms are more oxidizing and produce more oxidative stress. These molecules also interact directly with the nitrogenous bases of DNA, forming hydrogen bonds, and this may be an explanation for the toxicity. Since quinone-type metabolites of PCBs and PBDEs can cause neurotoxicity, examples of quinones are also investigated. Condensed Fukui functions are included to analyze local reactivity. These results are important as the reactivity of these compounds helps to explain the toxicity of PCBs and PBDEs.

METHODS

All DFT computations were performed using Gaussian16 at M06-2x/6-311 + g(2d,p) level of theory without symmetry constraints. Electro-donating (ω-) and electro-accepting (ω +) powers were used as global response functions and condensed Fukui functions as local parameters of reactivity.

Polybrominated diphenyl ether (PBDE) exposure and adverse maternal and infant health outcomes: Systematic review

Polybrominated diphenyl ethers (PBDEs) are flame retardants found in ambient environment and are measured in humans. There are reports on general PBDE toxicity, including endocrine disrupting properties. Studies on adverse maternal and infant outcomes and underlying toxicity mechanisms needs to be understood. The objective of this study was to conduct a systematic review to examine the state of science on the relationship between PBDE and adverse maternal/infant health outcomes and related maternal biomarker changes. This literature review was conducted using PubMed, Scopus, Embase and Web of Science for published articles from January 2005-February 2022. Article quality was assessed using Newcastle-Ottawa Scale. Of the 1518 articles, only 54 human observational studies were screened in for this review. A second reviewer examined the validity of these articles. Reports on associations between PBDE and maternal health outcomes included gestational hypertension/preeclampsia (N = 2) and gestational diabetes mellitus/glycemic index (N = 6). Meanwhile, reports on PBDE and infant outcomes (N=32) included effects on infant birth weight, birth length and cephalic perimeter, preterm birth, fetal growth restriction and APGAR scores. Although findings on PBDE exposure and adverse infant outcomes showed inconsistencies across studies, in general, negative correlations between maternal PBDEs and infant birth weight, birth length and cephalic perimeter were seen, in few cases, after stratification by sex. Association between maternal PBDE and maternal biomarkers (N=18) suggested negative impact of PBDE exposure on markers relevant to neuro-endocrine system and inflammatory processes. The review findings identified potential associations between maternal PBDE and adverse maternal/infant health outcomes. Furthermore, PBDE-related biomarker changes suggest disturbances in maternal mechanisms relevant to endocrine disrupting properties of PBDEs. The observed study heterogeneity can be attributed to factors namely, sample size, study design and statistical analysis. Overall review findings imply the necessity for further research to validate PBDE exposure-related adverse maternal/infant health effects and to validate underlying toxicity mechanisms.

Ex vivo exposure to polybrominated diphenyl ether (PBDE) selectively affects the immune response in autistic children

Children on the autism spectrum have been shown to have immune dysregulation that often correlates with behavioral deficits. The role of the post-natal environment in this dysregulation is an area of active investigation. We examined the association between plasma levels of polybrominated diphenyl ether (PBDE) and immune cell function in age-matched autistic children and non-autistic controls. Plasma from children on the autism spectrum (n = 38) and typically developing controls (TD; n = 60) were analyzed for 14 major PBDE congeners. Cytokine/chemokine production was measured in peripheral blood mononuclear cell (PBMC) supernatants with and without ex vivo BDE-49 exposure. Total plasma concentration (∑PBDE14) and individual congener levels were also correlated with T cell function. ∑PBDE14 did not differ between diagnostic groups but correlated with reduced immune function in children on the autism spectrum. In autistic children, IL-2 and IFN-γ production was reduced in association with several individual BDE congeners, especially BDE-49 (p = 0.001). Furthermore, when PBMCs were exposed ex vivo to BDE-49, cells from autistic children produced elevated levels of IL-6, TNF-α, IL-1β, MIP-1α and MCP-1 (p < 0.05). Therefore, despite similar plasma levels of PBDE, these data suggest that PBMC function was differentially impacted in the context of several PBDE congeners in autistic children relative to TD children where increased body burden of PBDE significantly correlated with a suppressed immune response in autistic children but not TD controls. Further, acute ex vivo exposure of PBMCs to BDE-49 stimulates an elevated cytokine response in AU cases versus a depressed response in TD controls. These data suggest that exposure to the toxicant BDE-49 differentially impacts immune cell function in autistic children relative to TD children providing evidence for an underlying association between susceptibility to PBDE exposure and immune anomalies in children on the autism spectrum.

Environmental chemical exposures and mental health outcomes in children: a narrative review of recent literature

Background: Mental health is an important factor for children's overall wellbeing. National health statistics show that millions of children are diagnosed with mental health disorders every year, and evidence from studies on chemical pollutants like lead and bisphenols indicate that environmental exposures are linked to mental health illnesses in youth. However, the relationship between children's mental health and the environment is not well understood. This paper aims to review recent literature on prenatal and/or childhood environmental chemical exposures and mental health problems related to mood, anxiety, and behavior. This work also identifies areas of insufficient data and proposes suggestions to fill the data gaps. Methods: A narrative review was performed by searching Google Scholar and PubMed for literature published in the last 6 years (2017-2022), using search terms related to children, mental health, and environmental chemical exposure. Additional relevant studies were identified by screening the references in these papers. Results: A total of 29 studies are included in this review and results are summarized by chemical category: heavy metals, endocrine-disrupting chemicals, and pesticides. The majority of studies reported positive and significant associations between chemical exposures and child mental health outcomes including internalizing and externalizing behaviors. Conclusion: This review demonstrates that there is a growing body of literature that suggests developmental exposure to some environmental chemicals increases a child's risk of mood, anxiety, and behavior problems. Future research should expand on these findings to understand cumulative impacts, chemical mixtures, neurotoxic mechanisms, sex differences, and windows of vulnerability.

Metabolomic insights into neurological effects of BDE-47 exposure in the sea cucumber Apostichopus japonicus

The persistent organic pollutant 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a prevalent congener among polybrominated diphenyl ethers (PBDEs), exhibits potent bioaccumulation and toxicity. Despite extensive research into the adverse effects of BDE-47, its neurotoxicity in sea cucumbers remains unexplored. Given the crucial role of the sea cucumber's nervous system in survival and adaptation, evaluating the impacts of BDE-47 is vital for sustainable aquaculture and consumption. In this study, we employed ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Triple-TOF-MS) to analyze metabolomic changes in neuro-related tissues of Apostichopus japonicus exposed to low (0.1 µg/L), medium (1.0 µg/L), and high (10.0 µg/L) BDE-47 concentrations. We identified significantly changed metabolites in each exposure group (87 in low, 79 in medium, and 102 in high), affecting a variety of physiological processes such as steroid hormone balance, nucleotide metabolism, energy metabolism, neurotransmitter levels, and neuroprotection. In addition, we identified concentration-dependent, common, and some other metabolic responses in the neuro-related tissues. Our findings reveal critical insights into the neurotoxic effects of BDE-47 in sea cucumbers and contribute to risk assessment related to BDE-47 exposure in the sea cucumber industry, paving the way for future neurotoxicological research in invertebrates.

Alternative and legacy flame retardants in marine mammals from three northern ocean regions

Flame retardants are globally distributed contaminants that have been linked to negative health effects in humans and wildlife. As top predators, marine mammals bioaccumulate flame retardants and other contaminants in their tissues which is one of many human-imposed factors threatening population health. While some flame retardants, such as the polybrominated diphenyl ethers (PBDE), have been banned because of known toxicity and environmental persistence, limited data exist on the presence and distribution of current-use alternative flame retardants in marine mammals from many industrialized and remote regions of the world. Therefore, this study measured 44 legacy and alternative flame retardants in nine marine mammal species from three ocean regions: the Northwest Atlantic, the Arctic, and the Baltic allowing for regional, species, age, body condition, temporal, and tissue comparisons to help understand global patterns. PBDE concentrations were 100-1000 times higher than the alternative brominated flame retardants (altBFRs) and Dechloranes. 2,2',4,5,5'-pentabromobiphenyl (BB-101) and hexabromobenzene (HBBZ) were the predominant altBFRs, while Dechlorane-602 was the predominant Dechlorane. This manuscript also reports only the second detection of hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO) in marine mammals. The NW Atlantic had the highest PBDE concentrations followed by the Baltic and Arctic which reflects greater historical use of PBDEs in North America compared to Europe and greater industrialization of North America and Baltic countries compared to the Arctic. Regional patterns for other compounds were more complicated, and there were significant interactions among species, regions, body condition and age class. Lipid-normalized PBDE concentrations in harbor seal liver and blubber were similar, but HBBZ and many Dechloranes had higher concentrations in liver, indicating factors other than lipid dynamics affect the distribution of these compounds. The health implications of contamination by this mixture of compounds are of concern and require further research.

