Current-use Brominated Flame Retardants Research Articles

Hydroxylated transformation products obtained after UV irradiation of the current-use brominated flame retardants hexabromobenzene, pentabromotoluene, and pentabromoethylbenzene

Hexabromobenzene (HBB), pentabromotoluene (PBT), and pentabromoethylbenzene (PBEB) are current-use brominated flame retardants (cuBFRs) which have been repeatedly detected in environmental samples. Since information on hydroxylated transformation products (OH-TPs) was scarcely available, the three polybrominated compounds were UV irradiated for 10 min in benzotrifluoride. Fractionation on silica gel enabled the separate collection and identification of OH-TPs. For more insights, aliquots of the separated OH-TPs were UV irradiated for another 50 min (60 min total UV irradiation time). The present investigation of polar UV irradiation products of HBB, PBT, and PBEB was successful in each case. Altogether, eight bromophenols were detected in the case of HBB (three Br3-, four Br4-, and one Br5-isomer), and nine OH-TPs were observed in the case of PBT/PBEB (six Br3- and three Br4-congeners). In either case, Br➔OH exchange was more relevant than H➔OH exchange. Also, such exchange was most relevant in meta- and ortho-positions. As a further point, and in agreement with other studies, the transformation rate decreased with decreasing degree of bromination. UV irradiation of HBB additionally resulted in the formation of tri- and tetrabrominated dihydroxylated compounds (brominated diphenols) that were subsequently identified. These dihydroxylated transformation products were found to be more stable than OH-TPs.

Occurrence, emission sources, and risk assessment of polybrominated diphenyl ethers and current-use brominated flame retardants in settled dust from end-of-life vehicle processing, urban, and rural areas, northern Vietnam.

Settled dust samples from Vietnamese end-of-life vehicle (ELV) processing, urban, and rural areas were analyzed for polybrominated diphenyl ethers (PBDEs) and other current-use brominated flame retardants (BFRs). PBDE levels found in dust samples collected from ELV workshops (median 390; range 120-520ng/g) and nearby living areas (110; 36-650ng/g) were generally higher than those in common house dust (25-170ng/g). BDE-209 was the most predominant congener detected in almost all the samples, indicating extensive application of products containing deca-BDE mixtures. The dust samples from ELV workplaces showed a more abundance of lower brominated congeners (e.g., tetra- to hexa-BDEs) that may originate from car interior materials treated by penta-BDE formulations. Concentrations of other BFRs decreased in the order urban > rural > ELV dust, reflecting the current use of these compounds in new consumer products. Decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) were the major alternative BFRs. Daily intake doses and hazard indexes of PBDEs and some other BFRs through dust ingestion were estimated and showed acceptable levels of risk. However, more comprehensive risk assessment considering multiple exposure pathways should be performed, especially for ELV workers and children in the ELV processing and urban areas.

Synthesis and evaluation of hydroxy‑ and dihydroxy brominated benzenes, methyl- and ethylbenzenes: Potential metabolites of current-use brominated flame retardants

Knowledge on the presence of occurrence of oxygen containing transformation products (OxyTPs) of the current-use flame retardants hexabromobenzene (HBB), pentabromotoluene (PBT) and pentabromoethylbenzene (PBEB) is limited due to the lack of standard compounds. For this purpose, we investigated the structures of tri- and tetrabrominated phenols, diphenols, methylphenols and ethylphenols. First, 13 non-brominated or partly brominated (alkyl) phenols and diphenols were brominated with the goal to generate all possible tri- and tetrabrominated isomers. Instead of compound isolation and spectroscopic analysis, the resulting products were interpreted by combinatoric evaluation of GC/MS data, data from undirected syntheses and UV transformation studies as well as theoretical considerations. Altogether, all 44 tri- to tetrabrominated OxyTPs existing in theory could be assigned and fed in a data base.

Full Characterization of the UV Hydrodebromination Products of the Current-Use Brominated Flame Retardants Hexabromobenzene, Pentabromotoluene, and Pentabromoethylbenzene.

