Hexabromocyclododecane Research Articles

Exposure, risk and predictors of hexabromocyclododecane and Tetrabromobisphenol-A in house dust from urban, rural and E-waste dismantling sites in Thailand.

In this study, for the first time, we determined concentrations of hexabromocyclododecane (HBCDD) and tetrabromobisphenol-A (TBBPA) in house dust and estimated human exposure to these substances in houses located in an e-waste dismantling site and in urban and rural residential areas of Thailand. The median HBCDD concentration in urban residential houses (2.10ngg-1) was similar to that in houses in an e-waste dismantling site (2.05ngg-1, p>0.05) and slightly higher than that in rural residential houses (1.11ngg-1, p>0.05). In contrast, significantly higher TBBPA concentrations were present in house dust from an e-waste dismantling site (median=720ngg-1; range=44-2300ngg-1) compared to those in urban (68.6ngg-1; 3.5-300ngg-1, p<0.001) and rural residential areas (17ngg-1; 2.0-201ngg-1, p<0.001). TBBPA concentrations increased with the increasing presence of electronic devices and a decreasing distance to the e-waste dismantling site. These results suggest that e-waste dismantling activities may contribute to TBBPA contamination of house dust. The median estimated daily intake (EDI) of HBCDD and TBBPA through dust ingestion for toddlers exceeded that for children and adults. However, EDI values for HBCDD and TBBPA from all age groups were below the oral reference dose guideline value suggested by the US National Research Council and National Toxicology Program (NTP).

Detection of Toxic Polychlorinated Biphenyls by Nanoporous Metal–Organic Frameworks

As a class of persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs) are highly hazardous to the ecosystem, and their effective and facile detection is of high importance. Herein, we present two nanoporous metal–organic frameworks (MOFs), (Me2NH2)[In(CPTTA)]·(DMF)1.5(H2O)3.5 (BUT-174) and (Et2NH2)[In(CPTTA)]·(DEF)(H2O)3 (BUT-175), constructed by In3+ ions and the aromatic-rich tetratopic carboxylate ligands, 5′-(4-carboxylatophenyl)-[1,1′:3′,1″-terphenyl]-3,4′′,5-tricarboxylate (CPTTA4–), which exhibit highly efficient turn-down fluorescence response toward 12 PCBs, especially for three highly toxic non-ortho-substituted PCBs (PCB-77, -126, and -169) with the so-called “coplanar” molecular configuration in various solvents with the limits of detection (LODs) down to the ppb level owing to the inner filter effect between MOFs and PCBs. In addition, the MOFs show high sensing selectivity toward PCBs over many relevant interferents, including hexabromocyclododecane (HBCD), decabromodiphenyl oxide (DBDPO), perfluorobutanoic acid (PFBA), and perfluorooctanoic acid (PFOA), as well as good recyclability and stability. It is demonstrated by this work that structurally well-defined MOFs could be promising sensory materials for the detection of highly toxic PCBs in a facile way.

Comparative Effects of Brominated Flame Retardants BDE-209, TBBPA, and HBCD on Neurotoxicity in Mice.

Brominated flame retardants (BFRs) are ubiquitous industrial chemicals. In China, BFRs that are applied in large quantities include decabromodiphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCD). Although findings are not always unequivocal, mounting evidence in vivo suggests that the BFRs have potential neurotoxicity. The present study aimed to assess and compare the neurotoxic effects of these three BFRs' exposure. Male mice were orally exposed to BDE-209, TBBPA, or HBCD at 50 and 100 mg/kg bw/day for 28 days. The cognitive behavior, oxidative stress (ROS, MDA, and GSH), apoptosis-related genes (caspase-3, bax, and bcl-2), memory-related proteins (BDNF and PSD-95), and neurotransmitters (AChE and ChAT) were detected comparatively. Results showed that high doses of BDE-209, TBBPA, and HBCD exposure impaired spatial memory of mice, elevated ROS and MDA and reduced GSH levels of hippocampus, upregulated caspase-3 and bax expressions, decreased BDNF and PSD-95 levels, and disordered AChE and ChAT levels. Notably, BDE-209 caused greater adverse effects > HBCD > TBBPA. This study confirms and extends that these three BFRs had similar neurotoxic effects at current concentrations, although they may be more or less toxic.

