Novel Brominated Flame Retardants Research Articles

The emerging and legacy persistent organic contaminants in corals of the South China Sea

Seawater warming, ocean acidification and chemical pollution are the main threats to coral growth and even survival. The legacy persistent organic contaminants (POCs), such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), and the emerging contaminants, including polybrominated diphenyl ethers (PBDEs), dechlorane plus (DPs) and novel brominated flame retardants (NBFRs) were studied in corals from Luhuitou fringing reef in Sanya Bay and Yongle atoll in Xisha Islands, the South China Sea (SCS). Total average concentrations of ∑16PAHs, ∑23OCPs, ∑34PCBs, ∑8PBDEs, ∑2DPs and ∑5NBFRs in 20 coral species (43 samples) from the SCS were 40.7 ± 34.6, 5.20 ± 5.10, 0.197 ± 0.159, 3.30 ± 3.70, 0.041 ± 0.042 and 36.4 ± 112 ng g−1 dw, respectively. PAHs and NBFRs were the most abundant compounds and they are likely to be dangerous pollutants for future coral growth. Compared to those found in other coral reef regions, these pollutants concentrations in corals were at low to median levels. Except for PBDEs, POCs in massive Porites were significantly higher than those in branch Acropora and Pocillopora (p < 0.01), as large, closely packed corals may be beneficial for retaining more pollutant. The current study contributes valuable data on POCs, particularly for halogenated flame retardants (HFRs, including PBDEs, DPs and NBFRs), in corals from the SCS, and will improve our knowledge of the occurrence and fate of these pollutants in coral reef ecosystems.

Bioaccumulation and Trophodynamics of Novel Brominated Flame Retardants (NBFRs) in Marine Food Webs from the Arctic and Antarctic Regions.

The pervasive contamination of novel brominated flame retardants (NBFRs) in remote polar ecosystems has attracted great attention in recent research. However, understanding regarding the trophic transfer behavior of NBFRs in the Arctic and Antarctic marine food webs is limited. In this study, we examined the occurrence and trophodynamics of NBFRs in polar benthic marine sediment and food webs collected from areas around the Chinese Arctic Yellow River Station (n = 57) and Antarctic Great Wall Station (n = 94). ∑7NBFR concentrations were in the range of 1.27-7.47 ng/g lipid weight (lw) and 0.09-1.56 ng/g lw in the Arctic and Antarctic marine biota, respectively, among which decabromodiphenyl ethane (DBDPE) was the predominant compound in all sample types. The biota-sediment bioaccumulation factors (g total organic carbon/g lipid) of NBFRs in the Arctic (0.85-3.40) were 4-fold higher than those in the Antarctica (0.13-0.61). Trophic magnification factors (TMFs) and their 95% confidence interval (95% CI) of individual NBFRs ranged from 0.43 (95% CI: 0.32, 0.60) to 1.32 (0.92, 1.89) and from 0.34 (0.24, 0.49) to 0.92 (0.56, 1.51) in the Arctic and Antarctic marine food webs, respectively. The TMFs of most congeners were significantly lower than 1, indicating a trophic dilution potential. This is one of the very few investigations on the trophic transfer of NBFRs in remote Arctic and Antarctic marine ecosystems, which provides a basis for exploring the ecological risks of NBFRs in polar regions.

Uptake and translocation of brominated flame retardants in tomato plants (Solanum lycopersicum L.): Results from a standard soil-based biotest

