Complex Mixtures of Brominated/Chlorinated Diphenyl Ethers and Dibenzofurans in Soils from the Agbogbloshie e-Waste Site (Ghana): Occurrence, Formation, and Exposure Implications

Characterizing organophosphate esters and chlorinated paraffins in surface soils affected by diverse e-waste disassembling process in South China: Occurrence, distinct emission, and risk assessment

E-waste recycling activities are a crucial emission source of organic pollutants, posing potential risks to the surrounding environment and human health. To understand the potential impact related to diverse e-waste dismantling activities, we investigated two categories of popular flame retardants (i.e., organophosphate esters (OPEs) and chlorinated paraffins (CPs) and their resultant possible ecological risk in 53 surface soil samples from Qingyuan, a well-known e-waste recycling region in South China. Varied concentrations of ΣOPEs (20.5-8720 ng/g) and ΣCPs (920-16800 ng/g) were observed at diverse dismantling sites, while relatively low levels of ΣOPEs (6.13-1240 ng/g) and ΣCPs (14.8-2870 ng/g) were found in surrounding soils. These results indicated that primitive e-waste dismantling processes were the primary emission source of OPEs and CPs in the studied area, with e-waste dumping and manual dismantling being the most important emission sources for OPEs and CPs. More importantly, CPs could be degraded/transformed into more toxic intermediates via dechlorination and decarbonization during the burning of e-waste. Furthermore, our results indicated the potential ecological risks posed by OPEs and CPs related to e-waste recycling.

Uptake, Elimination and Metabolism of Brominated Dibenzofurans in Mice

Polybrominated dibenzofurans (PBDFs) are major brominated dioxins in the environment, but information on their bioaccumulation potential and toxicokinetics is limited. This study conducted oral exposure experiments with C57BL/6J mice to investigate the uptake ratios, distribution in the liver, plasma and brain, metabolism, and elimination kinetics of four bromine/chlorine-substituted dibenzofurans (TrBDF: 2,3,8-tribromo, TeBDF: 2,3,7,8-tetrabromo, PeBDF: 1,2,3,7,8-pentabromo, TrBCDF: 2,3,7-tribromo-8-chloro) in comparison with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The hepatic uptake ratios of 2,3,7,8-substituted dibenzofurans were lower than that of TCDD (up to 84% of the administered doses) and decreased with the number of Br substitutions (42%, 33%, and 29% for TrBCDF, TeBDF, and PeBDF, respectively). The brain uptake ratios of these dibenzofurans were less than 0.05%, and the plasma-to-brain transfer ratio also decreased with the Br number. All 2,3,7,8-substituted compounds were eliminated from the liver following first-order kinetics, with half-times in the order of TrBCDF (5.6 days) < TeBDF (8.8 days) ≈ TCDD (8.7 days) < PeBDF (13 days). The non-2,3,7,8-substituted TrBDF was poorly retained in the liver (<0.01% of the dose at 1 day) and rapidly eliminated following two-phase kinetics. All dibenzofurans were metabolised into monohydroxylated products in the liver, but the contribution of this metabolic pathway to hepatic elimination was only significant for TrBDF. As the toxic effects of dioxin-like compounds are influenced by their biological persistence, the slow elimination of TrBCDF, TeBDF, and PeBDF observed in this study suggests that exposure risk of brominated dibenzofurans may be underestimated using the toxic equivalency factors of the less persistent chlorinated analogues.

Br-to-Cl Transformation Guided the Formation of Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans

Polyhalogenated dibenzo-p-dioxins/dibenzofurans (PXDD/Fs) are commonly released into the environment as byproducts of combustion processes, accompanied by flue gases. Chlorinated (Cl) and brominated (Br) precursors play crucial roles in forming PXDD/Fs. However, the specific contributions of Cl-precursors and Br-precursors to PXDD/Fs formation have not been fully elucidated. Herein, we demonstrate that the formation of Br-precursors can increase the fraction of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) congeners substituted at specific positions, such as 1,2,3,4,6,7,8-HpCDD, OCDD, 2,3,4,7,8-PeCDF, and 2,3,4,6,7,8-HxCDF. This is attributed to the electrophilic chlorination reaction of the Br-precursors, which includes the Br-to-Cl transformation pathway, following the principle of regioselectivity. The observed formation of polybrominated/chlorinated dibenzo-p-dioxins/benzofurans (PBCDD/Fs) from 1,2-dibromobenzene (1,2-DiBBz) as a Br precursor provides direct evidence supporting the proposed Br-to-Cl transformation. Quantum chemical calculations are employed to discuss the principle of regioselectivity in the Br-to-Cl transformation, clarifying the priority of the position for electrophilic chlorination. Additionally, the concentration of PCDD/Fs formed from 1,2-DiBBz is 1.6 μg/kg, comparable to that of polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) (2.4 μg/kg), highlighting the potential of brominated organic pollutants as precursors for PCDD/Fs formation. This study provides three potential pathways for PCDD/Fs formation from Br-precursors, establishing a theoretical foundation for elucidating the formation mechanism of PXDD/Fs in the coexistence of Cl and Br.

