Residue concentrations of polybrominated diphenyl ethers (PBDEs) in different kinds of samples including consumer products, indoor dust, sediment and fish collected from two e-waste recycling sites, and some industrial, urban and suburban areas in Vietnam were determined to provide a comprehensive assessment of the contamination levels, accumulation pattern, emission potential and human exposure through dust ingestion and fish consumption. There was a large variation of PBDE levels in plastic parts of obsolete electronic equipment (from 1730 to 97,300 ng/g), which is a common result observed in consumer plastic products reported elsewhere. PBDE levels in indoor dust samples collected from e-waste recycling sites ranged from 250 to 8740 ng/g, which were markedly higher than those in industrial areas and household offices. Emission rate of PBDEs from plastic parts of disposed electronic equipment to dust was estimated to be in a range from 3.4 × 10 to 1.2 × 10 (year) for total PBDEs and from 2.9 × 10 to 7.2 × 10 (year) for BDE-209. Some fish species collected from ponds in e-waste recycling villages contained elevated levels of PBDEs, especially BDE-209, which were markedly higher than those in fish previously reported. Overall, levels and patterns of PBDE accumulation in different kinds of samples suggest significant emission from e-waste sites and that these areas are potential sources of PBDE contamination. Intakes of PBDEs via fish consumption were generally higher than those estimated through dust ingestion. Intake of BDE-99 and BDE-209 through dust ingestion contributes a large proportion due to higher concentrations in dust and fish. Body weight normalized daily intake through dust ingestion estimated for the e-waste recycling sites (0.10-3.46 ng/day/kg body wt.) were in a high range as compared to those reported in other countries. Our results highlight the potential releases of PBDEs from informal recycling activities and the high degree of human exposure and suggest the need for continuous investigations on environmental pollution and toxic impacts of e-waste-related hazardous chemicals.

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Stack gas and fly ash samples were collected in two steel plants and three cement kiln plants for the determination of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). A standard sampling method (U.S EPA method 23) was used following the requirements for isokinetic sampling of stack gas emission. The quantification of PCDD/Fs was done by high resolution gas chromatography, coupled with high resolution mass spectrometry (HRGC/ HRMS). The results demonstrated that PCDD/F concentrations in steel plants varied from 0.234 to 0.577 ng/Nm 3 on a mass basis, and 0.048 to 0.166 ng/Nm 3 on a TEQ basis. In cement kiln plants, the mass concentration varied from 0.280 to 5.32 ng/Nm 3 , while TEQ concentration varied from 0.033 to 0.837 ng TEQ/Nm 3 . In general, PCDD/F emissions from steel industry in Vietnam were slightly lower than those reported for European Union, and were comparable to those reported for Taiwan and Korea. A similar trend was observed for the emissions of PCDD/Fs from cement kiln industry in Vietnam. PCDD/F emission factors for steel and cement kiln industries were also estimated to compare with the guidelines of the UNEP for persistent organic pollutants (POPs) inventory.

The Bien Hoa airbase (south of Vietnam) is known as one of the Agent Orange hotspots which have been seriously contaminated by Agent Orange/dioxin during the Vietnam War. Hundreds of samples including soil, sediment and fish were collected at the Bien Hoa Agent Orange hotspot for assessment of the environmental contamination caused by dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The toxicity equivalency quotient (TEQ) concentration of PCDD/Fs in soil and sediment varied from 7.6 to 962,000 and 17 to 4860 pg/g dry wt, respectively, implying very high contamination of PCDD/Fs in several areas. PCDD/F levels in fish ranged between 1.8 and 288 pg/g TEQ wet wt and was generally higher than advisory guidelines for food consumption. 2,3,7,8-Tetrachlorinated dibenzo-p-dioxins (2,3,7,8-TCDD) contributed 66-99 % of TEQ for most of the samples, suggesting 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) from Agent Orange as the major source of the contamination. The vertical transport of PCDD/Fs was observed in soil column with high TEQ levels above 1000 pg/g dry wt (Vietnamese limit for necessary remediation activities- TCVN 8183:2009 (2009)) even at a depth of 1.8 m. The vertical transport of PCDD/Fs has probably mainly taken place during the "Ranch Hand" defoliant spray activities due to the leaks and spills of phenoxy herbicides and solvents. The congener patterns suggest that transports of PCDD/Fs by weathering processes have led to their redistribution in the low-land areas. Also, an estimate for the total volume of contaminated soil requiring remediation to meet Vietnamese regulatory limits is provided.