New Mixed Bromine/Chlorine Transformation Products of Tetrabromobisphenol A: Synthesis and Identification in Dust Samples from an E-Waste Dismantling Site

Exposure to synthesized tribromobisphenol A and critical effects: Metabolic pathways, disease signature, and benchmark dose derivation

2,2',6-Tribromobisphenol A (Tri-BBPA), the main debrominated congener of tetrabromobisphenol A (TBBPA), is ubiquitous in the environment and human body but with unknown toxicity. Tri-BBPA was synthesized and applied to investigate its sub-chronic exposure effects on 28 organ coefficients and clinical health indicators related to liver function, kidney function, and cardiovascular system function in female mice. Results showed that the liver was the targeted organ of Tri-BBPA exposure. Compared to the control group, the changes in liver coefficient, cholinesterase, total protein, albumin, γ-glutamyl transpeptidase, lactate dehydrogenase, and creatine kinase levels ranged from -61.2 % to 35.5 % in the high-exposed group. Creatine kinase was identified as a critical effect indicator of Tri-BBPA exposure. Using the Bayesian benchmark dose derivation method, a lower reference dose than TBBPA was established for Tri-BBPA (10.6 μg/kg-day). Serum metabolomics revealed that Tri-BBPA exposure may primarily damage the liver by disrupting tryptophan metabolism related to L-alanine, tryptamine, 5-hydroxyindoleacetic acid, and 5-methoxyindoleacetate in liver cells and leading to liver dysfunction. Notably, epilepsy, schizophrenia, early preeclampsia, and late-onset preeclampsia were the top six enriched diseases, suggesting that the nervous system may be particularly affected by Tri-BBPA exposure. Our findings hinted a non-negligible health risk of exposure to debrominated products of TBBPA.

Mechanism of tartaric acid mediated dissipation and biotransformation of tetrabromobisphenol A and its derivatives in soil

Biotransformation is a major dissipation process of tetrabromobisphenol A and its derivatives (TBBPAs) in soil. The biotransformation and ultimate environmental fate of TBBPAs have been widely studied, yet the effect of root exudates (especially low-molecular weight organic acids (LMWOAs)) on the fate of TBBPAs is poorly documented. Herein, the biotransformation behavior and mechanism of TBBPAs in bacteriome driven by LMWOAs were comprehensively investigated. Tartaric acid (TTA) was found to be the main component of LMWOAs in root exudates of Helianthus annus in the presence of TBBPAs, and was identified to play a key role in driving shaping bacteriome. TTA promoted shift of the dominant genus in soil bacteriome from Saccharibacteria_genera_incertae_sedis to Gemmatimonas, with a noteworthy increase of 24.90-34.65% in relative abundance of Gemmatimonas. A total of 28 conversion products were successfully identified, and β-scission was the principal biotransformation pathway for TBBPAs. TTA facilitated the emergence of novel conversion products, including 2,4-dibromophenol, 3,5-dibromo-4-hydroxyacetophenone, para-hydroxyacetophenone, and tribromobisphenol A. These products were formed via oxidative skeletal cleavage and debromination pathways. Additionally, bisphenol A was observed during the conversion of derivatives. This study provides a comprehensive understanding about biotransformation of TBBPAs driven by TTA in soil bacteriome, offering new insights into LMWOAs-driven biotransformation mechanisms.

Bisphenol Chemicals in Surface Soil from E-Waste Dismantling Facilities and the Surrounding Areas: Spatial Distribution and Health Risk