The uptake and translocation of four polybrominated diphenyl ethers (PBDEs) and four novel brominated flame retardants (NBFRs) in tomato plants (Solanum lycopersicum L.) were investigated via the RHIZOtest, a standard soil-based biotest, optimized for organic compounds. Tomato plants were exposed to soil samples spiked with 0 (i.e. control), 5.00 or 50.00 ng g−1dw of each compound. Compared of those of the control, exposure to increasing spiking concentrations resulted in average reductions of 13% and 26% (w/w) in tomato plant biomass. Higher concentrations of NBFRs were analyzed both in roots, ranging from 0.23 to 8.01 ng g−1dw for PBDEs and from 1.25 to 18.51 ng g−1dw for NBFRs, and in shoots, ranging from 0.09 to 5.58 ng g−1dw and from 0.47 to 7.78 ng g−1dw for PBDEs and NBFRs, respectively. This corresponded to an average soil uptake of 5% for PBDEs and 9% for NBFRs at the lower soil-spiking level, and 3% for PBDEs and 6% for NBFRs at the higher soil spiking level. Consequently, among both initial spiking levels, the soil-root concentration factor (RCF) values were lower on average for PBDEs (0.13 ± 0.05 g dw soil g−1dw roots) than for NBFRs (0.33 ± 0.16 g dw soil g−1dw roots). Conversely, nondifferent values of the root-shoot transfer factor (TF) were calculated for both PBDEs (0.54 ± 0.13 g dw roots g−1dw shoots) and NBFRs (0.49 ± 0.24 g dw roots g−1dw shoots). The differences and similarities reported in the RCF and TF between and within the two groups of compounds can be explained by their properties. The calculated RCF and TF values of the PBDEs exhibited a decreasing trend as the number of bromine atoms increased. Additionally, a robust negative linear correlation was observed between RCF values and the respective logKow values for the PBDEs, at both soil-spiking levels. The root uptake of NBFRs exhibited a negative correlation with their hydrophobicity; however, this was not observed in the context of root-to-shoot transfer. The presence of a second aromatic ring appears to be the key factor influencing the observed variations in NBFRs, with biphenyl NBFRs (BTBPE and DBDPE) characterized by lower uptake and reduced translocation potential than monophenyl PBEB and HBB. Understanding the transfer of these compounds to crops, especially near plastic recycling waste sites, is crucial for understanding the risks of their potential inclusion in the human food chain.

Novel and legacy brominated flame retardants in human breast milk and house dust from Denmark

A suite of novel brominated flame retardants (NBFRs), hexabromocyclododecanes (HBCDDs), polybrominated diphenyl ethers (PBDEs) and dechlorane plus were measured in matched samples of house dust (n = 47) and human breast milk (n = 40) from Denmark sampled in 2007, i.e., shortly after PBDE restrictions were implemented in Europe providing a valuable reference point. The most abundant BFR in breast milk was BDE-153 with a median concentration of 0.79 ng/g lipid followed by BDE-47 (median: 0.61 ng/g lipid) and BDE-209 (median: 0.53 ng/g lipid). Levels of bis(2-ethylhexyl) tetrabromophthalate (BEH-TEBP) were comparable (median: 0.78 ng/g lipid); however, they were based on fewer samples. α-HBCDD was the most abundant HBCDD in breast milk (median: 0.24 ng/g lipid) and detected in all samples. The house dust samples were dominated by BDE-209 (median: 432 ng/g) and γ-HBCDD (median: 177 ng/g); among the NBFRs, the highest levels were found for decabromodiphenyl ethane (DBDPE) (median: 86.2 ng/g) and BEH-TEBP (median: 26.7 ng/g). BDE-28, 47 and 153 were significantly correlated between breast milk and serum (rs = 0.73-0.81, P &lt; 0.0001); however, this was not the case for any of the NBFRs. Intake estimates for a 3-month-old infant indicated that for most of the flame retardants, breast milk was by far the dominant route of exposure, whereas dust only contributed substantially for BDE-209, γ-HBCDD, and to some extent α-HBCDD. This study is the first to report on human exposure to NBFRs in Denmark and shows that internal exposure levels of NBFRs were similar to those of most PBDEs already at the time of PBDE restrictions.

