Bioaccessibility of halogenated flame retardants and organophosphate esters in settled dust: Influences of specific dust matrices from informal e-waste and end-of-life vehicle processing areas in Vietnam.

Bioaccessibility of halogenated flame retardants (HFRs) and organophosphorus esters (OPEs) is necessarily investigated to provide more accurate risk assessment and information about absorption behavior of these pollutants. In this study, total and bioaccessible concentrations of HFRs (including legacy and alternative substances) and OPEs were determined in settled dust samples collected from Vietnamese e-waste and end-of-life vehicle (ELV) processing areas. Concentrations of both HFRs and OPEs were significantly higher in the e-waste dust than ELV dust. Bioavailability of HFRs and OPEs in dust was determined by using an in vitro assay with human-simulated digestive fluids, dialysis membrane, and Tenax® TA sorptive sink. Bioaccessibility of HFRs was markedly lower than that of OPEs, which could be largely due to higher hydrophobicity of HFRs compared to OPEs. Bioaccessibility of almost hydrophobic compounds were markedly lower in the e-waste dust (containing micronized plastic debris) than in the ELV dust (containing oily materials), suggesting the influence of specific dust matrices on pollutant bioaccessibility. Although the daily uptake doses of selected HFRs and OPEs from dust were markedly higher in the e-waste sites compared to the ELV sites, the direct exposure risk was not significant. Our results suggest that bioaccessibility can partly explain the differences between dust and uptake profiles, which may relate to accumulation profiles of HFRs and OPEs in human samples.

Perfluoroalkyl substances in food contact materials: preliminary investigation in Vietnam and global comparison.

Per- and polyfluoroalkyl substances (PFASs) are a group of concerned persistent toxic substances, especially for their application or unintentional formation in food contact materials (FCMs). However, information about the occurrence, sources, and fate of these pollutants in food packaging materials from Vietnam as well as Southeast Asian countries is probably still obscured. In this study, levels of 13 perfluoroalkyl carboxylic acids (PFCAs) and 4 sulfonates (PFSs) were determined in various types of food packaging samples collected from Vietnamese markets. Generally low concentrations of total 17 PFASs (median 0.341; max 624 ng/g) suggested that these compounds were mainly inadvertently produced rather than intentionally added to the packaging materials. A few mochi paper tray samples had relatively high PFAS levels (372-624 ng/g), which were dominated by long-chain (C8-C12) PFCAs. A comprehensive and updated overview of PFASs in FCMs from different countries in the world was also provided. Current database could not provide conclusive trends of PFAS concentrations and profiles in FCMs between continents and countries. The highest levels up to ppm were reported for PFCAs (e.g., PFBA, PFHxA, PFOA, and PFDA) and several fluorotelomer alcohols and carboxylic acids, while PFSs were almost absent in FCMs. FPASs can emit from FCMs, migrate to food, and then contribute to dietary exposure in humans and animals. Additional investigations on the occurrence, sources, behavior and fate, and impacts of PFASs in FCMs are critically needed, especially in emerging and developing countries.

Polycyclic Aromatic Hydrocarbons in Air and Dust Samples from Vietnamese End-of-life Vehicle Processing Workshops: Contamination Status, Sources, and Exposure Risks.

Concentrations of 18 unsubstituted polycyclic aromatic hydrocarbons (PAHs) and 11 methylated derivatives (Me-PAHs) were measured in polyurethane foam-based passive air (PUF-PAS) and settled dust samples collected from end-of-life vehicle (ELV) processing workshops in northern Vietnam. Concentrations of total 29 PAHs ranged from 42 to 95 (median 57) ng/m3 and from 860 to 18,000 (median 5700) ng/g in air and dust samples, respectively. PAH levels in ELV air and dust samples were 1.5 ± 0.4 and 9.4 ± 7.9 times higher than levels found in a control house, suggesting ELV processing as potential PAH emission sources. Concentrations and proportions of Me-PAHs in total PAHs of the ELV air (26% ± 7%) and dust (41% ± 14%) were higher than those found in control house (18% in both air and dust). The occurrence of PAHs and Me-PAHs in the ELV workshops are attributed to not only pyrogenic but also petrogenic sources (i.e., improper treatment and management of fuels, lubricants, and vehicle oils).

Pharmaceuticals and personal care products (PPCPs) in surface water and fish from three Asian countries: Species-specific bioaccumulation and potential ecological risks.

