Levels and trends of PBDEs and HBCDs in the global environment: status at the end of 2012

Stereoisomer-specific occurrence, distribution, and fate of chiral brominated flame retardants in different wastewater treatment systems in Hong Kong

This study investigated the occurrence and fate of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), two chiral brominated flame retardants (BFRs) with sixteen different stereoisomers, in four Hong Kong wastewater treatment plants (WWTPs) featuring diverse treatment processes during a two-year sampling campaign. More effective HBCD removal was achieved via biodegradation as compared to sludge sorption, whereas both chemically enhanced primary treatment and secondary treatment yielded high TBECH elimination (>90%). α-HBCD (54-75%) predominated in all samples, and its proportions were increased in effluent as compared to influent and sludge. α- and β-TBECH (72.3-84.4% in total) were the predominant TBECH diastereomers, with a proportional shift from the latter to the former diastereomer mostly observed after treatment. More rapid biodegradation and preferential sorption of γ-HBCD as compared to α-HBCD as well as β-TBECH as compared to α-TBECH might account for this changing pattern. This is the first study to report the enantiomer-specific behavior of chiral BFRs in different wastewater treatment processes. A preferential elimination of (+)-α- and (+)-γ-HBCD and E₂-β-TBECH (the second enantiomeric elution order) took place consistently after biological treatment, possibly due to enantioselective adsorption and microbial degradation. Our results highlight the importance of conducting enantiospecific analysis for chiral pollutants in wastewater samples.

Halogenated flame retardants in mangrove sediments from the Pearl River Estuary, South China: Comparison with historical data and correlation with microbial community

Polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCDD) and dechlorane plus (DP) were measured in sediments collected from three mangrove wetlands of the Pearl River Estuary (PRE) in South China. This study aims to investigate the distribution of these halogenated flame retardants (HFRs) and the correlations between HFRs and microbial community structure in mangrove sediments. Concentrations of PBDEs, DBDPE, BTBPE, TBBPA, HBCDD and DP in mangrove sediments ranged from 6.97 to 216.1, 3.70-26.0, 0.02-0.73, 0.02-37.5, 0.44-127.5 and 0.07-2.23 ng/g dry weight, respectively. Higher levels of PBDEs, BTBPE, HBCDD and DP were observed in sediments from Futian mangrove wetland of Shenzhen, the only nature reserve located in the downtown of China. The highest concentration of TBBPA found in mangrove sediments from Guangzhou was proximate to a ferry terminal and a dockyard where TBBPA is widely used in the coatings. PBDEs were the predominant HFRs in mangrove sediments, with an average contribution of 63.0%. Mangrove sediments from Guangzhou and Zhuhai showed an enrichment of (-)-α-HBCDD, (-)-β-HBCDD and (-)-γ-HBCDD. Concentrations of HFRs in mangrove sediments from Guangzhou increased significantly from 2012 to 2015, which was probably due to the establishment and rapid development of Nansha Free Trade Zone of Guangzhou. Redundancy analysis showed that HFRs may cause a shift of microbial community structure in mangrove sediments and the variations were significantly correlated with TBBPA, syn-DP and BTBPE.

Autophagy impairment contributes to PBDE-47-induced developmental neurotoxicity and its relationship with apoptosis

Apoptosis is involved in 2,2',4,4'- tetrabromodiphenyl ether (PBDE-47)-induced developmental neurotoxicity. However, little is known about the role of autophagy, especially its relationship with apoptosis underlying such neurotoxic process.

Methods: Using female Sprague-Dawley rats exposed to low-dose PBDE-47 (0.1, 1.0 and 10 mg/kg/day) from pre-pregnancy until weaning of offspring to mimic human exposure, we investigated the effects of PBDE-47 on autophagy and apoptosis in relation to cognitive impairment of adult offspring rats. We also evaluated relationship between autophagy and apoptosis using neuroendocrine pheochromocytoma (PC12) cells, a widely used neuron-like cell line for neuronal development.

Results: In vivo, perinatal exposure to PBDE-47 induced memory deficits in adult rats. This is accompanied by hippocampal neuronal loss partly as a result of apoptosis, as evidenced by caspase-3 activation and PARP cleavage. Further study identified that PBDE-47 triggered autophagic vesicles accumulation, increased levels of microtubule-associated protein 1 light chain 3 (LC3)-II, an essential protein for autophagosomes formation, and autophagy substrate sequestosome 1 (SQSTM1/p62), but reduced levels of autophagy-related protein (ATG) 7, a key protein for autophagosomes elongation, suggestive of autophagy impairment. These findings were further demonstrated by an in vitro model of PBDE-47-treated PC12 cells. Mechanistically, autophagy alteration is more sensitive to PBDE-47 treatment than apoptosis induction. Importantly, while stimulation of autophagy by the chemical inducer rapamycin and adenovirus-mediated Atg7 overexpression aggravated PBDE-47-induced apoptosis and cell death, inhibition of autophagy by the chemical inhibitor wortmannin and siRNA knockdown of Atg7 reversed PBDE-47-produced detrimental outcomes. Interestingly, blockage of apoptosis by caspase-3 inhibitor Ac-DEVD-CHO ameliorated PBDE-47-exerted autophagy impairment and cell death, though in combination with autophagy inhibitor did not further promote cell survival.

Conclusion: Our data suggest that autophagy impairment facilitates apoptosis, which, in turn, disrupts autophagy, ultimately resulting in cell death, and that autophagy may act as a promising therapeutic target for PBDE-47-induced developmental neurotoxicity.

Global Historical Stocks and Emissions of PBDEs

The first spatially and temporally resolved inventory of BDE28, 47, 99, 153, 183, and 209 in the anthroposphere and environment is presented here. The stock and emissions of PBDE congeners were estimated using a dynamic substance flow analysis model, CiP-CAFE. To evaluate our results, the emission estimates were used as input to the BETR-Global model. Estimated concentrations were compared with observed concentrations in air from background areas. The global (a) in-use and (b) waste stocks of ∑₅BDE(28, 47, 99, 153, 183) and BDE209 are estimated to be (a) ∼25 and 400 kt and (b) 13 and 100 kt, respectively, in 2018. A total of 6 (0.3-13) and 10.5 (9-12) kt of ∑₅BDE and BDE209, respectively, has been emitted to the atmosphere by 2018. More than 70% of PBDE emissions during production and use occurred in the industrialized regions, while more than 70% of the emissions during waste disposal occurred in the less industrialized regions. A total of 70 kt of ∑₅BDE and BDE209 was recycled within products since 1970. As recycling rates are expected to increase under the circular economy, an additional 45 kt of PBDEs (mainly BDE209) may reappear in new products.

Human exposure pathways to organophosphate flame retardants: Associations between human biomonitoring and external exposure

Organophosphate flame retardants (PFRs) have largely replaced the market of polybrominated diphenyl ethers (PBDEs). Concerns about PFR contamination and its impact on human health have consequently increased. A comprehensive investigation on the human exposure pathways to PFRs is to be endeavoured. This study investigated the occurrence of PFR metabolites in human urine, serum and hair, correlating them with external exposure data that was presented in our previous studies. Participants from Oslo (n = 61) provided a set of samples, including dust, air, handwipes, food, urine, serum and hair. Associations between PFR metabolites analyzed in the biological samples and the PFRs in environmental samples were explored. Different sampling strategies for dosimeters (e.g. floor/surface dust, personal/stationary air) were also compared to understand which is better for predicting human exposure to PFRs. Seven out of the eleven target PFR metabolites, including diphenyl phosphate (DPHP) and bis(1-chloro-2-propyl)-1-hydroxy-2-propyl phosphate (BCIPHIPP), were frequently detected (DF > 30%) in urine. DPHP was the most frequently detected metabolite in both serum and hair. Several PFR metabolites had higher levels in morning urine than in afternoon urine. Floor dust appeared to be a better proxy for estimating PFR internal exposure than surface dust, air, and handwipes. Some PFRs in handwipes and air were also correlated with their metabolites in urine and hair. Age, beverage consumption and food consumption were negatively associated with DPHP levels in urine. Discrepancies observed between the external and internal exposure for some PFRs call for further investigation on PFR bioaccessibility and clearance.

Past and emerging topics related to electronic waste management: top countries, trends, and perspectives

A bibliometric analysis was performed to assess historical and recent research trends regarding e-waste studies from 1998 to 2018. Documents related to e-waste were identified from the Clarivate Analytics Web of Science© (WoS) database, and a total of 3311 academic articles was retrieved. The analysis was performed from four main aspects: (1) publication activity by year, by WoS category, and by geographic distribution; (2) journals; (3) most-cited papers; and (4) top 10 countries and author keyword analysis. The number of publications concerning e-waste issues has increased substantially over the last 20 years, especially in the environmental science category, and more than a third of the publications were produced in China (1181 records). Waste Management and Environmental Science & Technology were the most sought-after journals for disseminating the results. Studies related to "e-waste flow analysis," "recycling," "recovery of precious metals," and "risk assessment of recycling areas" have been the most common for several years. The analysis of keywords suggested that there are many topics on electronic waste and that each country has presented a different focus of research. Overall, the bibliometric analysis proved to be an efficient tool with which to monitor historical and current research trends and to evaluate the sheer volume of currently existing scientific literature on e-waste topics.

