Toxicity of the brominated flame retardant tris-(2,3-dibromopropyl) isocyanurate in zebrafish (Danio rerio)

COPD-Like Phenotypes in TBC-Treated Mice Can be Effectively Alleviated via Estrogen Supplement

Tris(2,3-dibromopropyl) isocyanurate (TBC), recognized as an endocrine disruptor, can cause inflammatory injury to the lung tissue of mice. To investigate the specific respiratory effects of TBC, male C57BL/6J mice were administered a daily dose of 20 mg/kg of TBC over 14 days. Postexposure, these mice developed chronic obstructive pulmonary disease (COPD)-like symptoms characterized by inflammatory lung damage and functional impairment. In light of the antiestrogenic properties of TBC, we administrated estradiol (E2) to investigate its potential protective role against TBC-induced damage and found that the coexposure of E2 notably mitigated the COPD-like phenotypes. Immunohistochemical analysis revealed that TBC exposure reduced estrogen receptor alpha (ERα) expression and increased nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) expression, while E2 treatment rebalanced the expression levels of ERα and NF-κB to their normative states. Our findings indicate that TBC, as an antiestrogenic agent, may contribute to the pathogenesis of COPD through an ERα-mediated inflammatory pathway, but that E2 treatment could reverse the impairment, providing a potentially promising remedial treatment. Given the lung status as a primary target of air pollution, the presence of antiestrogenic compounds like TBC in atmospheric particulates presents a significant concern, with the potential to exacerbate respiratory conditions such as COPD and pneumonia.

Unraveling the anti-androgenic mechanism of tris(2,3-dibromopropyl) isocyanurate (TBC) via the non-classical testosterone pathway and steroidogenesis: Potential human reproductive health implications

The decline in male reproductive health, characterized by diminishing sperm count and testosterone levels, has raised concerns about environmental influences, particularly endocrine-disrupting chemicals (EDCs). Tris(2,3-dibromopropyl)isocyanurate (TBC), a novel brominated flame retardant widely used in electronics, textiles, and furniture, has emerged as a significant environmental contaminant with potential reproductive health implications. In this study, we investigated the molecular mechanisms underlying TBC-induced reproductive toxicity, particularly focusing on its impact on steroidogenesis and androgen signaling pathways using the GC-1 spg cell line as an in vitro model. Exposure of GC-1 spg cells to TBC, alone or in combination with testosterone or the anti-androgen flutamide resulted in decreased metabolic activity and increased lactate dehydrogenase release, indicating cytotoxic effects. Furthermore, TBC exposure led to a reduction in progesterone synthesis, while testosterone production remained unaffected. Interestingly, estradiol synthesis was diminished after TBC exposure, suggesting a disruption in steroid hormone balance critical for spermatogenesis. Mechanistic investigations revealed alterations in key proteins involved in the non-classical testosterone pathway and steroidogenesis. TBC exposure downregulated epidermal growth factor receptor (EGFR), protein kinase B (AKT), and phosphorylated cyclic AMP response element-binding protein (p-CREB), indicating suppression of non-classical androgen signaling. Additionally, decreased levels of steroidogenic acute regulatory protein (StAR) and 3-beta-hydroxysteroid dehydrogenase (HSD3β1) suggest impaired steroidogenesis. Here we uncover the intricate molecular mechanisms underlying TBC-induced reproductive toxicity, highlighting its potential to disrupt steroid hormone synthesis and androgen signaling pathways. Understanding the adverse effects of TBC on male reproductive health is crucial for developing strategies to mitigate its environmental impact and safeguard human fertility.

Mechanistic insight into biotransformation of novel triazine-based flame retardant 1,3,5-tris(2,3-dibromopropyl)-1,3,5-triazinane-2,4,6-trione by human cytochrome P450s

The escalating focus on the environmental occurrence and toxicology of emerging pollutants underscores the imperative need for a profound exploration of their metabolic transformations mediated by human CYP450 enzymes. Such investigations have the potential to unravel the intricate metabolite profiles, substantially altering the toxicological outcomes. In this study, we integrated the computational simulations with in vitro metabolism experiments to investigate the metabolic activity and mechanism of an emerging pollutant, 1,3,5-tris(2,3-dibromopropyl)-1,3,5-triazinane-2,4,6-trione (TDBP-TAZTO), catalyzed by human CYP450s. The results highlight the important contributions of CYP2E1, 3A4 and 2C9 to the biotransformation of TDBP-TAZTO, leading to the identification of four distinct metabolites. The effective binding conformations governing biotransformation reactions of TDBP-TAZTO within active CYP450s are unveiled. Structural instability of primary hydroxyTDBP-TAZTO products suggests three potential outcomes: (1) generation of an alcohol metabolite through successive debromination and reduction reactions, (2) formation of a dihydroxylated metabolite through secondary hydroxylation by CYP450, and (3) production of an N-dealkylated metabolite via decomposition and isomerization reactions in the aqueous environment. The formation of a desaturated debrominated metabolite may arise from H-abstraction and barrier-free Br release during the primary oxidation, potentially competing with the generation of hydroxyTDBP-TAZTO. These findings provide detailed mechanistic insight into TDBP-TAZTO biotransformation by CYP450s, which can enrich our understanding of the metabolic fate and associated health risk of this chemical.