Occurrence and ecotoxicological impacts of polybrominated diphenyl ethers (PBDEs) in electronic waste (e-waste) in Africa: Options for sustainable and eco-friendly management strategies

Polybrominated diphenyl ethers (PBDEs) are persistent contaminants used as flame retardants in electronic products. PBDEs are contaminants of concern due to leaching and recalcitrance conferred by the stable and hydrophobic bromide residues. The near absence of legislatures and conscious initiatives to tackle the challenges of PBDEs in Africa has allowed for the indiscriminate use and consequent environmental degradation. Presently, the incidence, ecotoxicity, and remediation of PBDEs in Africa are poorly elucidated. Here, we present a position on the level of contamination, ecotoxicity, and management strategies for PBDEs with regard to Africa. Our review shows that Africa is inundated with PBDEs from the proliferation of e-waste due to factors like the increasing growth in the IT sector worsened by the procurement of second-hand gadgets. An evaluation of the fate of PBDEs in the African environment reveals that the environment is adequately contaminated, although reported in only a few countries like Nigeria and Ghana. Ultrasound-assisted extraction, microwave-assisted extraction, and Soxhlet extraction coupled with specific chromatographic techniques are used in the detection and quantification of PBDEs. Enormous exposure pathways in humans were highlighted with health implications. In terms of the removal of PBDEs, we found a gap in efforts in this direction, as not much success has been reported in Africa. However, we outline eco-friendly methods used elsewhere, including microbial degradation, zerovalent iron, supercritical fluid, and reduce, reuse, recycle, and recovery methods. The need for Africa to make and implement legislatures against PBDEs holds the key to reduced effect on the continent.

Environmental Injustice and Electronic Waste in Ghana: Challenges and Recommendations

Electronic waste (e-waste) or discarded electronic devices that are unwanted, not working, or have reached their end of life pose significant threats to human and environmental health. This is a major concern in Africa, where the majority of e-waste is discarded. In the year 2021, an estimated 57.4 million metric tons of e-waste were generated worldwide. Globally, COVID-19 lockdowns have contributed to increased e-waste generation. Although Africa generates the least of this waste, the continent has been the dumping ground for e-waste from the developed world. The flow of hazardous waste from the prosperous 'Global North' to the impoverished 'Global South' is termed "toxic colonialism". Agbogbloshie, Ghana, an e-waste hub where about 39% of e-waste was treated, was listed among the top 10 most polluted places in the world. The discard of e-waste in Ghana presents an issue of environmental injustice, defined as the disproportionate exposure of communities of color and low-income communities to pollution, its associated health and environmental effects, and the unequal environmental protection provided through policies. Despite the economic benefits of e-waste, many civilians (low-income earners, settlers, children, and people with minimal education) are exposed to negative health effects due to poverty, lack of education, and weak regulations. We critically examine the existing literature to gather empirical information on e-waste and environmental injustice. Comprehensive policies and regulations are needed to manage e-waste locally and globally.

Cracked and shucked: GC-APCI-IMS-HRMS facilitates identification of unknown halogenated organic chemicals in French marine bivalves

High resolution mass spectrometry (HRMS)-based non-target analysis coupled with ion mobility spectrometry (IMS) is gaining momentum due to its ability to provide complementary information which can be useful in the identification of unknown organic chemicals in support of efforts in unraveling the complexity of the chemical exposome. The chemical exposome in the marine environment, though not as well studied as its freshwater counterparts, is not foreign to chemical diversity specially when it comes to potentially bioaccumulative and bioactive polyhalogenated organic contaminants and natural products. In this work we present in detail how we utilized IMS-HRMS coupled with gas chromatographic separation and atmospheric pressure chemical ionization (APCI) to annotate polyhalogenated organic chemicals in French bivalves collected from 25 sites along the French coasts. We describe how we used open cheminformatic tools to exploit isotopologue patterns, isotope ratios, Kendrick mass defect (Cl scale), and collisional cross section (CCS), in order to annotate 157 halogenated features (level 1: 54, level 2: 47, level 3: 50, and level 4: 6). Grouping the features into 11 compound classes was facilitated by a KMD vs CCS plot which showed co-clustering of potentially structurally-related compounds. The features were semi-quantified to gain insight into the distribution of these halogenated features along the French coast, ultimately allowing us to differentiate between sites that are more anthropologically impacted versus sites that are potentially biodiverse.

Hydrogen-Donor-Controlled Polybrominated Dibenzofuran (PBDF) Formation from Polybrominated Diphenyl Ether (PBDE) Photolysis in Solutions: Competition Mechanisms of Radical-Based Cyclization and Hydrogen Abstraction Reactions

Polybrominated dibenzofurans (PBDFs) are characteristic dioxin-like products of polybrominated diphenyl ether (PBDE) photolysis. In this study, competition mechanisms of radical-based cyclization and hydrogen abstraction reactions are proposed in PBDF formation. Commonly, the ortho C-Br bond dissociation during photolysis generates aryl radicals, which undergo intramolecular cyclization to form PBDFs or hydrogen abstraction with hydrogen donors (such as organic solvents and water) to form lower brominated PBDEs. By using 2,4,4'-tribromodiphenyl ether (BDE-28) as the model reactant, the experimental PBDF formation ratios in various solutions are explained quantitatively by the calculated rate constants of cyclization and hydrogen abstraction reactions using the density functional theory (DFT) method. The solvent effect of pure and mixed solvents on PBDF formation is illustrated successfully. The structure-related hydrogen donation ability for hydrogen abstraction controls the bias of competition reactions and influences PBDF formation. Water resulted to be the most significant generation of PBDFs. Fulvic and humic acid display higher hydrogen donation ability than small-molecule organics due to the partitioning effect in aqueous solution. Quantitative structure-activity relationship (QSAR) models of the calculated rate constants for 512 cyclization and 319 hydrogen abstraction reactions using 189 PBDEs as the initial reactants in water are established, revealing the high risk of PBDF formation in aqueous solution.