Halogenated flame retardants in Irish waste polymers: Concentrations, legislative compliance, and preliminary assessment of temporal trends

Halogenated flame retardants (HFRs) were measured in 470 waste plastic articles from Ireland between 2019 and 2020. We identified articles containing concentrations of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and tetrabromobisphenol-A (TBBP-A) exceeding European Union limits. Enforcement of existing limits of 1000 mg/kg will render an estimated 3.1% (2800 t) of articles in the waste categories studied unrecyclable, increasing to: 4.0, 4.9, and 5.6% if limits were reduced to 500, 200, and 100 mg/kg respectively. Meanwhile, enforcing limits of 1,000, 500, 200, and 100 mg/kg will respectively remove 78, 82, 84, and 85% of PBDEs, HBCDD, and TBBP-A present in such waste. Other FRs targeted were detected infrequently and predominantly at very low concentrations. However, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ) was detected in 3 display/IT product samples at 14,000 to 32,000 mg/kg, indicating elevated concentrations of FRs used as alternatives to PBDEs and HBCDD, will likely increase in future. Comparison with data for Ireland in 2015–16, revealed concentrations and exceedances of limits for PBDEs, HBCDD, and TBBP-A were similar or have declined. For end-of-life vehicle fabrics and foams, HBCDD and ΣPBDE concentrations declined significantly (p < 0.05) since 2015–16. Moreover, ΣPBDE concentrations in waste small domestic appliances are significantly lower in 2019–20, with a similarly significant decline for TBBP-A in waste IT and telecommunications articles. In contrast, HBCDD concentrations in waste extruded polystyrene increased significantly between 2015–16 and 2019–20. For other waste categories studied, no statistically significant temporal trends are evident (p > 0.05). Fewer samples exceeded PBDE and HBCDD limits in 2019–20 (7.8%) than 2015–16 (8.7%), while exceedances for TBBP-A fell from 2.4% in 2015–16 to 0.57% in 2019–20. While comparison between the 2015–16 and 2019-20 datasets provide a preliminary indication of changes, further monitoring is required if the impact of legislation designed to eliminate HFRs from the waste stream is to be fully evaluated.

Legacy and alternative flame retardants in indoor dust from e-waste industrial parks and adjacent residential houses in South China: Variations, sources, and health implications

Many studies have elucidated health concerns of informal e-waste recycling activities, yet few has evaluated the effectiveness of the regulations as well as the human exposure risks to adjacent residents. Herein, legacy polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDs), and alternative organophosphate esters (OPEs) were investigated in indoor dust collected from three e-waste industrial parks and five adjacent villages located in south China. The levels and composition patterns varied significantly between workshop and home dust. BDE209 showed much higher (p < 0.01) concentrations in workshop dust versus home dust, while relatively comparable levels were found for OPEs and HBCDs. Principal component analysis revealed that OPEs and PBDEs were mainly related to home and workshop dust, respectively. Results strongly indicated that e-waste dismantling activities still contribute to a high burden of BDE209 to surrounding residents, whilst the sources of OPEs may also originated from household products, especially for TCEP. The estimated daily intakes (EDIs) via dust ingestion and dermal absorption for occupational worker and nearby toddlers were below available reference dose (RfD) values even at worst case scenario. This study highlights the significance of deca-BDEs rather than alternative OPEs in e-waste generated in China, which could provide scientific suggestions for policy formulation.