UV transformation was studied with three structurally closely related current-use brominated flame retardants (cuBFRs), i.e., hexabromobenzene (HBB), pentabromotoluene (PBT), and pentabromoethylbenzene (PBEB). Irradiation in toluene and benzotrifluoride (BTF) showed pseudo-first-order kinetics. Repeated high-performance liquid chromatographic (HPLC) fractionation, available reference standards, dedicated syntheses, gas chromatography with mass spectrometry (GC/MS), GC separation on two different phases including retention time rules based on dipole interactions, and proton magnetic resonance spectroscopy (1H NMR) evaluation enabled a full structural characterization of all 22 transformation products formed by hydrodebromination. In addition to pentabromobenzene (only transformation product with five bromine), tetra- and tribrominated transformation products were predominantly formed in the case of all three cuBFRs. Hydrodebromination was favored by bromine removal from positions with a high Br density. Br → H exchange was about 3 times faster in positions flanked by two vicinal Br atoms. This favored pathway explained why hydrodebromination sharply dropped at the level of tribrominated cuBFRs because readily degradable precursors were no more available at this point. Hence, a full degradation of tribrominated and lower-brominated transformation products may only be achieved in combination with a different process such as microbial transformation.

Determination of brominated flame retardants including polybrominated diphenyl ethers, pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane in sediment samples: Validation of a rapid and efficient clean-up method and application to a sediment core from Lake Biwa, Japan

The development of rapid and efficient analytical method for the determination of legacy and current-use brominated flame retardants (BFRs) has been performed due to environmental concern related to these pollutants. In the present study, we used an automated clean-up device equipped with pre-packed micro-column sets (containing sulfuric acid impregnated silica gel and silver-modified alumina) to develop an effective purification method for polybrominated diphenyl ethers (PBDEs), pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane (DBDPE) in sediment extracts. Matrix-spiked sediments (n = 6) and the Standard Reference Material® 1944 samples (n = 6) were tested. Our method showed acceptable accuracy, repeatability, and sensitivity for almost all the target compounds with reduced processing time, labor requirement, and solvent amounts as compared to conventional clean-up method (e.g., sulfuric acid treatment and self-packed chromatographic columns). The validated method was applied to sediment core samples (n = 16) collected in 2019 from Lake Biwa, the largest lake in Japan. PBDEs were detected in sediment samples of 0–13 cm depth (dated between 1990 and 2019) at relatively low concentrations (median 5.7; range 2.6–9.4 ng/g dry weight). PBDE profiles were dominated by BDE-209, which accounted for 91 ± 10% of total PBDEs. Among other BFRs, only DBDPE was found in sediment layers of 0–9 cm depth (deposited between 2005 and 2019). DBDPE concentrations ranged from 0.43 to 1.6 (median 0.71) ng/g and showed increasing trend toward shallower depths.

Contamination levels and temporal trends of legacy and current-use brominated flame retardants in a dated sediment core from Beppu Bay, southwestern Japan

Contamination levels and temporal trends of polybrominated diphenyl ethers (PBDEs) and some alternative brominated flame retardants (BFRs) were examined in a dated sediment core from the deepest part of the Beppu Bay, southwestern Japan. PBDEs were found in the upper layers of 0–15 cm depth at concentrations ranging from 5200 to 32,600 pg g−1 with the peak estimated at 1995. Decabromodiphenyl ether (BDE-209) was the most abundant congener, accounting for 96% in average of total PBDEs. The vertical profile of BDE-209 observed in our sediment core generally agreed with the historical pattern of domestic demand of commercial deca-BDE mixtures in Japan, and perfectly matched with maximum stock of these products (i.e., 42,000 tons in 1995). Among alternative BFRs, only decabromodiphenyl ethane (DBDPE), a replacement of deca-BDE, was found at significant levels with concentrations of 69–850 pg g−1 in sediment layers dated between 1991 and 2011. Ratios of DBDPE to BDE-209 gradually increased during this period, implying opposite trends of these two compounds and the role of DBDPE as a deca-BDE’s alternative. The occurrence of deca-BDE components in sediments may pose medium risk to benthic aquatic life, while the ecological risk of other PBDE homologs and DBDPE was negligible.