Framework of the Integrated Approach to Formation Mechanisms of Typical Combustion Byproducts─Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans (PXDD/Fs)

Understanding the mechanisms through which persistent organic pollutants (POPs) form during combustion processes is critical for controlling emissions of POPs, but the mechanisms through which most POPs form are poorly understood. Polyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) are typical toxic POPs, and the formation mechanisms of PXDD/Fs are better understood than the mechanisms through which other POPs form. In this study, a framework for identifying detailed PXDD/Fs formation mechanisms was developed and reviewed. The latest laboratory studies in which organic free radical intermediates of PXDD/Fs have been detected in situ and isotope labeling methods have been used to trace transformation pathways were reviewed. These studies provided direct evidence for PXDD/Fs formation pathways. Quantum chemical calculations were performed to determine the rationality of proposed PXDD/Fs formation pathways involving different elementary reactions. Many field studies have been performed, and the PXDD/Fs congener patterns found were compared with PXDD/Fs congener patterns obtained in laboratory simulation studies and theoretical studies to mutually verify the dominant PXDD/Fs formation mechanisms. The integrated method involving laboratory simulation studies, theoretical calculations, and field studies described and reviewed here can be used to clarify the mechanisms involved in PXDD/Fs formation. This review brings together information about PXDD/Fs formation mechanisms and provides a methodological framework for investigating PXDD/Fs and other POPs formation mechanisms during combustion processes, which will help in the development of strategies for controlling POPs emissions.

Unintentional formation of mixed chloro-bromo diphenyl ethers (PBCDEs), dibenzo-p-dioxins and dibenzofurans (PBCDD/Fs) from pyrolysis of polybrominated diphenyl ethers (PBDEs)

This study presents the comprehensive investigation for formation pathways of chloro-bromo-mixed products from the pyrolysis of polybrominated diphenyl ethers (PBDEs). In the study, a total of 23 PBDEs with bromination levels from mono-to deca-were selected. Each PBDE standard was sealed in the glass vial and then heated under 450 °C in the muffle furnace to simulate the pyrolysis process. The results demonstrated that PBDEs in the glass vials can unintentionally transform into chloro-bromo diphenyl ethers (PBCDEs) and dibenzo-p-dioxin and dibenzofurans (PBCDD/Fs) during the pyrolysis process. Atmosphere pressure gas chromatography (APGC) coupled with high-resolution mass spectrometry (HRMS) was used to identify these pyrolysis products, which demonstrated that all investigated nPBDEs (n represents the number of bromine substituents) can unintentionally transform into Cl₁-(n-1)BDEs, Cl₂-(n-2)BDEs, Cl₁-(n-1)BDFs, and Cl₁-(n-3)BDDs, while some nPBDEs can transform into Cl₁-(n-2)PBDD/Fs during pyrolysis. Experimental phenomena assisted with density functional theory (DFT) calculations reveal that Cl atom can substitute at C-Br rather than C-H, and Cl₁-(n-1)BDEs can be easily generated by Cl atom attacking at C-Br sites with low energy barriers (3.66-11.9 kcal/mol). In addition, nPBDEs with lower bromination levels are more favorable to generate Cl₁-(n-1)BDEs than those with higher bromination levels. Further DFT calculations suggest that PBDEs are preferentially first transformed into Cl₁-(n-1)BDEs, then subsequentially transform into PBCDD/Fs. We believe the results of this study can greatly improve our understanding of the transformation mechanism from PBDEs to cholo-bromo-mixed products in thermal treatment processes and provide new insight into controlling the emission of toxic cholo-bromo-mixed products.

Determination of the relative potencies of brominated dioxins for risk assessment in aquatic environments using the early-life stage of Japanese medaka

World Health Organization toxic equivalency factors (WHO-TEFs) are recommended for risk management of brominated dioxins in aquatic environments because limited information is available on their toxicity to fish. To validate this approach, we obtained the relative potencies of polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans and mixed-halogenated furans (PXDF, X = Cl/Br) against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) based on their toxicity to the early-life stage of Japanese medaka (Oryzias latipes). 2,3,7,8-substituted brominated dibenzofurans caused typical dioxin exposure effects, such as blue-sac disease. The TCDD-relative potency factors (REPs) of test substances were calculated based on the concentrations in water and eggs that caused 20% lethality on day 28 post-fertilization, and were in the order of: 2-chloro-3,7,8-tribromodibenzofuran (REP_water 3.3, REP_egg 4.6) > 2,3,7,8-tetrabromodibenzofuran (0.85, 0.92) > 2,3,4,7,8-pentabromodibenzofuran (0.053, 0.55) > 1,2,3,7,8-pentabromodibenzofuran (0.0091, 0.19). The transfer rate from water to eggs was lower for pentabrominated furans than tetrabrominated congeners, and was expected to decrease with the log K_ow of the test substance. Although the REP_egg value can be used to compare the toxicity potential of brominated dioxins, REP_water may be more suitable for environmental risk assessment because the uptake potential of these compounds from water should be considered. This study is the first to report higher toxicity of a PXDF congener compared with TCDD in vivo, further investigations of the toxicity of mixed-halogenated dioxins and environmental behavior are necessary for environmental risk assessment.