Assessing the impact of wastewater treatment works effluent on downstream water quality

The impact of wastewater treatment works (WwTW) effluent on downstream river water quality is of increasing concern, particularly owing to the presence in effluents of a range of trace substances. In the case of contamination by metals the question of bioavailability has recently been accounted for in setting water quality standards for several metals. In the UK over the past decade the Chemical Investigations Programme (CIP) has generated upstream and downstream river quality data as well as associated WwTW effluent monitoring for over 600 sites, for the main contaminants of regulatory interest under the Water Framework Directive. Data presented here show that at a local level WwTW discharges have little impact for many contaminants. Soluble reactive phosphorus, hexabromocyclododecane (HBCDD), cypermethrin, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been shown to be the principal substances where downstream concentrations were at least 10 % larger than the upstream value. Otherwise, poor compliance with riverine water quality standards tends to be associated with contamination at the river catchment scale, with corresponding implications for the nature of remedial actions that are likely to be successful. Compliance with water quality criteria for metals, taking account of bioavailability, is high overall.

Microplastics and Brominated Flame Retardants in Freshwater Fishes From Italian Lakes: Implication for Human Health

Microplastics (MPs) and brominated flame retardants (BFRs) represent a synergic threat for aquatic environments and organisms' health status, with an additional concern over food quality and food security for species of commercial interest. In this study, the ingestion of MPs, levels of polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecane (HBCDs) were assessed in organisms from two lakes of Central Italy, with the aims of exploring the bioavailability of these pollutants in freshwater environments, the possible translocation of MPs from digestive to edible tissues, and the relationship between MPs ingestion and bioaccumulation of BFRs. The fish Perca fluviatilis, Anguilla anguilla, Carassus auratus, and the crayfish Procambarus clarkii, all species commercialized for human consumption, were caught in Trasimeno Lake; moreover, P. fluviatilis and Rutilus rutilus were also sampled in Piediluco, a lake strongly influenced by industrial and anthropogenic activities, where fishing for commercial purpose is forbidden. With the exception of C. auratus which showed the highest frequency of MPs ingestion (75%), species from Piediluco Lake exhibited a more elevated percentage of organisms positive to MPs ingestion (45%) and higher levels of PBDEs and HBCDs (mean values of 343 and 792 pg/g, respectively, in P. fluviatilis; 445 and 677 pg/g, respectively, in R. rutilus) than Trasimeno species (25% frequency of MPs ingestion, mean values between 6 and 163 pg/g for PBDEs and 5-107 pg/g for HBCDs). Polyester fibers dominated among MP typologies, and a high occurrence of man-made natural fibers was recorded. The number of MPs extracted in the gastrointestinal tracts of fish and soft bodies of crayfishes positive to MPs ingestion ranged between 1 and 2, whereas no MPs were found in fish filets. Given these results, the risk related to human consumption of Trasimeno organisms appears very low, whereas further investigations are required to better elucidate the possible role of MPs pollution in modulating chemical bioaccumulation in edible tissues. This study contributed to assess both environmental quality and food safety, reinforcing the use of bioindicator species for monitoring plans, in accordance with European recommendations.

Hexabromocyclododecane in edible aquatic products in Guangzhou, China: Levels, compositions, human dietary exposure and health risk assessment

Hexabromocyclododecane (HBCD) is widely found in nature and accumulates in living organisms. To investigate the characteristics of ∑HBCD in aquatic products in Guangzhou, China, a total of 319 aquatic products were collected, the concentrations of ∑HBCD in their bodies were analyzed, and estimated daily intake (EDI) and hazard index (HI) were evaluated. The median concentrations of ∑HBCD in Grass carp (2.00 ng/g lw (lipid weight)), Crucian carp (2.34 ng/g lw), Tilapia (1.57 ng/g lw), Japanese sea perch (2.27 ng/g lw), Crab (4.14 ng/g lw), Undulating Venus (6.98 ng/g lw), Roche Spermatogenesis (1.74 ng/g lw) were in medium levels compare with other researches. A significant positive correlation was observed between ∑HBCD concentrations and lipid content of aquatic organisms, and α-HBCD is the main isomer in organisms. The highest concentration of ∑HBCD were found in samples collected in Huangpu district, which was related to a large number of industrial parks gathered in the administrative region. The EDI of HBCD in aquatic products (0.23–1.65 ng/kg bw*d−1) were at a medium level. The HI of HBCDs in aquatic products in Guangzhou was less than 1, indicating that it poses no threat to human health.

