Children's exposure to brominated flame retardants in indoor environments - A review

Global patterns of human exposure to flame retardants indoors

To fill the knowledge gaps regarding the global patterns of human exposure to flame retardants (FRs) (i.e., brominated flame retardants (BFRs) and organophosphorus flame retardants (OPFRs)), data on the levels and distributions of FRs in external and internal exposure mediums, including indoor dust, indoor air, skin wipe, serum and urine, were summarized and analysed. Comparatively, FR levels were relatively higher in developed regions in all mediums, and significant positive correlations between FR contamination and economic development level were observed in indoor dust and air. Over time, the concentration of BFRs showed a slightly decreasing trend in all mediums worldwide, whereas OPFRs represented an upward tendency in some regions (e.g., the USA and China). The occurrence levels of FRs and their metabolites in all external and internal media were generally correlated, implying a mutual indicative role among them. Dermal absorption generally contributed >60% of the total exposure of most FR monomers, and dust ingestion was dominant for several low volatile compounds, while inhalation was found to be negligible. The high-risk FR monomers (BDE-47, BDE-99 and TCIPP) identified by external exposure assessment showed similarity to the major FRs or metabolites observed in internal exposure mediums, suggesting the feasibility of using these methods to characterize human exposure and the contribution of indoor exposure to the human burden of FRs. This review highlights the significant importance of exposure assessment based on multiple mediums for future studies.

Toxic trespassers: Uncovering phthalates and organophosphate flame retardants in children's rooms and their health implications

Organophosphate flame retardants (OPEs) and phthalates have garnered significant attention due to their widespread presence in indoor environments. Many recent investigations have reported extensive contamination of indoor dust, air, children's toys, and other environmental compartments with these chemicals. This research aimed to analyze OPEs and phthalates in air (PM10) and dust samples collected from the bedrooms of children (N = 30) residing in various households in Jeddah, Saudi Arabia. High mean levels (ng/g) of phthalates namely DEHP (1438600) and DnBP (159200) were found in indoor dust while TPhP (5620) was the major OPEs in indoor dust. Similarly, DEHP and DnBP were the predominant phthalates in PM10 samples, exhibiting mean levels of 560 and 680 ng/m3, respectively. However, TCPP was the main OPEs with average levels of 72 ng/m3 in PM10 samples. The majority of individual phthalates and OPEs were detected in 90-100 % of the dust samples, whereas in PM10 samples, their presence ranged from 25 % to 100 %. The concentrations of OPEs were notably greater than those of PBDEs and other BFRs previously reported in these samples, suggesting their broader use than alternative BFRs. The estimated long-term non-carcinogenic risk, hazardous index (HI) and daily exposure via dust for children was above threshold levels for DEHP. On the other hand, the cumulative risk of cancer was below the concerning levels. Further research is required to explore diverse groups of chemicals in indoor microenvironments particularly significant for children, such as kindergartens, primary schools, and their rooms at home.

Transgenerational effects of BDE-47 to zebrafish based on histomorphometry and toxicogenomic analyses

Exposure to 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) has been found to have an impact on reproductive output and endocrine function in female zebrafish (Danio rerio). However, the transgenerational effects of BDE-47 have not been fully explored in previous reports. In this study, female zebrafish were exposed to BDE-47 for three consecutive weeks. The oogenesis, sex hormones, reproductive histology, and transcriptional profiles of genes along the hypothalamus-pituitary-gonad (HPG) axis were assessed in the exposed-F0 generation. After mating with unexposed males, the transgenerational effects of BDE-47 were evaluated on the basis of histopathology, morphometry and toxicogenome of the unexposed F1 generations at the larval stage. Results indicated that exposure to BDE-47 impaired reproductive capacity, disrupted endocrine system in F0 zebrafish, and compromised craniofacial skeletons and vertebrae development in F1 generations. In addition, through the use of toxicogenomics approach, immune-responsive pathways were found to be significantly enriched, and the transcript expression profiling of immune-related DEGs (IRDs) were dramatically inhibited in F1 generations following maternal BDE-47 exposure, indicating its immunotoxicity to offspring larvae. These findings advance our understanding of the transgenerational toxicity of BDE-47 and advocate for a more comprehensive assessment of other PBDE congeners through histomorphometry and toxicogenomic approaches.

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.

Extended exposure to tetrabromobisphenol A-bis(2,3-dibromopropyl ether) leads to subfertility in male mice at the late reproductive age

Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), a commonly used brominated flame retardant as a decabromodiphenyl ether substitute, has been detected in various environmental compartments, but its health hazards remain largely unknown. Our recent study showed that low-dose exposure of male mice to TBBPA-BDBPE from postnatal day (PND) 0 to 56 caused remarkable damage to the microtubule skeleton in Sertoli cells and the blood-testis barrier (BTB) but exerted little effect on conventional reproductive endpoints in adulthood. To investigate whether TBBPA-BDBPE may cause severe reproductive impairments at late reproductive age, here, we extended exposure of historically administrated male mice to 8-month age and allowed them to mate with non-treated females for the evaluation of fertility, followed by a general examination for the reproductive system. As expected, we found that 8-month exposure to 50 μg/kg/d as well as 1000 μg/kg/d TBBPA-BDBPE caused severe damage to the reproductive system, including reduced sperm counts, increased sperm abnormality, histological alterations of testes. Moreover, microtubule damage and BTB-related impairment were still observed following 8-month exposure. Noticeably, high-dose TBBPA-BDBPE-treated mice had fewer offspring with a female-biased sex ratio. All results show that long-term exposure to TBBPA-BDBPE caused severe reproductive impairment, including poor fertility at late reproductive age. It is therefore concluded that slight testicular injuries in early life can contribute to reproductive impairment at late reproductive age, highlighting that alterations in certain non-conventional endpoints should be noticed as well as conventional endpoints in future reproductive toxicity studies.

Organohalogenated flame retardants and organophosphate esters from home and preschool dust in Sweden: Pollution characteristics, indoor sources and intake assessment

This study analysed settled dust samples in Sweden to assess children's combined exposure to 39 organohalogenated flame retardants (HFRs) and 11 organophosphate esters (OPEs) from homes and preschools. >94 % of the targeted compounds were present in dust, indicating widespread use of HFRs and OPEs in Swedish homes and preschools. Dust ingestion was the primary exposure pathway for most analytes, except BDE-209 and DBDPE, where dermal contact was predominant. Children's estimated intakes of ∑emerging HFRs and ∑legacy HFRs from homes were 1-4 times higher than from preschools, highlighting higher exposure risk for HFRs in homes compared to preschools. In a worst-case scenario, intakes of tris(2-butoxyethyl) phosphate (TBOEP) were 6 and 94 times lower than the reference dose for children in Sweden, indicating a potential concern if exposure from other routes like inhalation and diet is as high. The study also found significant positive correlations between dust concentrations of some PBDEs and emerging HFRs and the total number of foam mattresses and beds/m2, the number of foam-containing sofas/m2, and the number of TVs/m2 in the microenvironment, indicating these products as the main source of those compounds. Additionally, younger preschool building ages were found to be linked to higher ΣOPE concentrations in preschool dust, suggesting higher ΣOPE exposure. The comparison with earlier Swedish studies indicates decreasing dust concentrations for some banned and restricted legacy HFRs and OPEs but increasing trends for several emerging HFRs and several unrestricted OPEs. Therefore, the study concludes that emerging HFRs and OPEs are replacing legacy HFRs in products and building materials in homes and preschools, possibly leading to increased exposure of children.

Novel biomonitoring method for determining five classes of legacy and alternative flame retardants in human serum samples

Flame retardants (FRs) are ubiquitous in environment and biota and may pose harm to human health. In recent years, concern regarding legacy and alternative FRs has been intensified due to their widespread production and increasing contamination in environmental and human matrices. In this study, we developed and validated a novel analytical method for simultaneous determination of legacy and alternative FRs, including polychlorinated naphthalenes (PCNs), short- and middle-chain chlorinated paraffins (SCCPs and MCCPs), novel brominated flame retardants (NBFRs), and organophosphate esters (OPEs) in human serum. Serum samples were prepared by liquid-liquid extraction using ethyl acetate, and purified with Oasis® HLB cartridge and Florisil-silica gel columns. Instrumental analyses were carried out using gas chromatography-triple quadrupole mass spectrometry, high-resolution gas chromatography coupled with high-resolution mass spectrometry, and gas chromatography coupled with quadrupole time-of-flight mass spectrometry, respectively. The proposed method was validated for linearity, sensitivity, precision, accuracy, and matrix effects. Method detection limits for NBFRs, OPEs, PCNs, SCCPs, and MCCPs were 4.6 × 10^-4-8.6 × 10^-2, 4.3 × 10^-3-1.3, 1.1 × 10^-5-1.0 × 10^-4, 1.5, and 9.0 × 10^-1 ng/mL, respectively. Matrix spike recoveries ranged from 73%-122%, 71%-124%, 75%-129%, 92%-126%, and 94%-126% for NBFRs, OPEs, PCNs, SCCPs, and MCCPs, respectively. The analytical method was applied for detection of real human serum. CPs were the dominant FRs in serum, indicating CPs were widely presented in human serum and should be pay more attention for their health risk.