Multi-year air monitoring of legacy and current-use brominated flame retardants in an urban center in northeastern China

The occurrence and temporal trends of polybrominated diphenyl ethers (PBDEs) and non-PBDE brominated flame retardants (NBFRs) were investigated in an urban atmosphere of Northeast China in consecutive six years (2008–2013). Among all chemicals, BDE-209, l,2,5,6,9,10-hexabromocyclododecane (HBCD), and decabromodiphenylethane (DBDPE) were the three most dominant compounds. During the period, the levels of pentabromodiphenyl ethers in the gas-phase and octabromodiphenyl ethers in the particle-phase significantly decreased, while the levels of BDE-209 and NBFRs increased in either the gas-phase or particle-phase. Ambient temperature was the most significant variable that influenced the gas-phase and particle-phase concentrations of BFRs, followed by wind speed and relative humidity. A stronger temperature dependence of the atmospheric concentrations was found for lower mass BFRs. Gas-particle partitioning studies suggested PBDEs in the urban atmosphere of Northeast China were at steady-state. Steady-state equation can also well describe the partitioning behavior for NBFRs, suggesting that the atmospheric partitioning behaviors of NBFRs were similar to those of PBDEs.

Legacy and current-use brominated flame retardants in the Barn Owl

The present study investigated the current-use brominated flame retardants (BFRs) tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD), simultaneously with legacy polybrominated diphenyl ethers (PBDEs), in Barn Owls (Tyto alba) collected from two regions with a contrasting degree of urbanisation and vicinity to point sources (Flanders in Belgium versus Normandy in France). Both tissues (muscle, liver, adipose and preen gland) and feathers (primary, tail and body feathers) showed elevated HBCD concentrations in Flanders, close to Europe's sole HBCD production plant in the Netherlands, and identified Normandy as a historical source region for PBDEs. In sharp contrast, the reactive BFR TBBPA bioaccumulated poorly (2.3%) in tissue samples, but was present in 96% of all body feather samples (0.36–7.07ngg−1dw), equally in both regions. PBDE concentrations in tissues (7.46–903ngg−1lw) were considerably lower in the investigated Flemish Barn Owls, collected in 2008/2009, compared to specimens collected in 2003/2004 (46–11,000ngg−1lw), possibly suggesting the effectiveness of the 2004 European ban of Penta- and Octa-BDE mixtures. Feathers showed a similar trend and additionally exhibited HBCD concentrations (0.02–333ngg−1dw) surpassing those of PBDEs (0.50–10.4ngg−1dw). While body feathers were a reliable matrix to predict both internal PBDE (0.21≤R2≤0.67) and HBCD body burdens (0.20≤R2≤0.37), the suitability of primary and tail feathers appeared to be confounded by external contamination and moult. In conclusion, the present study clearly showed that the reactive versus additive use of BFRs results in contrasting exposure scenarios in a species higher up the food chain, and therefore may have profound implications for environmental health. In addition, the presented results extend the promising use of feathers as a non-destructive sampling strategy for current-use BFRs, and show that birds of prey are valid early-warning systems for environmental contamination.

Widespread occurrence of polyhalogenated compounds in fat from kitchen hoods

Food and contaminated indoor environments are the most relevant sources of human exposure to polyhalogenated chemicals. This study analyzed for the first time fat residues in kitchen hoods for contaminations with polyhalogenated compounds. A wide range of contaminants was detected in all kitchen hoods (n = 15) and most of them could be quantified. Between 0.2 and 18μg polyhalogenated chemicals/g fat were detected, with chlorinated paraffins being the most relevant contaminant group. Aside from the chlorinated paraffins, each kitchen hood fat sample showed a distinct fingerprint. A wide range of old and current-use brominated flame retardants were also detected in the samples. In addition to these contaminants originating from their use in indoor equipment, residues of organochlorine pesticides and semi-volatile halogenated natural products verified that cooking of food, accompanied with the release of contaminants from the heated food, was another relevant source of contamination. Re-analyses of two samples after 3months only resulted in small variations in contaminant pattern and concentrations. Therefore, fat from kitchen hoods is proposed as an easily accessible matrix to assess contamination of these hazardous polyhalogenated chemicals.