Debromination of novel brominated flame retardants using Zn-based additives: A viable thermochemical approach in the mitigation of toxic effects during e-waste recycling

Brominated flame retardants (BFRs) are bromine-bearing additives added to the polymeric fraction in various applications to impede fire ignition. The Stockholm Convention and various other legislations abolished legacy BFRs usage and hence, the so-called novel BFRs (NBFRs) were introduced into the market. Recent studies spotlighted their existence in household dust, aquifers and aquatic/aerial species. Co-pyrolysis of BFRs with metal oxides has emerged as a potent chemical recycling approach that produces a bromine-free stream of hydrocarbon. Herein, we investigate the debromination of two prominent two NBFRs; namely tetrabromobisphenol A 2,3-dibromopropyl ether (TD) and tetrabromobisphenol A diallyl ether (TAE) through their co-pyrolysis with zinc oxide (ZnO) and franklinite (ZnFe2O4). Most of the zinc content in electrical arc furnace dust (EAFD) exists in the form of these two metal oxides. Conversion of these metal oxides into their respective bromides could also assist in the selective extraction of the valuable zinc content in EAFD. The debromination potential of both oxides was unveiled via a multitude of characterization studies to analyze products (char, gas and condensates). The thermogravimetric analysis suggested a pyrolytic run up to 500 °C and the TAE treatment with ZnO produced only a trivial amount of brominated compounds (relative area, 0.83%). Phenol was the sole common compound in condensable products; potentially formed by the β-scission debromination reaction from the parental molecular skeleton. Inorganic compounds and methane were the major constituents in the gaseous products. The pyrochar analyses confirmed the presence of metal bromides retained in the residue, averting the bromine release into the atmosphere. The ion chromatography analysis portrayed <8% of HBr gas release into the atmosphere upon pyrolysis with ZnO. The ZnO dominance herein envisaged further probes into other spinel ferrites in combating brominated polymers.

Impact of Legislation on Brominated Flame Retardant Concentrations in UK Indoor and Outdoor Environments: Evidence for Declining Indoor Emissions of Some Legacy BFRs.

Concentrations of polybrominated diphenyl ethers, hexabromocyclododecane (HBCDD), and novel brominated flame retardants (NBFRs) were measured in indoor dust, indoor air, and outdoor air in Birmingham, UK. Concentrations of ΣBFRs ranged from 490 to 89,000 ng/g, 46-14,000 pg/m3, and 22-11,000 pg/m3, respectively, in UK indoor dust, indoor air, and outdoor air. BDE-209 and decabromodiphenyl ethane (DBDPE) were the main contributors. The maximum concentration of DBDPE (10,000 pg/m3) in outdoor air is the highest reported anywhere to date. In contrast with previous studies of outdoor air in Birmingham, we observed significant correlations between concentrations of tri- to hepta-BDEs and HBCDD and temperature. This may suggest that primary emissions from ongoing use of these BFRs have diminished and that secondary emissions (e.g., evaporation from soil) are now a potentially major source of these BFRs in outdoor air. Conversely, the lack of significant correlations between temperature and concentrations of BDE-209 and DBDPE may indicate that ongoing primary emissions from indoor sources remain important for these BFRs. Further research to clarify the relative importance of primary and secondary sources of BFRs to outdoor air is required. Comparison with earlier studies in Birmingham reveals significant (p < 0.05) declines in concentrations of legacy BFRs, but significant increases for NBFRs over the past decade. While there appear minimal health burdens from BFR exposure for UK adults, dust ingestion of BDE-209 may pose a significant risk for UK toddlers.

Novel ultrasound assisted extraction and d-SPE clean-up for the analysis of multiple legacy and emerging organic contaminants in edible fish

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), phthalate esters (PAEs) are pervasive environmental pollutants, posing threats to both ecosystems and human health. Although several analytical methods were developed for these compounds, they are not performed simultaneously. This study addresses the need for a sustainable, novel, analytical approach capable of simultaneously determining these diverse chemical classes in edible fish muscles. Employing ultrasound extraction coupled with dispersive solid-phase extraction (d-SPE) as a cleanup procedure, the method was compared to conventional techniques, revealing significant improvements. Analytical parameters were thoroughly assessed, and the innovative method demonstrated notable advantages, reducing extraction and purification times by approximately 74–80 % and solvent consumption by around 94–97 %. Applied to Mediterranean Sea fish samples, the results underscore the method's potential as a viable, sustainable alternative to traditional approaches, promising enhanced efficiency and reduced environmental impact.