Proteomic analyses of primary human villous trophoblasts exposed to flame retardant BDE-47 using SWATH-MS

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants and recognized developmental toxicants that are detectable in placental tissues. Higher levels of in utero PBDE exposure have been associated with an increased risk of adverse birth outcomes. During pregnancy, cytotrophoblasts (CTBs) from the placenta play critical roles in the formation of the maternal-fetal interface via uterine invasion and vascular remodeling. The differentiation of these cells towards an invasive phenotype is crucial for proper placental development. We previously have shown that BDE-47 can impact CTB viability and hinder the ability of these cells to migrate and invade. To expand on potential toxicological mechanisms, we utilized quantitative proteomic approaches to identify changes in the global proteome of mid-gestation primary human CTBs after exposure to BDE-47. Using sequential window acquisition of all theoretical fragment-ion spectra (SWATH), we identified 3024 proteins in our CTB model of differentiation/invasion. Over 200 proteins were impacted as a function of BDE-47 exposure (1 μM and 5 μM) across the treatment period (15, 24, and 39 h). The differentially expressed molecules displayed time- and concentration-dependent changes in expression and were enriched in pathways associated with aggregatory and adhesive processes. Network analysis identified CYFIP1, a molecule previously unexplored in a placental context, to be dysregulated at BDE-47 concentrations previously seen to impact CTB migration/invasion. Our SWATH-MS dataset thus demonstrates BDE-47 impacts the global proteome of differentiating CTBs and serves as a valuable resource for further understanding of the relationship between environmental chemical exposures and placental development and function. AVAILABILITY OF DATA AND MATERIAL: Raw chromatograms are deposited on the MassIVE proteomic database (https://massive.ucsd.edu) under accession number MSV000087870. Normalized relative abundances are also available as Table S1.

Environmental Pollution and the Risk of Developing Metabolic Disorders: Obesity and Diabetes

To meet the increased need for food and energy because of the economic shift brought about by the Industrial Revolution in the 19th century, there has been an increase in persistent organic pollutants (POPs), atmospheric emissions and metals in the environment. Several studies have reported a relationship between these pollutants and obesity, and diabetes (type 1, type 2 and gestational). All of the major pollutants are considered to be endocrine disruptors because of their interactions with various transcription factors, receptors and tissues that result in alterations of metabolic function. POPs impact adipogenesis, thereby increasing the prevalence of obesity in exposed individuals. Metals impact glucose regulation by disrupting pancreatic β-cells, causing hyperglycemia and impaired insulin signaling. Additionally, a positive association has been observed between the concentration of endocrine disrupting chemicals (EDCs) in the 12 weeks prior to conception and fasting glucose levels. Here, we evaluate what is currently known regarding the link between environmental pollutants and metabolic disorders. In addition, we indicate where further research is required to improve our understanding of the specific effects of pollutants on these metabolic disorders which would enable implementation of changes to enable their prevention.

Comparative evaluation and prioritization of key influences on biodegradation of 2,2',4,4'-tetrabrominated diphenyl ether by bacterial isolate B. xenovorans LB400

Polybrominated diphenyl ethers (PBDEs) are a class of persistent organic pollutants being widely distributed and harmful to human health and wildlife, and the development of sustainable rehabilitation strategies including microbial degradation is of great concern. Although the increasing number of bacteria, especially the broad-spectrum and potent aerobes have been isolated for the efficient removal of PBDEs, the external influences and the corresponding influential mechanism on biodegradation are not fully understood yet. Given the wide-spectrum biodegradability of aerobic bacterial isolate, B. xenovorans LB400 for PBDEs, the dual impacts of many pivotal factors including pH, temperature, presence of dissolved organic matter (DOM) and cadmium ion etc. were comprehensively revealed on biodegradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47). Due to the structural resemblance and stimulation of specific enzyme activity in bacteria, the biphenyl as substrates showed the greater capacity than non-aromatic compounds in improving biodegradation. The individual adaptation to neutrality and cultivation at about 30 °C was beneficial for biodegradation since the bacterial cellular viability and enzyme activity was mostly preserved. Although it was possibly good for the induction of hormesis and favorable to enhance the permeability or bioavailability of pollutant, the exceeding increase of Cd²⁺ or DOM may not give the profitable increase of biodegradation yet for the detrimental effect. For biodegradation, the mechanistic relationship that took account of the integrative correlation with the influential factors was artfully developed using partial least square (PLS) regression technique. Relative to the most significant influence of culture time and initial concentration of BDE-47, the larger relevance of other factors primarily marked as pH and DOM was consecutively shown after the quantitative prioritization. This may not only help understand the influential mechanism but provide a prioritizing regulation strategy for biodegradation of BDE-47. The PLS-derived relationship was validated with the certain predictability in biodegradation, and could be used as an alternative to accelerate a priori evaluation of suitability or improve the feasibility of such bacteria in remediation of PBDEs in the environment.

Congener-specificity, dioxygenation dependency and association with enzyme binding for biodegradation of polybrominated diphenyl ethers by typical aerobic bacteria: Experimental and theoretical studies

Polybrominated diphenyl ethers (PBDEs) are a group of organic pollutants that have attracted much concerns of scientific community over the ubiquitous distribution, chemical persistence and toxicological risks in the environment. Though a great number of aerobic bacteria have been isolated for the rapid removal of PBDEs, the knowledge about biodegradation characteristics and mechanism is less provided yet. Herein, the congener-specificity of aerobic biodegradation of PBDEs by typical bacteria, i.e. B. xenovorans LB400 was identified with the different biodegradation kinetics, of which the changes were largely hinged on the bromination pattern. The more bromination isomerically at ortho-sites other than meta-sites or the single bromination at one of aromatic rings might always exert the positive effect. The biodegradation of PBDEs should be thermodynamically constrained to some extent because the calculated Gibbs free energy changes of initial dioxygenation by quantum chemical method increased with the increase of bromination. Within the transition state theory, the high correlativity between the apparent biodegradation rates and Gibbs free energy changes implied the predominance and rate-limiting character of initial dioxygenation, while the regioselectivity of dioxygenation at the ortho/meta-sites was also manifested for the more negative charge population. The molecular binding with the active domain of dioxygenase BphA1 in aerobe was firstly investigated using docking approach. As significantly illustrated with the positive relationship, the higher binding affinity with BphA1 should probably signify the more rapid biodegradation. Besides the edge-on π-π stacking of PBDEs with F227 or Y277 and π-cation formulation with histidines (H233, H239) in BphA1, the reticular hydrophobic contacts appeared as the major force to underpin the high binding affinity and rapid biodegradation of PBDEs. Overall, the experimental and theoretical results would not only help understand the aerobic biodegradation mechanism, but facilitate enhancing applicability or strategy development of engineering bacteria for bioremediation of PBDEs in the environment.