Involvement of estrogen receptor alpha (ERα) and impairment of steroidogenesis after exposure to tris(2,3-dibromopropyl) isocyanurate (TBC) in mouse spermatogenic (GC-1 spg) cells in vitro

Good-quality reproductive cells are essential for reproduction. Endocrine disruptors are widely available in the environment and are known to have an adverse effect on spermatogenesis and steroidogenesis. One of them is tris(2,3-dibromopropyl) isocyanurate (TBC), i.e. one of the novel brominated flame retardants (NBFR). TBC is a widely distributed ingredient used in the production of flame retardants. Currently, it is known to affect the hormonal system, but the exact mechanism of its action is unknown. Therefore, the aim of the study was to determine whether TBC alone and in cotreatment with BHPI (estrogen receptor alpha antagonist) has an impact on the expression of nuclear receptors involved in the formation of steroid hormones, proteins, and enzymes responsible for steroidogenesis and the levels of steroid hormones (E2, P4, and T) in the GC-1 spg cell line as a mouse model of spermatogenic cells in vitro. Our results indicate that ERα is involved in the mechanism of TBC action, while no activation of PPARγ, AhR, and IGF-1R was observed. In addition, a decrease in the levels of most of the analyzed proteins and enzymes involved in steroid conversion was observed. Only Cyp19a1 was upregulated after TBC, BHPI, and TBC with BHPI cotreatment. In all the analyzed groups, a significant decrease in P4 and a subtle decrease in T and E2 were observed in the production and secretion of the hormones to the culture medium, compared to the control. The obtained results confirm the involvement of TBC in the dysregulation of steroid biosynthesis, which may affect male fertility.

Disruption of neurosteroid synthesis and release by tris(2,3-dibromopropyl)isocyanurate in primary mouse cortical astrocytes in vitro

Neurosteroidogenesis in astrocytes is crucial for the proper development and functioning of the brain. During this process, key neurohormones such as progesterone (P4 ), testosterone (T), and estradiol (E2 ) are produced. Proper production and release of neurosteroids can be affected by substances referred to as endocrine-disrupting compounds (EDCs). Tris-(2,3-dibromopropyl)isocyanurate (TBC) is a representative of novel brominated flame retardants used to stop ignition or reduce fire-related property damage to plastics, polyolefin, polyphenyl alkene, unsaturated polyester, synthetic rubber, and fibers. Interestingly, previous studies have shown that TBC can enhance the proliferation of estradiol-sensitive breast cancers in vitro, which suggests that TBC has EDC properties. Therefore, given the suspected endocrine-disrupting properties of TBC, the aim of the present study was to determine the impact of TBC on the neurosteroid (P4 , T, and E2 ) production and secretion as well as the mRNA expression of key enzymes involved in its production in mouse astrocytes in vitro. Our paper shows that TBC increases P4 production with a strong decrease in T production, which is accompanied by a decrease in Cyp17a1 mRNA expression, that is, the main enzyme metabolizing P4 to T. Moreover, TBC in both studied concentrations increases P4 secretion in the culture medium. Finally, our studies have demonstrated an increase in the expression of Cyp19a1 mRNA, an enzyme metabolizing T to E2 , with a simultaneous increase in the amount of E2 in cells. Our data clearly show that TBC in an in vitro environment acts as EDCs, which may lead to serious consequences for the proper development and functioning of the brain.

Anti-androgenic activity of novel flame retardants in mixtures: Newly identified contribution from tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO)

In recent decades, male infertility has been on the rise, largely attributed to exposure to chemicals with endocrine-disrupting properties. The adverse effects of disrupting androgen actions on the development and reproductive health of children and adolescents have been extensively studied. Flame retardants (FRs), used in consumer products to delay flammability, have been identified as antagonists of the androgen receptor (AR), potentially leading to adverse outcomes in male reproductive health later in life. This study examined the interaction of eight novel FRs with the AR, employing an in vitro AR-dependent luciferase reporter gene assay utilizing MDA-kb2 cells. The investigation revealed the anti-androgenic activity of tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO), a frequently detected FR in the environment. Furthermore, TDBP-TAZTO contributed to anti-androgenic activity when combined with six other anti-androgenic FRs. The mixture effects were predicted by three commonly employed models: concentration addition (CA), generalized CA, and independent action, with the CA model showcasing the highest accuracy. This suggests that all FRs act through a similar mechanism, as further confirmed by in silico molecular docking, indicating limited synergy or antagonism. Importantly, in the mixtures, each FR contributed to the induction of anti-androgenic effects at concentrations below their individual effective concentrations in single exposures. This raises concern for public health, especially considering the co-detection of these FRs and their potential co-occurrence with other anti-androgenic chemicals like bisphenols. Therefore, our findings, along with previous research, strongly support the incorporation of combined effects of mixtures in risk assessment to efficiently safeguard population health.