Historical Occurrence and Composition of Novel Brominated Flame Retardants and Dechlorane Plus in Sediments from an Electronic Waste Recycling Site in South China.

Novel brominated flame retardants (NBFRs) and dechlorane plus (DP) have been widely used as alternatives to traditional BFRs. However, little is known about the temporal trends of NBFR and DP pollution in e-waste recycling sites. In the current study, three composite sediment cores were collected from an e-waste-polluted pond located in a typical e-waste recycling site in South China to investigate the historical occurrence and composition of NBFRs and DP. The NBFRs and DP were detected in all layers of the sediment cores with concentration ranges of 5.71~180,895 and 4.95~109,847 ng/g dw, respectively. Except for 2,3,5,6-tetrabromo-p-xylene (pTBX) and 2,3,4,5,6-pentabromoethylbenzene (PBEB), all the NBFR compounds and DP showed a clear increasing trend from the bottom to top layers. These results implied the long-term and severe contamination of NBFRs and DP. Decabromodiphenyl ethane (DBDPE) was the most abundant NBFR with the contribution proportions of 58 ± 15%, 73 ± 15%, and 71 ± 18% in three sediment cores, followed by 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) and pentabromobenzene (HBB). The ratios of BTBPE/Octa-BDEs and DBDPE/Deca-BDEs varied from 0.12 to 60 and from 0.03 to 0.49, respectively, which had no clear increase trends with a decrease in sediment depth. As for DP, the fanti values (the concentration ratios of anti-DP to the sum of anti-DP and syn-DP) in sediment cores ranged from 0.41 to 0.83, almost falling in the range of those in DP technical products, suggesting that DP degradation did not occur in sediment cores. The environmental burdens of DBDPE, BTBPE, HBB, PBT, PBEB, pTBX, and DP were estimated to be 34.0, 5.67, 10.1, 0.02, 0.02, 0.01, and 34.8 kg, respectively. This work provides the first insight into the historical contamination status of NBFRs and DP in the sediments of an e-waste recycling site.

Computational Risk Assessment of Persistence, Bioaccumulation, and Toxicity of Novel Flame-Retardant Chemicals.

Novel brominated flame retardants (NBFRs) have emerged as chemicals of environmental concern, as they have been widely used as an alternative to polybrominated diphenyl ethers (PBDEs). Considering the similar structural features of NBFRs and PBDEs necessitates a comprehensive investigation to understand the physicochemical relationships of these compounds and their ability to alter biological functions. In this study, we investigated the persistent nature of NBFRs in terms of thyroid-disrupting potential by understanding the structure-stability aspects using density functional theory (DFT)-based reactivity parameters and interactions via molecular docking and molecular dynamics (MD) simulations. The results indicate that the DFT-based stability descriptor (chemical hardness) is associated with the persistent nature of NBFRs. The computed molecular interaction profile revealed prominent interactions between thyroid receptor-β (TR-β) and NBFRs. Stable trajectory and interactions with TR-β were obtained with ATE, p-TBX, PBT, PBEB, and TBBPA-DBPE during 100 ns of MD simulation. The results of these studies have suggested that the presence of a higher number of halogenated atoms increases the stability vis-à-vis the persistence and endocrine disruption potential of NBFRs.

The transport and distribution of novel brominated flame retardants (NBFRs) and organophosphate esters (OPEs) in soils and moss along mountain valleys in the Himalayas