PCDD/Fs and PBDD/Fs in sediments from the river encompassing Guiyu, a typical e-waste recycling zone of China

Severe pollution of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and their brominated analogues (PBDD/Fs) was frequently reported for the waters located near unregulated e-waste recycling areas. However, the migrations of these high-level dioxins via waterways and their potential threats to the lower reaches were seldom investigated. In this study, we analyzed PCDD/Fs and PBDD/Fs in 27 surficial sediments collected from the Lian River encompassing the Guiyu, China e-waste recycling zone, and investigated their distributions, sources, migration behaviors and risks. Both PCDD/Fs and PBDD/Fs in these sediments exhibited a spatial trend of Guiyu > Guiyu downriver > Guiyu upriver, illustrating that the Guiyu e-waste recycling activities were the uppermost dioxin contributors in this watershed. Sediments from different Guiyu villages demonstrated big gaps in PCDD/F concentrations and congener compositions, and the reason was attributed to the diverse e-waste recycling activities practiced in these villages. Sediments near the e-waste open-burning areas demonstrated extremely high PCDD/F concentrations and unique PCDD/F profiles featured by low-chlorinated PCDFs (tetra- to hexa-), which is quite different from the OCDD-dominant PCDD/F profile found in most of the Lian River sediments. The geographical distributions of PCDD/F concentrations and profiles illustrate that the substantial amount of PCDD/Fs in Guiyu sediments were mainly retained in local and vicinal water bodies. The principal component analysis (PCA) results further confirm that the high-level PCDD/Fs in Guiyu sediments exhibited quite limited translocations downstream and therefore exerted little influences on the lower reaches. Pentachlorophenol use in history, ceramic industry and vehicle exhaust were diagnosed as the major PCDD/F sources for most sediments of the Lian River. Total toxicity equivalent quantities (TEQs) of 70% of the Lian River sediments surpassed the high-risk limit specified for mammalian life by the U.S.EPA (25 pg TEQ g^-1), and most of these sediments were from Guiyu and its near downstream, which merit continuous attention and necessary remediation measures.

Riverine transport dynamics of PBDEs and OPFRs within a typical e-waste recycling zone: Implications for sink-source interconversion

Despite ample evidence on spreading of e-waste derived hazardous materials, riverine transport of organic contaminants from e-waste recycling zones to surrounding areas has not been evaluated. To address this issue, passive and grab sampling methods were used to assess sediment-water diffusion and horizontal transport of polybrominated diphenyl ethers (PBDEs) and organophosphorus flame retardant (OPFRs) at upstream and downstream sites of two rivers in a typical e-waste recycling zone. Sediment acted as a source of BDE-17 with fluxes of 0.007-0.04 ng m^-2 d^-1 at all sampling sites. BDE-47 and BDE-99 reached equilibrium between overlying water and sediment porewater. Sediment interconverted from a sink at the upstream site to a source of OPFRs at the downstream site with a flux varying between -7.3 and 234 ng m^-2 d^-1. The amounts of OPFRs (11-45 g d^-1) via horizontal riverine transport were greater than those of PBDEs (0.68-2 g d^-1). The vertical sediment-water diffusion of PBDEs and OPFRs was not significant compared to horizontal riverine transport. The annual riverine outputs of PBDEs and OPFRs from the downstream sites were 250-330 g and 12,000-16,500 g, respectively, indicating the significance of riverine transport of organic contaminants from e-waste recycling zones to surrounding areas.

Concentrations and Toxic Implications of Dioxin-Like Polychlorinated Biphenyls in Soil Samples from Electrical Power Stations in Lagos, Nigeria

Dioxin-like polychlorinated biphenyls (dl-PCBs) are ubiquitous chemicals which mediate toxicity in a way similar to polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. In silico modeling was used to predict the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of eight dioxin-like PCBs in soil samples of 12 power stations in Lagos, Nigeria. Concentrations of Σdl-PCB₈ in soil samples ranged from 490 to 61,000 pg g^-1 , with mean concentrations of 17,000 pg g^-1 . The corresponding toxic equivalent (TEQ) concentrations of Ʃdl-PCB₈ ranged from 0.01 to 450 pg TEQ g^-1 , with a mean value of 42 pg TEQ g^-1 . Mean TEQ concentrations for Ʃdl-PCB₈ in soil samples from all but one of the sites exceeded the Canadian guideline value of 4 pg TEQ g^-1 and the US and German guideline values of 5-10 pg TEQ g^-1 . However, the TEQ concentrations obtained were all below the US action level of 1000 pg TEQ g^-1 . The ADMET predictions revealed that all studied dl-PCBs are inhibitors of three major isoforms (1A2, 2C9, and 2C19) of cytochrome P450 enzyme. Acute oral toxicity (median lethal dose) predictions revealed that all target dl-PCBs were class III compounds. Hepatotoxicity and carcinogenicity were positive, signifying that the studied compounds all have a tendency to elicit these effects. Occupational daily TEQ exposure via soil ingestion was estimated for an average adult worker weighing 70 kg. The maximum exposure obtained was 0.14 pg TEQ kg^-1  body weight day^-1 , which is half of the European Food Safety Authority (EFSA) tolerable daily intake (TDI) for dioxin-like compounds. This raises concern over the possible exceedance of the EFSA TDI for these workers if other dietary and nondietary exposure pathways and dioxin-like compounds are considered. Environ Toxicol Chem 2022;41:800-809. © 2021 SETAC.