Community reassemblies of eukaryotes, prokaryotes, and viruses in the hexabromocyclododecanes-contaminated microcosms

The microbial community in seriously contaminated environment were not well known. This research investigated the community reassemblies in microcosms made of two distinct mangrove sediments amended with high levels of hexabromocyclododecanes (HBCDs). After eight months of contamination, the transformation of HBCDs yielded various lower brominated products and resulted in acidification (pH ~2). Therefore, the degraders and dehalogenase homologous genes involved in transformation of HBCDs only presented in low abundance to avoid further deterioration of the habitats. Moreover, in these deteriorated habitats, 1344 bacterial, 969 archaeal, 599 eukaryotic (excluded fungi), 187 fungal OTUs, and 10 viral genera, were reduced compared with controls. Specifically, in two groups of microcosms, Zetaproteobacteria, Deinococcus-Thermus, Spirochaetes, Bacteroidetes, Euryarchaeota, and Ascomycota, were positively responding taxa to HBCDs. Caloneis (Bacillariophyta) and Ascomycota turned to the dominant eukaryotic and fungal taxa. Most of predominant taxa were related to the contamination of brominated flame retardants (BFRs). Microbial communities were reassembled in divergent and sediment-dependent manner. The long-term contamination of HBCDs leaded to the change of relations between many taxa, included some of the environmental viruses and their known hosts. This research highlight the importance of monitoring the ecological effects around plants producing or processing halogenated compounds.

Exposure to the Brominated Flame Retardant Hexabromocyclododecane Results in Systemic Changes in Polyunsaturated Fatty Acid Metabolism Within Phospholipids of Mice

Brominated flame retardants are used in many household products to reduce flammability, but often leach into the surrounding environment over time. Hexabromocyclododecane (HBCD) is one brominated flame retardant detected in human blood across the world. HBCD exposure can result in neurological problems and altered lipid metabolism, but to date the two remain unlinked. As lipids constitute ~50% of brain dry weight, lipid metabolism plays a critical role in neuronal function and homeostasis. To determine the effect of HBCD exposure on brain lipid metabolism, young adult male mice were exposed to 1 mg/kg HBCD every 3 days for 28 days. HBCD exposure altered lipid abundance of 8 major lipid classes in the dorsal striatum, including fatty acids (FA), lysophosphatidylcholines (LPC), lysophosphatidylethanolamines (LPE), phosphatidylcholines (PC), phosphatidylethanolamines (PE) alkylphosphatidylethanolamines (PEO), phosphatidylethanolamine plasmalogens (PEP), and sphingomyelins (SM). The liver, as a major lipid metabolism hub, and blood were also examined to determine whether these alterations correlated to systemic changes in lipid metabolism. Although several lipid classes changed in the liver and blood, only PE was consistently altered between organs. Despite the lack of commonalities between lipid class alterations of differing organs, phospholipid fatty acid tails displayed a consistent enrichment of Polyunsaturated Fatty Acids (PUFAs) such as Arachidonic Acid (AA) and Docosahexaenoic Acid (DHA) across lipid classes and organs. Free AA was enriched in the blood as well as AA contained within phospholipids of the liver (in PE), blood (in LPC, PEO, and PEP), and dorsal striatum (in PE, PEO). Additionally, although free DHA was unchanged in the blood, DHA‐containing phospholipids were enriched in the liver (in PE), blood (in LPC, LPE), and dorsal striatum (in PE, PEO, PEP, PS). These studies indicate that HBCD can cause systemic alterations in PUFA metabolism. Further study is necessary to determine the mechanisms underlying the lipid alterations and their functional consequences.

Levels, distribution and risk assessment of hexabromocyclododecane (HBCD) in fish in Xiamen, China.