Current status of indoor dust PBDE pollution and its physical burden and health effects on children

Polybrominated diphenyl ethers (PBDEs) are widely detected in indoor dust, which has been identified as a more important route of PBDE exposure for children than food intake. The physical burden and health hazards to children of PBDE exposure in house dust have not been adequately summarized; therefore, this article reviews the current status of PBDE pollution in indoor dust associated with children, highlighting the epidemiological evidence for physical burden and health risks in children. We find that PBDEs remain at high levels in indoor dust, including in homes, schools, and cars, especially in cars showing a significant upward trend. There is a trend towards an increase in the proportion of BDE-209 in household dust, which is indicative of recent PBDE contamination. Conversely, PBDE congeners in car and school indoor dust tended to shift from highly brominated to low brominated, suggesting a shift in current pollution patterns. Indoor dust exposure causes significantly higher PBDE burdens in children, especially infants in early life, than in adults. Exposure to dust also affects breast milk, putting infants at high risk of exposure. Although evidence is limited, available epidemiological studies suggest that exposure to indoor dust PBDEs promotes neurobehavioral problems and cancer development in children.

Distribution of flame retardants among indoor dust, airborne particles and vapour phase from Beijing: spatial-temporal variation and human exposure characteristics

The occurrence and distribution of 10 brominated flame retardants (BFRs) and 10 organophosphate flame retardants (OPFRs) were investigated in indoor dust, total suspended particles (TSP), and vapour phase from offices (n = 10), homes (n = 9), and day-care centres (n = 10) in Beijing, China. Three types of samples were collected biweekly from one office and one home over a year to examine temporal trends. BFRs in dust significantly correlated with those in TSP, while OPFRs significantly correlated among all three matrices. In addition, BFRs in dust (ng/g) and TSP (pg/m³) exhibited similar temporal trends with higher levels in the cold season, whereas OPFRs in TSP and vapour phase (pg/m³) showed similar temporal trends with higher levels in the warm season. The geometric mean concentrations of BFRs and OPFRs in the three matrices from the above mentioned three types of indoor microenvironments were used for exposure and health risk estimation, and ∑₇OPFRs showed much higher hazard index (HI) values than ∑₁₀BFRs for all subpopulations, and inhalation of OPFRs was a major risk source. With the volatility of flame retardants (FRs) decreasing, the contribution of dust ingestion and dermal absorption showed an increasing trend, and the contribution of inhalation exhibited a gradual decreasing trend, which implied the dominant exposure pathway to FRs is strongly related to the vapour pressure (25 °C, Pa) of these substances. Using a single type of microenvironment or the collection of samples at a single point in time can lead to overestimation or underestimation of overall exposure and risk for people to some extent. The correlations of FRs in dust, TSP, and vapour phase from indoor microenvironments, as well as their temporal trends were first reported in this study, which will provide a basis for more accurate FR exposure assessments in the future.

BDE-47, -99, -209 and Their Ternary Mixture Disrupt Glucose and Lipid Metabolism of Hepg2 Cells at Dietary Relevant Concentrations: Mechanistic Insight through Integrated Transcriptomics and Proteomics Analysis

Polybrominated diphenyl ethers (PBDEs) are persistent organic chemicals implied as flame retardants. Humans are mainly exposed to BDE-47, -99, and -209 congeners by diet. PBDEs are metabolic disruptors with the liver as the main target organ. To investigate their mode of action at a human-relevant concentration, we exposed HepG2 cells to these congeners and their mixture at 1 nM, analyzing their transcriptomic and proteomic profiles. KEGG pathways and GSEA Hallmarks enrichment analyses evidenced that BDE-47 disrupted the glucose metabolism and hypoxia pathway; all the congeners and the MIX affected lipid metabolism and signaling Hallmarks regulating metabolism as mTORC1 and PI3K/AKT/MTOR. These results were confirmed by glucose secretion depletion and increased lipid accumulation, especially in BDE-47 and -209 treated cells. These congeners also affected the EGFR/MAPK signaling; further, BDE-47 enriched the estrogen pathway. Interestingly, BDE-209 and the MIX increased ERα gene expression, whereas all the congeners and the MIX induced ERβ and PPARα. We also found that PBDEs modulated several lncRNAs and that HNRNAP1 represented a central hub in all the four interaction networks. Overall, the PBDEs investigated affected glucose and lipid metabolism with different underlying modes of action, as highlighted by the integrated omics analysis, at a dietary relevant concentration. These results may support the mechanism-based risk assessment of these compounds in relation to liver metabolism disruption.

Catalytic degradation of brominated flame retardants in the environment: New techniques and research highlights

Due to the extensive commercial use of brominated flame retardants (BFRs), human beings are chronically exposed to BFRs, causing great harms to human health, which imposes urgent demands to degrade them in the environment. Among various degradation techniques, catalytic degradation has been proven to be outstanding because of its rapidness and effectiveness. Therefore, much attention has been given to catalytic degradation, especially the extensively studied photocatalytic degradation and nanocatalytic reduction techniques. Recently, some novel advanced catalytic techniques have been developed and show excellent catalytic degradation efficiency for BFRs, including natural substances catalytic degradation, new Fenton catalytic degradation, new chemical reagent catalytic degradation, new material catalytic degradation, electrocatalytic degradation, plasma catalytic degradation, and composite catalytic degradation systems. In addition to the common features of traditional catalytic techniques, these novel techniques possess their own specific advantages in various aspects. Therefore, this review summarized the degradation mechanism of BFRs by the above new catalytic degradation methods under the laboratory conditions, simulated real environment, and real environment conditions, and further evaluated their advantages and disadvantages, aiming to provide some research ideas for the catalytic degradation of BFRs in the environment in the future. We suggested that more attention should focus on features of novel catalytic techniques, including eco-friendliness, cost-effectiveness, and pragmatic usefulness.

Legacy and novel brominated flame retardants in air of Ny-Ålesund, Arctic from 2011 to 2019

Concentrations of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in the atmosphere of Ny-Ålesund, Svalbard, were investigated. Passive air samples were collected for eight consecutive one-year periods from August 2011 to August 2019 at seven Arctic sampling sites. High-resolution gas chromatography coupled with high-resolution mass spectrometry (HRGC-HRMS) and gas chromatography coupled with election capture negative ionization mass spectrometry (GC-NCI-MS) were employed for PBDE and NBFR analysis, respectively. The median concentrations of Ʃ₁₁PBDEs and Ʃ₆NBFRs were 0.6 pg/m³ and 4.0 pg/m³, respectively. Hexabromobenzene and BDE-47 were the most abundant NBFR and PBDE congeners in the atmosphere, accounting for 31% and 24% of ƩNBFR and ƩPBDE concentrations, respectively. ƩNBFR concentration was approximately six times higher than that of ƩPBDEs in the same samples. Among NBFRs, the concentrations of 1,2,3,4,5-pentabromobenzene, 2,3,4,5,6-pentabromobenzene, and 2,3-dibromopropyl-2,4,6-tribromophenyl ether showed increasing temporal variations, with estimated doubling times of 3.0, 3.3, and 2.8 years, respectively. The concentrations of almost all PBDE congeners showed a decreasing variation, with halving times ranging from 2.1 to 9.5 years.

Development of human retinal organoid models for bisphenol toxicity assessment

Bisphenols, including Bisphenol A (BPA), Tetrabromobisphenol A (TBBPA), and Tetrabromobisphenol S (TBBPS), have been widely applied in the production of polycarbonate plastics and epoxy resins and have been detected in the environment worldwide. The frequent detection of bisphenols in maternal and fetal samples has raised concerns about their toxic effects on human embryonic development, especially on the development of the central nervous system. However, the effect of bisphenols on human retinal development is still unknown. In this study, to evaluate the toxicity of bisphenols on early retinal development, human embryonic stem cells were induced to differentiate into retinal organoids that responded to BPA, TBBPA, and TBBPS, at human exposure relevant concentrations. The global gene expression of retinal organoids was analyzed by RNA sequencing (RNA-seq). A set of retinal development-related biological processes, including neuron differentiation, phototransduction, axon guidance, and retina layer formation, were identified in retinal organoids corresponding to different developmental stages. The RNA-seq data also showed that BPA, TBBPA, and TBBPS influenced retinal development by interfering with the Cytokine-cytokine receptor interaction pathway. HSPA6, HIF1A-AS3, CDC20B, IL19, OAS1, HSPA7, and RN7SK were dysregulated by these chemicals. Additionally, BPA, TBBPA, and TBBPS exhibited different toxic effects on neural retina development, with TBBPA appearing to exert more toxicity than BPA and TBBPS. Furthermore, three bisphenols exhibited different effects at different stages of neural retina development. The sensitivity of retinal development to bisphenols depends on their developmental stage. This study provides new insights into the deep dissection of retinotoxicity after prenatal bisphenol exposure.