Distribution of the parent compound and its metabolites in serum, urine, and feces of mice administered 2,2',4,4'-tetrabromodiphenyl ether

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47) is a predominant polybromodiphenyl ether congener in the environment. Its absorption, excretion, and metabolism in animals have been investigated; however, the distribution of BDE-47 and its metabolites in excreta and blood at steady-state conditions has been unclear. In the present study, we addressed the issue by determining the amounts of BDE-47, eight monohydroxylated metabolites (OH-BDEs), and 2,4-dibromophenol (2,4-DBP) in serum, urine, and feces of gpt delta transgenic mice orally administered BDE-47 at 1.5, 10, and 30 mg/kg/d for 6 weeks during the 24 h period (for urine and feces) or at 24 h (for blood) post-last dosing. The distribution profiles in the three matrices showed that BDE-47, OH-BDEs, and 2,4-DBP were mostly distributed in urine (59-70%), feces (95-96%), and urine (51-80%), respectively. In each matrix, BDE-47 was the predominant compound under all doses, which accounted for 84-96% in serum, 68-98% in urine, and 37-92% in feces. However, exclusive of BDE-47, OH-BDEs were the predominant class of metabolites in serum (72-86%) and feces (67-87%), whereas 2,4-DBP was the major metabolite in urine (98-99%). Among monohydroxylated metabolites, the dominant compounds were 4-hydroxy-2,2',3,4'-tetrabromodiphenyl ether (4-OH-BDE-42) and 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether (4'-OH-BDE-49) in feces (27-33% and 25-43%, respectively), and 3-hydroxy-2,2',4,4'-tetrabromodiphenyl ether (3-OH-BDE-47) in serum (26-43%). Thus, BDE-47 and 2,4-DBP were mostly present in urine, and OH-BDEs were primarily found in feces. Blood was not an important carrier for either BDE-47 or its metabolites. The data provide information for distribution and elimination of BDE-47 and its metabolites in mice at steady-state conditions.

Why is high persistence alone a major cause of concern?

Persistence is a hazard criterion for chemicals enshrined in chemical regulation worldwide. In this paper, we argue that the higher the persistence of a chemical, the greater the emphasis that it should be given in chemicals assessment and decision making. We provide case studies for three classes of highly persistent chemicals (chlorofluorocarbons, polychlorinated biphenyls, and per- and polyfluoroalkyl substances) to exemplify problems unique to highly persistent chemicals, despite their otherwise diverse properties. Many well-known historical chemical pollution problems were the result of the release of highly persistent chemicals. Using evaluative modeling calculations, we demonstrate that if a chemical is highly persistent, its continuous release will lead to continuously increasing contamination irrespective of the chemical's physical-chemical properties. We argue that these increasing concentrations will result in increasing probabilities of the occurrence of known and unknown effects and that, once adverse effects are identified, it will take decades, centuries or even longer to reverse contamination and therefore effects. Based on our findings we propose that high persistence alone should be established as a sufficient basis for regulation of a chemical, which we term the "P-sufficient approach". We argue that regulation on high persistence alone is not over-precautionary given the historical and ongoing problems that persistent chemicals have caused. Regulation of highly persistent chemicals, for example by restriction of emissions, would not only be precautionary, but would serve to prevent poorly reversible future impacts.

Levels and temporal trends of persistent organic pollutants (POPs) in Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) from the southern Barents Sea

Liver samples of two gadoid species, Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus), sampled in the southern Barents Sea in the period 1992-2015, were studied for the levels of six types of persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), chlorinated organic pesticides (DDTs, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), trans-nonachlor (TNC)), and polybrominated diphenyl ethers (PBDEs). Higher average levels were found in cod than in haddock. Sampling approximately every third year allowed studies of temporal trends for all the compound groups except PBDEs. Time series are reported for 1992-2015 for Atlantic cod and for 1998-2015 for haddock. Decreasing temporal trends have been modeled in cod for the analyzed POPs for this time period. The decrease seems to be slowing down in the later years. HCB levels showed least decrease with time among all the contaminants, with the poorest fit to the proposed model. Similar time trends were found in haddock, but the decrease is less apparent due to shorter time series. The observed time trends of legacy POPs document the effectiveness of efforts during the 1990s to reduce the levels of these contaminants in the marine environment but question the possibility to eliminate them altogether from the marine environment in the foreseeable future.

Flame retardant concentrations and profiles in wild birds associated with landfill: A critical review

Given factors such as their persistence and toxicity, legacy brominated flame retardants (BFRs) like polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD), are designated as persistent organic pollutants (POPs) and are subject to regulation. Waste streams likely represent a substantial reservoir of legacy BFRs given that they were once widely applied to goods which are increasingly likely to be obsolete. Waste streams are also increasingly likely to be a source of emerging flame retardants, in particular, novel BFRs (NBFRs), the halogenated norbornene flame retardant Dechlorane Plus (DDC-CO) and the brominated, chlorinated or non-halogenated organophosphate triester flame retardants (PFRs). Many bird populations rely on landfill and its surrounding land-use for inter alia the opportunities it provides for activities such as foraging and resting. However, studies on captive and wild (free-living) birds have demonstrated deleterious effects of several FRs. Globally, approximately 250 bird species, including many of conservation concern, are reported to use landfill and surrounding habitat (including wastewater treatment operations), thus putting birds potentially at risk of exposure to such chemicals. We synthesise and critically evaluate a total of 18 studies covering eight avian species published between 2008 and 2018 (inclusive) across four continents that report flame retardant (FR) burdens in birds utilising landfill. Several such studies found FRs at among the highest concentrations detected in wild biota to date. We recommend that ongoing research be focused on landfill-associated birds, given that landfill is an important source of FRs and other anthropogenic chemicals, and particularly at sites where species are of conservation concern. We suggest ways in which the comparative power of studies could be enhanced in the future, the reporting of a minimum common suite of key chemicals, and where feasible, standardisation of the tissue compartments (i.e., eggs) to be studied. We conclude by identifying future research directions.

The role of analytical chemistry in exposure science: Focus on the aquatic environment

Exposure science, in its broadest sense, studies the interactions between stressors (chemical, biological, and physical agents) and receptors (e.g. humans and other living organisms, and non-living items like buildings), together with the associated pathways and processes potentially leading to negative effects on human health and the environment. The aquatic environment may contain thousands of compounds, many of them still unknown, that can pose a risk to ecosystems and human health. Due to the unquestionable importance of the aquatic environment, one of the main challenges in the field of exposure science is the comprehensive characterization and evaluation of complex environmental mixtures beyond the classical/priority contaminants to new emerging contaminants. The role of advanced analytical chemistry to identify and quantify potential chemical risks, that might cause adverse effects to the aquatic environment, is essential. In this paper, we present the strategies and tools that analytical chemistry has nowadays, focused on chromatography hyphenated to (high-resolution) mass spectrometry because of its relevance in this field. Key issues, such as the application of effect direct analysis to reduce the complexity of the sample, the investigation of the huge number of transformation/degradation products that may be present in the aquatic environment, the analysis of urban wastewater as a source of valuable information on our lifestyle and substances we consumed and/or are exposed to, or the monitoring of drinking water, are discussed in this article. The trends and perspectives for the next few years are also highlighted, when it is expected that new developments and tools will allow a better knowledge of chemical composition in the aquatic environment. This will help regulatory authorities to protect water bodies and to advance towards improved regulations that enable practical and efficient abatements for environmental and public health protection.

Levels of polybrominated diphenyl ethers and hexabromocyclododecane in treatment plant sludge: Implications on sludge management

Past usage of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) in commercial products resulted in their continuous emission from sources. Wastewater treatment plants (WWTP) are the main sinks resulting from their industrial and domestic usage as well as atmospheric deposition. This preliminary study examined levels of PBDEs and HBCDD in urban and industrial WWTP sludge samples for the first time from Turkey. PBDE concentrations (sum of 26 congeners) of eight samples collected from four WWTPs were between 300 and 655 ng g^-1 dw and 67-2.5*10⁷ ng g^-1 dw, and HBCDD concentrations (sum of α-, β-, and γ- diastereoisomers) ranged 75-616 ng g^-1 dw and 13-416 ng g^-1 dw, for urban and industrial WWTP samples, respectively. Although PBDEs have never been produced in Turkey, the highest PBDE concentration in sewage sludge worldwide was identified in one of the WWTPs. PBDE and HBCDD levels in other sludge samples were comparable to those reported in the literature. Application of a chemical mass balance model (CMB) suggested: (i) the main source of PBDEs as deca-BDE mixture; (ii) influence of a background air PBDE profile for one of the industrial WWTPs, having low contamination; (iii) indoor dust PBDE contamination as another source for urban WWTPs. The preliminary results for BFR levels in Turkey were discussed in terms of sludge disposal methods used worldwide, and the need for regulatory limits for BFRs in sludge management.

