Polybrominated Diphenyl Ether Flame Retardants Research Articles

Variations in thyroid hormone levels in endangered St. Lawrence Estuary belugas: Potential linkage with stress and organohalogen contaminant exposure

The St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population is highly exposed to an array of contaminants that were identified as one of the causes to the non-recovery of this endangered and declining population. In the last decade, an increasing number of parturition-associated complications and calf mortality has been reported in this population. It was suggested that elevated exposure to organohalogens (e.g., the halogenated flame retardants polybrominated diphenyl ethers [PBDEs]) and stress could play a role in this phenomenon by perturbing thyroid hormones. The objective of this study was to investigate the impact of concentrations of organohalogen contaminants and stress (cortisol levels) on thyroid hormone variations in adult male and female SLE belugas. Because plasma could not be collected in SLE belugas for ethical reasons, skin biopsy (n = 40) was used as a less-invasive alternative matrix to determine organohalogens (PBDEs and other halogenated flame retardants, polychlorinated biphenyls, and organochlorine pesticides), cortisol, and thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), and their metabolites reverse T3 and 3,5-diiodothyronine [3,5-T2]). Cortisol and thyroid hormones were analyzed by ultra-performance liquid chromatography-multiple reactions monitoring mass spectrometry (UPLC-MRM/MS). This method was compared using skin and plasma samples obtained from Arctic belugas. Comparisons of linear models showed that cortisol was a weak predictor for T4, rT3 and 3,5-T2. Specifically, there was a weak significant negative association between T4 and cortisol levels. Moreover, in male SLE belugas, a weak significant positive association was found between T3 and Σ34PBDE concentrations in skin. Our findings suggest that stress (i.e., elevated skin cortisol levels) along with organohalogen exposure (mainly PBDEs) may be associated with thyroid hormone level perturbations in skin of cetaceans.

Developmental hazards of 2,2′,4,4′-tetrabromodiphenyl ether induced endoplasmic reticulum stress on early life stages of zebrafish (Danio rerio)

Polybrominated diphenyl ether flame retardants are known to have adverse effects on the development of organisms. We investigated the molecular mechanisms associated with the developmental hazards of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in zebrafish, as well as the behavioral and morphological alterations involved, focusing on endoplasmic reticulum stress (ERS), oxidative stress, and apoptosis. Our study revealed behavioral alterations in zebrafish exposed to BDE-47, including impaired motor activity, reduced exploration, and abnormal swimming patterns. In addition, we observed malformations in craniofacial regions and other developmental abnormalities that may be associated with ERS-induced cellular dysfunction. BDE-47 exposure showed apparent changes in ERS, oxidative stress, and apoptosis biomarkers at different developmental stages in zebrafish through gene expression analysis and enzyme activity assays. The study indicated that exposure to BDE-47 results in ERS, as supported by the upregulation of ERS-related genes and increased activity of ERS markers. In addition, oxidative stress-related genes showed different expression patterns, suggesting that oxidative stress is involved in the BDE-47 toxic effects. Moreover, an assessment of apoptotic biomarkers revealed an imbalance in the expression levels of pro- and anti-apoptotic genes, suggesting that BDE-47 exposure activated the apoptotic pathway. These results highlight the complex interactions between ERS, oxidative stress, apoptosis, behavioral alterations, and morphological malformations following BDE-47 exposure in zebrafish. Understanding the mechanisms of toxicity of developmental hazards is essential to elucidate the toxicological effects of environmental contaminants. The knowledge can help develop strategies to mitigate their adverse effects on the health of ecosystems and humans.

Patterns of urinary organophosphate ester metabolite trajectories in children: the HOME Study.