In Asian developing countries, undeveloped and ineffective sewer systems are causing surface water pollution by a lot of contaminants, especially pharmaceuticals and personal care products (PPCPs). Therefore, the risks for freshwater fauna need to be assessed. The present study aimed at: i) elucidating the contamination status; ii) evaluating the bioaccumulation; and iii) assessing the potential risks of PPCP residues in surface water and freshwater fish from three Asian countries. We measured 43 PPCPs in the plasma of several fish species as well as ambient water samples collected from India (Chennai and Bengaluru), Indonesia (Jakarta and Tangerang), and Vietnam (Hanoi and Hoa Binh). In addition, the validity of the existing fish blood-water partitioning model based solely on the lipophilicity of chemicals is assessed for ionizable and readily metabolizable PPCPs. When comparing bioaccumulation factors calculated from the PPCP concentrations measured in the fish and water (BAFmeasured) with bioconcentration factors predicted from their pH-dependent octanol-water partition coefficient (BCFpredicted), close values (within an order of magnitude) were observed for 58-91 % of the detected compounds. Nevertheless, up to 110 times higher plasma BAFmeasured than the BCFpredicted were found for the antihistamine chlorpheniramine in tilapia but not in other fish species. The plasma BAFmeasured values of the compound were significantly different in the three fish species (tilapia > carp > catfish), possibly due to species-specific differences in toxicokinetics (e.g., plasma protein binding and hepatic metabolism). Results of potential risk evaluation based on the PPCP concentrations measured in the fish plasma suggested that chlorpheniramine, triclosan, haloperidol, triclocarban, diclofenac, and diphenhydramine can pose potential adverse effects on wild fish. Results of potential risk evaluation based on the PPCP concentrations measured in the surface water indicated high ecological risks of carbamazepine, sulfamethoxazole, erythromycin, and triclosan on Asian freshwater ecosystems.

Estrogenic, androgenic, and glucocorticoid activities and major causative compounds in river waters from three Asian countries.

Estrogen, androgen, and glucocorticoid receptors (ER, AR, and GR) agonist activities in river water samples from Chennai and Bangalore (India), Jakarta (Indonesia), and Hanoi (Vietnam) were evaluated using a panel of chemical-activated luciferase gene expression (CALUX) assays and were detected mainly in the dissolved phase. The ER agonist activity levels were 0.011-55 ng estradiol (E2)-equivalent/l, higher than the proposed effect-based trigger (EBT) value of 0.5 ng/l in most of the samples. The AR agonist activity levels were < 2.1-110 ng dihydrotestosterone (DHT)-equivalent/l, and all levels above the limit of quantification exceeded the EBT value of 3.4 ng/l. GR agonist activities were detected in only Bangalore and Hanoi samples at dexamethasone (Dex)-equivalent levels of < 16-150 ng/l and exceeded the EBT value of 100 ng/l in only two Bangalore samples. Major compounds contributing to the ER, AR, and GR agonist activities were identified for water samples from Bangalore and Hanoi, which had substantially higher activities in all assays, by using a combination of fractionation, CALUX measurement, and non-target and target chemical analysis. The results for pooled samples showed that the major ER agonists were the endogenous estrogens E2 and estriol, and the major GR agonists were the synthetic glucocorticoids Dex and clobetasol propionate. The only AR agonist identified in major androgenic water extract fractions was DHT, but several unidentified compounds with the same molecular formulae as endogenous androgens were also found.

A review on management practices, environmental impacts, and human exposure risks related to electrical and electronic waste in Vietnam: findings from case studies in informal e-waste recycling areas.

Electrical and electronic waste (e-waste) has become a global concern, especially in developing countries. In this review, we conducted a literature survey of e-waste management practices, processing activities, and adverse effects in Vietnam, an emerging country in Southeast Asia, by gathering data from peer-reviewed articles published between 2009 and 2021. This is the first review paper to comprehensively discuss management and research aspects regarding e-waste in an Asian developing country. Due to the lack of an effective management and recycling system, a certain portion of Vietnamese e-waste has been processed by informal sectors without appropriate recycling and pollution control technology, resulting in localized contamination and human exposure to toxic chemicals. Primitive processing activities, such as manual dismantling, open burning, and plastic recycling, have been identified as important contributors to the environmental emission and human exposure to toxic elements (notably As, Mn, Ni, Pb, Zn) and organic pollutants like flame retardants, PAHs, PCBs, and dioxin-related compounds. Informal e-waste processing from these small-scale workshops can release pollutants at similar levels compared to large-scale facilities in developed countries. This fact suggests an urgent need to develop management best practices for e-waste in Vietnam as well as other emerging and developing countries, in order to increase recycling efficiency and minimize their adverse impacts on environmental and human health.