Reprotoxic Effect of Tris(2,3-Dibromopropyl) Isocyanurate (TBC) on Spermatogenic Cells In Vitro

Tris(2,3-dibromopropyl) isocyanurate (TBC) belongs to the class of novel brominated flame retardants (NFBRs) that are widely used in industry. It has commonly been found in the environment, and its presence has been discovered in living organisms as well. TBC is also described as an endocrine disruptor that is able to affect male reproductive processes through the estrogen receptors (ERs) engaged in the male reproductive processes. With the worsening problem of male infertility in humans, a mechanism is being sought to explain such reproductive difficulties. However, so far, little is known about the mechanism of action of TBC in male reproductive models in vitro. Therefore, the aim of the study was to evaluate the effect of TBC alone and in cotreatment with BHPI (estrogen receptor antagonist), 17β-estradiol (E₂), and letrozole on the basic metabolic parameters in mouse spermatogenic cells (GC-1 spg) in vitro, as well as the effect of TBC on mRNA expression (Ki67, p53, Pparγ, Ahr, and Esr1). The presented results show the cytotoxic and apoptotic effects of high micromolar concentrations of TBC on mouse spermatogenic cells. Moreover, an increase in Pparγ mRNA levels and a decrease in Ahr and Esr1 gene expression were observed in GS-1spg cells cotreated with E₂. These results suggest the significant involvement of TBC in the dysregulation of the steroid-based pathway in the male reproductive cell models in vitro and may be the cause of the currently observed deterioration of male fertility. However, more research is needed to reveal the full mechanism of TBC engagement in this phenomenon.

Comprehensive review of the impact of tris(2,3-dibromopropyl) isocyanurate (TBC or TDBP-TAZTO) on living organisms and the environment

Tris(2,3-dibromopropyl) isocyanurate (TBC or TDBP-TAZTO) belongs to the group of brominated flame retardants (BFRs). The production of this compound is increasing due to the growing demand and wide application in electrical, electronic, musical instrument, and automotive component industries. The properties of TBC, e.g., the high octanol-air partition coefficient (Koa), high octanol-water partition coefficient (Kow), and high bioconcentration factor (BCF), indicate a possibility of its spread in aquatic and terrestrial ecosystems and bioaccumulation in living organisms. The presence of TBC has been confirmed in soil, sediments, river water, and such materials as microplastic, curtains, and e-waste devices. The compound has potential to bioaccumulate in the food chain of living organisms. TBC has been demonstrated to exert a harmful effect mainly on the nervous and endocrine systems, lungs, and liver. The possible mechanism of toxicity of the compound in the nervous system is based on the generation of oxidative stress by TBC leading to apoptosis of neuronal cells, while mitochondrial damage is considered to be responsible for changes in the respiratory organ. Moreover, the potential of mussels and earthworms to be bioindicators of TBC has been proven. Therefore, the literature review is focused on TBC properties and analysis of the identification and impact of the compound on the environment, living organisms, and human cell lines. Given the many toxic effects of TBC highlighted in the literature, there is a need for more profound research on the safety of TBC and methods for identification and degradation of this compound.

In vivo and in vitro study on hepatotoxicity of Tris-(2, 3-dibromopropyl) isocyanurate exposure via mitochondrial and death receptor pathway

Tri-(2,3-dibromopropyl) isocyanate (TBC), a newly brominated flame retardant, is widely used in the synthesis of flame retardant materials with characteristics of persistent organic pollutants. To obtain environmental exposure risks of TBC, Wistar rats and HepG2 cell were used for in vivo and in vitro studies on the toxicity of TBC and relevant ecotoxicological mechanisms of apoptosis. 80 Wistar rats were randomly selected and divided into four exposure groups (0, 0.313, 0.625, 1.250) g/(kg·bw) TBC, half male and half female, with oral administration for 28 days. Wistar rats exhibited appetite loss, weight loss, and dull hair with increasing period of TBC exposure. The pathological examinations revealed the most severe damage of liver and the ratio of liver/body weight of 35.497 × 10^-3 for high-dosed group (1.250 g/kg·bw) was higher than that of 32.792 × 10^-3 for control group in female rats with identical trend in male rats. The above indicators was fairly consistent with the serum test results which further confirmed the liver to be the target organ. The exposure dosages of HepG2 cell were (0, 12.5, 25, 50) μg/mL, individually. The HepG2 cells exposed to TBC for 72 h displayed hazy cell contour and decreased density of cell growth. And there was an inhibition detected by MTT assay, where the maximum inhibition rate was 19.93% under the dose of 50 μg/mL TBC. Apoptosis rate detected by flow cytometry which was demonstrated to be positively correlated to exposure dosage of TBC. The apoptosis rates of the low, medium and high dose groups of TBC exposure were (1.082 ± 0.109) %, (3.017 ± 0.09) % and (6.813 ± 0.233) %, individually. Targeted genes and corresponding protein expressions that triggering apoptosis both in vivo and in vitro were significantly altered. Overall, this work discloses the impacts of TBC exposure on hepatotoxicity, which provides new insights for chemical risk assessments of accelerate cell apoptosis via mitochondrial and death receptor pathway.