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

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

Profile occurrences and in vitro effects of toxic organic pollutants in metal shredding facilities in Wallonia (Belgium)

End-of-life vehicles and e-waste contain several hazardous substances that can contaminate the environment during treatment processes. Occurrences and adverse effects of toxic organic pollutants emitted from 3 shredder plants located in Wallonia, Belgium, were investigated by chemical and biological analyses of fluff, dust, and scrubbing sludge sampled in 2019. Site 1 showed the highest concentrations of chlorinated compounds in sludge with 7.5 ng/g polychlorinated dibenzo-dioxins/furans and 84.5 µg/g estimated total polychlorinated biphenyls, while site 3 led the brominated flame retardant levels in dust (53.4 µg/g). The level of polycyclic aromatic hydrocarbons was highest in the sludge samples, 78 and 71 µg/g for sites 2 and 3, respectively. The samples induced significant dioxin-like activities in murine and human cells at concentrations of around 0.01-0.1 and 0.5-1 ng (sample) per ml (medium), respectively, with the efficacy similar to 2,3,7,8-tetrachlorodibenzodioxin and EC₅₀ values of around 1 and 10 ng/ml. The samples also displayed high estrogenic activities, already at 1 ng/ml, and several induced a response as efficient as 17β-estradiol, albeit a low androgenic activity. Shredder workers were estimated to be highly exposed to dioxin-like compounds through dust ingestion and dermal absorption, which is of concern.

Polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in soil around municipal solid waste incinerator: A comparison with polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs)

Polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) and polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) share similar toxicities and thermal origins, e.g., municipal solid waste incinerator (MSWI). Recently, PBDD/Fs from MSWI attracted rising concern because their important precursors, i.e., brominated flame retardants (BFRs), were frequently found in various wastes for landfill or MSWI feedstock. So far, however, little is known about PBDD/Fs and their associated risks in the vicinal environments of MSWI. Here we analyzed PBDD/Fs and PCDD/Fs in 29 soil samples collected around a multiyear large-scale MSWI, and compared their spatial distributions, sources and risks. PBDD/Fs demonstrated comparable concentrations and toxic equivalent quantities (TEQs) to PCDD/Fs in these samples. Spatially, both the concentrations of PBDD/Fs and PCDD/Fs decreased outwards from the MSWI, and exhibited significant linear correlations with the distances from the MSWI in the southeast downwind soil, suggesting the influence of the MSWI on its vicinal soil environment. However, the existence of other dioxin sources concealed its influence beyond 6 km. PBDD/Fs in the soils were characterized by highly-brominated PBDFs, especially Octa-BDF, and their sources were diagnosed as the MSWI and diesel exhaust; PCDD/Fs, however, were dominated by highly-chlorinated PCDDs, particularly Octa-CDD, and were contributed individually or jointly by the MSWI, automobile exhaust and pentachlorophenol (PCP)/Na-PCP. The non-carcinogenic risks of dioxins in all the soil samples were acceptable, but their carcinogenic risks in 17% of the samples were unacceptable. These samples were all located close to the MSWI and highways, therefore, the land use of these two high-risk zones should be cautiously planed.

A contemporary review of electronic waste through the lens of inhalation toxicology

Inhalation is a significant route of exposure to toxic chemicals for electronic waste (e-waste) workers, especially for those whose activities take place in the informal sector. However, there remains a dearth of research on the health effects produced by the hazardous dismantling of e-waste and associated outcomes and biological mechanisms that occur as a result of inhalation exposure. This contemporary review highlights a number of the toxicological and epidemiological studies published on this topic to bring to light the many knowledge gaps that require further research, including in vitro and ex vivo investigations to address the health outcomes and underlying mechanisms of inhaled e-waste-associated pulmonary disease.

Nontarget Screening of Organohalogen Compounds in the Liver of Wild Birds from Osaka, Japan: Specific Accumulation of Highly Chlorinated POP Homologues in Raptors

Nontarget screening studies have recently revealed the accumulation of typically unmonitored organohalogen compounds (OHCs) in various marine animals, but information for terrestrial food chains is still lacking. This study investigated the accumulation profiles of known and unknown OHCs in the liver of representative wild bird specimens from Osaka, Japan using nontarget analysis based on two-dimensional gas chromatography-time-of-flight mass spectrometry. A large number of unmonitored OHCs were identified, including anthropogenic contaminants and marine halogenated natural products (HNPs), and their accumulation profiles were considered to be influenced by terrestrial and brackish water-based diets. Anthropogenic OHCs were highly accumulated in terrestrial predator species (peregrine falcon, hawks, and black kite), and some unmonitored highly chlorinated contaminants reached the levels of microgram per gram lipid in the liver, i.e., C₁₀-/C₁₅-based chlordane related compounds (CHLs) and their epoxides, dichlorodiphenyldichloroethylene (DDE) homologues, and polychlorinated terphenyls (PCTs). In contrast, HNPs were accumulated at higher levels in piscivorous birds (gray heron and common cormorant). Considering the enrichment of the unmonitored C₁₀-/C₁₅-based CHLs, PCTs, and DDE homologues relative to structurally similar persistent organic pollutants (POPs) in high trophic-level species such as raptors, further studies are needed to elucidate their environmental levels, behavior in terrestrial food chains, and ecotoxicological impacts.

Environmental characteristics and formations of polybrominated dibenzo-p-dioxins and dibenzofurans

Polybrominated dibenzo-p-dioxins and furans (PBDD/Fs) are emerging persistent organic pollutants (POPs) that have similar or higher toxicities than the notorious dioxins. Toxicities, formation mechanisms, and environmental fates of PBDD/Fs are lacking because accurate quantification, especially of higher brominated congeners, is challenging. PBDD/F analysis is difficult because of photolysis and thermal degradation and interference from polybrominated diphenyl ethers. Here, literatures on PBDD/F analysis and environmental occurrences are reviewed to improve our understanding of PBDD/F environmental pollution and human exposure levels. Although PBDD/Fs behave similarly to dioxins, different congener profiles between PBDD/Fs and dioxins in the environment indicates their different sources and formation mechanisms. Herein, potential sources and formation mechanisms of PBDD/Fs were critically discussed, and current knowledge gaps and future directions for PBDD/F research are highlighted. An understanding of PBDD/F formation pathways will allow for development of synergistic control strategies for PBDD/Fs, dioxins, and other dioxin-like POPs.