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

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

Silicone wristband- and handwipe-based assessment of exposure to flame retardants for informal electronic-waste and end-of-life-vehicle recycling workers and their children in Vietnam.

Measuring personal exposure to flame retardants (FRs) is crucial for assessing and controlling human health risks posed by FRs during the recycling of electronic waste (e-waste) and end-of-life vehicles (ELVs). Here, we examined the use of handwipes and silicone wristbands to measure personal FR exposure for e-waste and ELV recycling workers and their children in Vietnam. On the handwipes from the e-waste recycling workers, the predominant five FRs detected were TBBPA (median concentration: 3700 ng/wipe), BDE-209 (1700 ng/wipe), TPHP (500 ng/wipe), DBDPE (410 ng/wipe), and BPA-BDPP (360 ng/wipe). On the handwipes from ELV recycling workers, TPHP (60 ng/wipe), IPPDPP (47 ng/wipe), BIPPPP/DIPPDPP (33 ng/wipe), BDE-209 (26 ng/wipe), and TCIPP (23 ng/wipe) were detected as the five predominant FRs. On the wristbands from the e-waste recycling workers, the five predominant FRs detected were TBBPA (median concentration: 340 ng/g), BDE-209 (330 ng/g), DBDPE (65 ng/g), TPHP (50 ng/g), and TMPP (34 ng/g). On the wristbands from the ELV recycling workers, TPHP (34 ng/g), IPPDPP (18 ng/g), TCIPP (14 ng/g), TDMPP (13 ng/g), BIPPPP/DIPPDPP (9.3 ng/g) and TMPP (9.3 ng/g) were detected as the predominant FRs. The data obtained with the wristbands were comparable to those obtained with the handwipes. Similar FR profiles were found in between the workers and their children. The profiles indicate that the informal e-waste and ELV recycling caused FR exposure not only for workers but also for their children who live in the workshops. By using the handwipe and wristband sampling approaches, we determined types and concentrations of FRs to which the workers and their children were dominantly exposed. Silicone wristband- and handwipe-based assessment is expected to be effective means of measuring personal FR exposure for the informal e-waste and ELV recycling workers and their children.

Comprehensive characterization of halogenated flame retardants and organophosphate esters in settled dust from informal e-waste and end-of-life vehicle processing sites in Vietnam: Occurrence, source estimation, and risk assessment.

Information about the co-occurrence of halogenated flame retardants (HFRs) and organophosphate esters (OPEs) in the environment of informal waste processing areas is still limited, especially in emerging and developing countries. In this study, OPEs and HFRs including polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), and chlorinated flame retardants (CFRs) were determined in settled dust from Vietnamese e-waste recycling (WR) and vehicle processing (VP) workshops. Pollutant concentrations decreased in the order: OPEs (median 1500; range 230-410,000 ng/g) ≈ PBDEs (1200; 58-250,000) > NBFRs (140; not detected - 250,000) > CFRs (13; 0.39-2200). HFR and OPE levels in the WR workshops for e-waste and obsolete plastic were significantly higher than in the VP workshops. Decabromodiphenyl ether and decabromodiphenyl ethane are major HFRs, accounting for 60 ± 26% and 25 ± 29% of total HFRs, respectively. Triphenyl phosphate, tris(2-chloroisopropyl) phosphate, and tris(1,3-dichloroisopropyl) phosphate dominated the OPE profiles, accounting for 30 ± 25%, 25 ± 16%, and 24 ± 18% of total OPEs, respectively. The OPE profiles differed between WR and VP dust samples, implying different usage patterns of these substances in polymer materials for electric/electronic appliance and automotive industries. Human health risk related to dust-bound HFRs and OPEs in the study areas was low.

Perfluoroalkyl substances in freshwater and marine fish from northern Vietnam: Accumulation levels, profiles, and implications for human consumption.