In situ localization of tris(2,3-dibromopropyl) isocyanurate in mouse organs by MALDI-IMS with auxiliary matrix strategy

Tris(2,3-dibromopropyl) isocyanurate (TBC) is one of the novel brominated flame retardants that has been widely used in consumer goods. Humans may be exposed to TBC daily. Studies showed that TBC can induce significant toxicity. However, there is currently no report on its in situ localization in organs. In this study, we aimed to develop a reliable and reproductive method to determine the in situ localization of TBC in mouse organs by matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). As commercially available matrices were not able to detect TBC in tissue section, we then developed a novel MALDI-IMS method based on 1,5-diaminonaphthalene hydrochloride and silver trifluoromethanesulfonate (NDA/AgOTf) as the matrix for the in situ localization of TBC. AgOTf used as the auxiliary matrix in the negative-ion mode showed an excellent MS signal of TBC. The detection limit of [2AgOTf + Br]^- was at the μg/mL level. The developed MALDI-IMS method was successfully employed to obtain the TBC spatial distribution in the mouse organs collected from mice exposed to 160 mg/kg/day of TBC for 30 days. High-pressure liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS) was also used to evaluate the accumulation of TBC in liver, kidney, heart, and brain. The combination of MALDI-IMS and HPLC-MS/MS showed that TBC can accumulate in mice organs and it is mainly distributed in the renal parenchyma. In summary, an innovative method was developed for the analysis of TBC spatial distribution by MALDI-IMS using a novel NDA/AgOTf matrix, extending the application of MALDI-IMS in environmental pollutants.

Tris (2,3-Dibromopropyl) Isocyanurate (TDBP-TAZTO or TBC) Shows Different Toxicity Depending on the Degree of Differentiation of the Human Neuroblastoma (SH-SY5Y) Cell Line

Tris (2,3-dibromopropyl) isocyanurate (TDBP-TAZTO or TBC) is a heterocyclic hexabromated flame retardant. It is widely used during the production of many synthetic compounds. High concentrations of TDBP-TAZTO were found in river water, surface sediments, soil, earthworms, and carp tissues. Moreover, it has been shown that this compound can cross the blood–brain barrier and accumulate in the gut and brain of carp. The aryl hydrocarbon receptor (AhR) has been characterized as a multifunctional intracellular sensor and receptor. AhR is an activator of cytochrome P450 1A1 and 1A2, which metabolize various toxic compounds. The aim of the study was to explain how/whether TDBP-TAZTO increases the expression and/or activity of the CYP1A1 enzyme and the AhR and TUBB3 expression during SH-SY5Y cell differentiation. SH-SY5Y cells were differentiated for 7 and 14 days using retinoic acid. Cell viability, ethoxyresorufin-O-deethylase (EROD) activity, and mRNA expression of CYP1A1, AhR, and TUBB3 were assessed. Our experiment showed that, during the differentiation process, the ability of TDBP-TAZTO to induce EROD activity in SH-SY5Y cells subsequently decreased, which may have been an effect of cell differentiation into neurons. Moreover, the results suggest that TDBP-TAZTO can affect the differentiation process. Since no CYP2B6 mRNA expression was detected, the CAR receptor may not be involved in the TDBP-TAZTO mechanism of action. However, more research is needed in this field to elucidate this mechanism precisely.

New understanding of novel brominated flame retardants (NBFRs): Neuro(endocrine) toxicity

Traditional brominated flame retardants (BFRs) negatively affect the environment and human health, especially in the sensitive (developing) nervous system. Considering the physicochemical similarities between novel brominated flame retardants (NBFRs) and BFRs, more and more evidence reveals the neurotoxic effects of NBFRs. We reviewed the neuro(endocrine) toxic effects of NBFRs in vivo and in vitro and discussed their action mechanisms based on the available information. The neurotoxic potential of NBFRs has been demonstrated through direct neurotoxicity and disruption of the neuroendocrine system, with adverse effects on neurobehavioral and reproductive development. Mechanistic studies have shown that the impact of NBFRs is related to the complex interaction of neural and endocrine signals. From disrupting the gender differentiation of the brain, altering serum thyroid/sex hormone levels, gene/protein expression, and so on, to interfere with the feedback effect between different levels of the HPG/HPT axis. In this paper, the mechanism of neurotoxic effects of NBFRs is explored from a new perspective-neuro and endocrine interactions. Gaps in the toxicity data of NBFRs in the neuroendocrine system are supplemented and provide a broader dataset for a complete risk assessment.

Detection of potential biomarkers associated with outrageous diseases and environmental pollutants by nanoparticle-based immuno-PCR assays

Immuno-polymerase chain reaction (I-PCR) assay with advantages of both enzyme-linked immunosorbent assay (ELISA) and PCR exhibits several-fold enhanced sensitivity in comparison to respective ELISA, which has wide applications for ultralow detection of several molecules, i.e. cytokines, protooncogenes and biomarkers associated with several diseases. Conjugation of reporter DNA to the detection antibodies is the most crucial step of I-PCR assay that usually employs streptavidin-protein A, streptavidin-biotin conjugate or succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) system by a covalent binding. However, coupling of antibodies and oligonucleotides to nanoparticles (NPs) is relatively easier in the NP-based I-PCR (NP-I-PCR) that also displays better accuracy. This article is mainly focused on the detection of important biomarkers associated with several outrageous infectious and non-infectious diseases by NP-I-PCR assays, which would expedite an early initiation of therapy thus human health would be improved. Similarly, ultralow detection of environmental pollutants by these assays and their elimination would certainly improve human health.