Worker health in formal electronic waste recycling plants

Purpose

This article explores the protective measures and the occupational health and safety (OHS) prevention strategies in place in the formal electronic equipment recycling (e-recycling) industry, more specifically in the Greater Montreal area (Quebec, Canada) and their consequences: health inequalities and level of compliance with environmental standards.

Design/methodology/approach

Semi-structured interviews were conducted using two respondent-specific questionnaires, one for workers and one for supervisors. Data collection and analytic procedures drew from qualitative content analysis. It was tempted to identify differences in OHS practices in relation to the workers' employment status and to link the companies' OHS concerns to their level of compliance with environmental standards.

Findings

The article highlights specific OHS issues in the formal e-recycling industry. Enforcing compliance with environmental standards as a lever for promoting OHS appears to be a promising strategy. Another main finding was the workforce diversity and related OHS vulnerabilities in this industry and the challenges they pose to employers' ability to adequately and equally reach and protect all workers involved.

Originality/value

To date, too little attention appears to have been paid to working conditions and worker protection in this rapidly growing sector. Specific prevention programmes could be implemented and adapted to the industry's diverse workforce and its multiple OHS vulnerabilities. This issue calls for the international community to take responsibility, as many electronic waste (e-waste) generated worldwide is shipped to developing countries, where lack of regulation and control is much more striking in a sector that remains very largely informal.

Polybrominated dibenzo-p-dioxins and furans (PBDD/Fs): Contamination in food, humans and dietary exposure

Polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) have been recognised as environmental pollutants for decades but their occurrence in food has only recently been reported. They elicit the same type of toxic response as analogous polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) with similar potencies and effects, and share similar origins - inadvertent production during combustion and occurrence as by-products in industrial chemicals. Surprisingly, PBDD/Fs have received considerably less attention than PCDD/Fs, perhaps because determination requires a higher degree of analytical competence, a result of the higher adsorptivity and lability associated with carbon-bromine bonding. For most populations, the principal exposure pathway is dietary intake. The PBDD/F toxicity arising from occurrence in foods has often been expressed as toxic equivalents (TEQs) using the same scheme developed for PCDD/Fs. This approach is convenient, but resulting TEQ estimates are more uncertain, given the known differences in response for some analogous congeners and also the different patterns of PBDD/F occurrence confirmed by the newer data. Further studies to consolidate potency factors would help to refine TEQ estimates. Characteristically, most foods and human tissues show more frequent and higher PBDF concentrations relative to PBDDs, reflecting major source patterns. Occurrence in food ranges from <0.01 to several thousand pg/g (or up to 0.3 pg TEQ/g whole weight) which is comparable to PCDD/F occurrence (ΣPBDD/F TEQs are underestimated as not all relevant congeners are included). Plant based foods show higher PBDD/F: PCDD/F TEQ ratios. Reported PBDD/F dietary intakes suggest that some population groups, particularly young children, may exceed the revised tolerable weekly intake for dioxin-like contaminants (2 pg TEQ/kg bw/week), even for mean consumption estimated with lower bound data. It is evident that the omission of PBDD/Fs from the TEQ scheme results in a significant underestimation of the cumulative toxicity and associated risk arising from this mode of action.

Bromination of Carbon and Formation of PBDD/Fs by Copper Bromide in Oxidative Thermal Process

Brominated aromatic compounds are unintentionally generated during various thermal processes, including municipal solid waste incineration, electric-waste open burning, and secondary copper smelting. Copper (Cu) plays an important role in the formation of brominated aromatic compounds. In the present study, the thermochemical behaviors of Cu and Br in model samples, including copper bromide (CuBr₂) and activated carbon, were studied using in situ X-ray absorption near-edge structure (XANES) and thermogravimetry. Quantification of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) was also conducted by gas chromatograph-high resolution mass spectrometer. Three key reactions were identified: (i) the reduction of CuBr₂ to CuBr (room temperature to 300 °C), (ii) the generation of Br bonded with aromatic carbon (150-350 °C), and (iii) the oxidation of copper (>350 °C). Maximum amounts of PBDD/Fs were found in residual solid phase after heating at 300 °C. The analytical results indicated the direct bromination of aromatic carbon by the debromination of copper bromides (I, II) and that CuBr and CuO acted as catalysts in the oxidation of the carbon matrix. The bromination mechanisms revealed in this study are essential to the de novo formation of PBDD/Fs and other brominated aromatic compounds.

Multiple classes of chemical contaminants in soil from an e-waste disposal site in China: Occurrence and spatial distribution