Although the Himalayas act as a natural barrier, studies have demonstrated that certain traditional persistent organic pollutants (POPs) can be transported into the Tibetan Plateau (TP) through the mountain valleys. Herein, we selected five mountain valleys in the Himalayas to investigate novel flame retardants (NFRs), as representative novel POPs, their concentration, distribution, transport behavior, potential sources and ecological risk. The results revealed that total concentrations of 7 novel brominated flame retardants (NBFRs) ranged from 4.89 to 2853 pg/g dry weight (dw) in soil and from not detected (ND) to 4232 pg/g dw in moss. Additionally, total concentrations of 10 organophosphate esters (OPEs) ranged from ND to 84798 pg/g dw in soil. Among the NFRs, decabromodiphenylethane (DBDPE) and tri-phenyl phosphate (TPhP) were the predominant compounds. NBFRs and OPEs concentrations were slightly higher than those in the polar regions. The correlation between different compounds and altitude varies in different areas, indicating that the NFRs distribution in the mountain valleys result from a combination of long-range transport and local sources. The ecological risk assessment using risk quotient (RQs) revealed that TPhP and tris (2-chloroisopropyl) phosphate (TCIPP) exhibited medium or high risks at some sites. This study sheds light on the transport pathways and environmental behaviors of the NFRs in the valleys and highlights the need for increased attention to the ecological risks posed by OPEs in the TP.

Bioaccumulation of novel brominated flame retardants in crucian carp (Carassius auratus): Implications for electronic waste recycling area monitoring

Bioaccumulation factor (BAF) of pollutants is an important parameter for evaluating their bioaccumulation potential and an important indicator for evaluating their environmental risks. However, little study exits on the BAF of novel brominated flame retardants (NBFRs). The present study determined 17 NBFRs in 24 water samples in dissolved phase and 93 crucian carp samples collected from an electronic waste recycling site in northern China, in order to examine their contamination, distribution and bioaccumulation. The results showed that the targeted NBFRs were widely detectable in the dissolved phase and crucian carps. In dissolved phase, allyl 2,4,6-tribromophenyl ether (ATE) had the highest detectable rate (100%) and concentration (mean: 1.3 ± 0.62 ng/L), but in crucian carp, hexachlorocyclopentenyl-dibromocyclooctane (HCDBCO) was the one with the highest detectable rate (89%) and concentration (mean: 16 ± 9.2 ng/g wet weight (ww)) among all 17 NBFRs. The discharge and water solubility of NBFRs determined their concentration in the dissolved phase, while the concentration of NBFRs in crucian carp was the results of their discharge and food exposure. The estimated BAFs exceeded 5000 L/kg for petabromoethylbenzene (PBEB), pentabromotoluene (PBT), HCDBCO, pentabromobenzyl acrylate (PBBA), 1,2,3,4,5-pentabromobenzene (PBBZ), 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), hexabromobenzene (HBBZ), and α-1,2,5,6-tetrabromocyclooctane (α-TBCO), suggesting that these compounds were above the hazard standard of bioaccumulation. Although the BAFs of 2,3,5,6-tetrabromo-p-xylene (p-TBX), 1,2-bis(2,4,6-tribromophenoxy)-ethane (BTBPE), α-/β-tetrabromoethylcyclohexane (α-/β-TBECH) and ATE were less than 5000, the potential of bioaccumulation cannot be ignored. The log BAF of tested NBFRs showed a pattern of first increasing and then decreasing with the increase of log KOW, the water solubility of NBFRs, the exposure to fish, the uptake and depuration of fish were the key factor to this pattern. To our knowledge, the BAF values of the most of NBFRs calculated in this study were not reported in the published work previously.

Toxicity of decabromodiphenyl ethane on lettuce: Evaluation through growth, oxidative defense, microstructure, and metabolism

Decabromodiphenyl ethane (DBDPE) as the most widely used novel brominated flame retardants (NBFRs), has become a ubiquitous emerging pollutant in the environment. However, its toxic effects on vegetable growth during agricultural production have not been reported. In this study, we investigated the response mechanisms of hydroponic lettuce to DBDPE accumulation, antioxidant stress, cell structure damage, and metabolic pathways after exposure to DBDPE. The concentration of DBDPE in the root of lettuce was significantly higher than that in the aboveground part. DBDPE induced oxidative stress on lettuce, which stimulated the defense of the antioxidative system of lettuce cells, and the cell structure produced slight plasma-wall separation. In terms of metabolism, metabolic pathway disorders were caused, which are mainly manifested as inhibiting amino acid biosynthesis and metabolism-related pathways, interfering with the biosyntheses of amino acids, organic acids, fatty acids, carbohydrates, and other substances, and ultimately manifested as decreased total chlorophyll content and root activity. In turn, metabolic regulation alleviated antioxidant stress. The mechanisms of the antioxidative reaction of lettuce to DBDPE were elucidated by IBR, PLS-PM analysis, and molecular docking. Our results provide a theoretical basis and research necessity for the evaluation of emerging pollutants in agricultural production and the safety of vegetables.