Occurrence of two novel triazine-based flame retardants in an E-waste recycling area in South China: Implication for human exposure

The recent increase in the use of alternative flame retardants (FRs) in consumer products has led to emerging contaminants in the environment. Identification of novel FRs is urgently needed because the potential threat posed by these chemicals has provoked considerable attention, but the details of the threat are not yet widely understood. In this study, two novel triazine-based FRs, tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO) and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ), were identified in dust samples from an e-waste recycling area in China. Two legacy FRs, namely, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD), were also analyzed for comparison. The mean level of TDBP-TAZTO in the e-waste dust samples was found to be much higher (2060 ng g^-1) than that of HBCDD (526 ng g^-1), while the mean level of TTBP-TAZ in residential dust samples was moderately higher (119 ng g^-1) than that of HBCDD (35.7 ng g^-1). A comparison of the TDBP-TAZTO and TTBP-TAZ concentrations with those of other alternative and legacy FRs indicated that TDBP-TAZTO is a major FR that is currently used in China. The estimated daily intake of TDBP-TAZTO via dust ingestion for occupational workers was much higher than that of HBCDD and was also much higher than for local adults and children. Exposure to TDBP-TAZTO poses a potentially high risk to the health of the local population, especially for the occupational workers, when the multicomponent chemical 'cocktail' effects are taken into account. More investigations on the environmental behaviors and risk factors of TDBP-TAZTO and TTBP-TAZ in various environmental matrices, as well as their toxicological effects, should be performed in the future.

1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione: kinetic studies and phototransformation products

1,3,5-Tris-(2,3-dibromopropyl)-1,3,5-triazine-2,4,6-trione (TDBP-TAZTO) is an emerging brominated flame retardant which is widely used in several plastic materials (electric and electronic equipment, musical instruments, automotive components). However, until today, no photochemical studies as well as the identification of possible phototransformation products (PTPs) were described in literature. Therefore, in this study, UV-(C) and simulated sunlight irradiation experiments were performed to investigate the photolytic degradation of TDBP-TAZTO and to identify relevant PTPs for the first time. The UV-(C) irradiation experiments show that the photolysis reaction follows a first-order kinetic model. Based on this, the photolysis rate constant k as well as the half-life time t_1/2 were calculated to be k = (41 ± 5 × 10^-3) min^-1 and t_1/2 = (17 ± 2) min. In comparison, a minor degradation of TDBP-TAZTO and no formed phototransformation products were obtained under simulated sunlight. In order to clarify the photochemical behavior, different chemicals were added to investigate the influence on indirect photolysis: (i) H₂O₂ for generation of hydroxyl radicals and (ii) two quenchers (2-propanol, sodium azide) for scavenging oxygen species which were formed during the irradiation experiments. Herein, nine previously unknown PTPs of TDBP-TAZTO were detected under UV-(C) irradiation and identified by HPLC-(HR)MS. As a result, debromination, hydroxylation, and dehydrobromination reactions could be presumed as the main degradation pathways by high-resolution mass spectrometry. The direct as well as the OH radical-induced indirect photolysis were observed. Graphical abstract .

Sorption behaviors of tris-(2,3-dibromopropyl) isocyanurate and hexabromocyclododecanes on polypropylene microplastics

In recent years, microplastics in oceans have become a serious environmental problem and the focus of attention. In the present study, the sorption of TBC and HBCDs by microplastics in simulated seawater is examined. The effects of particle size, temperature, salinity, and concentration on the adsorption of TBC and HBCDs by microplastics are studied. Results indicate that the first-order adsorption kinetic model is more suitable than the pseudo-second-order kinetic model to describe adsorption. The equilibrium adsorption times are 15 h and 10 h for TBC and HBCDs, respectively. The adsorption capacity increases with the decrease in particle size. The adsorption capacity gradually increases at first and then decreases with the increase in salinity and temperature. The maximum adsorption capacity is at 15 °C and 14% salinity. Compared with the linear and Freundlich models, the Langmuir model is more suitable; this indicates that the main adsorption mechanism might be chemical adsorption.

High level of tris-(2,3-dibromopropyl) isocyanurate (TBC) and hexabromocyclododecanes (HBCDs) in sediments from the intertidal zone of New River Estuary-a polluted and degraded wetland

The levels and distribution of tris-(2,3-dibromopropyl) isocyanurate (TBC) and hexabromocyclododecanes (HBCDs) in sediments in the intertidal zone of the New River Estuary were investigated. The concentration of TBC ranged from 2.78 to 35.1 ng·g^-1dw, and the concentration of total HBCDs ranged from 10.3 to 43.5 ng·g^-1dw. The composition of the three HBCD isomers, α-, β-, and γ-HBCD, was 6.23%, 8.00% and 85.8%, respectively. Moreover, the mass inventory of TBC, α-, β-, γ-HBCD, and total HBCDs in sediments were estimated to be about 1465.49, 124.64, 154.98, 1707.54, 1987.16 kg, respectively. Compared to previous studies, the concentrations of TBC and HBCDs in the intertidal zone of the New River Estuary were relatively high. Therefore, more concern of the potential public health and environmental risks of TBC and HBCDs is necessary.