Indoor exposure to selected flame retardants and quantifying importance of environmental, human behavioral and physiological parameters

Indoor exposure to organic flame retardants (FRs) has raised extensive concern due to associated adverse health effects. Indoor-exposure induced daily intakes of six widely used FRs individually ranged 0.002-611 ng/day and 0.02-463 ng/day, respectively, for adults and 2-6-year-old children; and resulting internal exposure levels ranged 0.1-159 and 2.1-4500 ng/g lipid, respectively. A proportion of 0.001-5.9% and 0.006-10.3% of individual FRs emitted into indoor air ultimately entered bodies of adults and children respectively. Tris(2-chloroisopropyl)phosphate dominated in emissions, whilst 2-ethylhexyl-2,3,4,5-tetrabromobenzoate dominated in human bodies. Hand-to-mouth contact was the most important exposure pathway for less volatile FRs including most brominated FRs, whilst inhalation was the predominant intake pathway of tris(2-chloroisopropyl)phosphate. Relative importance of 29 environmental, behavioral and physiological parameters was ranked to explore key drivers influencing exposure and accumulation of FRs in humans. Results suggested that frequent bathing and handwashing can reduce exposure effectively, especially for children. Bodyweight and lipid fraction were only positively related to internal accumulation and body-weight-normalized concentrations of compounds with low metabolic rates (half-lives ≥10³ h) in humans. Our findings help control indoor exposure to FRs and are supportive of human exposome studies in the future.

Occurrence of persistent organic pollutants (POPs) in the atmosphere of South Korea: A review

Numerous studies found the presence of persistent organic pollutants (POPs) in various environmental compartments, including air, water, and soil. POPs have been discovered in various industrial and agricultural products with severe environmental and human health consequences. According to the data, South Korea is a hotspot for POP pollution in the southern part of Asia; hence, South Korea has implemented the Stockholm Convention's National Implementation Plan (NIP) to address this worldwide issue. The purpose of this review is to assess the distribution pattern of POPs pollution in South Korea's atmosphere. According to findings, PAHs, PCBs, BFRs, and PBDEs significantly polluted the atmosphere of South Korea; however, assessing their exposure nationwide is difficult due to a shortage of data. The POPs temporal trend and meta-analysis disclosed no proof of a decrease in PAHs and BFRs residues in the atmosphere. However, POP pollution in South Korea tends to decrease compared to contamination levels in neighboring countries like Japan and China.

Transcriptomics-based analysis of co-exposure of cadmium (Cd) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) indicates mitochondrial dysfunction induces NLRP3 inflammasome and inflammatory cell death in renal tubular epithelial cells

Environmental pollution often releases multiple contaminants resulting in as yet largely uncharacterized additive toxicities. Cadmium (Cd) is a widespread pollutant that induces nephrotoxicity in animal models and humans. However, the combined effect of Cd in causing nephrotoxicity with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), a typical congener of polybrominated diphenyl ethers (PBDEs), has not been evaluated and mechanisms are not completely clear. Here, we applied transcriptome sequencing analysis to investigate the combined toxicity of Cd and BDE-47 in the renal tubular epithelial cell lines HKCs. Cd or BDE-47 exposure decreased cell viability in a dose-dependent manner, and exhibited cell swelling and rounding similar to necrosis, which was exacerbated by co-exposure. Transcriptomic analysis revealed 2191, 1331 and 3787 differentially-expressed genes following treatment with Cd, BDE-47 and co-exposure, respectively. Interestingly, functional annotation and enrichment analyses showed involvement of pathways for oxidative stress, NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome and inflammatory cell death for all three treatments. Examination of indices of mitochondrial function and oxidative stress in HKC cells showed that the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and intracellular calcium ion concentration [Ca²⁺]i were elevated, while superoxide dismutase (SOD) and mitochondrial membrane potential (MMP) were decreased. The ratio of apoptotic and necrotic cells and intracellular lactate dehydrogenase (LDH) release were increased by Cd or BDE-47 exposure, and was aggravated by co-exposure, and was attenuated by ROS scavenger N-Acetyl-L-cysteine (NAC). NLRP3 inflammasome and pyroptosis pathway-related genes of NLRP3, adaptor molecule apoptosis-associated speck-like protein (ASC), caspase-1, interleukin-18 (IL-18) and IL-1β were elevated, while gasdermin D (GSDMD) was down-regulated, and protein levels of NLRP3, cleaved caspase-1 and cleaved GSDMD were increased, most of which were relieved by NAC. Our data demonstrate that exposure to Cd and BDE-47 induces mitochondrial dysfunction and triggers NLRP3 inflammasome and GSDMD-dependent pyroptosis leading to nephrotoxicity, and co-exposure exacerbates this effect, which could be attenuated by inhibiting ROS. This study provides a further mechanistic understanding of kidney damage, and co-exposure impact is worthy of concern and should be considered to improve the accuracy of environmental health assessment.

Human exposure to polybrominated diphenyl ethers (PBDEs) through the diet: An update of the scientific literature

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame-retardants (BFRs). As for other persistent organic pollutants, dietary intake (followed by dust inhalation) is the main route of human exposure to PBDEs. In 2012, we reviewed the scientific literature on the concentrations of PBDEs in foodstuffs and their dietary exposure. The current review is aimed at updating the results of recent studies (2012-2022) focused on determining the levels of PBDEs in food samples, as well as the dietary intake of these compounds. We have revised studies conducted over the world. The current information on the concentrations of PBDEs in food and their dietary intake is now much more notable than that available in our previous review, being China the country contributing with the highest number of studies. Because of the important differences in materials and methods used in the available studies, the comparison of results is certainly complicated. However, there seems to be a general trend towards a decrease in the levels of PBDEs in foods, and consequently, in the dietary intake of these contaminants. The lack of tolerable daily intakes of PBDEs is an issue that needs to be solved for assessing human health risks of these BFRs.

Environmental, Health, and Legislation Considerations for Rational Design of Nonreactive Flame-Retardant Additives for Polymeric Materials: Future Perspectives

Increasing polymer usage has demanded functional additives that decrease fire hazards for end users. While traditional flame-retardant (FR) additives, such as halogenated, phosphorus, and metal hydroxides, greatly reduce flammability and associated fire hazards, research has continually exposed a litany of health and environmental safety concerns. This perspective aims to identify the key components of a successful FR additive and address material, environmental, and health concerns of existing additives. Legislation surrounding FRs and persistent organic pollutants is also discussed to highlight political perception that has resulted in the increased chemical regulations and subsequent banning of FR additives. Finally, future directions of this field regarding nonreactive additives, focusing on the use of bioinspired materials and transition metal chemistries to produce alternatives for polymers with efficacies surpassing traditional additives are presented.

Effects of Polybrominated Diphenyl Ethers on Hormonal and Reproductive Health in E-Waste-Exposed Population: A Systematic Review

Electronic waste management is a global rising concern that is primarily being handled by informal recycling practices. These release a mix of potentially hazardous chemicals, which is an important public health concern. These chemicals include polybrominated diphenyl ethers (PBDEs), used as flame retardants in electronic parts, which are persistent in nature and show bioaccumulative characteristics. Although PBDEs are suspected endocrine disruptors, particularly targeting thyroid and reproductive hormone functions, the relationship of PBDEs with these health effects are not well established. We used the Navigation Guide methodology to conduct a systematic review of studies in populations exposed to e-waste to better understand the relationships of these persistent flame retardants with hormonal and reproductive health. We assessed nineteen studies that fit our pre-determined inclusion criteria for risk of bias, indirectness, inconsistency, imprecision, and other criteria that helped rate the overall evidence for its quality and strength of evidence. The studies suggest PBDEs may have an adverse effect on thyroid hormones, reproductive hormones, semen quality, and neonatal health. However, more research is required to establish a relationship of these effects in the e-waste-exposed population. We identified the limitations of the data available and made recommendations for future scientific work.