Electronic waste (e-waste) dismantling facilities are well-known bisphenol chemical (BP) sources. In this study, non-targeted screening combined with targeted analysis of BPs in surface soil from e-waste dismantling facilities and their surroundings revealed their presence, distribution, and exposure risk. A total of 14 BPs were identified including bisphenol A (BPA) and its novel structural analogs and halogenated BPs. The total concentrations of BPs ranged from 963 to 47,160 ng/g (median: 6970 ng/g) in e-waste soil, higher than those measured in surface soil from surrounding areas, i.e., 10-7750 ng/g (median 197 ng/g). BPA, tetrabromobisphenol A (TBBPA), and bisphenol F (BPF) were the dominant ones from the two areas. Concentrations of TBBPA and its debromination product from the surrounding area significantly decreased with increasing distances from the e-waste dismantling facilities. Estimation of daily intake via oral ingestion of soil suggests that current contamination scenarios are unlikely to pose health risks for e-waste dismantling workers and adults and toddlers living in the surrounding areas, with their intakes generally well below the tolerable daily intakes proposed for several BPs. However, the BPA intakes of workers exceeded the more strict tolerable daily intake for BPA established recently, which merits continuous environmental surveillance.

Exploring the residential exposome: Determination of hazardous flame retardants in air filter dust from HVAC systems

Dust is a sink for flame retardants, which are added to a myriad of consumer products in residential spaces. Organophosphate esters (OPEs) and brominated flame retardants (BFRs) are two classes of flame retardants that are frequently used in consumer products and consequently found in dust. In this present work, a novel solvent-limited microextraction technique, which we detailed in a companion study, was applied for the determination of four OPEs and two BFRs with limits of quantitation at the ng/g level by gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry from n = 47 air filter dust samples collected from forced air HVAC systems. Levels of the BFRs, including tetrabromobisphenol-A and its derivative tribromobisphenol-A, were found at levels <4 μg/g and not frequently detected. Conversely, all four OPEs were detected in all air filter dust samples. Total OPE load was dominated by tris(2,4-di-tert-butylphenyl) phosphate, T24DtBPP, a novel OPE not widely examined in the literature. Comparison of individual and total OPE concentrations to residential characteristics revealed statistically significant relationships to location of the home and dominant flooring type. Overall, this study motivates future work in examining the whole house exposome using air filter dust as a passive sampling regime with more examination of T24DtBPP loads within other indoor spaces.

Comprehensive characterization and prioritization of halogenated organic compounds in fish and their implications for exposure

Fish are an important pollution indicator for biomonitoring of halogenated organic compounds (HOCs) in aquatic environments, and HOCs in fish may pose health threats to consumers. This study performed nontarget and comprehensive analyses of HOCs in fish from an e-waste recycling zone by gas chromatography-high-resolution mass spectrometry, and further prioritized their human exposure risks. A total of 1652 formulas of HOCs were found in the fish, of which 1222, 117, and 313 were organochlorines, organobromines, and organochlorine-bromines, respectively. The total concentrations of HOCs were 15.4-18.7 μg/g (wet weight), and organobromines were the predominant (14.1-16.8 μg/g). Of the HOCs, 41 % were elucidated with tentative structures and divided into 13 groups. The estimated total daily exposures of HOCs via dietary consumption of the fish for local adult residents were 3082-3744 ng/kg bw/day. The total exposures were dominated by several groups of HOCs with the following contribution order: polyhalogenated biphenyls and their derivatives > polyhalogenated diphenyl ethers > halo- (H-)alkanes/olefines > H-benzenes > H-dioxins > H-polycyclic aromatic hydrocarbons > H-phenols. The comprehensive characterization and prioritization results provide an overview of the species and distributions of HOCs in edible fish, and propose an inventory of crucial HOCs associated with high exposure risks.

Co-occurrence of tetrabromobisphenol a and debromination products in human hair across China: Implications for exposure sources and health effects on metabolic syndrome

The large usage of Tetrabromobisphenol A (TBBPA) in consumer products leads to ubiquitous distribution globally, however, studies on the occurrence of their debromination compounds were rather scarce. Also, though many studies illustrate the effectiveness of hair analysis to assess human exposure to organic pollutants, evidence on the associations with health implications is still fairly limited. Herein, 598 participants from across China were employed to investigate chronic, low-level exposure to TBBPA and debromination products by hair analysis. The geomean concentrations of TBBPA, 2,2',6-tribromobisphenol A (Tri-BBPA), 2,2'- and 2,6-dibromobisphenol A (Di-BBPA), and 2-monobromobisphenol A (Mo-BBPA) were 1.07, 0.145, 0.135, and 0.894 ng/g, respectively, indicating nonnegligible health risks of debromination products. Hair analyte levels correlated with population age and population density among sampling regions. Sexual- and spatial-variations were observed with higher concentrations in females and in E-waste recycling sites. Logistic regression models showed that TBBPA exposure (adjusted odds ratio (OR): 1.02, 95 % confidential interval (CI): 1.01-1.05) was positively associated with risk of metabolic syndrome by adjusting for various covariates. These findings imply usefulness of hair as an alternative biomonitoring tool to assess human exposure to TBBPA and relative health effects, which highlights public concerns on co-exposure to these chemicals.