Alternative Flame Retardant, 2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine, in an E-waste Recycling Facility and House Dust in North America

A high molecular weight compound, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ), was detected during the analysis of brominated flame retardants in dust samples collected from an electrical and electronic waste (e-waste) recycling facility in Ontario, Canada. Gas chromatography coupled with both high-resolution and low-resolution mass spectrometry (MS) was used to determine TTBP-TAZ's chemical structure and concentrations. To date, TTBP-TAZ has only been detected in plastic casings of electrical and electronic equipment and house dust from The Netherlands. Here we report on the concentrations of TTBP-TAZ in selected samples from North America: e-waste dust ( n = 7) and air ( n = 4), residential dust ( n = 30), and selected outdoor air ( n = 146), precipitation ( n = 19), sediment ( n = 11) and water ( n = 2) samples from the Great Lakes environment. TTBP-TAZ was detected in all the e-waste dust and air samples, and in 70% of residential dust samples. The median concentrations of TTBP-TAZ in these three types of samples were 5540 ng/g, 5.75 ng/m³ and 6.76 ng/g, respectively. The flame retardants 2,4,6-tribromophenol, tris(2,3-dibromopropyl) isocyanurate, and 3,3',5,5'-tetrabromobisphenol A bis(2,3-dibromopropyl) ether, BDE-47 and BDE-209 were also measured for comparison. None of these other flame retardants concentrations was significantly correlated with those of TTBP-TAZ in any of the sample types suggesting different sources. TTBP-TAZ was not detected in any of the outdoor environmental samples, which may relate to its application history and physicochemical properties. This is the first report of TTBP-TAZ in North America.

Evaluating estrogenic and anti-estrogenic effect of endocrine disrupting chemicals (EDCs) by zebrafish (Danio rerio) embryo-based vitellogenin 1 (vtg1) mRNA expression

By measuring the vitellogenin 1 (vtg1) expression through quantitative PCR and in situ hybridization, we used the zebrafish embryo as an in vivo model to access the estrogenic or anti-estrogenic effects of several endocrine disrupting chemicals (EDCs), such as natural estrogen 17β-estradiol (E2), estriol (E3), synthetic hormones including diethylstilbestrol (DES), 4-octyl phenol (OP), bisphenol A (BPA), tamoxifen (TMX) and 3-(2,3-dibromopropyl) isocyanurate (TBC). According to our data, the estrogenic effect of the tested chemicals was ranked as: DES>E₂>E₃>OP>BPA, which is consistent with various in vivo and in vitro models. Therefore, the measurement of vtg1 gene expression in zebrafish embryos would be a valuable method for screening EDCs including both environmental estrogens and anti-estrogens.

Biological effects of new-generation dialkyl phosphinate flame retardants and their hydrolysates in BALB/C mice

Aluminum methylcyclohexylphosphinate (AMHP), calcium methylcyclohexylphosphinate (CMHP), aluminum diethylphosphinate (ADEP), and aluminum methylethylphosphinate (AMEP) are organic dialkyl phosphinates (DPs) and emerging phosphorus-based flame retardants. The broad-spectrum DPs flame retardants occupy high-end industrial markets, but their ecologic risk has been reported rarely. By exposing male BALB/c mice to DPs and dialkyl phosphinic acids, we studied the toxic effects of these chemicals, and measured AMHP and methylcyclohexylphosphinic acid (MHPA) in blood and feces. We found that DPs and their main hydrolysates had mild toxicity in BALB/c mice. Exposure to 10 and 50 mg/kg/d of AMEP and ADEP caused mild hepatotoxicity in mice. Toxicity of CMHP was in the liver and kidneys. Toxicity of AMHP and its hydrolysate MHPA was low and affected the liver. These data suggest that AMHP has lower toxicity than the other DPs that we tested. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1578-1586, 2017.

Levels and distribution of tris-(2,3-dibromopropyl) isocyanurate and hexabromocyclododecanes in surface sediments from the Yellow River Delta wetland of China

The levels and distribution of tris-(2,3-dibromopropyl) isocyanurate (TBC) and hexabromocyclododecanes (HBCDs) of surface sediments in the Yellow River Delta wetland had been investigated. The concentrations of TBC and ∑HBCDs ranged from 0.20 to 29.03ng·g^-1dw and below limits of detections (LODs) to 20.25ng·g^-1dw. The average composition profile of three HBCDs isomers were 10.1%, 6.1% and 83.8% for α-, β- and γ-HBCD, respectively. Moreover, correlation analysis indicated there are similar sources among three isomers and positive correlations between total organic carbon (TOC) content and concentrations of TBC and HBCDs. The mass inventory of TBC,α-, β-, γ-HBCD, ΣHBCDs in surface sediments of Yellow River Delta wetland were estimated about 725.50, 72.76, 44.29, 548.34, 665.39kg. Therefore, further investigations on potential human health and environmental risk assessments of TBC and HBCDs were needed.