Molecular mechanisms and tissue targets of brominated flame retardants, BDE-47 and TBBPA, in embryo-larval life stages of zebrafish (Danio rerio)

Brominated flame retardants are known to disrupt thyroid hormone (TH) homeostasis in several vertebrate species, but the molecular mechanisms underlying this process and their effects on TH-sensitive tissues during the stages of early development are not well characterised. In this study, we exposed zebrafish (Danio rerio) embryo-larvae to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and tetrabromobisphenol A (TBBPA) via the water for 96 h from fertilisation and assessed for lethality, effects on development and on the expression of a suite of genes in the hypothalamic-pituitary-thyroid (HPT) axis via both real time quantitative PCR (qRT-PCR) on whole body extracts and whole mount in situ hybridisation (WISH) to identify tissue targets. The 96-h lethal median concentration (96h-LC₅₀) for TBBPA was 0.9 μM and mortality was preceded by retardation of development (smaller animals) and morphological deformities including, oedemas in the pericardial region and tail, small heads, swollen yolk sac extension. Exposure to BDE-47 did not affect zebrafish embryo-larvae survival at any of the concentrations tested (1-100 μM) but caused yolk sac and craniofacial deformities, a curved spine and shorter tail at the highest exposure concentration. TBBPA exposure resulted in higher levels of mRNAs for genes encoding deiodinases (dio1), transport proteins (ttr), the thyroid follicle synthesis protein paired box 8 (pax8) and glucuronidation enzymes (ugt1ab) and lower levels of dio3b mRNAs in whole body extracts, with responses varying with developmental stage. BDE-47 exposure resulted in higher levels of thrb, dio1, dio2, pax8 and ugt1ab mRNAs and lower levels of ttr mRNAs in whole body extracts. TBBPA and BDE-47 therefore appear to disrupt the TH system at multiple levels, increasing TH conjugation and clearance, disrupting thyroid follicle development and altering TH transport. Compensatory responses in TH production/ metabolism by deiodinases were also evident. WISH analyses further revealed that both TBBPA and BDE-47 caused tissue-specific changes in thyroid receptor and deiodinase enzyme expression, with the brain, liver, pronephric ducts and craniofacial tissues appearing particularly responsive to altered TH signalling. Given the important role of TRs in mediating the actions of THs during key developmental processes and deiodinases in the control of peripheral TH levels, these transcriptional alterations may have implications for TH sensitive target genes involved in brain and skeletal development. These findings further highlight the potential vulnerability of the thyroid system to disruption by BFRs during early developmental windows.

Occurrence, levels and profiles of brominated flame retardants in daily-use consumer products on the Chinese market

With the global phasing-out of POP-BFRs (brominated flame retardants restricted under the Stockholm Convention on Persistent Organic Pollutants), the main challenge for their environmentally sound management has shifted from manufacturing and consumption to their recycling and disposal. For the end-of-life products containing POP-BFRs, material recycling and reuse in new articles is the favorite approach widely adopted by recyclers. This would result in POP-BFRs being transferred into daily-use consumer products. To identify the possible reservoirs of POP-BFRs in consumer products on the Chinese market, 120 samples were screened for Br by using a portable X-ray fluorescence (XRF) spectrometer, and the three traditional BFRs, i.e., polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA), were analyzed in 15 Br-positive samples. The results showed that 36.7% of products contained at least one test point positive for Br, and higher detection frequencies were found in electric appliances and toys. The concentrations of ∑BFRs ranged from 0.48 to 73.82 mg kg-1 with a general contribution in the order of ∑PBDEs > TBBPA > HBCD. BDE-209 was the dominant congener among PBDEs in most investigated samples, accounting for 48.18-99.36%. Relatively high proportions of the more bioaccumulative and toxic substances of lower brominated PBDE congeners and α-HBCD in products may increase the adverse impacts on the environment and human health. The obtained results will be helpful to understand the downstream flow of POP-BFRs with great significance to the control on their unintended contamination in daily life.

Roles of maize cytochrome P450 (CYP) enzymes in stereo-selective metabolism of hexabromocyclododecanes (HBCDs) as evidenced by in vitro degradation, biological response and in silico studies

In vitro biotransformation of HBCDs by maize cytochrome P450 (CYP) enzymes, responses of CYPs to HBCDs at protein and transcription levels, and in silico simulation of interactions between CYPs and HBCDs were investigated in order to elucidate the roles of CYPs in the metabolism of HBCDs in maize. The results showed that degradation reactions of HBCDs by maize microsomal CYPs followed the first-order kinetics and were stereo-selective, with the metabolic rates following the order (-)γ- > (+)γ- > (+)α- > (-)α-HBCD. The hydroxylated metabolites OH-HBCDs, OH-PBCDs and OH-TBCDs were detected. (+)/(-)-α-HBCDs significantly decreased maize CYP protein content and inhibited CYP enzyme activity, whereas (+)/(-)-γ-HBCDs had obvious effects on the induction of CYPs. HBCDs selectively mediated the gene expression of maize CYPs, including the isoforms of CYP71C3v2, CYP71C1, CYP81A1, CYP92A1 and CYP97A16. Molecular docking results suggested that HBCDs could bind with these five CYPs, with binding affinity following the order CYP71C3v2 < CYP81A1 < CYP97A16 < CYP92A1 < CYP71C1. The shortest distances between the Br-unsubstituted C atom of HBCD isomers and the iron atom of heme in CYPs were 4.18-11.7 Å, with only the distances for CYP71C3v2 being shorter than 6 Å (4.61-5.38 Å). These results suggested that CYP71C3v2 was an efficient catalyst for degradation of HBCDs. For (+)α- and (-)γ-HBCDs, their binding affinities to CYPs were lower and the distances to the iron atom of heme in CYPs were shorter than their corresponding antipodes, consistent with the in vitro experimental results showing that they had shorter half-lives and were more easily hydroxylated. This study provides solid evidence for the roles of maize CYPs in the metabolism of HBCDs, and gives insight into the molecular mechanisms of the enantio-selective metabolism of HBCDs by plant CYPs.

Polybrominated diphenyl ethers (PBDEs) in plasma from E-waste recyclers, outdoor and indoor workers in the Puget Sound, WA region

Polybrominated diphenyl ethers (PBDEs) were widely used as flame retardants in consumer products including electronic devices. Important routes of human exposure are contaminated food and contact with dust. In this study, we measured twelve PBDEs in household/workplace dust and blood plasma samples provided by 113 volunteers living in the Puget Sound region, WA and working at electronic waste (E-waste) recycling sites (n = 29) or non-specific indoor (n = 57) or outdoor occupations (n = 27). The volunteers in the outdoor group were also selected because of a history of high seafood consumption habits. Results indicated the sum PBDE levels varied between <2.5 and up to 310 ng g^-1 lipid. E-waste recyclers were predominantly men, generally consumed low amounts of seafood, and had PBDE blood levels (geometric mean, GM = 26.56 ng g^-1 lipid) that were similar to indoor workers (GM = 27.17 ng g^-1 lipid). The sum PBDE levels were highest in the outdoor group (GM = 50.63 ng g^-1 lipid). Dust samples from E-waste sites were highly enriched with BDE-209 and BDE-153 relative to non-E-waste businesses and homes. The concentrations of these BDE congeners in dust at E-waste sites were ∼32-39 times higher than in dust from other sites. However, the detection rate of BDE-209 in plasma was low across all groups (13%) and no statistical comparisons were made. Our results suggest that E-waste recyclers in this study population did not have elevated PBDE levels in comparison to volunteers working in other types of occupations.

Evaluation of PCDD/Fs, dioxin-like PCBs and PBDEs in sperm whales from the Mediterranean Sea

Numerous studies to date have reported concentrations of Persistent Organic Pollutants (POPs) in different marine mammal species worldwide. Yet data on sperm whales are scarce from rich and unique biodiverse areas such as the Mediterranean Sea. This work aimed to assess levels of dioxin-like polychlorinated biphenyls (dl-PCBs), polybrominated diphenyl ethers (PBDEs), and polychlorodibenzo-p-dioxins and furans (PCDD/Fs) in blubber of sperm whales stranded along the Italian coast between 2008 and 2016. POP mean concentrations (dl-PCBs: 6410 ng/g l.w.; PBDEs: 612 ng/g l.w.; PCDD/Fs: 57.8 pg/g l.w.) were mostly in line with what has been previously reported on the same species in the Mediterranean environment and tended to be higher than those reported from other geographical regions. The relative abundance followed the order dl-PCBs > PBDEs ≫ PCDD/Fs. Interestingly, the non-ortho dl-PCB pattern (126 > 169 > 77) was similar to that described in other studies worldwide and different from what is described in its main prey. This could be linked to particular metabolic activities in sperm whales against these highly toxic contaminants. Total TEQs ranged from 275 to 987 pg/g l.w. and showed the pattern Σnon-ortho-dl-PCBs > Σortho-dl-PCBs > PCDDs > PCDFs, with PCBs' contribution about 96%. These findings highlight the high abundance of PCBs still found in the Mediterranean environment despite having been banned for decades. All sperm whales analyzed in this study surpassed the threshold of 210 pg WHO-TEQ/g l.w. proposed as starting point of immunosuppression in harbour seals; a level of contamination that may have contributed to an impairment of their immune system.

