Abstract: In this study, the gas–particle distribution characteristics and emission sources of phthalate esters (PAEs) and volatile methyl siloxanes (VMSs) were evaluated for indoor air samples collected from different micro-environments such as homes, offices, kindergartens, hair salons, laboratories, and cars in 4 cities and provinces of Hanoi, Bac Ninh, Thai Binh, and Tuyen Quang, northern Vietnam. In general, total concentrations of PAEs and VMSs were higher in gas phase as compared to particle phase; however, phase distribution profiles of individual compounds were strongly related to their structures and physicochemical properties. For examples, low-molecular-weight compounds such as dimethyl phthalate, diethyl phthalate, D3, D4, L4, and L5 were more abundant in gas phase, while heavier compounds like di(2-ethylhexyl) phthalate and L8 were preferentially associated with particle phase. Assessment of PAE emission sources is relatively difficult because they have been applied in different consumer products and materials. Significant correlation between cyclic VMSs (e.g., D4, D5, and D6) was observed, suggesting their applications in cosmetics and personal care products. Keywords: Phthalate esters, volatile methyl siloxanes, indoor air, phase distribution, source apportionment.  

Abstract: In this study, a rapid analytical method was developed and validated for the determination of polybrominated diphenyl ethers PBDEs in house dust samples. The dust sample was solvent extracted by using a focused ultrasonic processor with reduced extraction time (total 30 min/sample) and solvent volume (about 30 mL/sample). The crude extract was purified by passing through a self-packed multilayer column containing 44% sulfuric acid impregnated silica gel, Florisil, and anhydrous sodium sulfate. PBDEs were eluted from the clean-up column by a mixture of dichloromethane in hexane (1:3,…). PBDEs (41 mono- to deca-BDE congeners) were analyzed by using gas chromatography/mass spectrometry (GC/MS) with negative chemical ionization (NCI) and selected ion monitoring (SIM) mode. The analytical method was validated by using procedural blank, matrix-spike, and standard reference material (SRM) samples. Recoveries of PBDEs in spiked samples ranged from 65% to 120%. Analytical results of the SRM 2585 (Organic Contaminants in House Dust, National Institute of Standards and Technology, USA) indicate method accuracy with ratios of measured to certified values of almost compounds ranging from 76% to 110%. All the experiments were conducted in duplicate, showing acceptable repeatability (RSD 〈 15%). This method can be applied for simultaneous determination of mono- to deca-BDE congeners in dust samples at ppb to ppm levels with several advantages such as simple, rapid, accurate, cost-effective, and reducing amounts of chemicals and solvents.

Abstract: Concentrations of polychlorinated biphenyls (PCBs) including 43 congeners of 10 homologs were determined in settled dust samples collected from urban houses and end-of-life vehicle (ELV) processing workshops in northern Vietnam. Concentrations of total 43 PCBs (ΣPCBs), 7 indicator PCBs (IN-PCBs), and 12 dioxin-like PCBs (DL-PCBs) in the ELV workshop dusts were significantly higher than those measured in the urban house dusts, suggesting ELV processing activities as potential sources of PCBs. However, concentrations of PCB-11 (3,3’-dichlorobiphenyl) in the urban house dusts (mean 4.5; range 1.2–8.7 ng/g) were markedly higher than levels found in the ELV workshop dusts (1.6; 0.46–5.4 ng/g). PCB-11 is a novel congener because it is only a trace component of technical PCB mixtures but identified as a major impurity of many organic pigments, especially diarylide yellow pigments. PCB patterns of the ELV workshop dusts were dominated by penta- and hexa-PCBs with major congeners as PCB-118, -138, -153, -110, and -101, which were also principal components of technical formulations such as Aroclor 1254, Kanechlor 500, and Sovol. Meanwhile, PCB-11 served as the most predominant congener detected in the urban house dusts, implying current emissions from paints and pigmented products; however, this point should be confirmed by further studies on the occurrence of PCBs in Vietnamese commercial products. Apart from PCB-11, the urban house dusts also contained elevated proportions of penta- and hexa-PCBs, suggesting residues from electrical equipment application in the past. Our results indicate that even though PCBs are legacy and banned chemicals, their presence has been observed in indoor environments due to their persistent nature and novel emission sources. Further studies on the occurrence and emission behavior of these pollutants should be conducted, including not only congeners in technical mixtures but also unintentionally produced compounds.

Abstract: Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in settled house dust and road dust samples collected from a core urban area of Hanoi. Levels of PAHs ranged from 830 to 3500 (median 2000) ng/g in house dust, and from 1400 to 4700 (median 1700) ng/g in road dust. Concentrations of PAHs in dust samples of this study were within the moderate range as compared with those from other countries in the world. Toxic equivalents to benzo[a]pyrene (BaP-EQs) in our samples ranged from 81 to 850 (median 330) ng BaP-EQ/g with principal contributors as BaP and dibenz[a,h] anthracene, which accounted for 69% to 93% of BaP-EQs. In almost all the samples, proportions of high-molecular-weight PAHs (HMW-PAHs with 4–6 rings) were higher than those of low-molecular-weight PAHs (LMW-PAHs with 2–3 rings), suggesting emission sources from combustion processes rather than direct contamination by petrogenic sources. 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