The accumulation profiles of nine perfluoroalkyl substances (PFASs) were determined in 95 muscle samples of seven freshwater (n = 65) and seven marine (n = 30) fish species collected in Northern Vietnam. In both groups of fish, perfluorooctane sulfonic acid (PFOS) was the most prevalent component, accounting for roughly 29 % of total PFASs. The total PFASs in freshwater fish species ranged from 0.08 to 8.06 ng/g wet weight (w.w), with the highest concentration found in topmouth culter (7.01 ± 1.23 ng/g w.w). In marine fish, the highest mean concentration of PFASs was detected in Asian sea bass (2.75 ± 0.54 ng/g, w.w). Estimation on the human dietary intake of PFASs from fish consumption resulted in hazard ratios (HR) ranging from 0.019 to 0.238 for freshwater fish and from 0.016 to 0.074 for marine fish, indicating low exposure risks associated with PFASs.

Perfluoroalkyl substances (PFAS) in freshwater fish from urban lakes in Hanoi, Vietnam: concentrations, tissue distribution, and implication for risk assessment.

Concentrations and profiles of 17 perfluoroalkyl substances (PFAS) including 13 perfluorocarboxylic acids (PFA) and 4 perfluoroalkyl sulfonates (PFS) were determined in whole blood, muscle, and liver samples of four freshwater fish species in West Lake and Yen So Lake (Hanoi, Vietnam). Concentrations of total 17 PFAS in fish blood samples ranged from 5.2 to 29 (median 16) ng/mL. Total 17 PFAS levels in liver samples (4.5; 2.7-6.6 ng/g wet weight) were significantly higher than in muscle samples (1.0; 0.51-2.6 ng/g wet weight). More than 90% PFAS burdens in our fish samples were attributed to muscle and blood rather than liver, but contributions of individual compounds varied greatly. The most predominant substances were perfluorooctanesulfonate (PFOS) and PFA with chain lengths from C10 to C14 (i.e., PFDA, PFUnDA, PFDoDA, PFTrDA, and PFTeDA). There is no significant difference in PFAS concentrations between the studied species (i.e., bighead carp, common carp, rohu, and tilapia), but common carp showed specific PFAS profiles as compared to other species (e.g., higher proportions of PFOS and long-chain PFA such as PFTrDA, PFTeDA, and PFHxDA). Daily intake doses of PFOS and perfluorooctanoic acid (PFOA) through fish consumption were markedly lower than the US EPA reference dose of 20 ng/kg/day. Weekly intakes of the sum of PFHxS, PFOS, PFOA, and PFNA in our study were still lower than the EFSA tolerable weekly intake of 4.4 ng/kg/week.

Mechanical recycling of plastic waste as a point source of microplastic pollution.

Plastic pollution has become one of the most pressing environmental issues. Recycling is a potential means of reducing plastic pollution in the environment. However, plastic fragments are still likely released to the aquatic environment during mechanical recycling processes. Here, we examined the plastic inputs and effluent outputs of three mechanical recycling facilities in Vietnam dealing with electronic, bottle, and household plastic waste, and we found that large quantities of microplastics (plastics <5 mm in length) are generated and released to the aquatic environment during mechanical recycling without proper treatment. Comparisons with literature data for microplastics in wastewater treatment plant effluents and surface water indicated that mechanical recycling of plastic waste is likely a major point source of microplastics pollution. Although there is a mismatch between the size of the microplastics examined in the present study and the predicted no-effect concentration reported, it is still possible that microplastics generated at facilities pose risks to the aquatic environment because there might be many plastic particulates smaller than 315 µm, as suggested by our obtained size distributions. With mechanical recycling likely to increase as we move to a circular plastics economy, greater microplastics emissions can be expected. It is therefore an urgent need to fully understand not only the scale of microplastic generation and release from plastic mechanical recycling but also the environmental risk posed by microplastics in the aquatic environment.

Assessment of binding potencies of polychlorinated biphenyls and polybrominated diphenyl ethers with Baikal seal and mouse constitutive androstane receptors: Comparisons across species and congeners.