Comparative antioxidant status in freshwater fish Carassius auratus exposed to six current-use brominated flame retardants: A combined experimental and theoretical study

Decabromodiphenyl ether (BDE-209) and several non-polybrominated diphenyl ether (PBDE) brominated flame retardants (BFRs), such as tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), decabromodiphenyl ethane (DBDPE), hexabromobenzene (HBB) and pentabromotoluene (PBT), are persistent halogenated contaminants ubiquitously detected in aquatic systems. However, data on comparative toxicological effects of these BFRs are lacking for fish. In this study, a combined experimental and theoretical approach was used to compare and analyze the effects of these BFRs on biochemical biomarkers in liver of Carassius auratus injected intraperitoneally with different doses (10 and 100mg/kg) for 7, 14 and 30 days. Oxidative stress was evoked evidently for the prolonged exposure, represented by the significantly altered indices (superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione, and malondialdehyde). The integrated biomarker response (IBR) index ranked biotoxicity as: PBT>HBB>HBCD>TBBPA>BDE-209>DBDPE. Quantum chemical calculations (electronic parameters, frontier molecular orbitals, and Wiberg bond order) were performed for theoretical analysis. Notably, some descriptors were correlated with the toxicity order, probably implying the existence of a potential structure–activity relationship when more BFRs were included. Besides, theoretical calculations also provided some valuable information regarding the molecular characteristics and metabolic pathways of these current-use BFRs, which may facilitate the understanding on their environmental behavior and fate. Overall, this study adopted a combined experimental and theoretical method for the toxicological determination and analysis of the BFRs, which may also be considered in future ecotoxicological studies.

The role of diet on long-term concentration and pattern trends of brominated and chlorinated contaminants in western Hudson Bay polar bears, 1991–2007

Adipose tissue was sampled from the western Hudson Bay (WHB) subpopulation of polar bears at intervals from 1991 to 2007 to examine temporal trends of PCB and OCP levels both on an individual and sum-(∑-)contaminant basis. We also determined levels and temporal trends of emerging polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), polybrominated biphenyls (PBBs) and other current-use brominated flame retardants. Over the 17-year period, ∑ DDT (and p,p′-DDE, p,p′-DDD, p,p′-DDT) decreased (−8.4%/year); α-hexachlorocyclohexane (α-HCH) decreased (−11%/year); β-HCH increased (+ 8.3%/year); and ∑ PCB and ∑ chlordane (CHL), both contaminants at highest concentrations in all years (> 1 ppm), showed no distinct trends even when compared to previous data for this subpopulation dating back to 1968. Some of the less persistent PCB congeners decreased significantly (−1.6%/year to −6.3%/year), whereas CB153 levels tended to increase (+ 3.3%/year). Parent CHLs ( c-nonachlor, t-nonachlor) declined, whereas non-monotonic trends were detected for metabolites (heptachlor epoxide, oxychlordane). ∑ chlorobenzene, octachlorostyrene, ∑ mirex, ∑ MeSO 2-PCB and dieldrin did not significantly change. Increasing ∑ PBDE levels (+ 13%/year) matched increases in the four consistently detected congeners, BDE47, BDE99, BDE100 and BDE153. Although no trend was observed, total-(α)-HBCD was only detected post-2000. Levels of the highest concentration brominated contaminant, BB153, showed no temporal change. As long-term ecosystem changes affecting contaminant levels may also affect contaminant patterns, we examined the influence of year (i.e., aging or “weathering” of the contaminant pattern), dietary tracers (carbon stable isotope ratios, fatty acid patterns) and biological (age/sex) group on congener/metabolite profiles. Patterns of PCBs, CHLs and PBDEs were correlated with dietary tracers and biological group, but only PCB and CHL patterns were correlated with year. DDT patterns were not associated with any explanatory variables, possibly related to local DDT sources. Contaminant pattern trends may be useful in distinguishing the possible role of ecological/diet changes on contaminant burdens from expected dynamics due to atmospheric sources and weathering.