Biological effects related to exposure to polychlorinated biphenyl (PCB) and decabromodiphenyl ether (BDE-209) on cats

As an animal familiar to humans, cats are considered to be sensitive to chemicals; cats may be exposed to polychlorinated biphenyls (PCBs) and decabromodiphenyl ether (BDE-209) from indoor dust, household products, and common pet food, leading to adverse endocrine effects, such as thyroid hormone dysfunction. To elucidate the general biological effects resulting from exposure of cats to PCBs and PBDEs, cats were treated with a single i.p. dose of a principal mixture of 12 PCBs and observed for a short-term period. Results revealed that the testis weight, serum albumin, and total protein of the treated group decrease statistically in comparison with those in the control group. The negative correlations suggested that the decrease in the total protein and albumin levels may be disturbed by 4'OH-CB18, 3'OH-CB28 and 3OH-CB101. Meanwhile, the serum albumin level and relative brain weight decreased significantly for cats subjected to 1-year continuous oral administration of BDE-209 in comparison to those of control cats. In addition, the subcutaneous fat as well as serum high-density lipoprotein (HDL) and triglycerides (TG) levels increased in cats treated with BDE-209 and down-regulation of stearoyl-CoA desaturase mRNA expression in the liver occurred. These results suggested that chronic BDE-209 treatment may restrain lipolysis in the liver, which is associated with lipogenesis in the subcutaneous fat. Evidence of liver and kidney cell damage was not observed as there was no significant difference in the liver enzymes, blood urea nitrogen and creatinine levels between the two groups of both experiments. To the best of our knowledge, this is the first study that provides information on the biochemical effects of organohalogen compounds in cats. Further investigations on risk assessment and other potential health effects of PCBs and PBDEs on the reproductive system, brain, and lipid metabolism in cats are required.

Thyroid hormone activities of neutral and anionic hydroxylated polybrominated diphenyl ethers to thyroid receptor β: A molecular dynamics study

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified as the strong endocrine disrupting chemicals to humans, which show structural similarity with endogenous thyroid hormones (THs) and thus disrupt the functioning of THs through competitive binding with TH receptors (TRs). Although previous studies have reported the hormone activities of some OH-PBDEs on TH receptor β (TRβ), the interaction mechanism remains unclear. Furthermore, hydroxyl dissociation of OH-PBDEs may alter their TR disrupting activities, which has not yet been investigated in depth. In this work, we selected 18 OH-PBDEs with neutral and anionic forms and performed molecular dynamics (MD) simulations to estimate their binding interactions with the ligand binding domain (LBD) of TRβ. The results demonstrate that most of OH-PBDEs have stronger binding affinities to TRβ-LBD than their anionic counterparts, and the hydroxyl dissociation of ligands differentiate the major driving force for their binding. More Br atoms in OH-PBDEs can result in stronger binding potential with TRβ-LBD. Moreover, 5 hydrophobic residues, including Met313, Leu330, Ile276, Leu346, and Phe272, are identified to have important contributions to bind OH-PBDEs. These results clarify the binding mechanism of OH(O^-)-PBDEs to TRβ-LBD at the molecular level, which can provide a solid theoretical basis for accurate assessment of TH disrupting effects of these chemicals.

J, Jacobsen JK, Scordino JJ, Lang AR, Baugh KA, Bolton JL, Brüniche-Olsen A, Calambokidis J, Martínez-Aguilar S, Subbiah S, Gribble MO, Godard-Codding CAJ. Influence of Life-History Parameters on Persistent Organic Pollutant Concentrations in Blubber of Eastern North Pacific Gray Whales (Eschrichtius robustus)

Exposure to persistent organic pollutants (POPs) can significantly impact marine mammal health, reproduction, and fitness. This study addresses a significant 20-year gap in gray whale contaminant monitoring through analysis of POPs in 120 blubber biopsies. The scope of this substantial sample set is noteworthy in its range and diversity with collection between 2003 and 2017 along North America's west coast and across diverse sex, age, and reproductive parameters, including paired mothers and calves. Mean blubber concentrations of polychlorinated biphenyls (∑PCBs), dichlorodiphenyltrichloroethanes (∑DDTs), and chlordanes (∑CHLs) generally decreased since previous reports (1968-1999). This is the first report of polybrominated diphenyl ethers (PBDEs) and select hexachlorocyclohexanes (HCHs) in this species. Statistical modeling of the 19 most frequently detected compounds in this dataset revealed sex-, age-, and reproductive status-related patterns, predominantly attributed to maternal offloading. Mean POP concentrations differed significantly by sex in adults (17 compounds, up to 3-fold higher in males) but not in immatures (all 19 compounds). Mean POP concentrations were significantly greater in adults versus immatures in both males (17 compounds, up to 12-fold) and females (13 compounds, up to 3-fold). POP concentrations were detected with compound-specific patterns in nursing calves, confirming maternal offloading for the first time in this species.

Assessment of polybrominated diphenyl ether contamination and associated human exposure risk at municipal waste dumping sites

The reports concerning the occurrence and fate of polybrominated diphenyl ethers (PBDEs) at municipal solid waste (MSW) dumping sites are scarce, and considering the Indian context, no study has been conducted to assess PBDE contamination at MSW dumping sites and associated exposure and health risk. Therefore, in the present study, the concentration of PBDE congeners was investigated in soil samples amassed from MSW dumping sites of India and the factors affecting the dissemination of different PBDE congeners in soil were evaluated. Also, the human exposure and health risk through soil intake and dermal contact were also evaluated the first time in India. The total PBDE concentrations from tri- to deBDE congeners in soil ranged from 6.81 to 33.67 μg/g dw and showed a trend towards higher levels of PBDEs in the dumping sites of more populous cities. BDE 183 was found to be the main congener in the soil of the dumping sites. The congener profile in the soil exhibited the composition of the octa- and deBDE technical mixture and possibilities of biological and photodegradation of deBDE into lower brominated congeners. A significant correlation was observed between the measures of BDE 183 and BDE 209 congeners and carbon, nitrogen and hydrogen contents of the soil. The measured exposure doses of PBDEs through soil intake and dermal contact and the hazard index was estimated higher in children as compared to adults, which indicates the increased risk and susceptibility of infants and children to PBDE exposure. The results of the present study revealed that the MSW dumping sites in India are a sink of PBDEs and might have detrimental effects on human health.

The effect of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) on locomotor behaviour and muscle physiology of the sea cucumber Apostichopus japonicus

The 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is the predominant congener of polybrominated diphenyl ethers, and it is also a persistent organic pollutant that with a higher detection rate in samples from environment and animals. To date, there have been few studies of the effects of BDE-47 on locomotion in sea cucumbers. In this study, we investigated the influence of different concentrations of BDE-47 (low: 0.1 μg/L; moderate: 1.0 μg/L; high: 10.0 μg/L) on locomotion of Apostichopus japonicus and evaluated changes in their muscle physiology using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The behavioural studies showed that the average and maximum velocity of movement decreased significantly in both the moderate and high BDE-47 groups after 1 day of exposure. In addition, levels of 55 metabolites were identified and characterized in the longitudinal muscle of A. japonicus exposed to BDE-47. The alteration of taurine and norepinephrine levels indicated that BDE-47 had drastic physiological effects on the longitudinal muscle of A. japonicus.

Towards a science-based testing strategy to identify maternal thyroid hormone imbalance and neurodevelopmental effects in the progeny-part III: how is substance-mediated thyroid hormone imbalance in pregnant/lactating rats or their progeny related to neurodevelopmental effects?

This review investigated which patterns of thyroid- and brain-related effects are seen in rats upon gestational/lactational exposure to 14 substances causing thyroid hormone imbalance by four different modes-of-action (inhibition of thyroid peroxidase, sodium-iodide symporter and deiodinase activities, enhancement of thyroid hormone clearance) or to dietary iodine deficiency. Brain-related parameters included motor activity, cognitive function, acoustic startle response, hearing function, periventricular heterotopia, electrophysiology and brain gene expression. Specific modes-of-action were not related to specific patterns of brain-related effects. Based upon the rat data reviewed, maternal serum thyroid hormone levels do not show a causal relationship with statistically significant neurodevelopmental effects. Offspring serum thyroxine together with offspring serum triiodothyronine and thyroid stimulating hormone appear relevant to predict the likelihood for neurodevelopmental effects. Based upon the collated database, thresholds of ≥60%/≥50% offspring serum thyroxine reduction and ≥20% and statistically significant offspring serum triiodothyronine reduction indicate an increased likelihood for statistically significant neurodevelopmental effects; accuracies: 83% and 67% when excluding electrophysiology (and gene expression). Measurements of brain thyroid hormone levels are likely relevant, too. The extent of substance-mediated thyroid hormone imbalance appears more important than substance mode-of-action to predict neurodevelopmental impairment in rats. Pertinent research needs were identified, e.g. to determine whether the phenomenological offspring thyroid hormone thresholds are relevant for regulatory toxicity testing. The insight from this review shall be used to suggest a tiered testing strategy to determine whether gestational/lactational substance exposure may elicit thyroid hormone imbalance and potentially also neurodevelopmental effects.