Concentrations and isomer profiles of hexabromocyclododecanes (HBCDDs) in floor, elevated surface, and outdoor dust samples from Basrah, Iraq

Concentrations of the α, β, and γ- diastereomers of hexabromocyclododecane (α-, β-, and γ-HBCDD) were measured in 60 dust samples from 20 homes across Basrah, Iraq. From each home, two indoor dust (ID) samples (specifically one collected from elevated surfaces (ESD) and one from the floor (FD)) were collected from the living room, with one outdoor dust (OD) sample collected from the front yard of the house. Concentrations of HBCDDs decreased in the following sequence ESD > FD > OD. For ID, ΣHBCDD concentrations varied from 5.3 ng g^-1 in FD to 150 ng g^-1 in ESD, with median levels of 60 and 40 ng g^-1 in ESD and FD respectively. Concentrations of γ-HBCDD, and consequently of ΣHBCDDs in ESD, significantly (p < 0.05) exceeded those in FD. For adults, this implies that exposure assessments based on FD only may underestimate exposure, as adults are more likely to ingest ESD. Concentrations of ΣHBCDDs in OD ranged between 7.4 and 120 ng g^-1 with a median of 35 ng g^-1 and were significantly exceeded (p < 0.05) by those in ID samples. Concentrations of ΣHBCDDs in OD from houses with car parking areas exceeded (p < 0.05) those in OD from other homes, implying vehicles as potential emission sources of HBCDDs. Simultaneously, there was moderate correlation (R = 0.510-0.609, p < 0.05) between concentrations in ID and OD, implying that the indoor environment is an important source of OD contamination. The isomer pattern of HBCDDs in dust samples displayed a predominance of α-HBCDD, which represented 56%, 52% and 59% ΣHBCDD in ESD, FD and OD samples respectively. Derived from the concentrations reported in this study, the median and 95^th percentile estimated daily intakes (EDI) for Iraqi adults and toddlers through house dust ingestion did not exceed the reference dose (RfD) value for HBCDD.

Characterization of 2,2'4,4'-Tetrabromodiphenyl ether (BDE47)-induced testicular toxicity via single-cell RNA-sequencing

Background

The growing male reproductive diseases have been linked to higher exposure to certain environmental compounds such as 2,2′,4,4′-tetrabromodiphenyl ether (BDE47) that are widely distributed in the food chain. However, the specific underlying molecular mechanisms for BDE47-induced male reproductive toxicity are not completely understood.

Methods

Here, for the first time, advanced single-cell RNA sequencing (ScRNA-seq) was employed to dissect BDE47-induced prepubertal testicular toxicity in mice from a pool of 76 859 cells.

Results

Our ScRNA-seq results revealed shared and heterogeneous information of differentially expressed genes, signaling pathways, transcription factors, and ligands-receptors in major testicular cell types in mice upon BDE47 treatment. Apart from disruption of hormone homeostasis, BDE47 was discovered to downregulate multiple previously unappreciated pathways such as double-strand break repair and cytokinesis pathways, indicative of their potential roles involved in BDE47-induced testicular injury. Interestingly, transcription factors analysis of ScRNA-seq results revealed that Kdm5b (lysine-specific demethylase 5B), a key transcription factor required for spermatogenesis, was downregulated in all germ cells as well as in Sertoli and telocyte cells in BDE47-treated testes of mice, suggesting its contribution to BDE47-induced impairment of spermatogenesis.

Conclusions

Overall, for the first time, we established the molecular cell atlas of mice testes to define BDE47-induced prepubertal testicular toxicity using the ScRNA-seq approach, providing novel insight into our understanding of the underlying mechanisms and pathways involved in BDE47-associated testicular injury at a single-cell resolution. Our results can serve as an important resource to further dissect the potential roles of BDE47, and other relevant endocrine-disrupting chemicals, in inducing male reproductive toxicity.

Migration of hazardous contaminants from WEEE contaminated polymeric toy material by mouthing

This study evaluated the migration of brominated flame retardants (BFRs), phosphate flame retardants (PFRs), bisphenols (BPA, BPF), and phthalate ester-based plasticizers from recycled polymeric toy material, containing waste electrical and electronic equipment (WEEE), in artificial saliva simulating 1 h of mouthing. In total 12 parts of 9 different toys were tested in triplicate after confirming WEEE specific contamination. Up to 11 contaminants were detected in saliva from one toy sample. The highest migration rate up to 128 ng/(cm² x h) was found for BPA followed by bis(2-ethylhexyl) phthalate (DEHP) and diisobutyl phthalate (DIBP) with migration rates up to 25.5 and 8.27 ng/(cm² x h), respectively. In addition to DecaBDE, which was detected in 3 saliva samples at migration rates between 0.09 and 0.31 ng/(cm² x h), the decaBDE replacements 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ), decabromodiphenyl ethane (DBDPE), resorcinol bis(diphenyl phosphate) (RDP), and hexabromocyclododecane (HBCDD) were detected as well with comparable migration rates. 2,4,6-tribromphenol (246-TBP) reached migration rates up to 1.15 ng/(cm² x h) in correspondence to the presence of TTBP-TAZ. Tetrabromobisphenol A (TBBPA), BPA, 246-TBP, DEHP, DIBP and triphenyl phosphate (TPHP) were predominantly observed in saliva with a detection frequency between 50 and 75%. Daily intake (DI) values were calculated for relevant analytes and compared to tolerable daily intake (TDI) values. The highest DI values of 72.4, 14.3, 5.74, 2.28 and 2.09 ng/(kg BW x day), were obtained for BPA, DEHP, DIBP, TBBPA, and TPHP, respectively. None of them exceed the TDI value or respective reference dose (RfD).

Per-and polyfluoroalkyl substances (PFAS) and persistent chemical mixtures in dust from U.S. colleges

Indoor spaces contain several classes of persistent organic chemicals, including per- and polyfluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs). However, concentrations of PFAS and persistent chemical mixtures and their associations with building characteristics on college campuses are understudied. We collected dust from 43 nonresidential spaces on four U.S. college campuses in 2016 and evaluated associations of room characteristics (carpeting, upholstered furniture, and years since last furnished) with dust concentrations of PFAS, PBDEs, PCBs, and OCPs. Nine PFAS, twelve PBDEs, two PCBs, and four OCPs were each detected in at least 75% of the spaces, including several chemicals (e.g., DDT) that have been banned for decades. Concentrations were correlated within and, in some cases, between chemical classes. Wall-to-wall carpeting (compared to rooms without wall-to-wall carpeting) was associated with higher concentrations of six individual PFAS and a mixture of PFAS, and the number of pieces of upholstered furniture was associated with increased concentrations of a mixture of PBDEs. These findings indicate that carpeting and furniture are current sources of PFAS and PBDEs, respectively. Building and finish materials should be carefully selected to avoid exposure to persistent chemicals.

Gestational exposure to BDE-209 induces placental injury via the endoplasmic reticulum stress-mediated PERK/ATF4/CHOP signaling pathway

Several epidemiological studies have reported significant associations between prenatal polybrominated diphenyl ethers (PBDEs) exposure and adverse birth outcomes. Placental injury is thought to mediate these associations. However, few study has investigated the adverse effects of PBDEs exposure on placental growth and development. We examined the impacts of gestational exposure to BDE-209, the most abundant PBDE conger detected in human samples, on placental structure and function, and its model of action in vivo and in vitro. Pregnant mice were exposed to 0, 2, 20, 200 mg/kg/day of BDE-209 by gavages from gestational day (GD) 0 to GD18. Results showed that gestational BDE-209 exposure significantly reduced placental weight, impaired placental vascular development and induced placental cell apoptosis. In addition, gestational BDE-209 exposure impaired placental transport and endocrine function as demonstrated by markedly downregulated expression of Glut1, Znt1, Pgf and Igf2 in BDE-209-treated placentas. Mechanistically, gestational exposure to BDE-209 upregulated the expression of GRP78, and 3 downstream proteins (p-eIF2α, ATF4 and CHOP) of the PERK signaling, suggesting the activation of endoplasmic reticulum (ER) stress and PERK signaling pathway in mouse placentas. Further in vitro study showed that PERK siRNA pretreatment markedly reversed BDE-209-induced cell apoptosis in human JEG-3 cells. Collectively, our results suggest that the activation of the ER stress-mediated PERK/ATF4/CHOP signaling pathway played a role in BDE-209-induced placental injury. Our findings provide new insight into the mechanisms of BDE-209 induced reproductive and developmental toxicity.

Human CYP enzyme-activated genotoxicity of 2,2',4,4'-tetrabromobiphenyl ether in mammalian cells

Polybrominated biphenyl ethers (PBDEs) are a group of persistent organic pollutants with endocrine-disrupting, neurotoxic, tumorigenic and DNA-damaging activities. They are hydroxylated by human liver microsomal CYP enzymes, however, their mutagenicity remains unknown. In this study, 2,2',4,4'-tetrabromobiphenyl ether (BDE-47, relatively abundant in human tissues) was investigated for micronuclei induction and DNA damage in mammalian cells. The results indicated that BDE-47 up to 80 μM under a 6 h/18 h (exposure/recovery, covering 2 cell cycles) regime did not induce micronuclei in V79-Mz and V79-derived cell lines expressing human CYP1A1 or 1A2, while it was moderately positive in human CYP2B6-, 2E1-and 3A4-expressing cell lines (V79-hCYP2B6, V79-hCYP2E1-hSULT1A1 and V79-hCYP3A4-hOR, respectively). Following 24 h exposure, BDE-47 induced micronuclei in V79-hCYP2E1-hSULT1A1 and V79-hCYP3A4 cells at increased potencies. In the human hepatoma (HepG2) cells BDE-47 (48 h exposure) was inactive up to 40 μM, however, pretreatment of the cells with ethanol (0.2%, v:v, inducer of CYP2E1) or rifampicin (10 μM, inducer of CYP3A4) led to significant micronuclei formation by BDE-47; pretreatment with bisphenol AF (100 nM) also potentiated BDE-47-induced micronuclei formation (which was blocked by a CYP2E1 inhibitor trans-1,2-dichloroethylene or a CYP3A inhibitor (ketoconazole). Immunofluorescent staining of centromere protein B with the micronuclei formed by BDE-47 in HepG2 cells pretreated with ethanol or rifampicin demonstrated selective formation of centromere-containing micronuclei. The increased phosphorylation of both histones H2AX and H3 in HepG2 by BDE-47 also indicated an aneugenic potential. Therefore, this study suggests that BDE-47 is an aneugen activated by several human CYP enzymes.