Organophosphate esters (OPEs) have replaced flame retardant polybrominated diphenyl ethers as flame retardants in consumer products, but few longitudinal studies have characterized childhood OPE exposure. We aimed to examine the exposure pattern of urinary OPE metabolites in children. We quantified three urinary OPE metabolites five times in children (1, 2, 3, 5, 8 years) from 312 mother-child pairs in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio, USA. We examined the associations of average maternal OPE metabolite concentrations with OPE metabolite concentrations in childhood, characterized childhood OPE trajectories with latent class growth analysis (LCGA), and examined factors related to trajectory membership. Bis(2-chloroethyl) phosphate (BCEP) had the lowest median concentrations over time (0.66-0.97 mg/L) while the median concentrations of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) increased with age (1.44-3.80 mg/L). The median concentrations of diphenyl phosphate (DPHP) fluctuated between 1.96 and 2.69 mg/L. Intraclass correlation coefficients for urinary metabolites measured at five time points indicated high variability within individuals (0.13-0.24). Average maternal urinary BCEP and BDCIPP were associated with concentrations in early childhood. Maternal education, the birth year of the child, and having a carpet in the main activity room were associated with BCEP and BDCIPP trajectory while none of the factors were associated with DPHP trajectory. The trajectory analysis showed different patterns of urinary OPE metabolite concentrations, suggesting the need to collect multiple samples to adequately reflect OPE exposure. In this well-established cohort, we evaluated the patterns of urinary OPE metabolites in children ages 1-8 years. The number of repeated measures over childhood has not been achieved in prior studies. Our results suggested the high variability of urinary OPE metabolites within individuals. Maternal metabolite concentrations during pregnancy were related to child concentrations at ages 1-3 years. BCEP, BDCIPP, and DPHP demonstrated different trajectories in children, which suggests that multiple samples may be required to capture OPE exposure patterns in childhood.

A Hitchhiker's guide to persistent organic pollutants (POPs) monitoring in air: Establishing a baseline network in Sri Lanka

This study provides guidance on establishing new passive air monitoring capacity for persistent organic pollutants (POPs) to address data gaps and the demands of the Stockholm Convention and its Global Monitoring Plan (GMP). The approach presented in this case study in Sri Lanka is particularly relevant to developing countries/regions facing social and environmental pressures that preclude large financial investment in air monitoring capacity and instrumentation. Monitoring data can also lead to co-benefits in addressing intersecting issues, such as human health and biodiversity. Guidance is presented for a simple and cost-effective approach to establish a baseline air monitoring program using polyurethane foam (PUF) disk passive air samplers (PUF-PAS), through a step-wise method that includes: i. Justification; ii. Capacity Creation; iii. Planning; iv. Implementation; v. Analysis and Reporting; and vi. Intersecting Issues. Sampling was initiated at three representative sites in Sri Lanka that include a dry zone agricultural region (n = 5), an urban site (n = 5), and a remote mountain site (n = 3). Samples from the first 15-month deployment period, which started in 2015, were analyzed for legacy and emerging chemicals including polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ether flame retardants, organophosphate ester, flame retardants, and polycyclic aromatic compounds - including parent and alkylated polycyclic aromatic hydrocarbons and dibenzothiophenes. The results represent the first baseline data for Sri Lanka, against which data from future monitoring intervals will be compared to assess effectiveness of domestic and international control measures on POPs and emerging chemicals.

Organophosphate Esters Disrupt Steroidogenesis in KGN Human Ovarian Granulosa Cells.