Characterizing novel brominated flame retardants in the coastal atmosphere of the northern Bohai and Yellow Seas

To enrich knowledge concerning occurrence and behavior of novel brominated flame retardants (NBFRs) in the Chinese marine environment, a group of 11 NBFRs were measured in the atmosphere over the northern Bohai and Yellow Seas. Samples were taken downwind of the primary NBFR production and application areas in North China. The total NBFR air concentrations (ΣNBFRs) varied from 80.9 to 934 pg/m3, with decabromodiphenyl ethane (DBDPE) being the most abundant component. The high spatial variability of ΣNBFRs and relatively weak correlations among individual compounds indicated the diverse impact of anthropogenic activities in the coastal regions. The KOA-based absorption model predicted the distributions of low-mass NBFRs, while a steady state model was more applicable for heavier compounds such as DBDPE. The partitioning of NBFRs between the gas and particle phases were significantly related with octanal–air partition coefficient (KOA) only for the notable pollution locations, suggesting absorptive contribution to NBFR sorption. The resulting relationships characterized by event differences possibly pointed out the influences including the sources of NBFRs and aerosol particles, the continental impact, and the sorption kinetics on NBFR partitioning behaviors. Dry particle-bound deposition estimations indicated that the NBFR inputs to the sea from the air was significant.

Rising concentrations of polybrominated diphenyl ethers (PBDEs) in Nigerian foodstuffs despite global restrictions

The presence of brominated flame retardants (BFRs) in foodstuffs of African origin is poorly understood. To fill this gap, animal-derived food samples comprising 13 different items originally from Nigeria were obtained in 2021, and concentrations of novel brominated flame retardants (NBFRs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDD) were measured. Arithmetic mean concentrations of NBFRs, PBDEs, and HBCDD in Nigerian foodstuffs were 2.1 ng/g (18 ng/g lipid weight (lw)), 1.3 ng/g (9.2 ng/g lw), and 0.42 ng/g (2.8 ng/g lw), with median concentrations of 1.7 ng/g (14 ng/g lw), 1.1 ng/g (8.2 ng/g lw), and <0.34 ng/g (<3.3 ng/g lw), respectively. Higher concentrations of NBFRs than of PBDEs and HBCDDs in Nigerian foodstuffs likely reflect use of NBFRs as substitutes for legacy BFRs in Nigeria. Comparison with previous dietary studies reveals rising concentrations of PBDEs in Nigerian foodstuffs in recent years with associated rises in dietary exposure, possibly due to active domestic use of PBDEs in Nigeria. Reassuringly, comparison of our exposure estimates with health-based limit values suggests adverse health effects of dietary intake of BFRs by Nigerians are unlikely to occur.

Eight novel brominated flame retardants in indoor and outdoor dust samples from the E-waste recycling industrial park: Implications for human exposure