E-waste recycling is well known for releasing halogenated organic compounds (HOCs) and heavy metals. This study investigated the occurrence and distribution of traditional and novel classes of contaminants, including chlorinated, brominated, and mixed halogenated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs, PBDD/Fs, PXDD/Fs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and polyhalogenated carbazoles (PHCZs), in soil from an e-waste disposal site in Hangzhou. PBDEs were the most abundant, at 343-69306 ng kg^-1, followed by PHCZs (896-41,362 ng kg^-1), PCDD/Fs (349-19,396 ng kg^-1), PCBs (51.3-1834 ng kg^-1), PBDD/Fs (2.99-524 ng kg^-1) and PXDD/Fs (0.104-21.2 ng kg^-1). The detected target compound concentrations were generally lower than those reported in the literature for informal e-waste sites. Nevertheless, they can serve as a basis of information for evaluation and subsequent control. The toxic equivalent (TEQ) contributions from these contaminants (except PBDEs) decreased as follows: PCDD/Fs > PXDD/Fs > PHCZs > PCBs > PBDD/Fs. ΣDioxins (PCDD/Fs + PBDD/Fs + PXDD/Fs) accounted for 47.7%-97.2% of the total TEQs in the soil. OCDD, 1,2,3,4,6,7,8-HpBDF and OBDF were the dominant congeners, mainly derived from combustion and transport because of their low saturated vapor pressure. PXDFs were more abundant than PXDDs, and homologue profiles suggested a similar formation mechanism for PXDFs and PBDFs involving successive Br-to-Cl exchange. PHCZs were reported in soil from an e-waste disposal area for the first time, and their concentrations were several orders of magnitude higher than those of the other contaminants. Although the risk of human exposure in this study was estimated to be lower than the values recommended by the WHO (1-4 pg TEQ/kg bw/day), health implications still exist, and further investigations are necessary.

Examination of barnacles' potential to be used as bioindicators of persistent organic pollutants in coastal ecosystem: A Malaysia case study

Barnacles are ubiquitous in coastal ecosystems of different geographical regions worldwide. This is the first study attempting to assess the suitability of barnacles as bioindicators of persistent organic pollutants (POPs) in coastal environments. Barnacles were collected from the coasts around Peninsular Malaysia and analyzed for POPs including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs). Among POPs, PCBs showed the highest concentrations with elevated contributions of CB28 and CB153. As for PBDEs, BDE47 was the most frequently detected congener, while BDE209 was detected in barnacles from two stations in Port Klang and the levels reached up to >70% of total PBDE concentrations. Concentrations of OCPs detected in barnacles were in the order of CHLs > DDTs > HCHs > HCB and 4,4'-DDE and cis- and trans-chlordane were the predominant OCP compounds. A comparison with previous studies in Malaysia showed consistent levels of POPs. Green mussels collected from selected barnacles' habitats, for the sake of a comparison, showed almost similar profiles but lower concentrations of POPs. The spatial distribution of POPs observed in barnacles and comparison of POP levels and profiles with mussels indicated that barnacles can be useful bioindicators for monitoring POPs contamination in the coastal ecosystems.

Effects on the Liver Transcriptome in Baltic Salmon: Contributions of Contamination with Organohalogen Compounds and Origin of Salmon

Hatchery-reared Atlantic salmon (Salmo salar) has been released to support the wild salmon stocks in the Baltic Sea for decades. During their feeding migration, salmon are exposed to organohalogen compounds (OHCs). Here, we investigated the OHC levels and transcriptome profiles in the liver of wild and hatchery-reared salmon collected from the Baltic main basin (BMB), the Bothnian Sea (BS), and the Gulf of Finland (GoF) and examined whether salmon origin and OHC levels contributed to the hepatic transcriptome profiles. There were no differences in the OHC concentrations between wild and reared fish but larger differences between areas. Several transcript levels were associated with non-dioxin-like polychlorinated biphenyls, polybrominated diphenylethers, chlordanes, and dichlorodiphenyltrichloroethane in a concentration-dependent manner. Between wild and reared salmon, lipid metabolism and related signaling pathways were enriched within the BMB and BS, while amino acid metabolism was altered within the GoF. When comparing the different areas, lipid metabolism, environmental stress and cell growth, and death-related pathways were enriched. Class coinertia analysis showed that the covariation in the OHC levels and the transcriptome were significantly similar. These results suggest that the hepatic transcriptomes in wild and hatchery-reared salmon are more affected by the OHC levels rather than the origin of salmon.

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

The large-scale production and usage of tetrabromobisphenol A (TBBPA) and its analogues have caused widespread contamination, raising concern about their potential endocrine disruption effects on both humans and ecosystems. In the present study, debromination and unknown mixed bromine/chlorine transformation products of TBBPA (X-BBPA) were screened in dust samples from an e-waste dismantling site. Five monochloro products (2-chloro-2',6,6'-TriBBPA, 2-chloro-2',6-DiBBPA, 2-chloro-2',6'-DiBBPA, 2-chloro-2'-MoBBPA, and 2-chloro-6-MoBBPA) and two dichloro products (2,2'-dichloro-6,6'-DiBBPA and 2,2'-dichloro-6-MoBBPA) were successfully synthesized and structurally identified. TBBPA and its transformation products were detected by comparison of their mass spectra and retention times with those of synthetic standards. The mean concentration of X-BBPA was 1.63 × 10⁴ ng/g in e-waste dismantling workshop dust samples based on dry weight, which was at a similar level to TBBPA. However, it was 1 order of magnitude lower than the concentrations of the debromination congeners. Thus, both debromination and chlorine-bromine exchange may be important reactions during the thermal processing of e-waste. The results on mixed chlorinated/brominated TBBPA transformation products provided new insights into TBBPA transformation. The elevated levels of the transformation products of TBBPA suggested that these products should be targeted to avoid underestimation of possible health risks.