Organophosphate esters (OPEs) are used extensively as flame retardants and plasticizers and are found ubiquitously in the environment and human matrices. Previous studies suggested that exposure to some of these chemicals may disrupt the homeostasis of female sex hormones and have detrimental effects on female fertility. Here, we determined the effects of OPEs on the function of KGN ovarian granulosa cells. We hypothesized that OPEs alter the steroidogenic ability of these cells by dysregulating the expression of transcripts involved in steroid and cholesterol biosynthesis. KGN cells were exposed for 48 hours to 1 of 5 OPEs (1-50μM): triphenyl phosphate (TPHP), tris(methylphenyl) phosphate (TMPP), isopropylated triphenyl phosphate (IPPP), tert-butylphenyl diphenyl phosphate (BPDP), and tributoxyethyl phosphate (TBOEP), or to a polybrominated diphenyl ether flame retardant, 2,2',4,4' tetrabromodiphenyl ether (BDE-47), in the presence or absence of Bu2cAMP. OPEs increased the basal production of progesterone (P4) and 17β-estradiol (E2) and had either no effect or inhibited Bu2cAMP-stimulated P4 and E2 synthesis; exposure to BDE-47 had no effect. Quantitative real-time polymerase chain reaction (qRT-PCR) analyses revealed that OPEs (≥5μM) increased the basal expression of critical genes (STAR, CYP11A1, CYP19A1, HSD3B2, and NR5A1) involved in steroidogenesis; upon stimulation, the expression of all genes tested was downregulated. An overall inhibition in cholesterol biosynthesis was induced by OPEs, characterized by a downregulation in HMGCR and SREBF2 expression. TBOEP consistently showed the least effect. Therefore, OPEs perturbed steroidogenesis in KGN granulosa cells by targeting the expression of steroidogenic enzymes and cholesterol transporters; these effects may have an adverse impact on female reproduction.

High resolution mass spectrometric suspect screening, wide-scope target analysis of emerging contaminants and determination of legacy pollutants in adult black-tailed godwit Limosa limosa limosa in the Netherlands – A pilot study

The Dutch breeding population of the black-tailed godwit Limosa limosa limosa has declined substantially over recent decades; the role of contaminants is unknown. We analysed liver samples from 11 adult birds found dead on their breeding grounds in SW Friesland 2016–2020, six from extensive, herb-rich grasslands, five from intensive grasslands. We carried out LC and GC wide-scope target analysis of more than 2400 substances, LC suspect screening for more than 60,000 substances, target analysis for Cd, Hg, Ni and Pb, organo-phosphate flame retardants (OPFRs), dechlorane plus compounds and selected polybrominated diphenyl ether flame retardants (PBDEs), and bioassay for polybrominated dibenzo-p-dioxins and dibenzofurans (PBDDs/PDBFs) and dioxin-like polychlorinated biphenyls (dl-PCBs). Residues of 29 emerging contaminants (ECs) were determined through wide-scope target analysis. Another 20 were tentatively identified through suspect screening. These contaminants include industrial chemicals (personal care products, surfactants, PAHs and others), plant protection products (PPPs) and pharmaceuticals and their transformation products. Total contaminant load detected by wide-scope target analysis ranged from c. 155 to c. 1400 ng g−1 and was generally lower in birds from extensive grasslands. Heatmaps suggest that birds from intensive grasslands have a greater mix and higher residue concentrations of PPPs, while birds from extensive grasslands have a greater mix and higher residue concentrations of per- and polyfluoroalkyl substances (PFAS). All four metals and two OPFRs were detected. All tested PBDEs were below the respective LODs. Bioassay revealed presence of PBDDs, PBDFs and dl-PCBs. Further research is required to elucidate potential health risks to godwits and contaminant sources.