Maternal exposure to the environmental pollutant "BDE-47" impairs the postnatal development of rat cerebellar cortex by modulating neuronal proliferation, synaptogenesis, NGF and BDNF pathways

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is an environmental contaminant that crosses the blood placental barrier and interferes with the homeostasis of fetal thyroid hormones.

AIM OF WORK

This study was designed to investigate the perinatal effect of BDE-47 exposure on the postnatal development of the rat cerebellar cortex.

MATERIALS AND METHODS

This study was carried out on 20 pregnant rats and 36 of their offspring. The pregnant rats were divided equally into control and BDE-47 treated mother groups; supplemented orally with BDE-47 (0.2 mg/kg/day from day 8 of gestation until the day of weaning). The offspring of both mother groups were subdivided, according to their developmental age, into three subgroups; PND14, PND21and PND42. SerumT3, T4 and TSH were assessed for dams and their offspring. Testing the motor coordination of the offspring via the rotarod test was conducted. Sections of the cerebellar cortex from offspring subgroups were stained with hematoxylin and eosin alongside immunohistochemical reactions and optical density of nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), proliferating cell nuclear antigen (PCNA) and synaptophysin (SYN). Also, the thickness of different layers of the cerebellar cortex was histomorphometrically measured.

RESULTS

BDE-47 treated mothers and their offspring subgroups showed a significant decrease in the serum free T3, T4 and increased TSH. The BDE-47 offspring displayed incoordination of the motor activity together with disturbed cytoarchitecture of the cerebellar cortical layers, and impaired migration of its germinative neuronal zones, particularly on PND14 and PND21. Moreover, these offspring displayed a decrease of the immune-expression and optical density of NGF, BDNF in the cerebellar cortical layers with impaired proliferation, and synaptogenesis.

CONCLUSION

Maternal exposure to BDE-47 during pregnancy and lactation effectuated a potential deleterious retarding effect on the postnatal development of the rat cerebellar cortex mostly via modulating neuronal proliferation, synaptogenesis, NGF and BDNF pathways secondary to its hypothyroid effect.

Enhancement of Thermal Stability, Conductivity and Smoke Suppression of Polyethylene Composites with Exfoliated MoS2 Functionalized with Magnetite

This work reports a facile fabrication method to modify exfoliated molybdenum disulfide (e-MoS2) nanosheets with magnetite nanoparticles with various size distribution. The obtained materials have been utilized as nanofillers of polyethylene to enhance its thermal properties and flame retardance. The incorporation of magnetite modified MoS2 nanosheets leads to the reduction of the peak heat release rate. The best thermal conductivity has been noticed for composites with e-MoS2/Fe3O4 with 2 wt. % of nanofillers. The lowest CO emission was observed for the PE/e-MoS2 composite containing also 2 wt. % of Fe3O4. All composites with exfoliated MoS2 exhibited greater thermal properties in respect to the pristine polyethylene.

Food Contamination: An Unexplored Possible Link between Dietary Habits and Parkinson’s Disease

Importance of a healthy lifestyle in maintaining the population’s well-being and health, especially in terms of balanced nutrition, is well known. Food choice of and dieting habits could impact disease management, which is especially true for Parkinson’s disease (PD). However, nowadays, it is not that simple to maintain a balance in nutrition, and the idea of a healthy diet tends to fade as the consequence of a western lifestyle. This should not only be dealt with in the context of food choice, but also from an environmental point of view. What we put into our bodies is strictly related to the quality of ecosystems we live in. For these reasons, attention should be directed to all the pollutants, which in many cases, we unknowingly ingest. It will be necessary to explore the interaction between food and environment, since human activity also influences the raw materials destined for consumption. This awareness can be achieved by means of an innovative scientific approach, which involves the use of new models, in order to overcome the traditional scientific investigations included in the study of Parkinson’s disease.

E-waste it wisely: lessons from Africa

E-waste is the world’s fastest growing and most valuable domestic waste stream. The increasing production of e-waste is driving elevated levels of export from developed to developing countries. Although countries worldwide are actively recognising the issues around e-waste and introducing policies, legislation or regulations governing e-waste, a large fraction of e-waste, goes undocumented at its end-of-life. Much of the global e-waste is accumulating in open dumpsites in several African countries. Using available data, we calculate the total e-waste in Africa (locally produced plus imported e-waste) for 2019 to be between 5.8 and 3.4 metric tonnes (Mt). This is believed to be an underestimate, large data gaps exist, hindering more precise estimates. The data is further complicated by, sometimes intentional, differences in labelling and reporting between formal and intermittent informal importers. Based on the available data, the main African recipients of e-waste are Nigeria, Ghana, and Tanzania, with Kenya, Senegal and Egypt featuring as countries of concern. The lack of proper waste management in the recipient developing countries, leads to environmental contamination and human exposure. A coordinated, regional and global, approach is needed in tackling e-waste. Regulatory frameworks, together with monitoring and compliance mechanisms need to be developed, financed, and enforced.

BDE-47 induced PC-12 cell differentiation via TrkA downstream pathways and caused the loss of hippocampal neurons in BALB/c mice

As the most abundant congener of polybrominated diphenyl ethers (PBDEs) detected in environment and human biotic samples, 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) has been found to accumulate in brain and induce neurotoxicity, however, the detailed mechanism has not been clearly elucidated. To investigate the neurotoxicity of BDE-47, undifferentiated PC-12 cells were exposed to different doses of BDE-47, and BDE-47 dissolved in corn oil was orally administered to mice for 8 consecutive weeks. Our data showed that BDE-47 obviously changed cell morphology, altered cell viability, promoted cell apoptosis, and induced reactive oxygen species (ROS) production. BDE-47 promoted the differentiation of PC-12 cells by enhancing the expression of TrkA receptor and the phosphorylation levels of ERK and Akt. Moreover, BDE-47-induced differentiation of PC-12 cells was suppressed by inhibitors of corresponding pathways (MAPK/ERK and PI3K/Akt). H&E staining of brain showed neurons in DG and CA1 areas of hippocampus decreased after BDE-47 exposure. Transcriptome sequencing of brain tissue suggested that multiple signaling pathways related to neuron death and nerve function were significantly regulated. In conclusion, these results provided new evidence for revealing the neurotoxicity of BDE-47, and offered important experimental basis for environmental controlling and post-exposure health risk assessment of BDE-47.

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.

Persistent autism-relevant behavioral phenotype and social neuropeptide alterations in female mice offspring induced by maternal transfer of PBDE congeners in the commercial mixture DE-71

Polybrominated diphenyl ethers (PBDEs) are ubiquitous persistent organic pollutants (POPs) that are known neuroendocrine disrupting chemicals with adverse neurodevelopmental effects. PBDEs may act as risk factors for autism spectrum disorders (ASD), characterized by abnormal psychosocial functioning, although direct evidence is currently lacking. Using a translational exposure model, we tested the hypothesis that maternal transfer of a commercial mixture of PBDEs, DE-71, produces ASD-relevant behavioral and neurochemical deficits in female offspring. C57Bl6/N mouse dams (F0) were exposed to DE-71 via oral administration of 0 (VEH/CON), 0.1 (L-DE-71) or 0.4 (H-DE-71) mg/kg bw/d from 3 wk prior to gestation through end of lactation. Mass spectrometry analysis indicated in utero and lactational transfer of PBDEs (in ppb) to F1 female offspring brain tissue at postnatal day (PND) 15 which was reduced by PND 110. Neurobehavioral testing of social novelty preference (SNP) and social recognition memory (SRM) revealed that adult L-DE-71 F1 offspring display deficient short- and long-term SRM, in the absence of reduced sociability, and increased repetitive behavior. These effects were concomitant with reduced olfactory discrimination of social odors. Additionally, L-DE-71 exposure also altered short-term novel object recognition memory but not anxiety or depressive-like behavior. Moreover, F1 L-DE-71 displayed downregulated mRNA transcripts for oxytocin (Oxt) in the bed nucleus of the stria terminalis (BNST) and supraoptic nucleus, and vasopressin (Avp) in the BNST and upregulated Avp1ar in BNST, and Oxtr in the paraventricular nucleus. Our work demonstrates that developmental PBDE exposure produces ASD-relevant neurochemical, olfactory processing and behavioral phenotypes that may result from early neurodevelopmental reprogramming within central social and memory networks.

