PubMed · 6719113
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J L Fox. 1984-05-25. Tentative Agent Orange settlement reached.. https://doi.org/10.1126/science.6719113
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There is an increasing interest in the end-of-life management of polymers present in waste electrical and electronic equipment (WEEE). This is mainly due to high recycling and recovery quotas set by the European WEEE directive, which can only be fulfilled by including the plastic fraction in recycling and recovery approaches. Previous studies identified a high material diversity and various contaminants in WEEE plastics, including heavy metals, polybrominated biphenyls (PBB), diphenyl ethers (PBDE), as well as polybrominated dibenzodioxins and dibenzofurans (PBDD/F). These substances are regulated by European directives that limit their levels in marketable products. Consequently, both material diversity and contaminants are strong arguments against material recycling and point to hazardous waste treatment. However, recent developments in the production of flame retardants and electrical and electronic goods aimed to reduce contaminants and material diversity. Thus, the present study summarises updated contaminant levels of plastic fractions of European WEEE, as well as data on materials in waste housing polymers. Material characterisation revealed housing fractions to be interesting sources for polymer recycling, which however has to implement potent material separation and/or bromine elimination techniques. With respect to contaminants, our data indicate an effective phase-out of PBB, but still high levels of PBDE and PBDD/F are found. Sources and implications for the material recycling and thermal recovery approaches are discussed in detail.
While the sources of releasing dioxins have received much attention, the health risks of incinerators are studied considerably more than those of other sources, such as metallurgical industry. Furthermore, risk assessments focus primarily on the effects of single sources; few have addressed the aggregate risks from multiple sources in a region. When many sources of dioxins exist in an area, such as the Industrial Park located in the densely populated district-Siaogang District in southern Taiwan where 17 primary known PCDD/F stationary emission sources are clustered, is the aggregate exposure to these sources imposing high risks even though individual sources comply with emission standards? The study combined the multimedia and multiple pathway exposure modeling and site-specific exposure scenario to assess dioxin risks contributed by the 17 emission sources in the District, including municipal waste incinerators, medical waste incinerators, sinter plants, electric arc furnace, secondary aluminum smelters, cement kilns, etc. The average cancer risk of a resident living in the District was found to be 3.43E-04 under the site-specific exposure scenario. The top emission source is the sinter plant, followed by the electric arc furnace. The information has driven the local government to conduct more complete assessment and at the same time to consider enforcing a stricter local standard of dioxin emissions in the Siaogang District.
The purposes of this study are to construct a simple dioxin detection system using peptides that bind to dioxin, and to test the system on real environmental samples. In this method, dioxin and N-NBD-3-(3',4'-dichlorophenoxy)-1-propylamine (NBD-DCPPA) are competitively bound to the peptides synthesized on beads. The fluorescence intensity of the bead decreases with increasing dioxin concentration. The concentration of dioxin is determined by measuring the fluorescence intensity using a fluorescence microscope equipped with a CCD camera. The fluorescence microscope system was equipped with a motor-driven stage and could be used with 96-well microplates and analytical software that automatically measured the fluorescence intensity of the bead images in the wells. Dioxin detection conditions, reaction temperature, number of beads and concentration of the organic solvent were optimized. About 0.5 nM (150 pg mL(-1)) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TeCDD) could be detected under the optimized conditions. Environmental soil samples were subjected to the detection system using the peptide beads. Although the results obtained correlated poorly with the toxicity equivalency quantity (TEQ) concentration obtained by a GC/MS method, our method is robust enough as a prescreening method to detect at least 250 pg-TEQ g(-1), the survey level for soil as stipulated in the law concerning special measures against dioxins in Japan.