Photolytic degradation of tris-(2,3-dibromopropyl) isocyanurate (TBC) in aqueous systems

Tris-(2,3-dibromopropyl) isocyanurate (TBC) is a brominated flame retardant, which has been found in several environmental and biological matrices in recent years. TBC has aroused high environmental concerns because of its bioaccumulation and biological toxicity. This work studied photodegradation of TBC for the first time. The optimal degradation conditions have been found that 95% of 10 μmol/LTBC was effectively decomposed after 120 min of UV radiation. UV lamp was found to be more effective than Xe lamp on the photodegradation. The degradation rate of TBC increased with increasing light intensity. Under UV illumination, the effect of pH on the photodegradation of TBC could be ignored and degradation reactions followed the pseudo-first-order kinetics. The addition of [Formula: see text] could not accelerate the degradation of TBC. The quenching experiments showed that TBC was directly photodegraded by UV illumination. These findings suggest that UV photodegradation is a potential method for the removal of TBC in aqueous solutions.

Tris-(2,3-dibromopropyl) isocyanurate induces depression-like behaviors and neurotoxicity by oxidative damage and cell apoptosis in vitro and in vivo

Tris-(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO), an emerging brominated flame retardant, possesses the characteristics of candidate persistent organic pollutants and has displayed toxicity to fish and rodents. TDBP-TAZTO can pass through the blood-brain barrier and accumulate in the brain. TDBP-TAZTO might also induce neuronal cell toxicity. However, the neurotoxicity and mechanisms of TDBP-TAZTO have not yet been studied. We hypothesize that TDBP-TAZTO could induce neurotoxicity in mouse hippocampal neurons and SH-SY5Y cells. The mice were exposed to TDBP-TAZTO of 5 and 50 mg/kg by gavage, daily for 30 days. TDBP-TAZTO resulted in depression-like behaviors, which may be related with TDBP-TAZTO-induced upregulation of oxidative stress markers and overexpression of pro-apoptotic proteins in hippocampus. Furthermore, TDBP-TAZTO treatment for 48 hr (12.5, 25 and 50 µM) damaged SH-SY5Y cells, and led to cell apoptosis and oxidative stress in concentration-dependent manner. Our findings suggested that cell apoptosis and oxidative stress are important mechanisms in neurotoxicity induced by TDBP-TAZTO.

Exposure to Bisphenol AF disrupts sex hormone levels and vitellogenin expression in zebrafish

Bisphenol AF (BPAF) is widely used in food-contact products, electronic devices, and as a cross-linking reagent in fluoroelastomers. There are growing concerns about its toxicity and endocrine-disrupting effects based on its structural similarity with bisphenol A (BPA). The endocrine-disrupting effects of BPAF were studied by exposing 2-month-old zebrafish to 0, 0.05, 0.25, or 1 mg/L BPAF for 28 days and evaluating the effect on growth, histopathology, hormone levels, enzyme activity, and gene expression. The overall fitness was not significantly affected. There were no apparent alterations in the gills and intestine tissues of both sexes after BPAF exposure. However, exposure to 1 mg/L BPAF caused damage to the liver in the male fish, characterized by hepatocellular swelling and vacuolation. There was no obvious effect in the liver of female fish, suggesting that the hepatic toxicity of BPAF is gender dependent. Gonadal examination indicated that exposure to 1 mg/L BPAF caused induction of acellular areas in the testis and retardation of oocyte development in the ovary. BPAF exposure increased free triiodothyronine levels of females in a dose-dependent manner. In males, the testosterone levels decreased in a concentration-dependent manner. In contrast, estradiol levels increased in a concentration-dependent manner and were significantly higher in males exposed to 1 mg/L BPAF compared with the controls. In females, 0.05 and 0.25 mg/L BPAF caused an increase in testosterone levels. Furthermore, the estradiol levels increased in females exposed to 0.05 and 1 mg/L. We observed an upregulation of hepatic vitellogenin in both sexes and significantly higher levels in males exposed to 1 mg/L BPAF and females exposed to 0.25 mg/L BPAF, suggesting that BPAF has an estrogenic activity. Our results indicate that BPAF is an endocrine-disrupting chemical that exerts reproductive toxicity and estrogenic effects on zebrafish.

Tris-(2,3-Dibromopropyl) Isocyanurate, a New Emerging Pollutant, Impairs Cognition and Provokes Depression-Like Behaviors in Adult Rats

Tris-(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO), an emerging brominated flame retardant, possesses the characteristics of candidate persistent organic pollutants and has displayed toxicity to fish and rodents. TDBP-TAZTO can pass through the blood brain barrier and accumulate in brain. However, the neurotoxicity of TDBP-TAZTO has not yet studied in rodents. We hypothesize that TDBP-TAZTO could induce the neurotoxicity in rat hippocampal neurons. The male adult rats were exposed to TDBP-TAZTO of 5 and 50 mg/kg by gavage, daily for 6 months. TDBP-TAZTO resulted in cognitive impairment and depression-like behaviors, which may be related with TDBP-TAZTO-induced hypothalamic-pituitary-adrenal axis hyperactivation, upregulation of inflammatory and oxidative stress markers, overexpression of pro-apoptotic proteins, downexpression of neurogenesis-related proteins in hippocampus, and hippocampal neurons damage in DG, CA1 and CA3 areas. Our findings suggested that TDBP-TAZTO induces significant hippocampal neurotoxicity, which provokes cognitive impairment and depression-like behaviors in adult rats. Therefore, this research will contribute to evaluate the neurotoxic effects of TDBP-TAZTO in human.