Risk assessment of PBDEs and PCBs in dust from an e-waste recycling area of China

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are widely used in outdated electronic and electrical products. In the present study, dust samples from houses, kindergartens, and roads were collected in Guiyu, where informal e-waste recycling activities have been sustained since the 1980s. Haojiang was chosen as a reference site without e-waste pollution. A total of 20 PBDE congeners and 18 PCB congeners was measured. Concentrations of total PBDEs and PCBs in dust samples from Guiyu were significantly higher than those from Haojiang. In Guiyu, kindergarten dust had the highest concentration of PCBs in these three typical environments, whereas the concentration of PBDEs showed no significant difference. Concentrations of PBDEs in Haojiang house dust were found significantly higher than other two environmental dusts. According to the questionnaires, we found that factors such as shoe cabinets, electrical products, and potted plants might affect PBDE and PCB concentrations in house dust. Daily intake of PBDEs and PCBs via dust ingestion was estimated after correction by their house, kindergarten, and road dust concentrations. The mean estimated daily intake (EDI) of PBDEs for Guiyu children was far lower than the oral reference dose recommended by the environmental protection agency (EPA). The Guiyu children seem to have a higher trend of daily intakes of PCBs although their EDIs not being calculated accurately due to the low detection rate. Child exposure to PBDEs via dust ingestion in Guiyu was 36 times higher than those in Haojiang. This indicates that children from e-waste-polluted areas stay in surroundings with heavy burdens of PBDEs, even PCBs. The risk to their health from contaminants is a severe concern.

Health risk assessment and development of human health ambient water quality criteria for PBDEs in China

Polybrominated diphenyl ethers (PBDEs) are not only a class of highly efficient brominated flame retardants (BFRs) but also a class of typical persistent organic pollutants (POPs) that are persistent and widely distributed in various environmental media. This study examined the concentrations of PBDEs in five environmental media (water, soil, air, dust, and food) and two human body media (human milk and blood) in China from 2010 to 2020. In addition, this study conducted multi-pathway exposure health risk assessments of populations of different ages in urban, rural, key regions, and industrial factories using the Monte-Carlo simulation. Finally, the human health ambient water quality criteria (AWQC) of eight PBDEs were derived using Chinese exposure parameters and bioaccumulation factors (BAFs). The results showed that the eastern and southeastern coastal regions of China were heavily polluted by PBDEs, and the variation trends of the ΣPBDEs concentrations in the different exposure media were not consistent. PBDEs did not pose a risk to urban and rural residents in ordinary regions, but the hazard indexes (HIs) for residents in key regions and occupational workers exceeded the safety threshold. Dust exposure was the primary exposure pathway for urban and rural residents in ordinary regions, but for residents in key regions and occupational workers, dietary exposure was the primary exposure pathway. BDE-209 was found to be the most serious individual PBDE congener in China. The following human health AWQC values of the PBDEs were derived: drinking water exposure: 0.233-65.2 μg·L^-1; and drinking water and aquatic products exposure: 8.51 × 10^-4-1.10 μg·L^-1.

Legacy brominated flame retardants in human milk from the general population in Beijing, China: Biomonitoring, temporal trends from 2011 to 2018, and nursing infant's exposure assessment

Three kinds of legacy brominated flame retardants (BFRs), including eight polybrominated diphenyl ether (PBDE) congeners, tetrabromobisphenol A (TBBPA), and three hexabromocyclododecane (HBCDD) isomers, were analyzed in 105 human milk samples collected in 2018 from Beijing, China. The tested BFRs all showed high detection frequencies, and HBCDD was the most abundant BFR, with a median level of 7.64 × 10³ pg/g lipid, followed by BDE-153 (389 pg/g lipid), BDE-209 (283 pg/g lipid), and TBBPA (271 pg/g lipid). By comparing the results of the present study with those of our previous Beijing human milk surveys conducted in 2014 and 2011, the contamination of TBBPA and HBCDD increased steadily from 2011 to 2018, whereas that of PBDEs decreased sharply during this period. Our results suggested that the production and consumption of BFRs in China have shifted from PBDEs to other FRs. Education level and the consumption of animal-derived foods such as eggs and meat were identified as major influencing factors for some BFRs. For nursing infants, the median levels of lower bound BFR daily intake via human milk ingestion ranged from 4.62 × 10^-2 ng/kg bw/day for BDE-154 to 30.6 ng/kg bw/day for HBCDD. The daily intake of most BFRs by breastfeeding is unlikely to pose significant health risks for Beijing nursing infants. However, the minimum margin of exposure (MOE) of HBCDD was below its threshold value, which indicated that its daily intake might raise health concerns for some breastfed infants.

Development and validation of a multi-residue method for the simultaneous analysis of brominated and organophosphate flame retardants, organochlorine pesticides, and polycyclic aromatic compounds in household dust

Household dust is a sink for multiple toxic chemicals with known or suspected potential health effects. However, most dust exposure studies focus on a few chemicals, which may limit overall understanding of human exposure characteristics because people spend most of their time indoors. This paper describes the development and evaluation of a multi-residue analysis of 20 organochlorine pesticides (OCPs), 15 polycyclic aromatic hydrocarbons (PAHs), 8 polybrominated diphenyl ether congeners (PBDEs), 3 hexabromocyclododecane (HBCDs), 8 synthetic musks (Musks), and 7 organophosphate esters (OPEs) in indoor dusts. After extraction with acetone/hexane (v/v, 1 : 1), all target compounds were fractionated with a Florisil solid-phase extraction (SPE) cartridge into two fractions: PAHs, PBDEs, HBCDs, OCPs and Musks, which were eluted with hexane/dichloromethane, and OPEs eluted with ethyl acetate. Further clean-up using acidified silica 44% cartridges was then performed to enable determination of PBDEs and HBCDs. Instrumental analysis of the target chemicals was performed using gas chromatography (GC) or liquid chromatography (LC) coupled with mass spectrometry (MS) or tandem mass spectrometry (MS/MS). A newly-optimized GC-MS/MS method was employed for the simultaneous determination of PAHs, OCPs, and Musks. The lower limit of quantification (LOQ) values of PAHs, OCPs, and Musks were 0.14-0.92 ng g^-1, 0.06-0.38 ng g^-1 and 0.07-0.40 ng g^-1, respectively. PBDEs were quantified by GC-MS with electron capture negative ionization, and HBCDs and OPEs by LC-MS/MS with electrospray ionization (ESI) in negative and positive ion mode, respectively. Recovery experiments showed that the average recoveries and relative standard deviations were 99-113% and 1-14% for PBDEs, 89-105% and 1-6% for HBCDs, 71-120% and 3-17% for PAHs, 71-112% and 2-17% for OCPs, 77-120% and 2-13% for Musks, and 80-127% and 1-14% for OPEs. Validation experiments showed that the method achieved good accuracy. The developed method was used to analyze SRM 2585 and real indoor dust samples to demonstrate its suitability for routine analysis. The target contaminants were widely detected in SRM 2585 and indoor dust collected from Wuhan of Central China, with PAHs the major species, followed by OPEs, OCPs, and PBDEs.

Transcriptomic Analysis of the Differential Nephrotoxicity of Diverse Brominated Flame Retardants in Rat and Human Renal Cells

Brominated flame retardants (BFRs) are environmentally persistent, are detected in humans, and some have been banned due to their potential toxicity. BFRs are developmental neurotoxicants and endocrine disruptors; however, few studies have explored their potential nephrotoxicity. We addressed this gap in the literature by determining the toxicity of three different BFRs (tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and tetrabromodiphenyl ether (BDE-47)) in rat (NRK 52E) and human (HK-2 and RPTEC) tubular epithelial cells. All compounds induced time- and concentration-dependent toxicity based on decreases in MTT staining and changes in cell and nuclear morphology. The toxicity of BFRs was chemical- and cell-dependent, and human cells were more susceptible to all three BFRs based on IC₅₀s after 48 h exposure. BFRs also had chemical- and cell-dependent effects on apoptosis as measured by increases in annexin V and PI staining. The molecular mechanisms mediating this toxicity were investigated using RNA sequencing. Principal components analysis supported the hypothesis that BFRs induce different transcriptional changes in rat and human cells. Furthermore, BFRs only shared nine differentially expressed genes in rat cells and five in human cells. Gene set enrichment analysis demonstrated chemical- and cell-dependent effects; however, some commonalities were also observed. Namely, gene sets associated with extracellular matrix turnover, the coagulation cascade, and the SNS-related adrenal cortex response were enriched across all cell lines and BFR treatments. Taken together, these data support the hypothesis that BFRs induce differential toxicity in rat and human renal cell lines that is mediated by differential changes in gene expression.