Construction of Models To Predict the Effectiveness of E-Waste Control through Capture of Volatile Organic Compounds and Metals/Metalloids Exposure Fingerprints: A Six-Year Longitudinal Study

The significant health implications of e-waste toxicants have triggered the global tightening of regulation on informal e-waste recycling sites (ER) but with disparate governance that requires effective monitoring. Taking advantage of the opportunity to implement e-waste control in the Guiyu ER since 2015, we investigated the temporal variations in levels of oxidative DNA damage, 25 volatile organic compound metabolites (VOCs), and 16 metals/metalloids (MeTs) in urine in 918 children between 2016 and 2021 to demonstrate the effectiveness of e-waste control in reducing population exposure risks. The hazard quotients of most MeTs and levels of 8-hydroxy-2'-deoxyguanosine in children decreased significantly during this time, indicating that e-waste control effectively reduces the noncarcinogenic risks of MeT exposure and levels of oxidative DNA damage. Using mVOC-derived indexes as a feature, a bagging-support vector machine algorithm-based machine learning model was constructed to predict the extent of e-waste pollution (EWP). The model exhibited excellent performance with accuracies >97.0% in differentiating between slight and severe EWP. Five simple functions established using mVOC-derived indexes also had high accuracy in predicting the presence of EWP. These models and functions provide a novel human exposure monitoring-based approach for assessing e-waste governance or the presence of EWP in other ERs.

Sorption in soils and bioaccumulation potential of 2,2'-DiBBPA

2,2'-Dibromobisphenol A (2,2'-DiBBPA) is frequently detected in the environment. However, the mobility of 2,2'-DiBBPA in the soil environment is poorly understood. The present study examined the effects of soil components such as the NaClO-resistant fraction, dithionite-citrate-bicarbonate -demineralized fraction, humin fraction, black carbon, DOC-removed fraction, exogenous dissolved organic carbon and heavy metal cations on the adsorption of 2,2'-DiBBPA on several types of agricultural soils. The adsorption isotherms on soils and soil components were well fitted to the linear isotherm equation. 2,2'-DiBBPA sorption onto soils was dominated by soil organic matter content (SOM) and affected by exogenous dissolved organic carbon. Linear regression relationships between adsorption capacity (K_d) and soil characteristics were evaluated to predict partitioning of 2,2'-DiBBPA. Black carbon played a predominant role in the adsorption of 2,2'-DiBBPA. Heavy metal ions significantly inhibited the adsorptive behavior of 2,2'-DiBBPA under alkaline conditions. Semiempirical linear relationships were observed between biota-sediment accumulation factors (1.18-2.47)/logarithm of bioconcentration factors (BCFs, 2.49-2.52) of 2,2'-DiBBPA in lugworms and K_d. These results allow for the prediction of the bioaccumulation of 2,2'-DiBBPA in other soils. Furthermore, values of log BCF > 1.0 indicate the preferential bioaccumulation of 2,2'-DiBBPA in biota. These data are of significance for understanding the migration of 2,2'-DiBBPA in agricultural soils and bioaccumulation in organisms.