Enhanced emissions of brominated flame retardants from indoor sources by direct contact with dust

The emissions of brominated flame retardants (BFRs) from consumer products have been considered the major to the ubiquitous occurrence of contaminants in indoor environments. Direct contact with dust covering the surface of source materials in a real environment could introduce significant uncertainty. This study investigated the effects of dust coverage on the emissions of four BFRs, including 1, 2, 5, 6, 9, and 10-hexabromocyclododecane (HBCD), bis(2-ethyl-1-hexyl) tetrabromophthalate (BEHTBP), tetrabromobisphenol A (TBBPA), and hexabromobenzene (HBBZ), from decorative laminate, cotton sound insulation, PVC floor, and carpet. Direct contact with dust was confirmed to increase the total emissions by 30.8-98.1% compared with the emissions in the non-dust group. The emissions of HBCD, TBBPA, and HBBZ from cotton sound insulation were obviously enhanced by dust with smaller particles but did not linearly increase along with the dust amounts. Thus, these findings have practical implications in that the frequent removal of dust could be important to minimize the exposure risk from indoor emissions of BFRs.

Measurement of legacy and emerging flame retardants in indoor dust from a rural village (Kopawa) in Nepal: Implication for source apportionment and health risk assessment

Under the Stockholm Convention, signatory countries are obliged to direct source inventories, find current sources, and provide ecological monitoring evidence to guarantee that the encompassing levels of persistent organic pollutants (POPs) are declining. However, such monitoring of different types of POPs are to a great degree constrained in most developing countries including Nepal and are primarily confined to suspected source area/ densely populated regions. In this study, 9 polybrominated diphenyl ethers (PBDEs), 2 dechlorane plus (DPs), 6 novel brominated flame retardants (NBFRs) and 8 organophosphate ester flame retardants (OPFRs) were investigated in indoor dust from a rural area (Kopawa) in Nepal in order to evaluate their occurrence/level, profile, spatial distribution and their sources. Additionally, health risk exposure was estimated to anticipate the possible health risk to the local population. The results showed that OPFRs was the most abundant FR measured in the dust. The concentration of ∑₈OPFRs was about 2, 3 and 4 orders of magnitude higher than the ∑₆NBFRs, ∑₉PBDEs, and ∑₂DPs, respectively. Tris (methylphenyl) phosphate (TMPP) and Tris (2-ethylhexyl) phosphate (TEHP) were the most abundant OPFRs analyzed in the dust; while decabromodiphenyl ethane (DBDPE) exceeded among NBFRs. Likewise, 2,2',3,3',4,4',5,5',6,6'-decabromodiphenylether (BDE-209) was the most identified chemical among PBDEs. The total organic carbon (TOC) content in dust was significantly and positively connected with octa-BDEs (Rho = 0.615, p < 0.01), BTBPE (Rho = 0.733, p < 0.01), TPHP (Rho = 0.621, p < 0.01), TEHP (Rho = 0.560, p < 0.01) and TMPPs (Rho = 0.550, p < 0.01), while black carbon (BC) was either weakly related or not related, suggesting little or no impact of BC in the distribution of FRs. Principal component analysis indicated the contribution from commercial penta-, octa- and deca-BDEs formulation, the adhesive substance, food packaging and paints, and degradation of BDE-209 as the essential sources of FRs. Health risk exposure estimates showed that dermal absorption via dust as the primary route of FRs intake. The estimated daily exposure of PBDEs, NBFRs and OPFRs were 2-10 orders of magnitude lower than their corresponding reference dose (RfD), suggesting insignificant risk. However, other routes such as inhalation and dietary intake might still be significant in the case of Kopawa which should be tested in future.

Brominated and organophosphate flame retardants along a sediment transect encompassing the Guiyu, China e-waste recycling zone

e-Waste recycling using crude techniques releases a complex, yet incompletely characterized mixture of hazardous materials, including flame retardants (FRs), to the environment. Their migration downstream and the associated risks also remain undocumented. We examined 26 FRs (18 brominated (BFRs: 12 polybrominated diphenyl ether (PBDE) congeners, plus 6 alternatives) and 8 organophosphate esters (OPEs)) in surficial sediments of the Lian River. Sampling encompassed the river's origin, through the Guiyu e-waste recycling zone, to its mouth, as well as associated tributaries. OPE exceeded BFR concentrations in most sediments, despite their far greater water solubilities. Among OPEs, tris(1-chloro-2-propyl) phosphate dominated upstream, but shifted to triphenyl phosphate in Guiyu and downstream sediments. For PBDEs, Deca-BDE dominated upstream, but Penta-BDE prevailed in Guiyu and at many downstream sites. Among emerging alternative BFRs, decabromodiphenyl ethane dominated upstream, transitioning to 1,2-bis(2,4,6,-tribromophenoxy)ethane in Guiyu sediments. Penta-BDE (BDE-47 + -99, 668-204,000 ng g^-1, ∑PBDEs 2280-287,000 ng g^-1), tetrabromobisphenol A (2,720-41,200 ng g^-1), 1,2-bis(2,4,6,-tribromophenoxy)ethane (222-9870 ng g^-1) and triphenyl phosphate (4260-1,710,000 ng g^-1, OPEs 6010-2,120,000 ng g^-1) concentrations in Guiyu sediments were among the highest reported in the world to date. The continuing dominance of these e-waste indicative FRs in sediments downstream of Guiyu suggested that FR migration from Guiyu occurred. Hazard quotients >1.0 indicated that the extreme sediment concentrations of individual FRs posed ecological risks in most Guiyu reach and downstream areas. Simultaneous exposure to multiple FRs likely increased risks. However, risks may be mediated if FRs were associated with strong sorbents, e.g. carbon black from burned debris, hydrophobic polymer fragments, or resided as additives within polymer fragments.

Perigestational exposure to low doses of PBDE-47 induces excessive ER stress, defective autophagy and the resultant apoptosis contributing to maternal thyroid toxicity

Brominated flame retardant 2,2',4,4'‑tetrabromodiphenyl ether (PBDE-47) is known to induce developmental neurotoxicity by disturbing thyroid hormones (THs). Evidence shows that maternal THs are crucial for brain development and growth of fetuses and infants. However, little is known about the effects of PBDE-47 on maternal thyroid status and its mode of action. Here, using female Sprague-Dawley rats orally exposed to low doses of PBDE-47 (0.1, 1.0, 10 mg/kg/day) from pre-pregnancy until weaning of offspring to mimic human exposure, we show that perigestational exposure to PBDE-47 elevated serum triiodothyronine and thyroxine levels in mother rats. This is accompanied by disrupted thyroid follicle structure including expanded follicles, hyperplastic epithelial cells and shed cell remnants filled in the exhausted follicular lumen. Mechanistically, PBDE-47 enhanced apoptosis in thyroid tissue, as demonstrated by Caspase-3 activation, PARP cleavage and DNA fragmentation. Further study identified that PBDE-47 upregulated the levels of GRP78, ATF4, active Caspase-12 and CHOP, suggesting endoplasmic reticulum (ER) stress and unfolded protein response activation. Moreover, PBDE-47 reduced the levels of LC3-II, an autophagy marker protein essential for the autophagosomes formation, while increased the autophagy substrate p62 accumulation, indicating autophagy defect. Importantly, the colocalization of apoptotic cells with CHOP, a key mediator of ER stress-induced apoptosis, or p62, uncovered the contribution of excessive ER stress and defective autophagy to apoptosis. Collectively, our results suggest that excessive ER stress, defective autophagy and the resultant apoptosis are implicated in maternal thyroid injury following perigestational PBDE-47 exposure, which offers insight into a better understanding of PBDE-47-induced maternal thyroid toxicity.

Priority substances in accumulated sediments in a stormwater detention basin from an industrial area

One of the most adopted solutions in developed countries to manage stormwater is detention/retention basins which generate large quantities of sediments that have to be removed regularly. In order to manage them properly, accurate data are needed about their physical and chemical characteristics, particularly on micropollutant concentrations and their associated risk. This work consisted in a two-year sampling of dry sediments from a detention-settling basin. Priority substances, including pesticides, polybrominated diphenyl ethers (PBDE), alkylphenols and bisphenol A (BPA), were monitored. Different sites in the basin bottom were sampled in order to investigate spatial distribution of the contamination. Results show that the increase of the sediment thickness in the basin was heterogeneous with a maximum of 15 cm after two years. Pesticides and PBDE were, if detected, mainly found in low concentrations from 2 ng/g to 286 ng/g. Conversely, alkylphenols and bisphenol A were always quantified at concentrations varying from 6 ng/g to 3400 ng/g. These high levels suggest that these sediments should be managed with precautions. Spatial heterogeneity of alkylphenol ethoxylates and BPA concentrations was observed, with higher contamination of alkylphenol ethoxylates in anaerobic zones and BPA levels correlated with total organic carbon and in a lesser extent to fine particles.