In this study, hexabromocyclododecane (HBCD) was detected in 114 fish samples collected from 6 administrative regions of Xiamen city, China. HBCD amounts ranged between ND (not detected) and 2.216ngg-1 ww (mean, 0.127 ± 0.318ngg-1 ww). Besides, α-HBCD was the main diastereoisomer in these fish specimens, followed by β-HBCD. Meanwhile, γ-HBCD was not detected in any of the samples. Significant differences were recorded among fish species. The results indicated that the levels and detection rates of HBCD were higher in Trachinotus ovatus compared with other aquatic organisms. Therefore, Trachinotus ovatus could be used as a marine biological indicator of HBCD. Within the regions investigated, Siming was significantly different from Jimei, Haicang, and Xiang'an. The spatial distribution of HBCD concentrations indicated higher mean levels in samples collected from Haicang, Jimei, and Xiang'an, respectively, with the highest detection rates in Jimei and Xiang'an, which might be related to geographical location and intense industrial and urban activities. Estimation of daily HBCD intake was performed according to fish consumption in Xiamen residents. The medium bound HBCD amounts in fish were approximately 0.073 and 0.088ngkg bw-1d-1 for male and female residents of Xiamen, respectively. Exposure doses of HBCD indicated no health concern for Xiamen residents.

Apoptotic p53 Gene Expression in the Regulation of Persistent Organic Pollutant (POP)-Induced Oxidative Stress in the Intertidal Crab Macrophthalmusjaponicus.

Persistent organic pollutants (POPs), some of the most dangerous chemicals released into the aquatic environment, are distributed worldwide due to their environmental persistence and bioaccumulation. In the study, we investigated p53-related apoptotic responses to POPs such as hexabromocyclododecanes (HBCDs) or 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in the mud crab Macrophthalmus japonicus. To do so, we characterized M. japonicus p53 and evaluated basal levels of p53 expression in different tissues. M. japonicus p53 has conserved amino acid residues involving sites for protein dimerization and DNA and zinc binding. In phylogenetic analysis, the homology of the deduced p53 amino acid sequence was not high (67–70%) among crabs, although M. japonicus p53 formed a cluster with one clade with p53 homologs from other crabs. Tissue distribution patterns revealed that the highest expression of p53 mRNA transcripts was in the hepatopancreas of M. japonicus crabs. Exposure to POPs induced antioxidant defenses to modulate oxidative stress through the upregulation of catalase expression. Furthermore, p53 expression was generally upregulated in the hepatopancreas and gills of M. japonicus after exposure to most concentrations of HBCD or BDE-47 for all exposure periods. In hepatopancreas tissue, significant increases in p53 transcript levels were observed as long-lasting apoptotic responses involving cellular defenses until day 7 of relative long-term exposure. The findings in this study suggest that exposure to POPs such as HBCD or BDE-47 may trigger the induction of cellular defense processes against oxidative stress, including DNA repair, cell cycle arrest, and apoptosis through the transcriptional upregulation of p53 expression in M. japonicus.

A nationwide survey of 20 legacy brominated flame retardants in indoor dust from China: continuing occurrence, national distribution, and implication for human exposure.

Despite the restrictions on polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDDs), these chemicals are still ubiquitous environmental pollutants. In this study, we measured the concentrations and profiles of 17 PBDE congeners and 3 HBCDD isomers in indoor dust samples collected from 23 provinces and cities across China. The summed concentrations of PBDEs (Σ17PBDEs) ranged from 4.19 to 817ng/g, with an average of 171 ± 184ng/g. BDE-209 was the most abundant congener. The concentrations of HBCDDs ranged from 6.65 to 1335ng/g, with an average of 236 ± 324ng/g. Unlike commercial HBCDD formulations, α-HBCDD was the predominant isomer in the indoor dust samples analyzed. Geographical distributions showed that the concentrations of PBDEs and HBCDDs varied significantly among different regions. Higher PBDE and HBCDD levels were observed in samples from eastern coastal and economically developed regions. Further, we estimated the daily intakes of PBDEs and HBCDDs through the routes of dust ingestion and dust dermal absorption for different age groups. Dust dermal absorption is an unneglectable exposure pathway to PBDEs and HBCDs for the Chinese population. Among the age groups, infants had the highest exposure via dust dermal absorption, and toddlers had the highest exposure via dust ingestion. Compared with the threshold values, the exposure doses of PBDEs and HBCDDs are unlikely to pose significant health concerns for both infants and adults in China. This is the first national survey of PBDEs and HBCDDs in indoor dust samples across China after the restriction.