The present study evaluated the binding potencies (equilibrium dissociation constant: KD) of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) with the constitutive androstane receptor (CAR)_ligand binding domain (LBD) of the Baikal seal (bsCAR_LBD) and mouse (mCAR_LBD) using a surface plasmon resonance (SPR) biosensor. The binding affinities of individual congeners with mCAR_LBD tended to be higher than those with bsCAR_LBD but the differences were within the same order of magnitude. Notably, PBDE congeners showed higher binding affinities for both CAR_LBDs than PCB congeners. In silico docking simulations demonstrated that PBDEs had more non-covalent interactions with specific amino acid residues in both CAR_LBDs than PCBs, supporting the results of their binding affinities. Binding affinity comparisons among congeners revealed the structural requirements for higher binding; mono or di ortho-, tri meta-, and di para­chlorine substitutions for PCBs, and di or tri ortho-, mono meta-, and di para­bromine substitutions for PBDEs. The binding potencies of these congeners unlikely accounted for their previously reported CAR-mediated transactivation potencies, implying that their transactivation is regulated in a ligand-dependent, but a distinct manner from ligand binding. Risk assessment analysis showed that the KD values of individual PCB and PBDE congeners were 1-4 orders of magnitude higher than their respective hepatic concentrations in wild Baikal seal population.

Antiandrogenic and Estrogenic Activity Evaluation of Oxygenated and Nitrated Polycyclic Aromatic Hydrocarbons Using Chemically Activated Luciferase Expression Assays.

To establish the risk of the endocrine disrupting activity of polycyclic aromatic compounds, especially oxygenated and nitrated polycyclic aromatic hydrocarbons (oxy-PAHs and nitro-PAHs, respectively), antiandrogenic and estrogenic activities were determined using chemically activated luciferase expression (CALUX) assays with human osteoblast sarcoma cells. A total of 27 compounds including 9 oxy-PAHs (polycyclic aromatic ketones and quinones) and 8 nitro-PAHs was studied. The oxy-PAHs of 7H-benz[de]anthracen-7-one (BAO), 11H-benzo[a]fluoren-11-one (B[a]FO), 11H-benzo[b]fluoren-11-one (B[b]FO), and phenanthrenequinone (PhQ) exhibited significantly the potent inhibition of AR activation. All nitro-PAHs exhibited high antiandrogenic activities (especially high for 3-nitrofluoranthene (3-NFA) and 3-nitro-7H-benz[de]anthracen-7-one (3-NBAO)), and the AR inhibition was confirmed as noncompetitive for 3-NFA, 3-NBAO, and 1,3-dinitropyrene (1,3-DNPy). Antiandrogenic activity of 3-NFA demonstrated characteristically a U-shaped dose-response curve; however, the absence of fluorescence effect on the activity was confirmed. The prominent estrogenic activity dependent on dose-response curve was confirmed for 2 oxy-PAHs (i.e., B[a]FO and B[b]FO). Elucidating the role of AR and ER on the effects of polycyclic aromatic compounds (e.g., oxy- and nitro-PAHs) to endocrine dysfunctions in mammals and aquatic organisms remains a challenge.

Characterization of unsubstituted and methylated polycyclic aromatic hydrocarbons in settled dust: Combination of instrumental analysis and in vitro reporter gene assays and implications for cancer risk assessment.

Concentrations of 34 unsubstituted and methylated polycyclic aromatic hydrocarbons (PAHs and Me-PAHs) and AhR-mediated activities in settled dust samples were determined by a combination of gas chromatography-mass spectrometry and an in vitro reporter gene assay (PAH-CALUX). The levels of Σ34PAHs and bioassay-derived benzo[a]pyrene equivalents (CALUX BaP-EQs) were significantly higher in workplace dust from informal end-of-life vehicle dismantling workshops than in common house dust and road dust. In all the samples, the theoretical BaP-EQs of PAHs (calculated using PAH-CALUX relative potencies) accounted for 28 ± 19% of the CALUX BaP-EQs, suggesting significant contribution of aryl hydrocarbon receptor (AhR) agonists and/or mixture effects. Interestingly, the bioassay-derived BaP-EQs in these samples were significantly correlated with not only unsubstituted PAHs with known carcinogenic potencies but also many Me-PAHs, which should be included in future monitoring and toxicity tests. The bioassay responses of many sample extracts were substantially reduced but not suppressed with sulfuric acid treatment, indicating contribution of persistent AhR agonists. Cancer risk assessment based on the CALUX BaP-EQs has revealed unacceptable level of risk in many cases. The application of bioassay-derived BaP-EQs may reduce underestimation in environmental management and risk evaluation regarding PAHs and their derivatives (notably Me-PAHs), suggesting a consideration of using in vitro toxic activity instead of conventional chemical-specific approach in such assessment practices.