Hexabromocyclododecane: concentrations and isomer profiles from sources to environmental sinks

Concentrations and isomer compositions of hexabromocyclododecane (HBCD) were measured in six matrices in the Czech Republic (HBCD technical mixture; consumer products; indoor and outdoor air at industrial, urban and background locations; soils; and sediments) to provide insight into changes in concentrations and isomer profiles between environmental sources and environmental sinks. A distinct gradient of air concentrations was observed, from 1600 ng/m³ in the industrial area to < 10 pg/m³ in urban and background air. Isomer profiles also showed a distinct gradient in air, from 95% γ-HBCD in industrial air to 40% γ-HBCD in background air, suggesting the influence of differential atmospheric transport and phototransformation of γ- to α-HBCD. Concentrations and isomer compositions in consumer products were highly variable and indicated differences between products with intentional addition of HBCD as a flame retardant versus those with HBCD as an impurity, e.g., from recycled plastic. Understanding the isomer-specific environmental distributions and processes remains important for risk assessment and toxicology, considering the continued use of HBCD and the isomer-specific differences in uptake, metabolism, and toxicity, and further, demonstrates the utility of isomer profiles to better understand environmental processes of HBCDs.

Decabromodiphenyl ether exacerbates hyperglycemia in diet-induced obese mice

Decabromodiphenyl ether (decaBDE) is a brominated flame retardant used in plastic and textile articles. It has become a ubiquitous environmental contaminant, however; the relationship between decaBDE and obesity remains to be elucidated. We aimed to clarify if oral decaBDE exposure can be a factor in obesity and its related metabolic dysfuctions. Male C57BL/6 J mice were fed a normal (ND, 9.0 kcal% fat) or high-fat (HFD, 62.2 kcal% fat) diet and treated with decaBDE (the equivalent of three doses of 0, 0.5 (L-DecaBDE), and 10 (H-DecaBDE) μg/kg body weight/day) ad libitum in drinking water from 5 to 20 weeks of age. In HFD-fed mice, decaBDE exposure markedly increased both fasting blood glucose levels compared with vehicle exposure, which was more prominent in H-DecaBDE-exposed mice. DecaBDE exposure significantly reduced mRNA levels of glucose transporter 4 and thyroid hormone receptor alpha in skeletal muscle and mechanistic target of rapamycin complex 2 in brown adipose tissue compared with vehicle exposure under HFD-feeding. The tendency for hyperglycemia and the remarkable activation of insulin signaling pathway-related genes were observed in ND + DecaBDE mice compared to the ND + Vehicle mice. These results demonstrate that decaBDE can contribute to the enhancement of diet-induced hyperglycemia through disruption of glucose homeostasis.

Maternal Transfer of Flame Retardants in Sharks from the Western North Atlantic Ocean

The present work represents a comprehensive study of in utero maternal transfer of legacy and emerging flame retardants (FRs) in marine predators. We analyzed liver tissues from pregnant sharks of five viviparous species, including blacknose shark ( Carcharhinus acronotus; n = 12), blacktip shark ( Carcharhinus limbatus; n = 2), bonnethead ( Sphyrna tiburo; n = 2), Atlantic sharpnose shark ( Rhizoprionodon terraenovae; n = 2), and spinner shark ( Carcharhinus brevipinna; n = 2), as well as their embryos ( n = 84 in total from five species), collected from the western North Atlantic Ocean. Concentrations of frequently detected emerging FRs in adult female blacknose sharks were determined to be 6.1-83.3 ng/g lipid weight (lw) for dechlorane analogues, 2.5-29.8 ng/g lw for tetrabromo- o-chlorotoluene, and nondetection -32.6 ng/g lw for hexabromobenzene. These concentrations were 1-2 orders of magnitude lower than those of legacy polybrominated diphenyl ether flame retardants (85.7-398 ng/g lw). Similar contamination profiles were also found in the other four species, although FR concentrations varied in different species. A total of 21 FRs were commonly found in developing embryos of female sharks from five species, demonstrating maternal transfer in utero. The maternal transfer ratio (i.e., ratio of the mean litter concentration to their mother's concentration) determined in blacknose shark mother/embryo groups for each FR chemical was negatively associated with its octanol-water partition coefficient. Our work lays a solid foundation for future investigation of the underlying mechanisms of in utero transfer and additional physical or chemical factors that affect maternal transfer.

In Vitro Assessment of Activation of Baikal Seal ( Pusa sibirica) Peroxisome Proliferator-Activated Receptor α by Polybrominated Diphenyl Ethers

We investigated the Baikal seal ( Pusa sibirica) peroxisome proliferator-activated receptor α (bsPPARα) transactivation potencies of polybrominated diphenyl ethers (PBDEs) using an in vitro bsPPARα reporter gene assay. BDE47, BDE99, and BDE153 induced bsPPARα-mediated transcriptional activities in a dose-dependent manner. To compare bsPPARα transactivation potencies of PBDEs, perfluorooctanoic acid (PFOA)-based relative potencies (REPs), a ratio of 50% effective concentration of PFOA to the test chemical, were determined. The order of REPs of PBDEs was BDE153 (13) > BDE99 (8.1) > BDE47 (6.6) > PFOA (1.0) > BDE100, BDE154, and BDE183 (not activated). PBDEs with two bromine atoms at the ortho position showed higher bsPPARα transactivation potencies than those with three bromine atoms. Comparison of the lowest-observed-effect concentration in bsPPARα reporter gene assays revealed that BDE99 was 7-fold more potent than CB99, a polychlorinated biphenyl congener with the same IUPAC number, indicating that brominated congeners could more efficiently activate bsPPARα than chlorinated congeners. The REPs of PBDEs for bsPPARα transactivation were approximately 7- to 13-fold higher than those of perfluorochemicals (PFCs), suggesting that the effects of PBDEs on the bsPPARα signaling pathway may be superior to those of PFCs. This study provides the first evidence that PBDE congeners activate PPARα in vitro.

Waterborne exposure to low concentrations of BDE-47 impedes early vascular development in zebrafish embryos/larvae

Polybrominated diphenyl ethers (PBDEs) are persistent flame retardants ubiquitously existing in various environment matrices. In spite of a recent reduction in use according to the phase-out policy, high levels of PBDEs are still found in both environmental and biological samples due to their persistent property and large-scale production over a long history. Developmental toxicity is a major health concern of PBDEs. However, the impact of PBDE exposure on vascular development remains poorly understood. In this study, we investigated the effect of low concentrations of 2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a predominant PBDE congener, in environmental matrices and biota, on early vascular development using zebrafish. Zebrafish embryos were continuously exposed to waterborne BDE-47 at 0.06, 0.2, 0.6 μM starting from 2 h post-fertilization (hpf). Fluorescent images of vasculatures in Tg(kdrl:eGFP) zebrafish were acquired using a confocal microscope. The results indicated that BDE-47 exposure had no effect on hatching rate, survival, body weight, body length or heart rate in the early stage within 72 hpf, whereas zebrafish exposed to BDE-47 exhibited impairments in the growth of multiple types of blood vessels. The percentage of completed intersegmental vessels (ISV) at 30 hpf decreased in embryos treated with BDE-47 in a dose-dependent fashion. BDE-47 exposure led to a slight decrease in the growth of common cardinal vein (CCV), while dramatically hindered CCV remodeling process reflected by the larger CCV area and wider ventral diameter. BDE-47 exposure significantly reduced sub-intestinal vessels (SIV) area as well as the vascularized yolk area in zebrafish larvae at 72 hpf. In addition, the expression of genes related to vascular growth and remodeling was markedly suppressed in BDE-47-exposed zebrafish. These findings demonstrate the adverse effects of BDE-47 on early vascular development, and confirm the vascular toxicity of PBDEs in vivo. The results indicate that developing vasculature in zebrafish is sensitive to BDE-47 exposure, and may serve as a powerful tool for the assessment of early exposure to PBDEs.

Factors influencing risk assessments of brominated flame-retardants; evidence based on seafood from the North East Atlantic Ocean

Brominated flame-retardants (BFRs) such as polybrominated diphenyl ethers (PBDE) and hexabromocyclododecane (HBCD) are considered hazardous to human health. Due to their persistence, they are still present in the environment and in biota and seafood is major contributor of BFRs to human exposure. Here, we used data from >9700 samples of wild and farmed fish, fish feed and fish feed ingredients collected from the North Atlantic between 2006 and 2016 aiming to investigate factors influencing the risk assessments of BFRs. Due to most representative number of analyses, PBDEs were the main focus of investigation. Mean ∑PBDE in fillet samples ranged from below quantification in Atlantic cod fillet to 2.0 μg kg^-1 in Atlantic halibut. The main congener contributing to the ∑PBDE in all species was BDE 47. Factors affecting the level of BFR in seafood were multifaceted, and the levels were within species mainly determined by fish age, geographical origin and time of sampling. BDE 47, 99, 153 and HBCD were selected for margin of exposure (MOE) evaluation. When other sources of BFR than seafood were excluded, our risk assessment showed low risk at the current dietary intake of seafood. However, the dietary intake of BDE 99 may be of concern for toddlers when all sources are considered. The choice of fish species, dietary studies, choice of statistics, as well as exposure from other sources than seafood, were all factors that influenced the final MOE of BFRs. We propose the use of regression on order statistics as a tool for risk assessment, to illustrate means and spreads in large surveillance datasets to avoid the issue of measurements below the limit of quantification. A harmonized, updated evaluation of the risk associated with exposure to BFRs from diet, air and dust is warranted, where the fish species most commonly consumed also is taken into consideration.