Integrated analysis of exoskeletal surface profile and chitin-related gene expression on Macrophthalmus japonicus mud crabs exposed to hexabromocyclododecane

Hexabromocyclododecanes (HBCDs), widely used brominated flame retardants, easily accumulate in aquatic organisms such as Macrophthalmus japonicus crabs, which inhabit tidal flat sediments. To analyze the effects of HBCD exposure in chitin-formed exoskeleton, we investigated molecular responses of chitin-related genes as well as physical changes of the exoskeletal surface form as a new biological end-point on M. japonicus. The expression patterns of chitin biosynthesis-, modification-, and degradation-related genes in the gills and hepatopancreases of M. japonicus were also analyzed. Additionally, the survivability and exoskeleton surface profiles of M. japonicus crabs were evaluated. M. japonicus chitin synthase expression was significantly downregulated, whereas that of the chitinase transcript was significantly upregulated upon exposure to all HBCD concentrations on day 7. Contrastingly, the gene expression of chitin deacetylase 1 significantly increased upon exposure to all HBCD concentrations on day 1, and this increase was significantly elevated on day 4. The expression of chitin deacetylase 1 was dose-dependent. Additionally, decreased survival and exoskeleton surface profile changes were observed in M. japonicus crabs exposed to all HBCD concentrations. These results suggest that exposure to HBCD induces changes in the synthesis, modification, and degradation of chitin, a pivotal component of the cuticular exoskeleton, and may disrupt the exoskeletal surface structure in M. japonicus crabs.

POPs monitoring in Mongolia – Core matrices

Persistent organic pollutants (POPs) are of global concern due to their negative effects on humans and the environment, and globally are regulated in the Stockholm Convention on POPs. The present study had Mongolia as a partner in a multinational project funded and coordinated by the United Nations Environment Programme with the aim to monitor POPs in core media, including air (with passive samplers), water, and a pooled human milk sample. Project implementation and all sampling were undertaken by the Institute of Chemistry and Chemical Technology whereas POPs analysis was performed in laboratories abroad. Brominated and chlorinated POPs were analyzed by gas chromatography/mass spectrometry, perfluorinated compounds (PFAS) and isomers of hexabromocyclododecane (HBCD) by liquid chromatography/mass spectrometry. The monitoring results found very low concentrations of PFAS in river water. Toxic equivalents (TEQs) for PCDD/PCDF were low in air and in human samples but had a relatively higher presence of TEQ from dioxin-like PCB than in other countries. With respect to chlorinated POPs, drins, chlordanes, DDTs, heptachlors, and mirex were very low in air and human milk. Elevated levels were found for polychlorinated biphenyls (PCB), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), pentachlorobenzene (PeCBz), and HBCD in air with extreme values for hexachlorobutadiene. The abundance of HCHs and HCB was confirmed in the human milk sample but not for PCB, PeCBz or HBCD. Short-chain chlorinated paraffins (170 ng/g lipid) were the highest among all human milk pools. It is recommended to continue POPs monitoring in the future, especially for those where high concentrations were found.