Polybrominated diphenyl ethers in the environment: a wake-up call for concerted action in India

Polybrominated diphenyl ethers (PBDEs) are a class of persistent organic pollutants (POPs) used as flame retardants in the products utilized in day-to-day life. Their bioaccumulation, low volatility, and high persistence in the environment have led to their global spread even to remote and distant regions. The present study identifies gaps in the investigation of the neurotoxic potential of PBDEs, their effects on brain development, toxicokinetic, and their potential as a carcinogen. In India, to date, only human breast milk was assessed for levels of PBDEs, and it is suggested that other human tissues can also be explored. No data on the reproductive toxicity of PBDEs are reported from Indian cohorts. Long-range transport and deposition of PBDEs in colder regions necessitates monitoring of Himalayan regions in India. An inventory of PBDEs is required to be made for addressing the worrisome situation of the unregulated import of E-waste from the developed countries in India. The study also emphasizes providing guidelines for the articulation of policies regarding sound surveillance and management of PBDE production, consumption, and release in the Indian context. It is recommended that a separate cell for monitoring and follow-up of PBDEs should be established in India. Also, the development of better alternatives and environment-friendly remediation technologies for PBDEs is the need of the hour.

Sublethal effects of DBE-DBCH diastereomers on physiology, behavior, and gene expression of Daphnia magna

1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (DBE-DBCH) is a brominated flame retardant used in commercial and industrial applications. The use of DBE-DBCH containing products has resulted in an increased release into the environment. However, limited information is available on the long-term effects of DBE-DBCH and its effects in aquatic invertebrates. Thus, the present study was aimed at determining how DBE-DBCH diastereomers (αβ and γδ) affects aquatic invertebrates using Daphnia magna as a model organism. Survival, reproduction, feeding, swimming behavior and toxicogenomic responses to environmental relevant concentrations of DBE-DBCH were analyzed. Chronic exposure to DBE-DBCH resulted in decreased lifespan, and reduced fecundity. Expression of genes involved in reproductive processes, vtg1 and jhe, were also inhibited. DBE-DBCH also induced hypoxia by inhibiting the transcription of genes involved in heme biosynthesis and oxygen transport. Furthermore, DBE-DBCH also inhibited feeding resulting in emptiness of the alimentary canal. Increased expression of the stress response biomarkers was observed following DBE-DBCH exposure. In addition, DBE-DBCH diastereomers also altered the swimming behavior of Daphnia magna. The present study demonstrates that DBE-DBCH cause multiple deleterious effects on Daphnia magna, including effects on reproduction and hormonal systems. These endocrine disrupting effects are in agreement with effects observed on vertebrates. Furthermore, as is the case in vertebrates, DBE-DBCH γδ exerted stronger effects than DBE-DBCH αβ on Daphnia magna. This indicate that DBE-DBCH γδ has properties making it more toxic to all so far studied animals than DBE-DBCH αβ.

Mechanistic insight into hydroxylation of 2,2',4,4'-tetrabromodiphenyl ether during biodegradation by typical aerobic bacteria: Experimental and computational studies

Polybrominated diphenyl ethers (PBDEs) are a group of persistent pollutants in the environment. Though aerobic biodegradation of PBDEs have been extensively studied, the involved hydroxylation mechanism decisive for whole biotransformation is not clear yet. During the effective biodegradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) by B. xenovorans LB400, the depletion of endogenous ∙OH by scavenger could bring about the significant decrease of biodegradation efficiency whereas ·O₂^- was nearly not influential. Given the importance of ∙OH in hydroxylation, the reaction mechanisms along major pathways of electrophilic addition and hydrogen abstraction were theoretically examined by density functional theory (DFT). For the less demand of activation energy, the relative preference of electrophilic addition was shown at aromatic C3-site. When the secondary reaction was considered after addition at C4-site, the barrierless association of ∙OH at C3-site and deprotonation by H₂O was validated as the energetically-favorable pathway that may cause dihydroxylation of BDE-47 into 3,4-dihydroxyl-BDE-17. The electrophilic addition followed by seconary barrierless trans-association of ∙OH and then dehydration seemed favorable for monohydroxylation as regards energetic barrier merely up to 194.01 kJ mol^-1, while the hydrogen abstraction by ∙OH from C5-site was more privileged actually. The theoretical insights would help well understand the hydroxylation mechanism of PBDEs by aerobes.

Disturbance of the Dlk1-Dio3 imprinted domain may underlie placental Dio3 suppression and extracellular thyroid hormone disturbance in placenta-derived JEG-3 cells following decabromodiphenyl ether (BDE209) exposure

Decabromodiphenyl ether (BDE209) has been widely used as a flame retardant in the past four decades, leading to human health consequences, especially neurological impairments. Our previous in vivo studies have suggested that developmental neurotoxicity in offspring may be the result of BDE209-induced placental type III iodothyronine deiodinase (Dio3) disturbance and consequent thyroid hormone (TH) instability. Dio3 is paternally imprinted gene, and its balanced expression is crucial in directing normal development and growth. In this study, we used placenta-derived cells to investigate how BDE209 affected Dio3 expression through interfering imprinting mechanisms in the delta-like homolog 1 (Dlk1)-Dio3 imprinted region. Gene chip analysis and RT-qPCR identified miR409-3p, miR410-5p, miR494-3p, miR668-3p and miR889-5p as potential candidates involved in Dio3 deregulation. The sodium bisulfite-clonal sequencing revealed the BDE209 affect methylation status of two differentially methylated regions (DMRs), intergenic-DMR (IG-DMR) and maternally expressed gene 3-DMR (MEG3-DMR). Our data indicate that placental Dio3 may be a potential molecular target for future study of BDE209 developmental toxicity. In particular, miRNAs, IG-DMR and MEG3-DMR in the Dlk1-Dio3 imprinted locus may be informative in directing studies in TH disturbance and developmental toxicity induced by in utero exposure to environmental persistent organic pollutants (POPs), and those candidate miRNAs may prove to be convenient and noninvasive biomarkers for future large-scale population studies.

Polybrominated diphenyl ethers quinone exhibits neurotoxicity by inducing DNA damage, cell cycle arrest, apoptosis and p53-driven adaptive response in microglia BV2 cells

Polybrominated diphenyl ethers (PBDEs) are world-wide used flame retardants before they were listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention. Previously, our studies indicated that a quinone type of PBDE metabolite (PBDEQ) exposure was linked with neurotoxicity via excess free radical formation and oxidative stress. However, it is current unknown the effect of PBDEQ on genetic biomacromolecules DNA and corresponding biological consequences in neurological cells. Here, by employing phosphorylated histone H2AX in Serine 139 (γ-H2AX) and comet assay in microglia BV2 cells, our data suggested PBDEQ could triggered DNA damage. Furthermore, PBDEQ exposure led to the caspase 3-dependent cell apoptosis. Moreover, PBDEQ induced G2/M-phase cell arrest in a p53-dependent manner. Notably, p53 activation coordinated cell cycle progression, alleviated DNA damage and ultimately mitigated apoptosis in BV2 cells. Finally, antioxidant N-acetyl-l-cysteine (NAC) inhibited p53 activation upon PBDEQ exposure, and then ameliorated PBDEQ-induced DNA damage, cell cycle arrest and apoptosis, which illustrated that PBDEQ-induced DNA damage and p53 activation were mediated by reactive oxygen species (ROS). Together, the current findings unveil the fundamental toxicological mechanisms of PBDEQ, which propose a potential therapeutic strategy against the adverse effect caused by PBDE exposure.