Chronic toxicity of hexabromocyclododecane(HBCD) induced by oxidative stress and cell apoptosis on nematode Caenorhabditis elegans

In order to gain insights into the chronic effects and mechanisms of hexabromocyclododecane (HBCD), the animal model Caenorhabditis elegans (C. elegans) was chosen for toxicity study. Multiple endpoints, including the physiological (growth and locomotion behaviors), biochemical (reactive oxygen species (ROS) production, lipofuscin accumulation, and cell apoptosis), and molecular (stress-related gene expressions) levels, were tested by chronic exposure for 10 d to low concentrations of HBCD (0.2 nM-200 nM). The results revealed that chronic exposure to HBCD at concentrations more than 20 nM would significantly influence the growth, locomotion behaviors, ROS formation, lipofuscin accumulation, and cell apoptosis of nematodes. Treatment with antioxidants of ascorbate and N-acetyl-l-cysteine (NAC) suppressed the toxicity induced by HBCD. The integrated gene expression profiles showed that the chronic exposure to 200 nM of HBCD significantly increased the expression levels of stress-related genes (e.g., hsp-16.2, hsp-16.48, sod-1, sod-3, and cep-1 genes). Among these genes, the sod-1, sod-3, and cep-1 gene expressions were significantly correlated with HBCD-induced physiological effects by the Pearson correlation test. The mutations of sod-3 and cep-1 induced more severe toxicity compared to wild-type nematodes. Therefore, HBCD exposure induced oxidative stress by ROS accumulation and cell apoptosis, which resulted in HBCD-induced toxicity on nematodes, and sod-3 and cep-1 played important roles in protecting nematodes against HBCD-induced toxicity.

Polybrominated diphenyl ethers and perfluorinated alkyl substances in blood serum of New Zealand adults, 2011-2013

A national survey was conducted in 2011-2013 to assess serum concentrations of brominated flame retardants (BFRs) and perfluorinated alkyl substances (PFASs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 geographic regions, 2 ethnic groups (Māori/non-Māori) and sex. Eligible participants (n = 734; response rate of contacted individuals = 37%) donated up to 30 mL of blood, after which serum was pooled (49 pools for BFRs, 63 pools for PFASs) according to demographic strata. BFRs were analysed by GC-HRMS and PFASs by LC-MS/MS. Associations between serum BFRs and PFASs and demographic variables (age, region, ethnicity, sex) were assessed using regression analysis. The weighted geometric mean (GM) serum concentrations of BDE47, BDE99, BDE100, and BDE153 were 2.0, 0.66, 0.43, and 1.2 ng/g lipid, respectively. The weighted geometric mean (GM) serum concentrations of PFOS, PFOA, PFHxS, and PFNA were 3.4, 2.4, 1.0, and 0.66 ng/mL, respectively. The majority of BFRs showed higher serum concentrations in younger age groups. Conversely, the four PFASs showed higher serum concentrations in older age groups. Concentrations of BFRs and PFASs were generally lower in females compared to males. In New Zealand, both age and sex are important determinants of BFR and PFAS serum concentrations.

Elucidating the Variability in the Hexabromocyclododecane Diastereomer Profile in the Global Environment

Hexabromocyclododecane (HBCDD) is a hazardous flame retardant subject to international regulation. Whereas γ-HBCDD is a dominant component in the technical HBCDD mixture, the diastereomer profile in environmental samples shows substantial temporal and spatial variations, ranging from γ- to α-HBCDD-dominant. To explain such variability, we simulate the global emissions and fate of HBCDD diastereomers, using a dynamic substance flow analysis model (CiP-CAFE) coupled to a multimedia environmental fate model (BETR-Global). Our modeling results indicate that, as of 2015, 340-1000 tonnes of HBCDD have been emitted globally, with slightly more γ-HBCDD (50%-65%) than α-HBCDD (30%-50%). Emissions of γ-HBCDD primarily originate from production and other industrial processes, whereas those of α-HBCDD are mainly associated with the use and end-of-life disposal of HBCDD-containing products. Presently, α-HBCDD dominates the contamination in the air of populated areas, while γ-HBCDD is more abundant in remote background areas and in regions with HCBDD production and processing facilities. Globally, the relative abundance of α-HBCDD is anticipated to increase after production of HBCDD is banned. Due to isomerization, α-HBCDD accumulates to a larger extent than γ-HBCDD in Arctic surface media. Since α-HBCDD is more persistent and bioaccumulative than other diastereomers, isomerization has bearing on the potential environmental and health impacts on a global scale.

Brominated flame retardants: Recommendation for different listing under the Hong Kong Convention

When the Hong Kong International Convention for the Safe and Environmentally Sound Recycling of Ships, 2009 enters into effect, ships to be sent for recycling will be required to carry an Inventory of Hazardous Materials (IHM) on board, which identifies the hazardous materials contained in the ship's structure or equipment. In its current form, IHM covers two classes of brominated flame retardants (BFRs), namely polybrominated biphenyls and polybrominated diphenyl ethers. Emerging evidence from recent literature suggests that members of all classes of BFRs are present in all environmental compartments and that exposure to them is associated with a wide range of harmful effects in humans and animals, effects that include endocrine disruption. Despite a growing body of research, the necessary data to perform health and environmental risk assessment are still lacking. This paper reviews environmental and human health impacts and discusses some issues of BFR environmental management. It is suggested that based on a precautionary approach, the inclusion of all classes of BFRs in IHM is warranted.

Responses of antioxidant and biotransformation enzymes in Carassius carassius exposed to hexabromocyclododecane

The ubiquitous existence of hexabromocyclododecane (HBCD) in environmental matrices has made it attractive to both field investigators as well as laboratory researchers. However, literature on the biological effects caused by HBCD on aquatic vertebrates seldom exist. This has inevitably increased the difficulty of toxicological assessment in the aquatic environment. Juvenile crucian carp (Carassius carassius) were exposed (flow-through) to different concentrations of technical HBCD (nominal 2, 20, 200 μg L^-1) for 7 days to determine the responses of antioxidant and biotransformation enzymes. HBCD was found to be increasingly bioconcentrated in the fish livers as time proceeds. Also, the contribution of α-HBCD exhibited an enhancement from 13% in the exposure solutions to 24% in crucian carp, still much lower than in wild fishes (ca. 80%). HBCD induced activities of antioxidant enzymes in most cases, as well as increased level of lipid peroxidation. In contrast to the weak response of 7-ethoxyresorufin-O-deethylase (EROD), 7-pentoxyresorufin-O-depentylase (PROD) activity was generally induced in a time-dependent manner with peaks at day 2. Phase II enzyme Glutathione-S-transferase (GST) showed a dose-dependent induction with maximums in the 20 μg L^-1 treatment at all the four timepoints of 1, 2, 4 and 7 days. Some enzymatic responses showed good associations, indicating coordinated functions. To sum up, tHBCD exposure in the present circumstance had produced an ecological stress to crucian carp. The low levels of biotransformation and slow rates of bioisomerization suggest a possible long-term toxic effect, especially around HBCD point sources.

Dermal contact with furniture fabrics is a significant pathway of human exposure to brominated flame retardants

Despite extensive application in consumer products and concerns over their adverse health effects, how external exposure to brominated flame retardants (BFRs) contributes to their human body burdens is not yet fully understood. While recent studies focused on inadvertent indoor dust ingestion and diet as potential major pathways of exposure, dermal uptake has been largely overlooked. We provide the first experimentally-based assessment of dermal uptake of BFRs via contact with indoor dust and flame-retarded furniture fabrics. Results reveal substantial uptake from furniture fabrics (e.g. 8.1 ng pentaBDE/kg bw/day for adults in summer), exceeding the overall adult intake of pentaBDE estimated previously via other exposure pathways. For HBCDs, despite the low absorption fraction (<2.5%) from the studied fabrics, the estimated dermal uptake of UK adults and toddlers (101 and 76.9 ng/kg bw/day) exceed the reported average daily intakes of 7.9 and 43.0 ng/kg bw/day for these UK age groups. Conversely, uptake from dust was low (0.05 and 0.19 ng pentaBDE/kg bw/day for adults and toddlers, respectively), indicating previous pharmacokinetic approaches may have overestimated the significance of this route. Future exposure and risk assessment studies should consider dermal contact with treated products as a significant pathway of human exposure to BFRs and related chemicals.

Assessment of POPs in air from Spain using passive sampling from 2008 to 2015. Part I: Spatial and temporal observations of PBDEs

The Stockholm Convention (SC) on Persistent Organic Pollutants (POPs) calls for the Parties' effectiveness evaluation of those measures taken to meet the reduction and eventual elimination of POPs from the environment. With that goal, air concentrations of different POP families have been measured uninterruptedly since 2008 under the Spanish Monitoring Program (SMP) by means of passive air sampling. This work focuses on data for polybrominated diphenyl ethers (PBDEs) determined in a total of 321 samples collected seasonally each year in 5 urban and 7 background sites. Neither significant temporal trends nor significant seasonal variations for total PBDE air burdens were detected. In contrast, significant variations were found among PBDE congeners. Those related to the octa-PBDE formulation significantly decreased in the study period. However, PBDEs related to the penta-formulation showed steady concentrations while PBDE-209, the congener found at the greatest levels, showed increasing or steady levels in most sampling sites. Seasonal variations were also markedly different among congeners. Concentrations of the lightest PBDEs (tri- to penta-substituted) were highly influenced by ambient temperature (T), showing maximum values in summer probably due to higher volatilization rates compared to those of heavier PBDEs. Contrarily, no clear seasonal trends were found for hexa- to deca-PBDEs, which were negatively related to precipitation; thereby, indicating an efficient atmospheric wash out by wet deposition episodes. Regarding spatial patterns, overall significant greater PBDE levels were found in cities compared to background areas, pointing out the role of highly populated areas as sources for these pollutants in Spain. Yet and especially in the case of PBDE-209, our results suggested the presence of significant unknown sources of PBDEs in some background sites. Further monitoring efforts are needed to assess potential unknown sources in the sampling network as well as to ensure temporal trends of these pollutants in Spain.