Insight into microbial degradation of hexabromocyclododecane (HBCD) in lake sediments under different hydrodynamic conditions

Hexabromocyclododecane (HBCD), an emerging persistent organic pollutant, has been widely detected in aquatic ecosystems with various hydrodynamic conditions, however, the effects of hydrodynamic changes on microbial degradation of HBCD in aquatic sediment remains unclear. Here, we conducted an annular flume experiment to characterize variation in HBCD removal from contaminated sediment under three hydrodynamic conditions with different flow velocities, as well as clarify the underlying microbial mechanisms. We detected significant HBCD removal and bromine ion generation in all contaminated sediments, and microbial reduction debromination was an important process for HBCD removal. At the end of the 49-day experiment, both HBCD removal percentage and the bromine ion concentration were significantly lower under dynamic water condition with higher sediment redox potential, compared with static water conditions. The dynamic water conditions resulted a relatively high sediment redox potential and decreased the iron reduction rate and the abundance of organohalide-respiring bacteria (OHRB) in the genera Geobatcer, Dehalogenimonas, Dehalobacter, and Dehalococcoide, which reduced the microbial degradation of HBCD in contaminated sediments. The community composition of both total bacteria and OHRB also differed significantly among hydrodynamic conditions. Some bacterial groups with HBCD degradation abilities such as Pseudomonas and Sulfuricurvum were less abundant under dynamic water conditions, and the HBCD degradation efficiencies were lower. These findings enhance our understanding of the bioremediation potential of HBCD-contaminated sediments in different hydrodynamic areas.

Atmospheric concentrations of polychlorinated biphenyls, brominated flame retardants, and novel flame retardants in Lagos, Nigeria indicate substantial local sources.

Polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) like polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD), and novel flame retardants (NFRs) like decabromodiphenyl ethane (DBDPE) are ubiquitous environmental pollutants. Despite this, little is known about their concentrations in outdoor air in the African continent. To address this knowledge gap, concentrations of BFRs, NFRs, and PCBs were measured in outdoor air at 8 sites located within the metropolitan area of Lagos, Nigeria. Concentrations of ∑8BDEs, ∑HBCDD, ∑7NFRs and ∑8PCBs were: 21-750 (median=100) pg/m3, <12-180 (median =<12) pg/m3, 34-900 (median=300) pg/m3 and 85-460 (median=300) pg/m3, respectively. Decabromodiphenyl ether (BDE-209, range: <16-620pg/m3, median=71pg/m3) and DBDPE (range: <37-890pg/m3, median=280pg/m3) were the dominant BFRs detected, while the non-Arochlor PCB 11 (range: 49-220pg/m3, median=100pg/m3) was the dominant PCB. To the authors' knowledge, these are the first data on the non-Arochlor PCB 11 in outdoor air in Africa. In general, concentrations of all target contaminants in this study were within the range reported elsewhere in Africa and worldwide. Likely due to the tropical climate of Lagos, no seasonal variation in concentrations was discernible for any of the target contaminants. While concentrations of PBDEs and some NFRs were correlated with population density, concentrations of PCBs appear more impacted by leaks from electrical transformers and for PCB 11 to proximity to activities like textile factories that produce and use dyes.

Diastereomer- and enantiomer-selective accumulation and depuration of 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexanes (DBE-DBCHs) and 1,2,5,6-tetrabromocyclooctanes (TBCOs) in earthworms (Eisenia fetida)

Due to the regulation of hexabromocyclododecane (HBCD), much attention has been paid to its potential substitutes, 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (DBE-DBCH) and 1,2,5,6-tetrabromocyclooctane (TBCO). DBE-DBCH and TBCO contain several diastereomers and enantiomers, which may exhibit different environmental behaviors and biological effects. In this study, the accumulation and depuration of individual DBE-DBCH and TBCO diastereomers by earthworms (Eisenia fetida) from diastereomer-contaminated soils were evaluated. The accumulation and depuration kinetics of DBE-DBCH and TBCO diastereomers followed one-compartment first-order kinetics. The biota soil accumulation factor (BSAF) of β-DBE-DBCH (2.74 goc glip−1) was 1.26 times that of α-DBE-DBCH (2.18 goc glip−1), while the BSAF of β-TBCO (2.15 goc glip−1) was 1.62 times that of α-TBCO (1.3 goc glip−1), showing the diastereomer-specific accumulation of DBE-DBCH and TBCO. DBE-DBCH and TBCO diastereomers appeared to be transformed in earthworm-soil systems; however, no evidence of bioisomerization of the four diastereomers in earthworms was found, and no potential metabolites of debromination and hydroxylation were detected. Furthermore, the selective enrichment of E1-α-DBE-DBCH and E1-β-DBE-DBCH (E1 represents the first enantiomer eluted) occurred in earthworms as the enantiomer fractions (EFs) for α-DBE-DBCH (0.562–0.763) and β-DBE-DBCH (0.516–0.647) were significantly greater than those in the technical products (0.501 for α-DBE-DBCH and 0.497 for β-DBE-DBCH, p < 0.05), especially in the depuration stage. The results demonstrated the diastereomer- and enantiomer-selective accumulation of DBE-DBCH and the diastereomer-selective accumulation of TBCO in the earthworm.