Proliferation toxicity and mechanism of novel mixed bromine/chlorine transformation products of tetrabromobisphenol A on human embryonic stem cell

Mixed bromine/chlorine transformation products of tetrabromobisphenol A (Cl_yBr_xBPAs) are mixed halogenated-type compounds recently identified in electronic waste dismantling sites. There are a lack of toxicity data on these compounds. To study their development toxicity, the proliferation toxicity was investigated using human embryonic stem cells (hESC) exposed to the lowest effective dose of two Cl_yBr_xBPA analogues (2-chloro-2',6-dibromobisphenol A and 2,2'-dichloro-6-monobromobisphenol A). For comparison, tetrabromobisphenol A, 2,2',6-tribromobisphenol A, and bisphenol A were also assessed. It was observed that Cl_yBr_xBPAs inhibited hESCs proliferation in a concentration-dependent manner. The cell bioaccumulation efficiency of Cl_yBr_xBPAs was higher than that of tetrabromobisphenol A. Also, Cl_yBr_xBPAs were more toxic than tetrabromobisphenol A, with 2,2'-dichloro-6-monobromobisphenol A exhibiting the most potent toxicity. Furthermore, flow cytometry and oxidative stress results showed that increased reactive oxygen species raised the degree of apoptosis and reduced DNA synthesis. Metabolomics analysis on the effect of Cl_yBr_xBPAs on metabolic pathway alteration showed that Cl_yBr_xBPAs mainly interfered with four metabolic pathways related to amino acid metabolism and biosynthesis. These results provide an initial perspective on the proliferation toxicity of Cl_yBr_xBPAs, indicating development toxicity in children.

Emission and gas-particle partitioning characteristics of atmospheric halogenated and organophosphorus flame retardants in decabromodiphenyl ethane-manufacturing functional areas

The emission and gas-particle partitioning characteristics in various functional areas of production lines are still unknown. However, flame-retardant manufacturing activities are the primary emission source of flame retardants. Thus, fine particles and gases were investigated in three functional areas of a decabromodiphenyl ethane production line, i.e., polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), dechlorane plus (DPs), and organophosphorus flame retardants (OPFRs) in a flame-retardant manufacturing factory. High levels of PBDEs (8.02 × 10³-4.16 × 10⁴ pg/m³), NBFRs (6.05 × 10³-1.92 × 10⁵ pg/m³), and DPs (89.5-5.20 × 10³ pg/m³) were found in various functional areas, suggesting manufacturing activities were a primary emission source. In contrast, OPFRs were derived from long-range transport or other non-industrial sources. Varied concentrations of PBDEs, NBFRs, and DPs were observed in different production lines, higher in the reaction zone area than others. As the predominant compounds, decabromodiphenyl ether, decabromodiphenyl ethane, syn-DP, and tris(chloropropyl) phosphate accounted for 54.7%, 89.3%, 93.4%, and 34.7% of PBDEs, NBFRs, DPs, and OPFRs, respectively. Three models were used to predict the gas-particle partitioning of the halogenated flame retardants emitted from manufacturing activities. The Li-Jia Empirical Model predicted the gas-particle partitioning behavior well. This research shows that the adsorption-desorption process of the halogenated flame retardants between the gaseous and particulate phases did not reach equilibrium.

Debromination with Bromine Recovery from Pyrolysis of Waste Printed Circuit Boards Offers Economic and Environmental Benefits

Bromine is an important resource that is widely used in medical, automotive, and electronic industries. Waste electronic products containing brominated flame retardants can cause serious secondary pollution, which is why catalytic cracking, adsorption, fixation, separation, and purification have gained significant attention. However, the bromine resources have not been effectively reutilized. The application of advanced pyrolysis technology could help solve this problem via converting bromine pollution into bromine resources. Coupled debromination and bromide reutilization during pyrolysis is an important field of research in the future. This prospective paper presents new insights in terms of the reorganization of different elements and adjustment of bromine phase transition. Furthermore, we proposed some research directions for efficient and environmentally friendly debromination and reutilization of bromine: 1) precise synergistic pyrolysis should be further explored for efficient debromination, such as using persistent free radicals in biomass, polymer hydrogen supply, and metal catalysis, 2) rematching of Br elements and nonmetal elements (C/H/O) will be a promising direction for synthesizing functionalized adsorption materials, 3) oriented control of the bromide migration path should be further studied to obtain different forms of bromine resources, and 4) advanced pyrolysis equipment should be well developed.