Spatial Distribution of Novel and Legacy Brominated Flame Retardants in Soils Surrounding Two Australian Electronic Waste Recycling Facilities

Informal recycling of electronic waste (e-waste) has been shown to cause significant brominated flame retardant (BFR) contamination of surrounding soils in a number of Asian and West African countries. However, to the authors' knowledge, there have been no published studies demonstrating polybrominated diphenyl ether (PBDE) and novel brominated flame retardant (NBFR) soil contamination from regulated "formal" e-waste processing facilities in developed countries. This study reports on PBDEs (-28, -47, -99, -100, -153, -154, -183, and -209) and NBFRs (PBT, PBEB, HBB, EH-TBB, BTBPE and DBDPE) in 36 soil samples surrounding two Australian e-waste recycling plants and a further eight reference soils. Overall ∑PBDE concentrations ranged 0.10-98 000 ng/g dw (median; 92 ng/g dw) and ∑NBFRs ranged ND-37 000 ng/g dw (median 2.0 ng/g dw). Concentrations in soils were found to be significantly negatively associated with distance from one of the e-waste facilities for ∑penta-BDEs, BDE-183, BDE-209, and ∑NBFR compound groups. ANOVA tests further illustrated the potential for e-waste recycling to significantly elevate concentrations of some BFRs in soils over distances up to 900 m compared to references sites. This study provides the first evidence of soil contamination with PBDEs and NBFRs originating from formal e-waste recycling facilities in Australia, which may have implications for e-waste recycling practices throughout the world.

Stereoisomer-Specific Trophodynamics of the Chiral Brominated Flame Retardants HBCD and TBECH in a Marine Food Web, with Implications for Human Exposure

Stereoisomers of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) were determined in sediments and 30 marine species in a marine food web to investigate their trophic transfer. Lipid content was found to affect the bioaccumulation of ΣHBCD and ΣTBECH in these species. Elevated biomagnification of each diastereomer from prey species to marine mammals was observed. For HBCD, biota samples showed a shift from γ- to α-HBCD when compared with sediments and technical mixtures; trophic magnification potential of (-)-α- and (+)-α-HBCD were observed in the food web, with trophic magnification factors (TMFs) of 11.8 and 8.7, respectively. For TBECH, the relative abundance of γ- and δ-TBECH exhibited an increasing trend from abiotic matrices to biota samples; trophic magnification was observed for each diastereomer, with TMFs ranging from 1.9 to 3.5. The enantioselective bioaccumulation of the first eluting enantiomer of δ-TBECH in organisms at higher TLs was consistently observed across samples. This is the first report on the trophic transfer of TBECH in the food web. The estimated daily intake of HBCD for Hong Kong residents was approximately 16-times higher than that for the general population in China, and the health risk to local children was high, based on the relevant available reference dose.

Emissions of selected brominated flame retardants from consumer materials: the effects of content, temperature, and timescale

The ubiquitous presence of brominated flame retardants (BFRs) in indoor air, dust, and even in human tissue could be attributed to their emissions from BFR-containing products. Nevertheless, the emission behavior of BFRs, especially novel BFRs from consumer materials, to the indoor environment has still not been well understood. To evaluate the effects of chemical content, temperature, and time on the emissions of BFRs, we used a batch of small glass chambers to conduct emission tests on carpet, computer casings, sound insulation, circuit boards, decorative laminate, and PVC floors at temperatures from 20 to 80 °C, as well as different emission times of up to 35 days. Seven BFRs were extracted from the tested materials with contents ranging from 50 to 35,803 μg g^-1, and four BFRs were detected with emission rates between 5.9 and 418 pg g^-1 h^-1 at room temperature (20 °C); 1,2,5,6,9,10-hexabromocyclododecane (HBCD) was considered to be the dominant compound, which was found in and could be emitted from all of the tested materials. Emission rates are significantly and positively correlated with both the contents of tested materials and the elevated temperature. These results indicate that BFR-containing products have the potential to be a major source of indoor contamination.

Diastereoisomer-Specific Biotransformation of Hexabromocyclododecanes by a Mixed Culture Containing Dehalococcoides mccartyi Strain 195

Hexabromocyclododecane (HBCD) stereoisomers may exhibit substantial differences in physicochemical, biological, and toxicological properties. However, there remains a lack of knowledge about stereoisomer-specific toxicity, metabolism, and environmental fate of HBCD. In this study, the biotransformation of (±)α-, (±)β-, and (±)γ-HBCD contained in technical HBCD by a mixed culture containing the organohalide-respiring bacterium Dehalococcoides mccartyi strain 195 was investigated. Results showed that the mixed culture was able to efficiently biotransform the technical HBCD mixture, with 75% of the initial HBCD (∼12 μM) in the growth medium being removed within 42 days. Based on the metabolites analysis, HBCD might be sequentially debrominated via dibromo elimination reaction to form tetrabromocyclododecene, dibromocyclododecadiene, and 1,5,9-cyclododecatriene. The biotransformation of the technical HBCD was likely diastereoisomer-specific. The transformation rates of α-, β-, and γ-HBCD were in the following order: α-HBCD > β-HBCD > γ-HBCD. The enantiomer fractions of (±)α-, (±)β-, and (±)γ-HBCD were maintained at about 0.5 during the 28 days of incubation, indicating a lack of enantioselective biotransformation of these diastereoisomers. Additionally, the amendment of another halogenated substrate tetrachloroethene (PCE), which supports the growth of strain 195, had a negligible impact on the transformation patterns of HBCD diastereoisomers and enantiomers. This study provided new insights into the stereoisomer-specific transformation patterns of HBCD by anaerobic microbes and has important implications for microbial remediation of anoxic environments contaminated by HBCD using the mixed culture containing Dehalococcoides.

The influence of microplastics and halogenated contaminants in feed on toxicokinetics and gene expression in European seabass (Dicentrarchus labrax)

When microplastics pollute fish habitats, it may be ingested by fish, thereby contaminating fish with sorbed contaminants. The present study investigates how combinations of halogenated contaminants and microplastics associated with feed are able to alter toxicokinetics in European seabass and affect the fish. Microplastic particles (2%) were added to the feed either with sorbed contaminants or as a mixture of clean microplastics and chemical contaminants, and compared to feed containing contaminants without microplastics. For the contaminated microplastic diet, the accumulation of polychlorinated biphenyls (PCBs) and brominated flame retardants (BFRs) in fish was significantly higher, increasing up to 40 days of accumulation and then reversing to values comparable to the other diets at the end of accumulation. The significant gene expression results of liver (cyp1a, il1β, gstα) after 40 days of exposure indicate that microplastics might indeed exacerbate the toxic effects (liver metabolism, immune system, oxidative stress) of some chemical contaminants sorbed to microplastics. Seabass quickly metabolised BDE99 to BDE47 by debromination, probably mediated by deiodinase enzymes, and unlike other contaminants, this metabolism was unaffected by the presence of microplastics. For the other PCBs and BFRs, the elimination coefficients were significantly lower in fish fed the diet with contaminants sorbed to microplastic compared to the other diets. The results indicate that microplastics affects liver detoxification and lipid distribution, both of which affect the concentration of contaminants.

Complete genome sequence of Bacillus sp. HBCD-sjtu, an efficient HBCD-degrading bacterium

Environmental pollution caused by the release of industrial chemicals is currently one of the most important environmental harms. Manufacturing chemicals can be biodegraded, and valuable intermediates can be used as pharmacophores in drug targeting and have several other useful purposes. Hexabromocyclododecane (HBCD), a non-aromatic brominated flame retardant, is a toxic compound that consists of a cycloaliphatic ring of 12 carbon atoms to which six bromine atoms are attached. It is formed by bromination of cis-trans-trans-1,5,9-cyclododecatriene, but its use is now restricted in several countries, because it is an environmental pollutant. Little is known about whether bacteria can degrade HBCD. A bacterial strain that degrades HBCD was recently isolated using enrichment culture techniques. Based on morphological, biochemical and phylogenetic analysis this isolate was categorized as Bacillus cereus and named strain HBCD-sjtu. Maximum growth and HBCD-degrading activity were observed when this strain was grown at 30 °C, pH 7.0 and 200 RPM in mineral salt medium containing 0.5 mm HBCD. The genome of strain HBCD-sjtu, which consists of only one circular chromosome, was sequenced. This whole genome sequence will be crucial for illuminating the molecular mechanisms of HBCD degradation.