Current-Use Brominated Flame Retardants in Water, Sediment, and Fish from English Lakes

Current-Use Brominated Flame Retardants in Water, Sediment, and Fish from English Lakes

Current-Use Brominated Flame Retardants in Water, Sediment, and Fish from English Lakes

Concentrations are reported of hexabromocyclododecanes (HBCDs) and tetrabromobisphenol-A (TBBP-A) in water (n = 27), sediment (n = 9), and fish samples (n = 30) from nine English lakes. Seasonal variation in concentrations in water is minimal. Concentrations of TBBP-A range from 140 to 3200 pg L(-1) (water), 330 to 3800 pg g(-1) dry weight (sediment), and <0.29 to 1.7 ng g(-1) lipid weight (fish). Those of SigmaHBCDs range between 80 and 270 pg L(-1) (water), 880 and 4800 pg g(-1) dry weight (sediment), and 14 and 290 ng g(-1) lipid weight (fish). Aqueous concentrations of SigmaHBCDs and TBBP-A are significantly positively correlated, indicating a common source. Average +/-sigma(n) "freely-dissolved" phase proportions are 47 +/- 4.7% (SigmaHBCDs) and 61 +/- 2.9% (TBBP-A). Average field-derived bioaccumulation factors are 5900, 1300, 810, and 2100 for alpha-, beta-, gamma-, and SigmaHBCDs, respectively. Tetrabromocyclododecadienes are detected in all sediments, with pentabromocyclododecenes present in some. This suggests HBCD degrades via sequential loss of HBr. The delta-HBCD meso form was quantified in 43% of fish samples (1.0-11% SigmaHBCDs). Its absence from temporally and spatially consistent water and sediment samples suggests it is formed via bioisomerization. While HBCD chiral signatures are racemic in water and sediment, our data reveal enantiomeric enrichment of (-)alpha-HBCD and (+)gamma-HBCD in fish.

Brominated Flame Retardants in Glaucous Gulls from the Norwegian Arctic: More Than Just an Issue of Polybrominated Diphenyl Ethers

Several, unregulated, current-use brominated flame retardants (BFRs), including hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), pentabromoethylbenzene (PBEB), pentabromotoluene (PBT), and hexabromocyclododecane (as total-(alpha)-HBCD), were examined in egg yolk and plasma of male and female glaucous gulls (Larus hyperboreus) from the Norwegian Arctic. Also examined were BDE209 and 38 tri- to nona-BDE congeners and brominated biphenyl (BB) 101. The HBB, BTBPE, PBEB, and PBT had high detection frequencies and variability in male and female plasma and egg yolk samples, and their concentrations ranged from nondetectable (< 0.02-0.27 ng/g wet wt) to 2.64 ng/g wet wt. The detection frequencies and range of concentrations of non-BDE BFRs were generally highest in plasma of males relative to females. Total-(alpha)-HBCD concentrations were highest among the non-PBDE BFRs (up to 6.12 and 63.9 ng/g wet wt in plasma and egg yolk, respectively). Next highest was HBB with concentrations within a range comparable to the minor PBDEs monitored (e.g., BDE28, 116 and 155). Sum (sigma)38PBDE concentrations ranged from 2.49 to 54.5 ng/g wet wt in plasma and 81.2 to 321 ng/g wet wt in egg yolk. The BDE209 was virtually nondetectable, whereas six octa-BDEs (i.e., BDE196, 197, 201, 202, 203, and 205), as well as three nona-BDEs (i.e., BDE206, 207, and 208, and potential BDE209 debromination products) were found sporadically in plasma and egg yolk. The results from this study suggestthat in addition to PBDEs, several current-use, non-BDE BFRs undergo long-range atmospheric transport and bioaccumulate at low levels in and are maternally transferred (to eggs) in glaucous gulls from the Norwegian Arctic.