Mechanochemical destruction and mineralization of solid-phase hexabromocyclododecane assisted by microscale zero-valent aluminum

Hexabromocyclododecane (HBCD) has been listed in Annex A of the Stockholm Convention as a persistent and bio-accumulative chemical. While HBCD is often present in the solid form for its low solubility, cost-effective technologies have been lacking for the degradation of solid-phase HBCD. In this work, mechanochemical (MC) destruction of high-energy ball milling was employed for direct destruction of solid-phase HBCD, where a strong reducer, microscale zero-valent aluminum (mZVAl), was used as the co-milling agent. The new mZVAl-assisted MC process achieved complete debromination and mineralization of HBCD within 3 h milling. The optimal operating parameters were determined, including the milling atmosphere, the milling speed, the mZVAl-to-HBCD molar ratio, and the ball-to-mZVAl mass ratio. Fourier transform infrared spectrometry and Raman analyses revealed that the organic structures of HBCD were destroyed and organic bromine was completely converted into inorganic bromide, accompanied by the generation of amorphous and graphite carbon. Analysis of the milled samples by GC–MS demonstrated the absence of obvious organic matter after MC treatment, also indicating the complete degradation and conversion of HBCD to inorganic compounds. Further X-ray photoelectron spectroscopic analysis indicates that the fresh surface of mZVAl was generated upon the MC treatment, and Al(0) served as a strong reducing agent (e-donor) for reductive debromination and destruction of the carbon skeleton. The mZVAl-assisted MC milling appears promising as a non-combustion approach for effective destruction and carbonization/mineralization of solid-phase HBCD or potentially other persistent organic pollutants.

A metagenomics study of hexabromocyclododecane degradation with a soil microbial community

Hexabromocyclododecanes (HBCDs) are globally prevalent and persistent organic pollutants (POPs) listed by the Stockholm Convention in 2013. They have been detected in many environmental media from waterbodies to Plantae and even in the human body. Due to their highly bioaccumulative characterization, they pose an urgent public health issue. Here, we demonstrate that the indigenous microbial community in the agricultural soil in Taiwan could decompose HBCDs with no additional carbon source incentive. The degradation kinetics reached 0.173 day-1 after the first treatment and 0.104 day-1 after second exposure. With additional C-sources, the rate constants decreased to 0.054–0.097 day-1. The hydroxylic debromination metabolites and ring cleavage long-chain alkane metabolites were identified to support the potential metabolic pathways utilized by the soil microbial communities. The metagenome established by Nanopore sequencing showed significant compositional alteration in the soil microbial community after the HBCD treatment. After ranking, comparing relative abundances, and performing network analyses, several novel bacterial taxa were identified to contribute to HBCD biotransformation, including Herbaspirillum, Sphingomonas, Brevundimonas, Azospirillum, Caulobacter, and Microvirga, through halogenated / aromatic compound degradation, glutathione-S-transferase, and hydrolase activity. We present a compelling and applicable approach combining metagenomics research, degradation kinetics, and metabolomics strategies, which allowed us to decipher the natural attenuation and remediation mechanisms of HBCDs.