Polybrominated dibenzo-p-dioxins (PBDDs) and - dibenzofurans (PBDFs) in cod (Gadus morhua) liver-derived products from 1972 to 2017

Literature data on the occurrence and prevalence of polybrominated dibenzo-p-dioxins (PBDDs) and polybrominated dibenzofurans (PBDFs) in foods including seafood are scarce. In this study, a number of cod-derived products including medicinal grade cod liver oils sourced from Northern Atlantic waters (Iceland, Norway) and the Baltic Sea (Poland) during 1972-2001 and canned cod liver sourced from the Baltic Sea in 2017, showed detectable levels of PBDFs: such as 2,3,8-TrBDF at 0.57 to 5.249 pg g^-1 fat and 1,2,3,4,6,7,8-HpBDF at <0.018 to 0.302 pg g^-1 fat. PBDDs were not detected in the cod liver oils. Canned cod liver products showed low levels of 2,3,7,8-TeBDD in the range <0.017 to 0.022 pg g^-1 whole weight and 1,2,3,7,8-PeBDD at <0.03 to 0.039 pg g^-1 whole weight. These concentrations were computed to yield upper bound toxic equivalences (TEQs) of 0.14 to 0.17 pg g^-1 for the oils and 0.12 to 0.25 pg g^-1 for the canned products (0.08 pg g^-1 ww for both products). The resulting supplementary and dietary intakes are low (0.02 to 0.11 pg kg^-1 bm day^-1 for the oils and 0.07 to 0.17 pg kg^-1 bm week^-1 for the canned livers) in comparison to the recently expressed tolerable weekly intake of 2 pg kg^-1 bm week^-1. However, the intakes are underestimates, as due to a lack of analytical standards not all PBDD/F TEQ contributing congeners could be included. The PBDD/F TEQ contributes to the cumulative toxicity arising from other contaminants such as chlorinated dioxins and polychlorinated biphenyls.

Recent progresses in analytical GC and LC mass spectrometric based-methods for the detection of emerging chlorinated and brominated contaminants and their transformation products in aquatic environment

This paper is an overview of screening methods recently developed for emerging halogenated contaminants and their transformation products. The target screening methods are available only for a limited number of emerging pollutants since the reference standards for these compounds are not always available, but a risk assessment of those micropollutants in environment must be performed anyhow. Therefore, the chromatographic techniques hyphenated with high resolution mass spectrometry (HRMS) trend to become indispensable methods for suspect and non-target screening of emerging halogenated contaminants. HRMS is also an effective tool for tentatively identification of the micropollutants' transformation products existing in much lower concentrations. To assess the transformation pathway of halogenated contaminants in environment, the non-target screening methods must be combined with biodegradation lab experiments and also with advanced oxidation and reduction processes that can mimic the transformation on these contaminants in environment. It is expected that in the future, the accurate-mass full-spectra of transformation products recorded by HRMS will be the basic information needed to elucidate the transformation pathways of emerging halogenated contaminants in aquatic environment.

Severe dioxin-like compound (DLC) contamination in e-waste recycling areas: An under-recognized threat to local health

Electrical and electronic waste (e-waste) burning and recycling activities have become one of the main emission sources of dioxin-like compounds (DLCs). Workers involved in e-waste recycling operations and residents living near e-waste recycling sites (EWRS) are exposed to high levels of DLCs. Epidemiological and experimental in vivo studies have reported a range of interconnected responses in multiple systems with DLC exposure. However, due to the compositional complexity of DLCs and difficulties in assessing mixture effects of the complex mixture of e-waste-related contaminants, there are few studies concerning human health outcomes related to DLC exposure at informal EWRS. In this paper, we have reviewed the environmental levels and body burdens of DLCs at EWRS and compared them with the levels reported to be associated with observable adverse effects to assess the health risks of DLC exposure at EWRS. In general, DLC concentrations at EWRS of many countries have been decreasing in recent years due to stricter regulations on e-waste recycling activities, but the contamination status is still severe. Comparison with available data from industrial sites and well-known highly DLC contaminated areas shows that high levels of DLCs derived from crude e-waste recycling processes lead to elevated body burdens. The DLC levels in human blood and breast milk at EWRS are higher than those reported in some epidemiological studies that are related to various health impacts. The estimated total daily intakes of DLCs for people in EWRS far exceed the WHO recommended total daily intake limit. It can be inferred that people living in EWRS with high DLC contamination have higher health risks. Therefore, more well-designed epidemiological studies are urgently needed to focus on the health effects of DLC pollution in EWRS. Continuous monitoring of the temporal trends of DLC levels in EWRS after actions is of highest importance.

Quantitative speciation of insoluble chlorine in E-waste open burning soil: Implications of the presence of unidentified aromatic-Cl and insoluble chlorides

Open burning of electronic waste (E-waste) produces numerous organochlorine compounds (OCs). Although the presence of unidentified OCs has been suggested, the mass balance of identified and unidentified OCs in E-waste open burning soils (EOBSs) still remains unknown. In this study, the concentrations of Cl bonded with aromatic carbon (aromatic-Cl) and aliphatic carbon (aliphatic-Cl), and inorganic Cl in EOBSs were determined by focusing on chlorine (Cl) in water-insoluble fractions (insoluble Cl) and applying Cl K-edge X-ray absorption spectroscopy in conjunction with combustion ion chromatography. The concentrations of identified Cl (Cl in five individual OCs: polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, chlorinated polycyclic aromatic hydrocarbons and chlorinated benzenes) were calculated from the concentrations previously reported for the same samples. The proportions of identified Cl were less than 1% to aromatic-Cl, indicating the abundance of unidentified OCs. The concentrations of both aromatic-Cl and identified Cl were highest in the sample collected from the site in Vietnam (VN), where wires and cables were mainly burned, suggesting that unidentified aromatic-Cl were produced through pathways similar to those of identified OCs, and the pathway could be related to burning of wires and cables. Further, insoluble Cu (II) compound, Cu₂(OH)₃Cl were assumed to be present in EOBSs and the concentration was highest in VN, implying that insoluble inorganic chlorides could be related to the formation of aromatic-Cl and identified Cl.