Detection of Brominated Plastics from E-Waste by Short-Wave Infrared Spectroscopy

In this work, the application of Short-Wave Infrared (SWIR: 1000–2500 nm) spectroscopy was evaluated to identify plastic waste containing brominated flame retardants (BFRs) using two different technologies: a portable spectroradiometer, providing spectra of single spots, and a hyperspectral imaging (HSI) platform, acquiring spectral images. X-ray Fluorescence (XRF) analysis was preliminarily performed on plastic scraps to analyze their bromine content. Chemometric methods were then applied to identify brominated plastics and polymer types. Principal Component Analysis (PCA) was carried out to explore collected data and define the best preprocessing strategies, followed by Partial Least Squares—Discriminant Analysis (PLS-DA), used as a classification method. Plastic fragments were classified into “High Br content” (Br > 2000 mg/kg) and “Low Br content” (Br < 2000 mg/kg). The identified polymers were acrylonitrile butadiene styrene (ABS) and polystyrene (PS). Correct recognition of 89–90%, independently from the applied technique, was achieved for brominated plastics, whereas a correct recognition ranging from 81 to 89% for polymer type was reached. The study demonstrated as a systematic utilization of both the approaches at the industrial level and/or at laboratory scale for quality control can be envisaged especially considering their ease of use and the short detection response.

Contamination status, emission sources, and human health risk of brominated flame retardants in urban indoor dust from Hanoi, Vietnam: the replacement of legacy polybrominated diphenyl ether mixtures by alternative formulations

This study investigated the occurrence, distribution of several additive brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and some novel brominated flame retardants (NBFRs) in urban indoor dust collected from ten inner districts of Hanoi, Vietnam to assess the contamination status, emission sources, as well as their associated human exposure through indoor dust ingestion and health risks. Total concentrations of PBDEs and NBFRs in indoor dust samples ranged from 43 to 480 ng g^-1 (median 170 ng g^-1) and from 56 to 2200 ng g^-1 (median 180 ng g^-1), respectively. The most abundant PBDE congener in these dust samples was BDE-209 with concentrations ranging from 29 to 360 ng g^-1, accounting for 62.6-86.5% of total PBDE levels. Among the NBFRs analyzed, decabromodiphenyl ethane (DBDPE) was the predominant compound with a mean contribution of 98.6% total NBFR amounts. Significant concentrations of DBDPE were detected in all dust samples (median 180 ng g^-1, range 54-2200 ng g^-1), due to DBDPE as a substitute for deca-BDE. Other NBFRs such as 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), pentabromoethylbenzene (PBEB) and 2,2',4,4',5,5'-hexabromobiphenyl (BB-153) were found at very low levels. Based on the measured BFR concentrations, daily intake doses (IDs) of PBDEs and NBFRs via dust ingestion at exposure scenarios using the median and 95^th percentile levels for both adults and children were calculated for risk assessment. The results showed that the daily exposure doses via dust ingestion of all compounds, even in the high-exposure scenarios were also lower than their reference dose (RfD) values. The lifetime cancer risks (LTCR) were much lower than the threshold level (10^-6), which indicated the acceptable health risks resulting from indoor BFRs exposure for urban residents in Hanoi.

Different co-culture models reveal the pivotal role of TBBPA-promoted M2 macrophage polarization in the deterioration of endometrial cancer

Tetrabromobisphenol A (TBBPA), an emerging organic pollutant widely detected in human samples, has a positive correlation with the development of endometrial cancer (EC), but its underlying mechanisms have not yet been fully elucidated. Tumor-associated macrophages (TAM), one of the most vital components in tumor microenvironment (TME), play regulatory roles in the progression of EC. Consequently, this study mainly focuses on the macrophage polarization in TME to unveil the influence of TBBPA on the progression of EC and involved mechanisms. Primarily, low doses of TBBPA treatment up-regulated M2-like phenotype biomarkers in macrophage. The data from in vitro co-culture models suggested TBBPA-driven M2 macrophage polarization was responsible for the EC deterioration. Results from in vivo study further confirmed the malignant proliferation of EC promoted by TBBPA. Mechanistically, TBBPA-mediated miR-19a bound to the 3'-UTR regions of SOCS1, resulting in down-regulation of SOCS1 followed by the phosphorylation of JAK and STAT6. The present study not only revealed for the first time the molecular mechanism of TBBPA-induced EC's deterioration based on macrophage polarization, but also established co-culture models, thus providing a further evaluation method for the exploration of environmental pollutants-induced tumor effects from the role of TME.

Brominated Flame Retardants in Children's Room: Concentration, Composition, and Health Risk Assessment

Children spend most of their daily time indoors. Many of the items used indoors, such as furniture, electronics, textile, and children toys, are treated with chemicals to provide longevity and fulfil the safety standards. However, many chemicals added to these products are released into the environment during leaching out from the treated products. Many studies have reported brominated flame retardants (BFRs) in indoor environments; however, few have focused on environments specified for young children. In this study, paired air (PM₁₀) and dust samples were collected from the rooms (n = 30) of Saudi children. These samples were analyzed for different congeners of polybrominated diphenyl ethers (PBDEs) and three important alternative flame retardants using gas chromatography-mass spectrometry. Decabromodiphenyl ether (BDE 209) was the most important analyzed BFR in dust and PM₁₀ samples with a median value of 3150 ng/g of dust and 75 pg/m³. This indicates the wider application of BDE 209 has implications for its occurrence, although its use has been regulated for specified uses since 2014. Among alternative BFRs, 2-Ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), Bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (TBPH), and 1,2-Bis(2,4,6-tribromophenoxy)ethane (BTBPE) were found with a median levels of 10, 15 and 8 ng/g of dust, respectively. However, alternative BFRs were present in <50% of the PM₁₀ samples. The calculated long term and daily exposures via indoor dust and PM₁₀ of Saudi children from their rooms were well below the respective reference dose (RfD) values. Nonetheless, the study highlights BDE 209 at higher levels than previously reported from household dust in Saudi Arabia. The study warrants further extensive research to estimate the different classes of chemical exposure to children from their rooms.

In Utero and Lactational Exposure to Flame Retardants Disrupts Rat Ovarian Follicular Development and Advances Puberty

Brominated flame retardants (BFRs), including polybrominated diphenyl ethers and hexabromocyclododecane, leach out from consumer products into the environment. Exposure to BFRs has been associated with effects on endocrine homeostasis. To test the hypothesis that in utero and lactational exposure to BFRs may affect the reproductive system of female offspring, adult female Sprague Dawley rats were fed diets formulated to deliver nominal doses (0, 0.06, 20, or 60 mg/kg/day) of a BFR dietary mixture mimicking the relative congener levels in house dust from prior to mating until weaning. Vaginal opening and the day of first estrus occurred at a significantly earlier age among offspring from the 20 mg/kg/day BFR group, indicating that the onset of puberty was advanced. Histological analysis of ovaries from postnatal day 46 offspring revealed an increase in the incidence of abnormal follicles. A toxicogenomic analysis of ovarian gene expression identified upstream regulators, including HIF1A, CREB1, EGF, the β-estradiol, and PPARA pathways, predicted to be downregulated in the 20 or 60 mg/kg/day group and to contribute to the gene expression patterns observed. Thus, perinatal exposure to BFRs dysregulated ovarian folliculogenesis and signaling pathways that are fundamental for ovarian function in the adult.

COVID-19 and children's health in the United States: Consideration of physical and social environments during the pandemic

Public health measures necessary to counteract the coronavirus disease 2019 (COVID-19) pandemic have resulted in dramatic changes in the physical and social environments within which children grow and develop. As our understanding of the pathways for viral exposure and associated health outcomes in children evolves, it is critical to consider how changes in the social, cultural, economic, and physical environments resulting from the pandemic could affect the development of children. This review article considers the environments and settings that create the backdrop for children's health in the United States during the COVID-19 pandemic, including current threats to child development that stem from: A) change in exposures to environmental contaminants such as heavy metals, pesticides, disinfectants, air pollution and the built environment; B) changes in food environments resulting from adverse economic repercussion of the pandemic and limited reach of existing safety nets; C) limited access to children's educational and developmental resources; D) changes in the social environments at the individual and household levels, and their interplay with family stressors and mental health; E) social injustice and racism. The environmental changes due to COVID-19 are overlaid onto existing environmental and social disparities. This results in disproportionate effects among children in low-income settings and among populations experiencing the effects of structural racism. This article draws attention to many environments that should be considered in current and future policy responses to protect children's health amid pandemics.