As alternatives for legacy brominated flame retardants, novel brominated flame retardants (NBFRs) have a wide array of applications in the electronic and electrical fields. The shift of recycling modes of electronic and electrical waste (e-waste) from informal recycling family workshop to formal recycling facilities might come with the change the chemical landscape emitted including NBFRs, however, little information is known about this topic. This study investigated the occurrence characteristics, distribution, and exposure profiles of eight common NBFRs and their derivatives in an e-waste recycling industrial park in central China and illustrated the differences in various functional zones in the recycling park. The highest level of ΣNBFRs in dust samples was found in e-waste storage area at median concentration of 27,400 ng/g, followed by e-waste dismantling workshops (23,300 ng/g), workshop outdoor area (7770 ng/g), and residential area outdoor (536 ng/g). In the e-waste dismantling associated dust samples, tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), tetrabromobisphenol A (TBBPA) and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ) were the predominant components. This paper presented the first evidence regarding the occurrence characteristic and distribution of tetrabromobisphenol S (TBBPS), tetrabromobisphenol A bismethyl ether (TBBPA-BME) and tetrabromobisphenol S bis(2,3-dibromopropyl ether) (TBBPS-BDBPE) in the e-waste associated dust samples. By comparing with previous studies performed in China, this paper also noticed the significant decrease of TBBPA concentrations in the dust probably due to the shift of e-wastes sources and recycling modes. We further assessed the risk of occupational workers exposure to NBFRs. The median EDI (estimated daily intake) value of ΣNBFRs among e-waste dismantling workers was 9.71 ng/kg BW/d with the maximum EDI value being 19.6 ng/kg BW/d, hundreds of times higher than those exposed by general population. The study raises great concern for the health risk of occupational exposure to NBFRs in the e-waste recycling industrial park.

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.

Insight into Bioaccumulation of Decabromodiphenyl Ethane in Eisenia fetida Increased by Microplastics.

The rise of electronics inevitably induced the co-pollution of novel brominated flame retardants (NBFRs) and microplastics (MPs). However, studies on how they interact to influence their bioavailability are scarce. Here, we explored the influence mechanism of acrylonitrile butadiene styrene (ABS)-MPs on the bioaccumulation of decabromodiphenyl ethane (DBDPE) in soil-earthworm microcosms. The influence exhibited a temporal pattern characterized by short-term inhibition and long-term promotion. After 28 days of exposure, DBDPE bioaccumulation in a co-exposure (10 mg kg-1 DBDPE accompanied by 1000 mg kg-1 ABS-MPs) was 2.61 times higher than that in a separate exposure. The adsorption process in the soil, intestines, and mucus introduced DBDPE-carried MPs, which had a higher concentration of DBDPE than the surrounding soil and directly affected the bioavailability of DBDPE. MP-pre-exposure (100, 1000, and 10000 mg kg-1) reduced epidermal soundness, mucus secretion, and worm cast production. This eventually promoted the contact between earthworm and soil particles and enhanced the DBDPE of earthworm tissue by 6%-61% in the next DBDPE-postexposure period, confirming that MPs increased DBDPE bioaccumulation indirectly by impairing the earthworm health. This study indicates that MPs promoted DBDPE bioaccumulation via adsorption and self-toxicity, providing new insight into the combined risk of MPs and NBFRs.

Evaluation of the oral bioaccessibility of legacy and emerging brominated flame retardants in indoor dust.

Indoor dust is the main source of human exposure to brominated flame retardants (BFRs). In this study, in vitro colon-extended physiologically-based extraction test (CE-PBET) with Tenax as a sorptive sink was applied to evaluate the oral bioaccessibility of twenty-two polybrominated diphenyl ethers (PBDEs) and seven novel BFRs (NBFRs) via indoor dust ingestion. The mean bioaccessibilities of two NBFRs pentabromotoluene (PBT) and 1,2-Bis(2,4,6-tribromophenoxy) ethane (BTBPE) were first proposed, reaching 36.0% and 26.7%, respectively. In order to maintain homeostasis of the gastrointestinal tract, 0.4g Tenax was added in CE-PEBT, which increased BFRs bioaccessibility by up to a factor of 1.4-1.9. The highest bioaccessibility of legacy PBDEs was tri-BDEs (73.3%), while 2-ethylhexyl-tetrabromo-benzoate (EHTBB), one of penta-BDE alternatives, showed the highest (62.2%) among NBFRs. The influence of food nutrients, liquid to solid (L/S) ratio, and octanol-water partition coefficient (Kow) on bioaccessibility was assessed. The oral bioaccessibility of BFRs increased with existence of protein or carbohydrate while lipid did the opposite. The bioaccessibilities of PBDEs and NBFRs were relatively higher with 200:1 L/S ratio. PBDEs bioaccessibility generally decreased with increasing LogKow. No significant correlation was observed between NBFRs bioaccessibility and LogKow. This study comprehensively evaluated the bioaccessibilities of legacy and emerging BFRs via dust ingestion using Tenax-assisted CE-PBET, and highlighted the significance to fully consider potential influencing factors on BFRs bioaccessibility in further human exposure estimation.