Polycyclic aromatic hydrocarbons in airborne particulate matter samples from Hanoi, Vietnam: Particle size distribution, aryl hydrocarbon ligand receptor activity, and implication for cancer risk assessment.

Concentrations and profiles of unsubstituted and methylated polycyclic aromatic hydrocarbons (PAHs and Me-PAHs) were analyzed in airborne particulate matter (PM) samples collected from high-traffic roads in Hanoi urban area. Levels of PAHs and Me-PAHs ranged from 210 to 660 (average 420) ng/m3 in total PM, and these pollutants were mainly associated with fine particles (PM2.5) rather than coarser ones (PM > 10 and PM10). Proportions of high-molecular-weight compounds (i.e., 5- and 6-ring) increased with decreasing particle size. Benzo[b+k]fluoranthene, indeno[1,2,3-cd]pyrene, and benzo[ghi]perylene were the most predominant compounds in the PM2.5 samples. In all the samples, Me-PAHs were less abundant than unsubstituted PAHs. The PAH-CALUX assays were applied to evaluate aryl hydrocarbon receptor (AhR) ligand activities in crude extracts and different fractions from the PM samples. Benzo[a]pyrene equivalents (BaP-EQs) derived by the PAH-CALUX assays for low polar fractions (mainly PAHs and Me-PAHs) ranged from 300 to 840 ng/m3, which were more consistent with theoretical values derived by using PAH-CALUX relative potencies (270-710 ng/m3) rather than conventional toxic equivalency factor-based values (22-69 ng/m3). Concentrations of PAHs and Me-PAHs highly correlated with bioassay-derived BaP-EQs. AhR-mediated activities of more polar compounds and interaction effects between PAH-related compounds were observed. By using PAH-CALUX BaP-EQs, the ILCR values ranged from 1.0 × 10-4 to 2.8 × 10-4 for adults and from 6.4 × 10-5 to 1.8 × 10-4 for children. Underestimation of cancer risk can be eliminated by using effect-directed method (e.g., PAH-CALUX) rather than chemical-specific approach.

Inhalation bioaccessibility and health risk assessment of flame retardants in indoor dust from Vietnamese e-waste-dismantling workshops.

Although bioaccessibility testing is applied worldwide for appropriate chemical risk assessment, few studies have focused on the bioaccessibility of flame retardants (FRs), especially inhalation exposure. This study assessed inhalation exposure to FRs in indoor dust by workers at e-waste-dismantling workshops in northern Vietnam, by using modified simulated epithelial lung fluid (SELF) and artificial lysosomal fluid (ALF). The average mass concentrations of FRs were 130,000 ng/g for workplace dust (n = 3), 140,000 ng/g for floor dust (n = 3), and 74,000 ng/g for settled dust (n = 2), whereas the average bioaccessible concentrations of FRs were 1900, 1400, and 270 ng/g in the SELF condition and 2600, 770, and 490 ng/g in the ALF condition, respectively. Results clearly indicate that the bioaccessible concentrations of FRs are markedly lower than their mass concentrations. Tris(2-chloroethyl) phosphate (TCEP, ~19%), tris(2-chloroisopropyl) phosphate (TCIPP, ~35%), and tris(1,3-dichloroisopropyl) phosphate (TDCIPP, ~22%) showed comparably high bioaccessibility in both SELF and ALF conditions. In contrast, the bioaccessibility of tetrabromobisphenol A (TBBPA, ~20%) was high in the SELF condition, but not in the ALF condition. With regard to the test compounds' physicochemical properties, the inhalation bioaccessibility of FRs in both conditions increased as molecular weight or octanol-water partition coefficient decreased, and it decreased as water solubility decreased. Health risk assessment clearly indicated that the hazard quotient of FRs via inhalation exposure for workers in the e-waste-dismantling workshops was less than 1, suggesting that the inhalation exposure to FRs during indoor dismantling of e-waste at this site was negligible based on the current methodology of non-cancer health risk assessment used in this study.

Assessment and source identification of As and Cd contamination in soil and plants in the vicinity of the Nui Phao Mine, Vietnam.