Metabolite alterations in zebrafish embryos exposed to hydroxylated polybrominated diphenyl ethers.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) are formed by metabolism from the flame retardants polybrominated diphenyl ethers (PBDEs). In the aquatic environment, they are also produced naturally. OH-PBDEs are known for their potential to disrupt energy metabolism, the endocrine system, and the nervous system. This is the first study focusing on the effects of OH-PBDEs at the metabolite level in vivo. The aim of the current study was to investigate the metabolic effects of exposure to OH-PBDEs using metabolomics, and to identify potential biomarker(s) for energy disruption of OH-PBDEs. Zebrafish (Danio rerio) embryos were exposed to two different concentrations of 6-OH-BDE47 and 6-OH-BDE85 and a mixture of these two compounds. In total, 342 metabolites were annotated and 79 metabolites were affected in at least one exposure. Several affected metabolites, e.g. succinic acid, glutamic acid, glutamine, tyrosine, tryptophan, adenine, and several fatty acids, could be connected to known toxic mechanisms of OH-PBDEs. Several phospholipids were strongly up-regulated with up to a six-fold increase after exposure to 6-OH-BDE47, a scarcely described effect of OH-PBDEs. Based on the observed metabolic effects, a possible connection between disruption of the energy metabolism, neurotoxicity and potential immunotoxicity of OH-PBDEs was suggested. Single compound exposures to 6-OH-BDE47 and 6-OH-BDE85 showed little overlap in the affected metabolites. This shows that compounds of similar chemical structure can induce different metabolic effects, possibly relating to their different toxic mechanisms. There were inter-concentration differences in the metabolic profiles, indicating that the metabolic effects were concentration dependent. After exposure to the mixture of 6-OH-BDE47 and 6-OH-BDE85, a new metabolic profile distinct from the profiles obtained from the single compounds was observed. Succinic acid was up-regulated at the highest, but still environmentally relevant, concentration of 6-OH-BDE47, 6-OH-BDE85, and the mixture. Therefore, succinic acid is suggested as a potential biomarker for energy disruption of OH-PBDEs.

Highly contaminated river otters (Lontra canadensis) are effective biomonitors of environmental pollutant exposure

River otters (Lontra canadensis) are apex predators that bioaccumulate contaminants via their diet, potentially serving as biomonitors of watershed health. They reside throughout the Green-Duwamish River, WA (USA), a watershed encompassing an extreme urbanization gradient, including a US Superfund site slated for a 17-year remediation. The objectives of this study were to document baseline contaminant levels in river otters, assess otters’ utility as top trophic-level biomonitors of contaminant exposure, and evaluate the potential for health impacts on this species. We measured a suite of contaminants of concern, lipid content, nitrogen stable isotopes (δ15N), and microsatellite DNA markers in 69 otter scat samples collected from twelve sites. Landcover characteristics were used to group sampling sites into industrial (Superfund site), suburban, and rural development zones. Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ether flame-retardants (PBDEs), dichlorodiphenyl-trichloroethane and its metabolites (DDTs), and polycyclic aromatic hydrocarbons (PAHs) increased significantly with increasing urbanization, and were best predicted by models that included development zone, suggesting that river otters are effective biomonitors, as defined in this study. Diet also played an important role, with lipid content, δ15N or both included in all best models. We recommend river otter scat be included in evaluating restoration efforts in this Superfund site, and as a potentially useful monitoring tool wherever otters are found. We also report ΣPCB and ΣPAH exposures among the highest published for wild river otters, with almost 70% of samples in the Superfund site exceeding established levels of concern.

Exposure to Polybrominated Diphenyl Ether Flame Retardants Causes Deoxyribonucleic Acid Damage in Human Thyroid Cells In Vitro

IntroductionThe incidence of papillary thyroid cancer (PTC) in the United States has tripled in the past 30 y. Polybrominated diphenyl ethers (PBDEs) are flame retardants that were ubiquitously used over that time period, and exposure to PBDEs has been associated with PTC prevalence. They are potential carcinogens via their induction of reactive oxygen species (ROS) formation and resultant deoxyribonucleic acid (DNA) damage. We sought to determine the effects of PBDE and tris(2-chloroethyl) phosphate (TCEP), another flame retardant implicated in PTC incidence, on thyrocytes in vitro and measure PBDE levels in human thyroid tissue to determine their carcinogenic potential. MethodsNthy-Ori, an immortalized benign human thyroid follicular cell line was used as a model of normal human thyroid. MTT assays were used to measure cell viability after exposure to PBDEs and TCEP. ROS levels and double-stranded and single-stranded DNA breaks were measured to determine genotoxicity. DNA damage response protein levels were measured with immunoblotting. ResultsExposure to 20μM PBDE or TCEP for 48 h had minimal effects on thyrocyte viability. There was no significant increase in intracellular ROS up to 6 h following PBDE or TCEP exposure in thyrocytes; however, cells exposed to PBDE 47 showed evidence of DNA single-stranded and double-stranded breaks. There was a dose-dependent increase in γH2AX levels following exposure to PBDEs 47 and 209 in Nthy-Ori cells but not with TCEP treatment. ConclusionsPBDE 47 and 209 demonstrated genotoxicity but not cytotoxicity in follicular thyrocytes in vitro. Therefore, PBDE 47 and 209 may be carcinogenic in human thyroid cells.