Application of triolein-embedded cellulose acetate membrane (TECAM) passive sampler to study phase distribution of hexabromocyclododecanes (HBCDs) in sediment

Hexabromocyclododecanes (HBCDs) are a class of widely used brominated flame retardants (BFRs) that exhibit strong hydrophobicity. The ubiquity and persistence of HBCDs in sediment have attracted significant attention because of public health concerns. The environmental fate and ecological risks of HBCDs closely depend on their phase distribution in sediments. However, little information is available regarding the freely dissolved concentrations (C_free) of HBCDs in sediment porewater. In this study, we developed a method to measure C_free of HBCDs in sediment porewater using triolein-embedded cellulose acetate membranes (TECAM). The TECAM-to-water partitioning coefficient (log K_TECAM) was 4.69, 4.77, and 4.63 for α-HBCD, β-HBCD, and γ-HBCD, respectively. In sediments, HBCDs sorbed to the sediment solid phase accounted for more than 99% of the total chemical mass. The dissolved organic carbon (DOC)-water partition coefficient (K_DOC) values were derived from TECAM measurements, and the log K_DOC values ranged from 5.77 to 6.23 for the three HBCD diastereomers, suggesting a strong tendency for HBCDs to sorb to DOC. The high sorption of HBDCs for DOC implies a potential for DOC-facilitated transport which may enhance the environmental mobility of HBCDs.

Organohalogen contaminants in common loons (Gavia immer) breeding in Western Alberta, Canada

We examined the influence of biological and geographical factors on the levels and patterns of organohalogen contaminants in blood of adult common loons (Gavia immer) collected from 20 lakes in Alberta, Canada. The loons were captured in the 2006 and 2007 breeding seasons over a 900 m elevation gradient across the eastern slope of the Canadian Rocky Mountains. While PCBs dominated the composition of these contaminants in loons at all sites (∑PCBs > p,p'-DDE > ∑PBDEs > ∑Chlordanes > HCB), p,p'-DDE and ∑PBDEs were also important, averaging approximately 50% and 20% of total PCB concentrations, respectively. ∑PCBs and ∑PBDEs were higher in males than in females. Inter-lake variation was apparent for contaminant concentrations and patterns and were largely explained by dietary signatures (δ¹⁵N and δ¹³C) and proximity to a large hydroelectric dam. Mean ∑PCB (19.6 ng/g wet weight (ww)) and organochlorine pesticide (OCP) (p,p'-DDE: 11.8 ng/g, cis-nonachlor: 0.10 ng/g, trans-nonachlor: 0.32 ng/g, HCB: 0.34 ng/g ww) concentrations in loons were approximately 4- to 17-fold lower than average concentrations reported in common loons from Atlantic Canada and were well below concentrations which have been associated with impaired reproductive success and eggshell thinning in other piscivorous birds. Dominant PBDE congeners were BDE47, BDE99, and BDE100. The regional mean for ∑PBDEs (4.04 ng/g ww) in loons from the present study was within the range reported for ∑PBDEs in nestling bald eagle plasma from British Columbia. This is the first report of PBDEs in loons and the first report of PCBs and OCPs in common loons from Western North America.

Polybrominated diphenyl ethers (PBDEs) in car and house dust from Thailand: Implication for human exposure

This study examines concentrations of tri- to hexa-bromodiphenylethers (BDEs 17, 28, 47, 49, 66, 85, 99, 100, 153 and 154; Σ₁₀PBDEs (polybrominated diphenyl ethers)) in car (n = 30) and house dust samples (n = 53) collected from different provinces in Thailand. The specific objectives of this study were: (i) to monitor levels of tri- to hexa-bromodiphenylethers (BDEs 17, 28, 47, 49, 66, 85, 99, 100, 153 and 154; Σ₁₀PBDEs) in vehicle and residential dust sampled from various provinces in Thailand; (ii) to compare PBDE concentrations with those detected for domestic and automobile dust in studies from other countries and (iii) to estimate exposure of the Thai population to the target PBDEs via dust ingestion. Levels of Σ₁₀PBDEs in vehicle and domestic dust were 0.68-38 and 0.59-260 ng g^-1, respectively. BDEs 99 and 47 were the most abundant congeners in all automobile and residential dust samples. A t-test analysis indicated that Σ₁₀PBDE concentrations in dust samples from dwellings exceeded significantly those from cars (p = 0.001). Furthermore, contents in dust of all PBDEs studied, except for BDE-28, were significantly higher in homes than in vehicles (p = 0.000-0.004). Principal Component Analysis (PCA) demonstrated no differences in PBDE congener patterns between Thai house and automobile dust, but revealed some subtle differences in the congener pattern between household dust samples in Thailand and those reported previously for the United Kingdom. Estimated environmental exposure of Thai adults and children for BDE-99 via dust ingestion were well within a chronic oral reference dose (RfD) for BDE-99 (100 ng/kg bw/day) proposed by the United States Environmental Protection Agency (US EPA).

Isomer-Specific Hexabromocyclododecane (HBCDD) Levels in Top Predator Fish from Across Canada and 36-Year Temporal Trends in Lake Ontario

Hexabromocyclododecane (HBCDD) is a high concern environmental pollutant due to its persistent, bioaccumulative, and toxic properties. The spatial distribution of HBCDD was investigated in top predator fish (lake trout, walleye, or brook trout) collected in 2013 ( n = 165) from 19 sampling sites and in 2015 ( n = 145) from 20 sites across Canada. HBCDD was measurable in at least one sample at each sampling site regardless of sampling year with the exception of walleye from the south basin of Lake Winnipeg (2013). Sampling sites in or near the Laurentian Great Lakes had greater ΣHBCDD concentrations compared to locations to the west or east. The greatest mean ΣHBCDD concentration was 72.6 ng/g lw in fish from Lake Huron-Goderich (2015). Regardless of the sampling sites, α-HBCDD was the dominant congener followed by γ-HBCDD, whereas β-HBCDD was barely detectable. In fish from the same waterbody there were comparable α/γ isomer concentration ratios. The greatest ratio was 20.8 in fish from Lake Ontario, whereas the lowest ratio was 6.3 for fish from Lac Memphrémagog (Québec) likely related to more recent emissions of a technical HBCDD mixture. Temporal trends of HBCDD in lake trout from Lake Ontario showed a significant decreasing trend for γ-HBCDD with a half-life estimate of 10 years over a 36-year period (1979-2015), and for α-HBCDD with a half-life of 11 years over the years of 2008 to 2015. The proportion of α-HBCDD to ΣHBCDD increased significantly during 1979 to 2015. The present study provided novel information on the isomer-specific HBCDDs in Canada freshwater fish.

The effect of zerovalent iron on the microbial degradation of hexabromocyclododecane

Hexabromocyclododecane (HBCD), a commonly used brominated flame retardant (BFR), has been listed as a persistent organic pollutant (POP). In order to remediate HBCD in the environment, the influence of microscale zerovalent iron (MZVI) on the HBCD degrading microcosm was evaluated. In the acclimated microcosm collected from river sediment, 49% of HBCD was initially removed through adsorption and then 30% of HBCD was biodegraded through non-debromination processes. In contrast to MZVI only, over 60% of HBCD was gradually degraded by MZVI through a debromination reaction. In the microcosm-MZVI combined system, the biodegradation ability of the microcosm was inhibited. The aqueous chemistry was changed by the addition of MZVI, which led to the alteration of microbial composition and biodegradation ability. These better understandings can facilitate an evaluation of the impact of MZVI on HBCD biodegradation when ZVI was used to remediate this BFR.

Photodegradation of 2,4,4'-tribrominated diphenyl ether in various surfactant solutions: kinetics, mechanisms and intermediates

Currently, photodegradation has been proven to be an important way of eliminating polybrominated diphenyl ethers (PBDEs) from the environment. However, the mechanism of PBDE photodegradation in surfactants by UV light is still unclear. In this study, 2,4,4'-tribrominated diphenyl ether (BDE-28) was selected as the target pollutant to investigate the photodegradation of PBDEs in Triton X-100 (TX-100), sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) solutions. All photolysis experiments were performed above the critical micelle concentration (CMC). The results showed that photodebromination was the major pathway of BDE-28 photodestruction in different surfactants. From 1.5 CMC to 4 CMC, the photodegradation rates of BDE-28 increased as the concentration of TX-100 increased, and the increased concentration of SDBS has a negative effect on the photodegradation rate of BDE-28 due to the light barrier of SDBS. There was no obvious change in the case of CTAB. BDE-28 was debrominated to 4,4'-dibrominated diphenyl ether (BDE-15), 4-dibrominated diphenyl ether (BDE-3) and diphenyl ether (DE), subsequently. In addition, 2,8-dibrominated dibenzofuran (2,8-BDF), 2-monobrominated dibenzofuran (2-monoBDF), and dibenzofuran (DF) were produced via an intramolecular elimination of HBr from the PBDEs that had an ortho-bromine substituent. Moreover, DF can also be formed from DE and the generated amount of DF in CTAB was higher than that generated in SDBS and TX-100. We have also detected ortho-hydroxydiphenyl and para-hydroxydiphenyl during the photodegradation process.