Mixed bromine/chlorine transformation products of tetrabromobisphenol A formed in the combustion of printed circuit boards: Emission characteristics and transformation pathways

Recently, mixed bromine/chlorine transformation products of tetrabromobisphenol A (Cl_yBr_xBPAs) were found to be possibly related to the thermal treatment processes of electronic wastes. To explore their emission characteristics and formation mechanism, printed circuit board scraps were combusted in a tube furnace, under the temperature from 25 °C to 600 °C. The emission factor of the debromination products of tetrabromobisphenol A (Br_xBPAs) was the highest, whereas that of Cl_yBr_xBPAs was the lowest. Among three phases, most of the target compounds were partitioned into the oil and particle phases, and only negligible gaseous 2-BrBPA and bisphenol A were detected. The emission rates of most compounds were fastest at 300 °C, although 2-BrBPA, 2,6-Br₂BPA, and 2-Cl-6-BrBPA peaked at 350 °C. Among the chemicals in total emission, 2-BrBPA was the dominant congener in Br_xBPAs, whereas 2-Cl-2',6,6'-Br₃BPA, 2-Cl-2',6^#-Br₂BPA, and Σ₂Cl₁Br₁BPAs shared similar proportions in Cl_yBr_xBPAs. Meanwhile, the composition profiles at 300 °C showed that 2,2',6-Br₃BPA and 2-Cl-2',6,6'-Br₃BPA occupied the largest proportions in Br_xBPAs and Cl_yBr_xBPAs, respectively. To reveal the possible transformation pathways, the Gibbs free energy was calculated based on a radical substitution reaction. After "•Br" removal from tetrabromobisphenol A or other Br_xBPAs, the intermediate was more easily combined with "•H" than with "•Cl." In addition, the Cl_yBr_xBPA formation via "-•H + •Cl" by Br_xBPAs is nonspontaneous, thus limiting the further generation of Cl_yBr_xBPAs. This study not only provides ideas for the study of other mixed halogenated products, but also provides constructive suggestions for environmental source analysis by combining previous research on the occurrence of Cl_yBr_xBPAs in various environmental matrices.

Identification and occurrence of TBBPA and its debromination and O-methylation transformation products in sediment, fish and whelks from a typical e-waste dismantling site

Tetrabromobisphenol A (TBBPA) and its debromination (∑BBPA) and O-methylation (∑MeO-TBBPA) products were widely detected in matched sediments, fish, and whelks samples collected from a typical electronic waste (e-waste) dismantling site in Southern China, with concentrations ranging from 19.8 to 1.52 × 10⁴, 8.05 to 1.84 × 10³, and 0.08 to 11.9 ng/g dry weight in sediments, and 6.96 to 1.97 × 10⁵, 3.84 to 7.07 × 10³, and 3.42 to 472 ng/g lipid in biotas, for TBBPA, ∑BBPA, and ∑MeO-TBBPA, respectively. Significantly higher concentrations of these targets were found in samples collected close to the e-waste site, indicating their potential e-waste sources. Tri-BBPA was the most abundant debromination products in sediments, whereas diMeO-TBBPA was the dominant O-methylation product in biotas. Relatively higher levels of diMeO-TBBPA found in liver and kidneys, suggesting these chemicals might be mainly derived from the in vivo biotransformation. Furthermore, significantly higher biota-sediment accumulation factor values were found for diMeO-TBBPA than these of TBBPA, indicating that O-methylation would increases their accumulation in aquatic organisms. Our study provides insights into the accumulation and biotransformation of TBBPA in aquatic systems. Further studies should pay attention to the occurrence as well as potential health risks of these transformation products.