Developmental exposure to the DE-71 mixture of polybrominated diphenyl ether (PBDE) flame retardants induce a complex pattern of endocrine disrupting effects in rats.

Polybrominated diphenyl ethers (PBDEs) are legacy compounds with continued widespread human exposure. Despite this, developmental toxicity studies of DE-71, a mixture of PBDEs, are scarce and its potential for endocrine disrupting effects in vivo is not well covered. To address this knowledge gap, we carried out a developmental exposure study with DE-71. Pregnant Wistar rat dams were exposed to 0, 40 or 60 mg/kg bodyweight/day from gestation day 7 to postnatal day 16, and both sexes were examined. Developmental exposure affected a range of reproductive toxicity endpoints. Effects were seen for both male and female anogenital distances (AGD), with exposed offspring of either sex displaying around 10% shorter AGD compared to controls. Both absolute and relative prostate weights were markedly reduced in exposed male offspring, with about 40% relative to controls. DE-71 reduced mammary gland outgrowth, especially in male offspring. These developmental in vivo effects suggest a complex effect pattern involving anti-androgenic, anti-estrogenic and maybe estrogenic mechanisms depending on tissues and developmental stages. Irrespective of the specific underlying mechanisms, these in vivo results corroborate that DE-71 causes endocrine disrupting effects and raises concern for the effects of PBDE-exposure on human reproductive health, including any potential long-term consequences of disrupted mammary gland development.

Analysis of Polybrominated Diphenyl Ethers and Lipid Composition in Human Breast Milk and Their Correlation with Infant Neurodevelopment.

Breastfeeding is recommended over formula feeding, but human breast milk (HBM) composition varies and can be affected by food additives. Whether flame-retardant polybrominated diphenyl ethers (PBDEs) found in HBM interact with lipid components of HBM to impede infant neurodevelopment is a critical public health issue. Using lipidomic analysis, we examined the association of PBDEs in HBM and HBM lipid components with infant neurodevelopment. HBM samples (n = 100) were collected at the beginning stage of breastfeeding and analyzed for 30 PBDE congeners as well as a group of lipid components by using high-resolution gas chromatography, mass spectrometry, and liquid chromatography time-of-flight mass spectrometry. Infants were examined at 8 to 12 months of age by using the Bayley-III to assess neurodevelopment. A total of seven PBDEs, 35 lipids, and 27 fatty acids in HBM showed significant associations with Bayley-III scores. Multivariate analysis confirmed that these candidate PBDEs and lipid components were significant predictors of infant neurodevelopment. Eicosapentaenoic acid and docosapentaenoic acid in HBM showed no association with infant neurodevelopment in the general Taiwanese population. While certain PBDEs may play a role, our findings indicate that the lipid components of HBM are directly important for infant neurodevelopment.