Polybrominated diphenyl ethers exert genotoxic effects in pantropic spotted dolphin fibroblast cell lines

Cetaceans accumulate persistent and toxic substances such as polybrominated diphenyl ethers in their tissue. PBDEs are ubiquitous in marine environments, and their exposure to mammals is linked to numerous health effects such as endocrine disruption, neurotoxicity, carcinogenicity, and fetal toxicity. However, the toxicological effects and mechanism of toxicity in cetaceans remains poorly understood. The effects of BDE-47 (0.1-0.5 μg mL^-1), BDE-100 (0.1-0.5 μg mL^-1), and BDE-209 (0.25-1.0 μg mL^-1) exposure on cell viability, oxidative stress, mitochondrial structure, and apoptosis were evaluated using a recently established pantropical spotted dolphin (Stenella attenuata) skin fibroblast cell line (PSD-LWHT) as an in vitro model. However, the production of reactive oxygen species (ROS) increased following exposure to 1.0 μg mL^-1 PBDE while superoxide anion, hydroxyl radicals, and inducible nitric oxide increased in a dose-dependent manner. At 0.5-1.0 μg mL^-1, PBDEs significantly reduced the mitochondrial membrane potential. In addition, exposure to BDE-47 and -209 significantly affected mitochondrial structure as well as cell signaling and transduction compared to BDE-100. Although PBDE exposure did not affect cell viability, a significant increase in cell apoptosis markers (Bcl2 and caspase-9) was observed. This study demonstrated that BDE-47, -100, and -209 congeners might cause cytotoxic and genotoxic effects as they play a crucial role in the dysregulation of oxidative stress and alteration of mitochondrial and cell membrane structure and activity in the fibroblast cells. Hence, these results suggest that PBDEs might have adverse health effects on cetaceans inhabiting contaminated marine environments.

40 Years of Research on Polybrominated Diphenyl Ethers (PBDEs)-A Historical Overview and Newest Data of a Promising Anticancer Drug

Polybrominated diphenyl ethers (PBDEs) are a group of molecules with an ambiguous background in literature. PBDEs were first isolated from marine sponges of Dysidea species in 1981 and have been under continuous research to the present day. This article summarizes the two research aspects, (i) the marine compound chemistry research dealing with naturally produced PBDEs and (ii) the environmental toxicology research dealing with synthetically-produced brominated flame-retardant PBDEs. The different bioactivity patterns are set in relation to the structural similarities and dissimilarities between both groups. In addition, this article gives a first structure-activity relationship analysis comparing both groups of PBDEs. Moreover, we provide novel data of a promising anticancer therapeutic PBDE (i.e., 4,5,6-tribromo-2-(2',4'-dibromophenoxy)phenol; termed P01F08). It has been known since 1995 that P01F08 exhibits anticancer activity, but the detailed mechanism remains poorly understood. Only recently, Mayer and colleagues identified a therapeutic window for P01F08, specifically targeting primary malignant cells in a low µM range. To elucidate the mechanistic pathway of cell death induction, we verified and compared its cytotoxicity and apoptosis induction capacity in Ramos and Jurkat lymphoma cells. Moreover, using Jurkat cells overexpressing antiapoptotic Bcl-2, we were able to show that P01F08 induces apoptosis mainly through the intrinsic mitochondrial pathway.

Endocrine-Disrupting Compounds in Fish Physiology, with Emphasis on their Effects on the Arginine Vasotocin/Isotocin System

The purposes of this review are to promote better use of existing knowledge of marine pollutants especially endocrine-disrupting compounds (EDCs) and to draw attention to the slow progression of the research on the influence of those compounds on arginine vasotocin/isotocin system (AVT/IT) in fish. EDCs are leading to the degradation of fish habitats, reducing their spawning potential and possibly their population parameters (e.g. growth, maturation), by preventing fish from breeding and rebuilding their populations. Therefore, searching for new welfare indicators such as AVT and IT and developing research procedures mimicking environmental conditions using a versatile fish model is extremely important. Fish species such as Zebrafish (Daniorerio) and round goby (Neogobiusmelanostomus) can be recommended as very suitable modelsfor studying estrogenic EDCs on the AVT/IT system and other hormones involved in the neuroendocrine regulation of physiological processes in fish.These studies would not only improve our understanding of the effects of EDCs on vertebrates but could also help safeguard the well-being of aquatic and terrestrial organisms from the harmful effects of these compounds.

Organophosphorus flame retardants are developmental neurotoxicants in a rat primary brainsphere in vitro model

Due to regulatory bans and voluntary substitutions, halogenated polybrominated diphenyl ether (PBDE) flame retardants (FR) are increasingly substituted by mainly organophosphorus FR (OPFR). Leveraging a 3D rat primary neural organotypic in vitro model (rat brainsphere), we compare developmental neurotoxic effects of BDE-47-the most abundant PBDE congener-with four OPFR (isopropylated phenyl phosphate-IPP, triphenyl phosphate-TPHP, isodecyl diphenyl phosphate-IDDP, and tricresyl phosphate (also known as trimethyl phenyl phosphate)-TMPP). Employing mass spectroscopy-based metabolomics and transcriptomics, we observe at similar human-relevant non-cytotoxic concentrations (0.1-5 µM) stronger developmental neurotoxic effects by OPFR. This includes toxicity to neurons in the low µM range; all FR decrease the neurotransmitters glutamate and GABA (except BDE-47 and TPHP). Furthermore, n-acetyl aspartate (NAA), considered a neurologic diagnostic molecule, was decreased by all OPFR. At similar concentrations, the FR currently in use decreased plasma membrane dopamine active transporter expression, while BDE-47 did not. Several findings suggest astrogliosis induced by the OPFR, but not BDE-47. At the 5 µM concentrations, the OPFR more than BDE-47 interfered with myelination. An increase of cytokine gene and receptor expressions suggests that exposure to OPFR may induce an inflammatory response. Pathway/category overrepresentation shows disruption in 1) transmission of action potentials, cell-cell signaling, synaptic transmission, receptor signaling, (2) immune response, inflammation, defense response, (3) cell cycle and (4) lipids metabolism and transportation. Taken together, this appears to be a case of regretful substitution with substances not less developmentally neurotoxic in a primary rat 3D model.

Prenatal exposure to polybrominated diphenyl ethers (PBDEs) and cognitive ability in early childhood

BACKGROUND

Prenatal exposure to polybrominated diphenyl ethers (PBDEs) has been associated with adverse neurodevelopmental outcomes in children, but evidence remains mixed regarding sex differences in this association.

OBJECTIVE

To examine the prospective association between prenatal PBDE exposure and cognitive ability in young children, as well as potential sex differences.

METHODS

The study was conducted in a multi-site Canadian pregnancy cohort recruited in 2008-11. PBDEs were measured in maternal plasma samples collected early in pregnancy. Cognitive ability was assessed using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) in children at age 3 years (mean = 3.4). Multiple linear regression was used to analyze the association between maternal PBDE plasma concentrations (lipid-standardized and log10-transformed) and Verbal, Performance, and Full Scale IQ scores on the whole sample and stratified by sex, adjusting for confounders.

RESULTS

The sample was composed of 592 children (291 boys and 301 girls). A tenfold increase in maternal blood PBDE concentration (sum of BDE-47, -99, -100, and -153) was associated with lower Full Scale scores in boys (-3.4 points; 95% CI: -7.0, 0.1), after adjusting for confounders. BDE-47 was the congener with the highest concentrations in maternal blood and a tenfold increase in exposure was associated with significantly lower Full Scale IQ scores in boys (-4.4 points; 95% CI: -7.9, -0.9), after adjusting for confounders. Verbal and Performance IQ scores were similarly associated with PBDE exposure. Maternal blood PBDE concentrations were not associated with IQ scores in girls.

