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A kinetic model has been developed for the formation of selected congeners of PCDD/Fs during the thermal decomposition of different wastes in a horizontal reactor. Previously published data on the decomposition of wastes have been correlated using a kinetic model that only considers process parameters, such as the presence of different amounts of oxygen in the atmosphere of reaction, chlorine and metals in the waste. The effect of both chlorine and metals is modelled through an equation assuming a "saturation effect", i.e., that a certain amount of each substance produces the maximum rate, and that higher amounts do not increase the rate. The presence of oxygen is modelled by a destruction reaction over part of the PCDD/Fs produced. The model, which uses data from more than 64 experiments, correlated the emissions of three selected congeners: 1,2,3,6,7,8-HxCDD, OCDF and 2,3,7,8-TCDF, which are enough to estimate the total amount and toxicity of an emission. • Description of a new model for PCDD/F formation. • Data taken from combustion and pyrolisis of several wastes. • The dependence between PCDD/F congeners reduces the parameters needed by the model. • The model considers process variables such as temperature, O 2 , Cl and metal ratios. [ABSTRACT FROM AUTHOR]

The formation of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/F) is governed by complex chemical reactions with complex kinetic models. The simulation of Municipal Solid Waste incinerators, or other industrial thermal processes, is a powerful tool that can be used to optimize and control them, and reducing the number of components to simulate is mandatory for a proper use. In this study it has been determined that only the formation of 3 of the 17 main PCDD/F congeners can be considered as linearly independent. This fact has been used to establish linear regression models that are able to estimate properly the total amount and toxicity of a sample considering only the amount of 1,2,3,6,7,8-HxCDD, OCDF and 2,3,7,8-TCDF. All models have been validated using new samples performing a close approach to the real values provided by complete analytical studies. The average relative error is 3.5% and the maximum relative error is below 9% for these new testing samples. The main goal of our investigation is to build a dynamic simulation process of a MSW facility and include the dioxins formation on it using these models. [ABSTRACT FROM AUTHOR]

This study has investigated the photochemical degradation of polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and some organochlorine pesticides, such as hexachlorobenzene (HCB) or dichloro-diphenyl-trichloroethane (DDT) in hexane under UV irradiation at 254 nm. All pollutants were completely degraded after 3.5 h of exposition to the UV light. Moreover, this technique was applied to remove persistent organic pollutants from fish oil, with eliminations of a 34% for PCDD/Fs, 53% for PCBs, 59% for HCB, 67% for PBDEs and 73% for DDTs after 12 h of exposition to the UV light (254 nm). Dioxin-like PCBs increased their concentration after the treatment, probably due to the dehalogenation of other more chlorinated congeners. The fatty acids analysis of the fish oil revealed that the most important ω-3 fatty acids –EPA and DHA-were degraded to 67 and 70% of their initial content respectively. For these reasons elimination of persistent organic pollutants with photochemical treatment has limited applications for oils with food-purposes. However, it still can be a useful technique for decontamination of industrial oils. [Display omitted] • The degradation rate of POPs in hexane followed the order PBDEs >> marker PCBs > DDTs and HCB > dl PCBs > PCDD/Fs. • Photodegradation pathway occurs via dehalogenation following a pseudo-first order kinetic. • POPs in fish oil can be partially eliminated by photodegradation, but it also altered the fatty acid composition. • Photodegradation might not be suitable for food purposes, but it can be used for the decontamination of industrial oils. [ABSTRACT FROM AUTHOR]

Abstract: Fish oils are one of the main sources of ω-3 fatty acids in animal and human diet. However, they can contain high concentrations of persistent organic pollutants due to their lipophilic properties. The aim of this study is the reduction of persistent organic pollutants in fish oil using silicon-based and carbon-based solid adsorbents. A wide screening study with different commercially available adsorbents was carried out, in order to determine their capacity of pollutant removal from fish oil. Moreover, adsorption conditions were evaluated and optimized with using an experimental design and adjustment of the experimental results to response surfaces, obtaining removals rates of more than 99% of PCDD/Fs, 81% of dioxin-like PCBs, 70% of HCB, 41% of DDTs, 16% of marker PCBs and 10% of PBDEs. Finally, fish oil fatty acids were analyzed before and after the treatment with solid adsorbents, confirming that it did not affect its nutritive properties. [Copyright &y& Elsevier]

Abstract: During the last years, consumption of health supplements has increased in our society. They are recommended as an additional source of minerals, vitamins, omega-3 and omega-6 fatty acids, in the diet. A lot of these supplements contain oils among their components (fish oils or vegetable oils), especially those recommended for their omega-3 content. Due to their persistence and lipophilic characteristics, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (PCBs), marker PCBs, and polybrominated diphenyl ethers (PBDEs) bioaccumulate in fat tissues, especially in those animals, as fish, which show low metabolic capability. Therefore, the consumption of nutritional supplements with oil components can increase the intake of persistent organic pollutants (POPs) through the diet. The aim of this study was to analyse 15 of these supplements commercialized in Spain to determinate their POPs concentrations and their intake for their consumers. Concentrations of POPs in the dietary supplements studied (PCDD/Fs: 0.04–2.4pgTEQg−1; dl-PCBs: 0.01–12.1pgTEQg−1; marker PCBs: 0.17–116ngg−1; and PBDEs: 0.07–18.2ngg−1) were in the low-medium range of those reported in literature for other countries. Vegetable oil and mineral-based supplements showed concentrations of POPs clearly lower than those based on fish oil. Among these, those based on cod liver oil presented the highest concentrations detected in the study, exceeding the maximum levels established in European regulations for marine oils for human consumption. In general, the intake of POPs via the consumption of these supplements would be lower than the intake derived from fish consumption. [Copyright &y& Elsevier]

Studies the baseline levels of polychlorinated dibenzo-p-dioxins in soil and herbage samples collected in the vivinity of a harzdous waste incinerator in Catalonia, Spain.