Combination of Soxhlet extraction and catalytic hydrodebromination for remediation of tetrabromobisphenol A contaminated soil

As a widely used brominated flame retardants (BFRs), tetrabromobisphenol A (TBBPA) has been detected in various environmental matrices and is known to cause negative effects on both the environment and human health. In this study, a combined method was developed for the abatement of TBBPA contaminated soil based on successive steps of solvent extraction (SE) and catalytic hydrodebromination (HDB) over Pd/C. The results showed that TBBPA could be efficiently extracted from the TBBPA contaminated soil with polar solvents. Subsequently, TBBPA could be completely hydrodebrominated over Pd/C in ethanol, via multistep ultimately yielding bisphenol A. Moreover, NaOH, NH₃H₂O, and Et₃N were more favorable to promote the HDB of 4-TBBPA over Pd/C, and 100% bromide atom removal ratio of TBBPA was achieved within 40 min when [NaOH]₀/[organic-Br]₀ was more than 1.10 in ethanol. However, the catalytic activity of Pd/C decreased with the repeated use in ethanol. To study the mechanism for this phenomenon, fresh and used catalysts were analyzed by characterization techniques including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectrometer (EDS). It was found that the deactivation of Pd/C catalyst caused by the gradual accumulation of NaBr could be recovered by washing with water. On the basis of these studies, an effective and practical system for the combined method of SE and catalytic HDB over Pd/C was developed to dispose BFRs contaminated soils.

E-waste dismantling-related occupational and routine exposure to melamine and its derivatives: Estimating exposure via dust ingestion and hand-to-mouth contact

Melamine (MEL) and its derivatives are increasingly applied as nitrogenous flame retardants in consumer products. Nevertheless, limited information is available on their environmental occurrence and subsequent human exposure via multiple exposure pathways. In this study, we analysed MEL and its derivatives in dust (indication of the dust ingestion route) and hand wipe samples (indication of the hand-to-mouth route) collected in various microenvironments. The levels of ∑MELs in both dust (median: 24,100 ng/g) and participant hand samples (803 ng/m²) collected in e-waste dismantling workshops were significantly higher than those in samples collected in homes (15,600 ng/g and 196 ng/m², respectively), dormitories (13,100 ng/g and 227 ng/m², respectively) and hotel rooms (11,800 ng/g and 154 ng/m², respectively). Generally, MEL dominated in dust samples collected in e-waste dismantling workshops, whereas cyanuric acid dominated in hand wipe samples. This may occur partly because the latter is an ingredient in disinfection products, which are more frequently employed in daily lives during the COVID-19 pandemic. Exposure assessment suggests that dust ingestion is an important exposure pathway among dismantling workers and the general population, whereas hand-to-mouth contact could not be overlooked in certain populations, such as children and dismantling workers not wear gloves at work.

Mixed bromine/chlorine transformation products of tetrabromobisphenol A: Potential specific molecular markers in e-waste dismantling areas

Mixed bromine/chlorine transformation products (Cl_yBr_xBPAs) of tetrabromobisphenol A (TBBPA) were recently identified for the first time in an electronic waste (e-waste) dismantling site. To determine whether these compounds can be used as specific molecular markers of e-waste dismantling activities, the environmental occurrences and distributions of TBBPA and its transformation products including debromination products (Br_xBPAs) and Cl_yBr_xBPAs were analyzed in soil samples from three sites in China: Guiyu (an e-waste site), Qingyuan (a former e-waste site now mainly used for old wire and cable recycling), and Shouguang (a flame retardant production base). Levels of the target analytes in Guiyu were significantly higher than in Qingyuan and Shouguang. Br_xBPAs and Cl_yBr_xBPAs were widely detected in Guiyu at concentrations between 1 and 4 orders of magnitude lower than their parent compound TBBPA. The highest concentration was found in an e-waste dismantling park, with lower concentrations in surrounding area. The levels of Cl_yBr_xBPAs in Qingyuan were much lower, indicating that the Cl_yBr_xBPAs may come from the processing of wires and cables, but not rule out the incubation on their own in soils. None of Cl_yBr_xBPAs were detected in Shouguang. Cl_yBr_xBPAs may thus be useful as specific molecular markers for determining the intensity of e-waste dismantling activities.