CONCLUSIONS

Prenatal exposure to background levels of PBDEs, especially BDE-47, was associated with lower IQ scores in boys, but not in girls. Our results support that exposure to PBDEs during early development may be sex-dependent and detrimental to a child's neurodevelopmental trajectory.

Determinants of flame retardants in non-occupationally exposed individuals - A review

Flame retardants (FRs) constitute a large group of different substances, some of which have been phased out of the market due to health concerns, while others are still used in many common consumer products to prevent fire hazards. This review addressed the determinants of FRs in non-occupationally exposed individuals based on surveys and questionnaire data. For this literature review, three databases (Scopus, Pubmed and Web of Knowledge) were searched by applying suitable terms, inclusion and exclusion criteria, producing a final selection of 78 articles for review. Based on these surveys there is epidemiological evidence for a significant association (p < 0.05) among human exposure and demographic factors, as well as a significant correlation between exposure to FRs and behavioural and environmental factors. Age, gender, housing characteristics, electrical and electronic equipment and mouthing behaviour (in children) play a leading role in human exposure to FRs as published studies demonstrated. However, the methodological differences among studies such as population size, questionnaire design and statistical analysis did not reveal a complete pattern of human exposure routes. Risk perception and communication are also discussed based on limited available data. Knowledge gaps and future perspectives relating to standardized protocols, elucidation of contamination sources, and risk response of health information from different target groups were also identified.

Human Health Risk Assessment by Dietary Intake and Spatial Distribution Pattern of Polybrominated Diphenyl Ethers and Dechloran Plus from Selected Cities of Pakistan

A class of intractable bio accumulative halogenated compounds polybrominated diphenyl ethers (PBDEs) was studied. Specifically, PBDEs and dechloran plus (DP) contamination in wheat and the assaulted environment—agricultural soil and dust—from metropolitan cities of Pakistan was the focus. The exposure of brominated flame retardants (BFRs) to humans, their probable toxicological impact on health, source apportionment, and the spatial tendency of BFRs were studied. Chromatographic analysis was performed, and concentrations (ng g⁻¹) of ΣPBDE and ΣDP in soil, dust, and cereal crops were estimated in a range from 0.63 to 31.70 n.d. to 6.32 and n.d. to 3.47, respectively, and 0.11 to 7.05, n.d. to 4.56 and 0.05 to 4.95, respectively. Data analysis of source apportionment reflected that the existence of solid and e-waste sites, long-range transport, urban and industrial fraction can be the potential source of PBDE and DP pollution. Moreover, potential hazardous risks to human health across the study area via the dietary intake of cereal foods were deemed trifling, and were gauged on the basis of existing toxicological data.

Absorption, distribution, metabolism, and excretion of three [14C]PBDE congeners in laying hens and transfer to eggs

Polybrominated diphenyl ethers (PBDEs) levels in environmental matrices have generally declined following their phaseout as flame retardants. The objective of this study was to determine the absorption, distribution, metabolism, and excretion of three persistent PBDEs in laying hens and their transfer into eggs. Laying hens (n = 4 per congener) received a single oral dose of BDE-99, -153, or -209 and eggs and excreta were collected daily for 7 days, then tissues were collected and analysed. Cumulative BDE-209 excretion was 93% of dose, and bioavailability was approximately 17%. Lesser amounts of BDE-99 (41%) and -153 (26%) were excreted with bioavailabilities of 87% and 79%, respectively. Phenolic metabolites were observed in excreta extracts from BDE-99 dosed birds. Cumulative transfers based on bioavailability of BDE-99, -153, and -209 to eggs were 17%, 34%, and 15%, respectively. Egg residues were primarily present in yolk (12.3%, 23.5%, and 2.1% of the total dose for BDE-99, -153, and -209, respectively). Adipose, skin, ova, intestine, and thigh muscle contained the highest levels of radioactive tissue residues. These studies demonstrate movement of PBDE residues into edible tissues and eggs of laying hens.

Maternal transfer of environmentally relevant polybrominated diphenyl ethers (PBDEs) produces a diabetic phenotype and disrupts glucoregulatory hormones and hepatic endocannabinoids in adult mouse female offspring

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardant chemicals and environmental contaminants with endocrine-disrupting properties that are associated with diabetes and metabolic syndrome in humans. However, their diabetogenic actions are not completely characterized or understood. In this study, we investigated the effects of DE-71, a commercial penta-mixture of PBDEs, on glucoregulatory parameters in a perinatal exposure model using female C57Bl/6 mice. Results from in vivo glucose and insulin tolerance tests and ex vivo analyses revealed fasting hyperglycemia, glucose intolerance, reduced sensitivity and delayed glucose clearance after insulin challenge, decreased thermogenic brown adipose tissue mass, and exaggerated hepatic endocannabinoid tone in F1 offspring exposed to 0.1 mg/kg DE-71 relative to control. DE-71 effects on F0 dams were more limited indicating that indirect exposure to developing offspring is more detrimental. Other ex vivo glycemic correlates occurred more generally in exposed F0 and F1, i.e., reduced plasma insulin and altered glucoregulatory endocrines, exaggerated sympathoadrenal activity and reduced hepatic glutamate dehydrogenase enzymatic activity. Hepatic PBDE congener analysis indicated maternal transfer of BDE-28 and -153 to F1 at a collective level of 200 ng/g lipid, in range with maximum values detected in serum of human females. Given the persistent diabetogenic phenotype, especially pronounced in female offspring after developmental exposure to environmentally relevant levels of DE-71, additional animal studies should be conducted that further characterize PBDE-induced diabetic pathophysiology and identify critical developmental time windows of susceptibility. Longitudinal human studies should also be conducted to determine the risk of long-lasting metabolic consequences after maternal transfer of PBDEs during early-life development.

Exploring the environmental fate of novel brominated flame retardants in a sediment-water-mudsnail system: Enrichment, removal, metabolism and structural damage

Novel brominated flame retardants (NBFRs) are now ubiquitous in the environment with the extensive production and application. In the present study, pentabromotoluene (PBT), hexabromobenzene (HBB) and decabromodiphenyl ethane (DBDPE) were spiked into the sediments where mudsnails (Bellamya aeruginosa) were cultivated. In the 35-day enrichment process, the highest concentration of the three NBFRs measured in mudsnail is 2.0 mg/kg, 22 mg/kg and 5.2 mg/kg dry weight (dw), respectively. The average enrichment of NBFRs in viscera was about 3 times of pleopod with the same mass. Meanwhile, the parent mudsnails can transfer NBFRs to their offspring. The removal half-life of the three NBFRs was in the range of 2.6 and 5.7 days according to the first-order kinetic equation. Several degradation products of the NBFRs were detected in mudsnail samples, which were exposed to single substance. 2,4,6-tribromotoluene was identified as degradation product of PBT; 1,2,4,5-tetrabromobenzene and 1,2,4-tribromobenzene were identified as debromination products of HBB. Possible degradation pathways were further proposed. Additionally, mudsnails after exposed to 50 mg/kg of NBFRs were observed under a scanning electron microscope, indicating that shrinkage, tissue hyperplasia and perforation occurred on the visceral surface. Such damage might be related to the accumulation of more pollutants in mudsnails viscera. As one of the few studies to explore the biological process of NBFRs, our observation could provide a scientific basis for evaluating the environmental risks of NBFRs to benthic organisms.