Impacts of PBDE-47 exposure before, during and after pregnancy on the maternal gut microbiome and its association with host metabolism

Maternal gut microbiota play an important role in the modulation of offspring disease susceptibility and gut microbiota dysbiosis has been proposed as a mechanism through which toxic environmental chemicals exert their adverse impacts on health. The brominated flame retardants polybrominated diphenyl ethers (PBDEs) are developmental toxicants and induce dysbiotic gut microbiota in offspring. Yet, whether and how PBDEs impact the maternal gut microbiota remain unclear. Here, we sought to investigate the effect of 2,2′,4,4′-tetrabromodiphenyl ether (PBDE-47) exposure from preconception through lactation cessation on maternal gut microbiota and its link to host serum metabolic consequences. Female Sprague-Dawley rats were daily exposed to 10 mg/kg PBDE-47 via oral gavage from ten days before conception until offspring were weaned on postnatal day 21, then maternal fecal and blood samples were collected for microbiome and metabolome analyses by using 16S ribosomal RNA gene sequencing and gas chromatography-mass spectrometry, respectively. Maternal exposure to PBDE-47 showed a distinct profile in gut microbiota compared to control dams, as evidenced by increased Actinobacteria phylum and genera Blautia, Gemella and Phascolarctobacterium, and decreased genera AF12 and Oscillospira. Additionally, global metabolomics analysis identified 26 differential serum metabolites to distinguish PBDE-47 from controls, which were mainly involved in amino acid, lipid, carbohydrate and energy metabolism, further confirmed by pathway analysis. Importantly, the differential serum metabolites are closely correlated with the disturbed gut microbiota in response to PBDE-47. Collectively, our results suggest that maternal gut microbial dysbiosis may serve as a potential mechanism underlying PBDE-47-elicited health hazards to mothers or even offspring.

Evaluation of polybrominated diphenyl ether (PBDE) flame retardants from various materials in professional seating furnishing wastes from French flows.

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that are used in polymeric materials. Due to their adverse health effects, the use of recycled wastes has been forbidden if the total PBDE content exceeds 0.1% (w/w). The objective was to estimate the proportion of PBDEs in professional seating furnishing wastes to identify the materials in which the content of PBDEs (and particularly BDE-209) could exceed the limit to eliminate them from recycling. An analytical process (microwave extraction followed by purification and chromatographic analysis) was adapted to assess with a unique methodology the amounts of eight PBDEs in materials that result from various seating wastes, such as hard plastics, foams and accompanying textiles. X-ray fluorescence (XRF) was used to rapidly predict critical PBDE concentrations via Br. From 100 samples, the total PBDE content did not exceed the current tolerated threshold. The examined materials contained only trace levels of former PBDE formulations, and BDE-209 was identified at higher amounts, mainly in hard plastics, but these amounts were less than 312mgkg-1. Since XRF was not reliable for quantitative measurements and was not specific, no direct correlation could be identified between Br and PBDE levels. Br was strongly associated with As in all the materials, but the presence of PBDEs was not clearly associated with the presence of other metals that are used in flame retardants.

Association of exposure to organophosphate flame retardants and children's behavior at a median age of 18 months

Exposure to polybrominated diphenyl ether (PBDE) flame retardants (FRs) could have adverse effects on neurodevelopment in children. Some organophosphate (OPFRs) are used as alternatives for the phased-out decabromodiphenylether such as resorcinol bis(diphenyl phosphate (PBDPP) and bisphenol A bis(diphenyl phosphate (BPA-BDPP). This study aims to investigate the relationship between indoor OPFR exposure and neurodevelopmental behavior in children. OPFRs were measured in house dust and hand wipes from 42 children, aged 8-16 months, from the LInking maternal Nutrition to Child health (LINC) study. At the median age of 18 months, the children's behavior was assessed with the Child Behavior Checklist, using three composite behavior scales: externalizing problems, internalizing problems, and total problems. Linear regression analysis was performed, adjusting for maternal education and smoking by the partner. Children with higher BPA-BDPP, PBDPP, and tris(chloroethyl) phosphate (TCEP) house dust concentrations were found to have higher scores on the behavioral problems scales. A 10-fold increase in BPA-BDPP and PBDPP concentration was associated with a 4.1 and 2.6 point increase on the internalizing problems scale (respectively p=0.004 and p=0.042). Increased BPA-BDPP concentrations were associated with elevated scores on the externalizing problems scale and total behavioral problems scale (respectively 7.6 and 16 points increase per 10-fold BPA-BDPP concentration increase, p=0.015 and p=0.007). TCEP dust concentrations were associated with the externalizing problems scale (13 point increase per 10-fold TCEP concentration increase, p=0.043). This study showed the importance of investigating the health effects of exposure to organophosphate flame retardants. Further research on neurodevelopmental health effects of OPFR exposure is warranted.