Combating toxic emissions from thermal recycling of polymeric fractions laden with novel brominated flame retardants (NBFRs) in e-waste: an in-situ approach using Ca(OH)2.

Legacy brominated flame retardants (BFRs) in printed circuit boards are gradually being replaced by novel BFRs (NBFRs). Safe disposal and recycling of polymeric constituents in the polymeric fractions of e-waste necessitate the removal of their toxic and corrosive bromine content. This is currently acquired through thermal recycling operations involving the pyrolysis of BFRs-containing materials with metal oxides. Nonetheless, the debromination capacity toward NBFRs is yet to be established. Thus, this study aims to address these two crucial gaps in the current knowledge pertaining to the plausible formation of brominated toxicants from the thermal decomposition of NBFRs and their thermal recycling potential. Herein, we investigate the pyrolysis of a mixture of 2,4,6-tribromophenol (TBP), allyl 2,4,6-tribromophenyl ether (ATE) and Tetrabromobisphenol A-bis (2,3-dibromo propyl ether) (TBBPA-DBPE) in the presence of acrylonitrile butadiene styrene (ABS) polymers at various loads. To demonstrate a viable debromination route, pyrolysis of NBFRs-ABS mixture with Ca(OH)2 was also investigated. The latter is a potent debromination agent for legacy BFRs. Upon pyrolysis with Ca(OH)2, the bromine content in the collected oil was reduced up to 80.49% between 25-500 °C. Products of the co-pyrolysis process generally feature non-brominated aromatic and aliphatic compounds; a finding that indicates an effective thermal recycling approach. As evident by IC measurements, no HBr emission could be detected when Ca(OH)2 is added to the mixture. As XRD patterns show, Ca(OH)2 is partially converted into CaBr2. DFT calculations provide pathways for the observed surface debromination characterized by surface-assisted fission of aromatic C-Br bonds and the formation of CaBr sites. Outcomes reported herein are instrumental to designing and operating a thermal recycling facility of polymeric materials contaminated with high loads of bromine, i.e., most notably during scenarios encountered in the thermal recycling of e-waste.

Multi-process regulation of novel brominated flame retardants: Environmentally friendly substitute design, screening and environmental risk regulation

Novel brominated flame retardants (NBFRs), one of the most widely used synthetic flame-retardant materials, have been considered as a new group of pollutants that potentially affect human health. To overcome the adverse effects of NBFRs, a systematic approach for molecular design, screening, and performance evaluation was developed to generate environmentally friendly NBFR derivatives with unaltered functionality. In the present study, the features of NBFRs (long-distance migration, biotoxicity, bioenrichment, and environmental persistence) were determined and characterized by the multifactor comprehensive characterization method with equal weight addition, and the similarity index analysis (CoMSIA) model was constructed. Based on the three-dimensional equipotential diagram of the target molecule 2-ethylhexyl tetrabromobenzoic acid (TBB), 23 TBB derivatives were designed. Of these, 22 derivatives with decreased environmental impact and unaltered functional properties (i.e., flame retardancy and stability) were selected using 3D-QSAR models and density functional theory methods. The health risks of these derivatives to humans were assessed by toxicokinetic analysis; the results narrowed down the number of candidates to three (Derivative-7, Derivative-10, and Derivative-15). The environmental impact of these candidates was further evaluated and regulated in the real-world environment by using molecular dynamics simulation assisted by the Taguchi experimental design method. The relationship between the binding effects and the nonbonding interaction resultant force (TBB derivatives-receptor proteins) was also studied, and it was found that the larger the modulus of the binding force, the stronger the binding ability of the two. This finding indicated that the environmental impact of the designed NBFR derivatives was decreased. The present study aimed to provide a new idea and method for designing NBFR substitutes and to provide theoretical support for restraining the potential environmental risks of NBFRs.