Maternal organophosphate flame-retardant exposure alters offspring energy and glucose homeostasis in a sexually dimorphic manner in mice

Persistent organic pollutants such as organophosphate flame retardants (OPFRs) can accumulate in the body and interact with nuclear receptors that control energy homeostasis. One sensitive window of exposure is during development, either in utero or neonatal. Therefore, we investigated if maternal exposure to a mixture of OPFRs alters metabolism on a low-fat diet (LFD) or a high-fat diet (HFD) in both male and female offspring. Wild-type C57Bl/6J dams were orally dosed with vehicle (sesame oil) or an OPFR mixture (1 mg/kg each of tris(1,3-dichloro-2-propyl)phosphate, triphenyl phosphate, and tricresyl phosphate) from gestation day 7 to postnatal day 14. After weaning, pups were fed LFD or HFD. To assess metabolism, we measured body weight and food intake weekly and determined body composition, metabolism, activity, and glucose homeostasis at 6 months of age. Although maternal OPFR exposure did not alter body weight or adiposity, OPFR exposure altered substrate utilization and energy expenditure depending on diet in both sexes. Systolic and diastolic blood pressure was increased by OPFR in male offspring. OPFR exposure interacted with HFD to increase fasting glucose in females and alter glucose and insulin tolerance in male offspring. Plasma leptin was reduced in male and female offspring when fed HFD, whereas liver expression of Pepck was increased in females and Esr1 (estrogen receptor α) was increased in both sex. The physiological implications indicate maternal exposure to OPFRs programs peripheral organs including the liver and adipose tissue, in a sex-dependent manner, thus changing the response to an obesogenic diet and altering adult offspring energy homeostasis.

Metabolomic insights into the lasting impacts of early-life exposure to BDE-47 in mice

Early-life exposure to toxicants may have lasting effects that adversely impact later development. Thus, although the production and use of a toxicant have been banned, the risk to previously exposed individuals may continue. BDE-47, a component of commercial penta-BDEs, is a persistent organic pollutant with demonstrated neurotoxicity. To investigate the persistent effects of BDE-47 and the mechanisms thereof, we employed a metabolomics approach to analyze the brain, blood and urine of mice exposed to BDE-47 for 28 days and then 3 months post-exposure. In the brain, BDE-47 was detectable just after exposure but was below the limit of detection (LOD) 3 months later. However, the metabolomic alterations caused by early-life exposure to BDE-47 persisted. Potential biomarkers related to these alterations included phosphatidylcholine, lysophosphatidylcholine, sphingomyelin and several amino acids and biogenic amines. The metabolic pathways involved in the response to BDE-47 in the brain were mainly those related to glycerophospholipid metabolism, sphingomyelin metabolism and neurotransmitter regulation. Thus, our study demonstrates the utility of metabolomics, as the omics most closely reflecting the phenotype, in exploring the mechanisms underlying the lasting effects induced by early-life BDE-47 exposure.

Racial/ethnic and geographic differences in polybrominated diphenyl ether (PBDE) levels across maternal, placental, and fetal tissues during mid-gestation

Prenatal polybrominated diphenyl ether (PBDE) exposures are a public health concern due to their persistence and potential for reproductive and developmental harm. However, we have little information about the extent of fetal exposures during critical developmental periods and the variation in exposures for groups that may be more highly exposed, such as communities of color and lower socioeconomic status (SES). To characterize maternal-fetal PBDE exposures among potentially vulnerable groups, PBDE levels were examined in the largest sample of matched maternal serum, placenta, and fetal liver tissues during mid-gestation among a geographically, racially/ethnically, and socially diverse population of pregnant women from Northern California and the Central Valley (n = 180; 2014-16). Maternal-fetal PBDE levels were compared to population characteristics using censored Kendall's tau correlation and linear regression. PBDEs were commonly detected in all biomatrices. Before lipid adjustment, wet-weight levels of all four PBDE congeners were highest in the fetal liver (p < 0.001), whereas median PBDE levels were significantly higher in maternal serum than in the fetal liver or placenta after lipid-adjustment (p < 0.001). We also found evidence of racial/ethnic disparities in PBDE exposures (Non-Hispanic Black > Latina/Hispanic > Non-Hispanic White > Asian/Pacific Islander/Other; p < 0.01), with higher levels of BDE-100 and BDE-153 among non-Hispanic Black women compared to the referent group (Latina/Hispanic women). In addition, participants living in Fresno/South Central Valley had 34% (95% CI: - 2.4 to 84%, p = 0.07) higher wet-weight levels of BDE-47 than residents living in the San Francisco Bay Area. PBDEs are widely detected and differentially distributed in maternal-fetal compartments. Non-Hispanic Black pregnant women and women from Southern Central Valley geographical populations may be more highly exposed to PBDEs. Further research is needed to identify sources that may be contributing to differential exposures and associated health risks among these vulnerable populations.

Theoretical investigation of AhR binding property with relevant structural requirements for AhR-mediated toxicity of polybrominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are more frequently suspected with the induction of toxicity via signal transduction pathway of cytosolic aryl hydrocarbon receptor (AhR), the initial binding to which is assumed to be an essential prerequisite during the ligand-dependent activation. However, the AhR binding property and associated toxicity of PBDEs is yet to be clearly known for lacking insights into the structural requirements at molecular level. To understand the AhR binding property of PBDEs, the ligand binding domain (LBD) of AhR was simulatively developed on homologous protein after basic validation of geometrical rationality and the binding interaction profile was visually described using molecular docking approach. For AhR binding, the offset or edge-on π-π stackings with aromatic motifs including Phe289, Phe345 and His285 were shown to be structurally required whereas the electrostatic attraction validated for AhR binding to dioxins might be less effective for 2,2',3,4,4'-pentabromodiphenyl ether (BDE-85). Besides the demands of less steric hindrance from alanines and weak formulation of hydrogen bonds, the dispersion force through large contact and polarization of S-π electrons seemed to be impactful when BDE-85 were closer to Cys327, Met334 or Met342. With theoretical computation of AhR binding energies, the more significant correlativity with bioassays was derived especially for the lowly/moderately brominated congeners, and could be used to predict the AhR binding affinity on certain degree. The informative results would thus not only help well understand the molecular basis of AhR-mediated toxicity but give an approach for accelerative evaluation of AhR binding and toxicity of PBDEs.

Exposure to Heavy Metals in Electronic Waste Recycling in Thailand

Electronic waste recycling can release heavy metals into the environment and cause adverse health effects. We assessed the association between exposure to heavy metals from electronic waste recycling and the prevalence of asthma in a nested case-control study of 51 subject pairs with and without asthma. House dust, airborne dust, blood, and urine were collected from residents of two neighboring sites in Ubon Ratchathani province, Thailand. Multiple electronic waste-handling activities are conducted in the first site, while the second site is mostly agricultural. Concentrations of chromium, mercury, nickel, and lead in house dust and airborne dust were higher in the electronic waste-handling site (p < 0.05), but levels of exposure were similar in subjects with and without asthma. Although we did not find an association between exposure to these metals and the prevalence of asthma, control measures should be implemented to reduce health risks from long-term exposure to heavy metals.

Lactational exposure of polybrominated diphenyl ethers and its association with infant developmental measurements

This study was designed to assess the effect of lactational polybrominated diphenyl ether (PBDE) exposure on early physical development of both healthy and fetal growth restriction (FGR) infants. Z scores of head circumference-for-age (ZHC), length-for-age (ZLEN), weight-for-age (ZWEI) and weight-for-length (ZWFL) were calculated according to the WHO Child Growth Standards. FGR infants had a higher PBDE exposure level and faster growth speed from 42 days to 6 months compared with healthy infants. Exposure of lower brominated BDEs (BDE28∼154) and the sum of 18 BDE congeners (BDE28∼209) negatively associated with ZHC [mean difference estimate (95 % CI): -0.71 (-1.22, -0.22) and -0.81 (-1.31, -0.33)] in FGR boys. Both BDE153 and BDE196 exposure had a significant correlation with ZLEN of boys in FGR group [mean difference estimate (95 % CI): -0.28 (-0.48, -0.07) and -0.52 (-0.91, -0.14)]. Each 10 ng/g lipid increase in the concentrations of BDE154 were respectively associated with 0.16 increase in ZWEI among boys in healthy group. No significant association was found in girls. Lactational PBDE exposure had effects on the early growth of both FGR and healthy infants. The encouragement of breastfeeding should therefore be considered in conjunction with PBDE contamination levels.