Synthesis of haptens and development of an indirect enzyme-linked immunosorbent assay for tris(2,3-dibromopropyl) isocyanurate

A competitive indirect enzyme-linked immunosorbent assay (ciELISA) was developed for detection of tris(2,3-dibromopropyl) isocyanurate (TBC). Polyclonal antibodies against TBC were raised from synthesized haptens and then screened against various coating antigens. After optimization of the immunoassay conditions, the linear range and IC₅₀ value of the assay were 0.30-100 and 5.17 μg/L, respectively, with little cross-reactivity (≤2%). Recovery of various samples (water, serum, soil) was tested and the values ranged from 68% to 110%. This ciELISA was also applied to determine TBC in the riverside soil of the Liuyang River, and the results were compared with the data obtained by UHPLC-MS/MS. The experimental assay results confirmed that this proposed immunoassay is a specific, sensitive, and reliable method for determination and monitoring of TBC.

Spatial distribution and inter-year variation of hexabromocyclododecane (HBCD) and tris-(2,3-dibromopropyl) isocyanurate (TBC) in farm soils at a peri-urban region

Hexabromocyclododecane (HBCD) is a high production volume brominated flame retardant (BFR) which has been of increasing environmental and public health concern due to its potential environmental persistency, bioaccumulation and toxicity. Tris-(2,3-dibromopropyl) isocyanurate (TBC) is another BFR which has recently been found in environmental matrices near a manufacturing plant, but its production volume and environmental distribution is currently not well known. This study was conducted to investigate the presence and distribution of these two BFRs in farm soils at a region in southeast Beijing. Total HBCD levels ranged from 0.17 to 34.5 ng g(-1) on a dry weight basis (dw) with a median level of 2.97 ng g(-1)dw. The composition profile of HBCD diastereoisomers was, on average, 28%, 13% and 59% for α-, β- and γ-HBCD, respectively. Detection frequency of TBC was only 25% in 2010 but was detected in all soil samples in 2011, and the median level was 0.19 ng g(-1)dw with the range between below detection limit to 1.62 ng g(-1) dw. There were no significant differences of HBCD and TBC levels among different irrigation sources in the region. The soil HBCD and TBC levels in samples collected in 2011 were significantly higher than in 2010. The increasing short-term temporal levels in farm soil might be due to the rapid urbanization in this region or could also reflect the increasing usage of HBCD and TBC after the phase out of other BFRs.

Tris(2,3-dibromopropyl) isocyanurate, hexabromocyclododecanes, and polybrominated diphenyl ethers in mollusks from Chinese Bohai Sea

A novel brominated flame retardant (BFR), tris(2,3-dibromopropyl) isocyanurate (TBC), as well as hexabromocyclododecanes (HBCDs) and polybrominated diphenyl ethers (PBDEs), were analyzed in 11 species of mollusks collected from nine coastal cities around the Chinese Bohai Sea in 2009 and 2010. The detection frequencies were 100%, 99%, and 77% for PBDEs, HBCDs, and TBC, respectively. Concentrations of ∑HBCDs ranged from below detection limit (nd) to 28.8 ng g(-1) on a dry weight (dw) basis, followed by ∑(12)PBDE (0.01-20.4 ng g(-1) dw) and TBC (nd-12.1 ng g(-1) dw). Statistically significant linear correlations were found among the three BFRs. Positive correlations were found between BFRs concentrations and lipid content in mollusks. The concentrations tend to decrease with increasing trophic levels of the mollusks, implying trophic dilution rather than biomagnifications of the BFRs in the aquatic food chains of the sampling area. Among the 11 mollusks species, Mytilus edulis showed higher bioaccumulation capability than others and was therefore considered to be an appropriate bioindicator of contamination by the BFRs in the Chinese Bohai Sea, in agreement with its previous selection for the biomonitoring of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). A dramatic decrease in PBDE concentrations in mollusks of the area was found for the time period from 2003 to 2010, with a half-life of only 2.3 ± 1.7 years, reflecting a rapid response of mollusks to the change in pollution of the marine environment.

Impaired gas bladder inflation in zebrafish exposed to a novel heterocyclic brominated flame retardant tris(2,3-dibromopropyl) isocyanurate

The teleost gas bladder is a gas-filled internal organ that processes gas exchange and controls buoyancy. Here we report that an emerging heterocyclic brominated flame retardant, tris(2,3-dibromopropyl) isocyanurate (TBC), causes defects in the inflation of the gas bladder of zebrafish larvae. This could cause impaired motility, which can ultimately lead to their death. Exposure to zebrafish embryos revealed that TBC had the most significant influence on the larvae at 72-96 h postfertilization, which coincided with the time that the gas bladder first inflates. Critical factors involved in early zebrafish gas bladder development remained at normal levels, which indicated that TBC caused defects in the inflation of the gas bladder without disrupting early organogenesis. However, the ultrastructure of the gas bladder was altered in the TBC-treated groups: the electron density of cytoplasmic vesicles was changed and the mitochondria were damaged. We deduce that TBC causes damage to mitochondria that influences the secretion of mucus-like material, resulting in defects in gas bladder inflation. For the first time, we report that the gas bladder could be a primary target organ for TBC, and assessment of the gas bladder should be included in toxicity testing protocols of zebrafish embryos.