Value-added products from thermochemical treatments of contaminated e-waste plastics

The rise of electronic waste (e-waste) generation around the globe has become a major concern in recent times and its recycling is mostly focused on the recovery of valuable metals, such as gold, silver, and copper, etc. However, e-waste consists of a significant weight fraction of plastics (25-30%) which are either discarded or incinerated. There is a growing need for recycling of these e-waste plastics. The majority of them are made from high-quality polymers (composites), such as acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS), polycarbonate (PC), polyamide (PA), polypropylene (PP) and epoxies. These plastics are often contaminated with hazardous materials, such as brominated flame retardants (BFRs) and heavy metals (such as Pb and Hg). Under any thermal stress (thermal degradation), the Br present in the e-waste plastics produces environmentally hazardous pollutants, such as hydrogen bromide or polybrominated diphenyl ethers/furans (PBDE/Fs). The discarded plastics can lead to the leaching of toxins into the environment. It is important to remove the toxins from the e-waste plastics before recycling. This review article gives a detailed account of e-waste plastics recycling and recovery using thermochemical processes, such as extraction (at elevated temperature), incineration (combustion), hydrolysis, and pyrolysis (catalytic/non catalytic). A basic framework of the existing processes has been established by reviewing the most interesting findings in recent times and the prospects that they open in the field recycling of e-waste plastics.

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

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

Accumulation and influencing factors of novel brominated flame retardants in soil and vegetation from Fildes Peninsula, Antarctica

The concentrations and distributions of nine novel brominated flame retardants (NBFRs) were analyzed in soil, lichen (Usnea aurantiaco-atra), and moss (Sanionia uncinata) samples collected from the Chinese Antarctic Great Wall Station and surrounding Fildes Peninsula area in west Antarctica. Total NBFR concentrations ranged from 61.2-225 pg/g dry weight (dw) in soil, 283-1065 pg/g dw in moss, and 135-401 pg/g dw in lichen, respectively. Decabromodiphenyl ethane (DBDPE) was the dominant NBFR in all samples, accounting for 65.2%, 50.1%, and 72.4% of cumulative NBFR concentration in soil, moss, and lichen, respectively. The concentrations of NBFRs in plant samples were higher than those in soil, which may be related to plant bioaccumulation. Significant log/log-linear correlations (p < 0.05) were found between the concentrations of BEHTEBP and total organic carbon (TOC) in soil, and between DBDPE and lipid content in mosses, indicating that TOC and lipid content potentially affect certain NBFRs in Antarctic soil and moss. This study presents the first report on NBFR contamination in soil and various vegetation in Antarctica.

Current progress in degradation and removal methods of polybrominated diphenyl ethers from water and soil: A review

The widespread of polybrominated diphenyl ethers (PBDEs) in the environment has caused rising concerns, and it is an urgent endeavor to find a proper way for PBDEs remediation. Various techniques such as adsorption, hydrothermal and thermal treatment, photolysis, photocatalytic degradation, reductive debromination, advanced oxidation processes (AOPs) and biological degradation have been developed for PBDEs decontamination. A comprehensive review of different PBDEs remediation techniques is urgently needed. This work focused on the environmental source and occurrence of PBDEs, their removal and degradation methods from water and soil, and prospects for PBDEs remediation techniques. According to the up-to-date literature obtained from Web of Science, it could be concluded that (i) photocatalysis and photocatalytic degradation is the most widely reported method for PBDEs remediation, (ii) BDE-47 and BDE-209 are the most investigated PBDE congeners, (iii) considering the recalcitrance nature of PBDEs and more toxic intermediates could be generated because of incomplete degradation, the combination of different techniques is the most potential solution for PBDEs removal, (iv) further researches about the development of novel and effective PBDEs remediation techniques are still needed. This review provides the latest knowledge on PBDEs remediation techniques, as well as future research needs according to the up-to-date literature.

Concentrations and distribution of novel brominated flame retardants in the atmosphere and soil of Ny-Ålesund and London Island, Svalbard, Arctic

Novel brominated flame retardants (NBFRs) were investigated in Arctic air and soil samples collected from Ny-Ålesund and London Island, Svalbard, during Chinese scientific research expeditions to the Arctic during 2014-2015. The concentrations of Σ₉NBFRs in the Arctic air and soil were 4.9-8.7 pg/m³ (average 6.8 pg/m³) and 101-201 pg/g dw (average 150 pg/g dw), respectively. The atmospheric concentration of hexabromobenzene (HBB) was significantly correlated with that of pentabromotoluene (PBT) and pentabromobenzene (PBBz), suggesting similar source and environmental fate in the Arctic air. No significant spatial difference was observed among the different sampling sites, both for air and soil samples, indicating that the effects of the scientific research stations on the occurrence of NBFRs in the Arctic were minor. The fugacities from soil to air of pentabromoethylbenzene (PBEB), 2,3-dibromopropyl 2,4,6-tribromophenyl ether (DPTE), and decabromodiphenylethane 1,2-bis (pentabromophenyl) ethane (DBDPE) were lower than the equilibrium value, indicating a nonequilibrium state of these compounds between air and soil, the dominant impact of deposition and the net transport from air to soil. The correlation analysis between the measured and predicted soil-atmosphere coefficients based on the absorption model showed that the impact of the soil organic matter on the distribution of NBFRs in the Arctic region was minor. To the best of our knowledge, this work is one of the limited reports on atmospheric NBFRs in the Arctic and the first study to investigate the occurrence and fate of NBFRs in the Arctic soil.

Inevitable human exposure to emissions of polybrominated diphenyl ethers: A perspective on potential health risks

Polybrominated diphenyl ethers (PBDEs) serve as flame retardants in many household materials such as electrical and electronic devices, furniture, textiles, plastics, and baby products. Though the use of PBDEs like penta-, octa- and deca-BDE greatly reduces the fire damage, indoor pollution by these toxic emissions is ever-growing. In fact, a boom in the global market projections of PBDEs threatens human health security. Therefore, efforts are made to minimize PBDEs pollution in USA and Europe by encouraging voluntary phasing out of the production or imposing compelled regulations through Stockholm Convention, but >500 kilotons of PBDEs still exist globally. Both 'environmental persistence' and 'bioaccumulation tendencies' are the hallmarks of PBDE toxicities; however, both these issues concerning household emissions of PBDEs have been least addressed theoretically or practically. Critical physiological functions, lipophilicity and toxicity, trophic transfer and tissue specificities are of utmost importance in the benefit/risk assessments of PBDEs. Since indoor debromination of deca-BDE often yields many products, a better understanding on their sorption propensity, environmental fate and human toxicities is critical in taking rigorous measures on the ever-growing global deca-BDE market. The data available in the literature on human toxicities of PBDEs have been validated following meta-analysis. In this direction, the intent of the present review was to provide a critical evaluation of the key aspects like compositional patterns/isomer ratios of PBDEs implicated in bioaccumulation, indoor PBDE emissions versus human exposure, secured technologies to deal with the toxic emissions, and human toxicity of PBDEs in relation to the number of bromine atoms. Finally, an emphasis has been made on the knowledge gaps and future research directions related to endurable flame retardants which could fit well into the benefit/risk strategy.

Mitochondrial-related effects of pentabromophenol, tetrabromobisphenol A, and triphenyl phosphate on murine BV-2 microglia cells

The predominant reliance on bromated flame retardants (BFRs) is diminishing with expanded use of alternative organophosphate flame retardants. However, exposure related issues for susceptible populations, the developing, infirmed, or aged, remain given environmental persistence and home-environment detection. In this regard, reports of flame retardant (FR)-related effects on the innate immune system suggest process by which a spectrum of adverse health effects could manifest across the life-span. As representative of the nervous system innate immune system, the current study examined changes in microglia following exposure to representative FRs, pentabromophenol (PBP), tetrabromobisphenol A (2,2',6,6',-tetrabromo-4,4'-isopropylidine diphenol; TBBPA) and triphenyl phosphate (TPP). Following 18hr exposure of murine BV-2 cells, at dose levels resulting in ≥80% viability (10 and 40 μM), limited alterations in pro-inflammatory responses were observed however, changes were observed in mitochondrial respiration. Basal respiration was altered by PBP; ATP-linked respiration by PBP and TBBPA, and maximum respiration by all three FRs. Basal glycolytic rate was altered by PBP and TBBPA and compensatory glycolysis by all three. Phagocytosis was decreased for PBP and TBBPA. NLRP3 inflammasome activation was assessed using BV-2-ASC (apoptosis-associated speck-like protein containing a CARD) reporter cells to visualize aggregate formation. PBP, showed a direct stimulation of aggregate formation and properties as a NLRP3 inflammasome secondary trigger. TBBPA showed indications of possible secondary triggering activity while no changes were seen with TPP. Thus, the data suggests an effect of all three FRs on mitochondria metabolism yet, different functional outcomes including, phagocytic capability and NLRP3 inflammasome activation.