This study investigated the contamination levels and sources of As and Cd vicinity area from Nui Phao mine that is one of the largest tungsten (W) open pit mines in the world. Soil and plant samples were collected from the study area to identify the concentrations of As and Cd using aqua-regia or HNO3 digestion. According to the Vietnamese agricultural soil criteria, all soil samples were contaminated with As and Cd. The distribution of As concentration is related to the distance from the Nui Phao mine. The higher As concentrations were measured in the area close to the mine. However, the Cd distribution in the soil showed a different pattern from As. Enrichment factor and Geoaccumulation Index (Igeo) indicated that As in the soil is derived from the mining activities, while Cd could have other geogenic or anthropogenic sources. The ranges of As and Cd concentration in polished rice grains in the Nui Phao mine area exceeded the CODEX criteria (0.2 mg/kg), which indicated extreme contamination. The arsenic concentration between soil and plant samples was determined to be a positive correlation, while the Cd concentration showed a negative correlation, implying that As and Cd have different geochemical behavior based on their sources.

Polychlorinated biphenyls in settled dusts from an end-of-life vehicle processing area and normal house dusts in northern Vietnam: Occurrence, potential sources, and risk assessment.

Concentrations and congener-specific profiles of total 209 polychlorinated biphenyls (PCBs) were investigated in settled dust samples collected from end-of-life vehicle (ELV) processing, urban, and rural areas in northern Vietnam. Concentrations of total 209 PCBs, seven indicator congeners, and twelve dioxin-like PCBs decreased in the order: ELV working > ELV living ≈ urban > rural dusts. Penta- and hexa-CBs dominated the homolog patterns in all the samples with higher proportions in the ELV dusts compared to the urban and rural house dusts. The abundance and pattern of PCBs in the ELV dusts suggest on-going emissions of these compounds related to processing of vehicular oils and lubricants containing PCBs, whereas the presence of PCBs in the urban and rural house dusts indicate long-time releases. However, levels of some PCBs identified as by-products of pigment manufacturing (e.g., PCB-11 and PCB-209) were higher in the urban house dusts than those from other locations, resulting from human activities utilizing paints and pigments. Daily intake doses (ID), non-carcinogenic hazard quotient (HQ), and lifetime cancer risk (CR) of PCBs through dust ingestion were estimated for ELV workers and residents in the studied areas. The workers and children in the ELV sites were estimated to be at higher risk of PCB exposure, however almost all of the HQ < 1 and CR < 10-4 indicate no serious risk related to dust-bound PCBs.

Contamination of heavy metals in paddy soil in the vicinity of Nui Phao multi-metal mine, North Vietnam.

Nui Phao mine in Thai Nguyen Province, Vietnam, is the second-largest tungsten (W) open-pit mine in the world, but the level of environmental impacts is not well known. In order to examine the heavy metal contamination in the ecosystem of this mining area, we analyzed six trace elements (As, Cd, Cr, Cu, Pb and Zn) in the collected soil samples. The analytical results showed that all the soil samples were contaminated by Cd and As. Most of the soil samples were contaminated by As (mean value 50.93 ± 55.44 mg/kg) and Cd (mean value 15.22 ± 9.51 mg/kg), which figures are up to 16 and 23 times higher, respectively, compared with the Vietnamese soil quality standard for agriculture (QCVN 03-MT:2015/BTNMT) of 15 mg/kg for As and 1.5 mg/kg for Cd. Contamination factor (CF), enrichment factor (EF), geo-accumulation index (Igeo), principal component analysis (PCA) and hierarchical clustering analysis (HCA) were used to identify the influence of mining activity in the contamination. The CF, EF, pollution index (PI) and Igeo indicated that this area was extremely polluted by Cd, severely to moderately-heavily polluted by As and slightly to moderately polluted by other elements such as Cr, Cu, Pb and Zn. The PCA and HCA results also attribute the source of As, Pb and Zn contamination and enrichment of Cd, Cr and Cu in the study area to Nui Phao mining activities. The PI and contamination degree (Cd) values of soil quality indicate that the study area was contaminated with particular reference to Cd and As and the level of contamination was decreased in the order of Pb > Cr > Cu > Zn. The study area had high potential ecological risk, and the carcinogenic risk value was higher than the acceptable value (1 × 10-6 to 1 × 10-4). This means that the local resident health is strongly affected by Nui Phao mining activities both directly and indirectly via food consumption, when rice plant grown in the paddy field is the dominant crop in the study area.