Effects of flame retardants on ovarian function

Flame retardants have been added to a variety of consumer products and are now found ubiquitously throughout the environment. Epidemiological, in vivo, and in vitro studies have shown that polybrominated diphenyl ether (PBDE) flame retardants may have a negative impact on human health; this has resulted in their phase-out and replacement by alternative flame retardants, such as hexabromocyclododecane (HBCDD), tetrabromobisphenol A (TBBPA), and organophosphate esters (OPEs). Evidence suggests that some of these chemicals induce ovarian dysfunction and thus may be detrimental to female fertility; however, the effects of many of these flame retardants on the ovary remain unclear. In this review, we present an overview of the effects of brominated and organophosphate ester flame retardants on ovarian function and discuss the possible mechanisms which may mediate these effects.

Exposure to 4-bromodiphenyl ether during pregnancy blocks testis development in male rat fetuses

4-Bromodiphenyl ether (BDE3) is a photodegradation product of higher polybrominated diphenyl ether flame retardants and is known as an endocrine disruptor. However, it is unclear whether and how BDE3 affects the development of fetal testes. This study aimed to investigate the effect of in utero exposure to BDE3 on fetal testicular development in rats. From gestational day (GD) 12–21, BDE3 (0, 50, 100, and 200 mg/kg) was daily gavaged to female pregnant Sprague Dawley rats. BDE3 significantly reduced serum testosterone levels of male pups starting at 50 mg/kg. BDE3 reduced fetal Leydig cell number at a dose of 200 mg/kg without affecting fetal Leydig cell cluster frequency and Sertoli cell number. In addition, BDE3 down-regulated the expression of fetal Leydig cell genes (Cyp11a1, Hsd3b1, Cyp17a1, and Hsd17b3) and their proteins at 100 and/or 200 mg/kg. RNA-seq analysis showed that genes responsive to cAMP (Ass1, Gpd1, Rpl13a) were down-regulated and hypoxia-related genes (Egln3 and P4ha1) were up-regulated at 200 mg/kg. In utero exposure to BDE3 can promote autophagy and apoptosis of fetal Leydig cells via increasing the levels of Beclin1, LC3-II, BAX, and by decreasing the levels of p62 and BCL2. In conclusion, in utero exposure to BDE3 blocks the development of fetal rat testes.

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.

Abstract IA26: Carcinogens in consumer products: How science can inform policy to benefit public health

Abstract Flame-retardant chemicals have been added to furniture, baby products, electronics, and building materials since the 1970s to meet flammability standards, but their effectiveness is questionable and many are associated with serious health and environmental concerns. Flame-retardant chemicals are associated with health concerns including loss of IQ in children, ADHD, fertility problems, and cancer. Flame retardants do not stay inside products; they migrate out into indoor air and dust and result in human exposure through inhalation, ingestion, and dermal contact. Significant exposure disparities are seen by age, race, and socioeconomic status (SES), with higher flame-retardant levels documented in infants/ toddlers, nonwhite children, and children of lower SES. Exposures to the flame retardants polybrominated diphenyl ethers (PBDEs) are associated with increased risks for testicular cancer, estimated to result in thousands of excess cancer cases in the U.S. population at a cost of over $80 million annually. The phaseout of PBDEs resulted in a large number of halogenated and nonhalogenated chemicals being used as replacement flame retardants, with studies finding almost 50 unique replacement flame retardants in U.S. indoor dust samples alone. A number of these replacement flame retardants, especially chlorinated chemicals, have identified cancer hazards. A recent assessment from the European Chemicals Agency found increased risks of cancer from infants’ exposures to “chlorinated Tris” flame retardants in children’s products and furniture. Chemical policies have generally managed flame retardants through a paradigm of allowing use while conducting an in-depth, quantitative risk assessment of specific chemicals to inform risk management. Risk assessments include studies of human exposures and effects, and if the chemical is found to be harmful, health damages may already have occurred prior to regulatory decisions. However, there is increasing recognition that this paradigm is insufficient to address current chemicals and their exposures before harm or keep pace with the proliferation of new chemicals. This presentation will review policy approaches attempting to address existing and emerging flame retardants and where possible, present data on their effectiveness in reducing chemical risks. Citation Format: Veena Singla, Tracey Woodruff. Carcinogens in consumer products: How science can inform policy to benefit public health [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr IA26.