Exposure pathways, levels and toxicity of polybrominated diphenyl ethers in humans: A review

Polybrominated diphenyl ethers (PBDEs) are extensively used as brominated flame retardants (BFRs) in different types of materials, which have been listed as Persistent Organic Pollutants (POPs) by the Stockholm Convention in 2009 and 2017. Due to their ubiquities in the environment and toxicities, PBDEs have posed great threat to both human health and ecosystems. The aim of this review is to offer a comprehensive understanding of the exposure pathways, levels and trends and associated health risks of PBDEs in human body in a global scale. We systematically reviewed and described the scientific data of PBDE researches worldwide from 2010 to March 2020, focusing on the following three areas: (1) sources and human external exposure pathways of PBDEs; (2) PBDE levels and trends in humans; (3) human data of PBDEs toxicity. Dietary intake and dust ingestion are dominant human exposure pathways. PBDEs were widely detected in human samples, especially in human serum and human milk. Data showed that PBDEs are generally declining in human samples worldwide as a result of their phasing out. Due to the common use of PBDEs, their levels in humans from the USA were generally higher than that in other countries. High concentrations of PBDEs have been detected in humans from PBDE production regions and e-waste recycling sites. BDE-47, -153 and -99 were proved to be the primary congeners in humans. Human toxicity data demonstrated that PBDEs have extensively endocrine disruption effects, developmental effects, and carcinogenic effects among different populations.

Indoor Dust as a Source of Virulent Strains of the Agents of Cryptococcosis in the Rio Negro Micro-Region of the Brazilian Amazon

Cryptococcosis, a potentially fatal mycosis in humans, is acquired via exposure to exogenous environmental sources. This study aimed to investigate the frequency, genetic diversity, and virulence of cryptococcal strains isolated from indoor dust in the Rio Negro micro-region of the Brazilian Amazon. A total of 8.9% of the studied houses were positive, recovering nine Cryptococcus neoformans VNI and 16 C. gattii VGII isolates, revealing an endemic pattern in domestic microenvironments. The International Society for Human and Animal Mycology (ISHAM) consensus multilocus sequence typing (MLST) scheme for the C. neoformans/C. gattii species complexes identified two sequence types (STs), ST93 and ST5, amongst C. neoformans isolates and six STs amongst C. gattii isolates, including the Vancouver Island Outbreak ST7 (VGIIa) and ST20 (VGIIb), the Australian ST5, and ST264, ST268 and ST445, being unique to the studied region. Virulence studies in the Galleria mellonella model showed that five C.gattii strains and one C. neoformans strain showed a similar pathogenic potential to the highly virulent Vancouver Island outbreak strain CDR265 (VGIIa). The findings of this study indicate that humans can be exposed to the agents of cryptococcosis via house dust, forming the basis for future studies to analyze the impact of early and continuous exposure to indoor dust on the development of subclinical or clinical infections.

Knowledge and attitudes regarding exposure to brominated flame retardants: a survey of Croatian health care providers

The exposure of pregnant and lactating women and their children to environmental contaminants such as brominated flame retardants (BFRs) is a subject of international concern, but the perception of these contaminants by health providers has not been extensively investigated. The aim of this study was to assess Croatian health care providers' knowledge of exposure to BFRs and their attitudes towards the responsibility to inform the public about the possible negative effects on human health. A cross-sectional survey was conducted from December 2017 to November 2018 with a sample of 400 health care providers. The instrument was a questionnaire consisting of sociodemographic questions, a BFR knowledge test and a BFR attitude assessment. Descriptive and inferential statistical analyses were performed with the STATISTICA 13 software. The results of our study indicate that health providers' knowledge of BFR exposure is lacking, as evidenced by the high frequency of incorrect responses, irrespective of the field of medicine or profession. Neither age nor interest in the topic was significantly correlated with the correctness of answers. Participants expressed a moderate interest in the topic, regardless of the profession or field of medicine. Therefore, we suggest including additional information for health providers about the health effects of BFRs in continuing education programmes organized by Croatian medical associations, nurse associations and other professional bodies as well as in existing high school and university education programmes for health professionals.

Low Concentrations of Tetrabromobisphenol A Disrupt Notch Signaling and Intestinal Development in in Vitro and in Vivo Models

Tetrabromobisphenol A (TBBPA) was recently reported to upregulate Notch target gene expression in embryonic stem cells differentiating to neurons in vitro, implying activation on Notch signaling, a crucial signaling involved in multiple organ development and homeostasis.The present study aimed to determine whether TBBPA at low concentrations can disrupt Notch signaling in the intestine and subsequently its development using in vitro and in vivo models, given TBBPA uptake mainly via the intestine. In rat intestinal epithelium cells (IEC-6), an in vitro model for intestinal development and homeostasis, we found 5-500 nM TBBPA upregulated Notch-related gene expression and stimulated cell proliferation as well as the growth of microvilli in a linear concentration-dependent manner. When Notch inhibitor DAPT had no obvious effects on all end points, DAPT significantly antagonized all changes caused by TBBPA, indicating that TBBPA activated Notch signaling in IEC-6 cells and subsequently stimulated cell proliferation and differentiation. Then we employed Xenopus laevis, an ideal model species for intestinal development with the strong similarities to mammals, to further confirm the action of TBBPA in vivo. Expectedly, we observed the stimulatory effects of TBBPA on Notch signaling and cell proliferation and differentiation in X. laevis intestines, which agrees with the results in vitro. Antagonistic actions of Notch inhibitor DBZ on TBBPA-caused intestinal changes show that TBBPA affected intestinal development via disrupting Notch signaling. Interestingly, TBBPA stimulated cell differentiation into secretory cells, which is generally believed to be regulated by Wnt signaling, suggesting disruption of Wnt signaling besides Notch signaling. All the results for the first time demonstrate that TBBPA at low concentrations, including environmentally relevant concentrations, disrupt Notch signaling and subsequently affect intestinal development by altering cell proliferation and differentiation in vertebrates. Our study highlights the intestine as a new target of TBBPA and broaden our understanding of developmental toxicity of TBBPA.

Ammoniated MOF-74(Zn) derivatives as luminescent sensor for highly selective detection of tetrabromobisphenol A

In this study, a porous framework MOF-74(Zn) (Zn₂ (DHBDC)(DMF)(H₂O)₂, H₄dondc = 1, 5-dioxido-2, 6-naphthalenedicarboxylic acid) with open metal sites was successful synthesized. MOF-74(Zn) as a template was grafted on the open metal sites with ethylenediamine (en) named MOF-74(Zn)-en to develop a highly selective and sensitive fluorescence detector for rapid determination of tetrabromobisphenol A (TBBPA). The obtained MOF-74(Zn)-en was well characterized by Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM) and showed ideal properties of photoluminescence. The fluorescence enhancement showed a good linear relationship with the concentrations of TBBPA in the range of 50-400 μg/L, and its limit of detection could reach to 0.75 μg/L. Furthermore, the possible sensing mechanism of the fluorescence enhancement could be attributed to Förster resonance energy transfer (FRET). The results will provide a convenient and quick method for detection of TBBPA. To the best of my knowledge, this is the first case to detect TBBPA by fluorescence enhancement with MOF derivatives.

Polybrominated diphenyl ethers in the environment and human external and internal exposure in China: A review

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants. Because of their toxicity and persistence, some PBDEs were restricted under the Stockholm Convention in 2009. Since then, many studies have been carried out on PBDEs in China and in many other countries. In the present review, the occurrences and contamination of PBDEs in air, water, sediment, soil, biota and daily food, human blood, hair, and other human tissues in China are comprehensively reviewed and described. The human exposure pathways and associated health risks of PBDEs are summarized. The data showed no obvious differences between North and South China, but concentrations from West China were generally lower than in East China, which can be mainly attributed to the production and widespread use of PBDEs in eastern regions. High levels of PBDEs were generally observed in the PBDE production facilities (e.g., Jiangsu Province and Shandong Province, East China) and e-waste recycling sites (Taizhou City, Zhejiang Province, East China, and Guiyu City and Qingyuan City, both located in Guangdong Province, South China) and large cities, whereas low levels were detected in rural and less-developed areas, especially in remote regions such as the Tibetan Plateau. Deca-BDE is generally the major congener. Existing problems for PBDE investigations in China are revealed, and further studies are also discussed and anticipated. In particular, non-invasive matrices such as hair should be more thoroughly studied; more accurate estimations of human exposure and health risks should be performed, such as adding bioaccessibility or bioavailability to human exposure assessments; and the degradation products and metabolites of PBDEs in human bodies should receive more attention. More investigations should be carried out to evaluate the quantitative relationships between internal and external exposure so as to provide a scientific basis for ensuring human health.