An energy-saving and environment-friendly technology for debromination of plastic waste: Novel models of heat transfer and movement behavior of bromine

The recovery and reuse of waste brominated resin, which is a typical plastic waste, is troublesome because it contains toxic brominated flame retardants. Conventional pyrolysis of brominated resin was suggested to be an effective approach for debromination. However, conventional pyrolysis caused high energy consumption and high yield of toxic volatiles. An energy-saving and environment-friendly technology called infrared heating was reported in this study. According to computation of the developed heat transfer models, the critical debromination temperature was 260 °C in infrared heating, which was 271 °C lower than conventional pyrolysis. Meanwhile, no volatile product appeared in the reported technology. In the pyrolysis residue after infrared heating, bromine concentrated orientationally in the fixed and limited area on the resin particles. Free radicals, such as •CH₃, H•, and Br•, were combined with Br• generated in infrared heating to form the concentrated bromine. Compared to the chaotic distribution of bromine in conventional pyrolysis, the orientational concentration of bromine was a progress for removing and collecting bromine in infrared heating. Moreover, compared to conventional pyrolysis, infrared heating could decrease 76.2% energy consumption. This work contributed to provide the novel technology for recovery of plastic wastes.

Organophosphate flame retardants, tetrabromobisphenol A, and their transformation products in sediment of e-waste dismantling areas and the flame-retardant production base

Due to the prohibition of polybrominated diphenyl ethers, organophosphate flame retardants (OPFRs) and tetrabromobisphenol A (TBBPA) have become emerging flame retardants. However, knowledge about their occurrence, especially their transformation products, is still limited. This study collected sediment samples from two rivers, i.e., Lianjiang River (located at an e-waste dismantling area) and Xiaoqing River (situated at a flame retardant production base), to investigate the occurrence, composition, and spatiality distribution of OPFRs, TBBPA, and their transformation products. Both targets were detected in the Lianjiang River in the range of 220-1.4 × 10⁴ and 108-3.1 × 10³ ng/g dw (dry weight) for OPFRs and TBBPA, and 0.11-2.35 and 4.8-414 ng/g dw for their respective transformation products, respectively. The concentrations of OPFRs and TBBPA in the Xiaoqing River ranged from 4.15 to 31.5 and 0.76-2.51 ng/g dw, respectively, and no transformation products were detected. Different compositional characteristics of OPFRs and distinct spatial distribution from mainstream and tributary observed between the two rivers are attributed to the difference in the local industries. Spatial distribution and principal component analysis indicated that e-waste dismantling activities could be a vital source of local pollution. Besides, the confluence of tributaries seemed to determine the contaminant levels in the Xiaoqing River. Also, concentration ratios and Spearman's correlation between metabolites and parent chemicals were analyzed. Low concentration ratios (3.6 ×10^-4 to 0.16) indicated a low transformation degree, and Spearman's correlation analysis suggested transformation products were partly stemming from commercial products. Considering the limited study of these transformation products, more studies on their sources, transform mechanism, and toxicity are required.

Low concentration Tetrabromobisphenol A (TBBPA) elevating overall metabolism by inducing activation of the Ras signaling pathway

Tetrabromobisphenol A (TBBPA), one of the most common flame retardants, affects neurodevelopment, disrupts the endocrine system, and increases the possibility of tumorigenesis. This study investigates the cytotoxic effects, genetic effects, and metabolic effects from exposure to low concentration TBBPA. The cell exposure was measured by mimicking the residual TBBPA concentrations in human plasma, specifically in occupational populations. Our results revealed that long-term TBBPA exposure, especially at 1 nM concentration, significantly promoted the proliferation of HepG2 cells. Furthermore, long-term TBBPA exposure can double the levels of reactive oxygen species (ROS) released from mitochondria, thereby increasing Adenosine Monophosphate activated Protein kinase (AMPK) gene expression level to promote cellular proliferation. However, ROS can also mediate the apoptosis process through the mitochondrial membrane potential (MMP). The RNA-seq analysis confirmed that the Ras signaling pathway was activated by the growth factor to mediate cell detoxification mechanism, increasing lipid and vitamin metabolic rate. Our work uncovers a cellular mechanism by which long-term exposure to low concentration TBBPA can induce the activation of the Ras signaling pathway and demonstrates potential metabolic disorder in the human hepatic cells upon plasma TBBPA exposure.