Effects of brominated and organophosphate ester flame retardants on male reproduction

Environmental chemicals that interfere with the production and/or action of hormones may have adverse effects on male reproduction. This review focuses on the possible impact of exposure to flame retardant chemicals on male reproduction. Flame retardants are added to a wide variety of combustible materials to prevent fires from starting, slow their spread, and provide time to escape. However, these chemicals are often additive so they leach out into the environment. Governments have restricted the use of polybrominated diphenyl ether flame retardants based on evidence that they are persistent and bioaccumulate and have adverse effects on health. The phasing out of these "legacy" flame retardants has resulted in their replacement with alternatives, such as tetrabromobisphenol A and the organophosphate esters. To review the literature on the effects of brominated and organophosphate ester flame retardant chemicals on male reproduction. PubMed database was searched for studies reporting the effects of brominated and organophosphate ester flame retardants on male reproduction. Cell-based, animal model, and human studies provide evidence that the polybrominated diphenyl ethers act as endocrine-disrupting chemicals; further, exposure during critical windows of development may be associated with a permanent impact on male reproduction. In vitro and animal model data are accumulating with respect to the effects of tetrabromobisphenol A and organophosphate esters, but few studies have evaluated their impact on human health. More research on human exposure to replacement flame retardants and the possibility that they may be associated with adverse reproductive health outcomes is a high priority.

Temporal trends and determinants of PFR exposure in the Hokkaido Study.

The phase-out of polybrominated diphenyl ethers (PBDE) flame retardants has led to the rapid increase of alternatives such as phosphate flame retardants and plasticizers (PFRs) in many consumer products. Exposure to these additive chemicals is widespread and potentially harmful to humans and the environment. In the present study, we assessed the exposure to PFRs through the analysis of metabolites in urine collected from 7-year old children from Hokkaido, Japan between 2012 and 2017. This allowed us to investigate temporal and seasonal trends for PFR metabolite concentrations and to study determinants of exposure. Thirteen metabolites of seven PFRs were measured in morning spot urine samples (n=400). Multiple regression models were used to quantify the yearly increase in metabolite concentrations per sampling year. Information on the demographics, indoor environment and dietary habits of the participants were derived from self-administered questionnaires. PFR metabolite concentrations were comparable to our previous study of school children (7-12 years old). Eight PFR metabolites were detected in >50% of the samples. During the study time period, concentrations of three metabolites increased significantly: bis(1,3-dichloro-2-propyl) phosphate (BDCIPP; 13.3% per year), 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP; 12.9% per year), and 2-ethylhexyl phenyl phosphate (EHPHP; 6.7% per year). We also found seasonality as a determinant for several PFR metabolites, with 2-fold higher levels in summer for BCIPHIPP and BDCIPP. Concentrations were also significantly impacted by ventilation habits. More frequent window opening or use of mechanical ventilation was consistently associated with higher levels of PFR metabolites in children's urine. This is the first study to show that human exposure to PFRs has increased in recent years in Japan, which indicates that further research into this class of chemicals is warranted.