Dioxins in fly ash extract

The origin of the dioxin problem can be traced back to the Second World War when the production of polychlorophenol-based pesticides was launched. In particular, the industrial production of 2,4,5-trichlorophenol and its corresponding herbicide 2,4,5-trichlorophenoxyacetic acid has led to a number of accidents resulting in the release of 

8- tetrachlorodibenzo(p)dioxin into the environment. Workers exposed to the compounds released were found to suffer from an unknown skin disease caused by 

8- tetrachlorodibenzo(p)dioxin, as identified by a German team in 1957 [18]. The occurrence of a number of accidents, one of which was the well known Seveso explosion in Italy in 1976, made the dioxin problem into what it is today a top-priority, scientific, social, economic and political topic. 

In the last twenty years, PCDD and PCDF were identified as by-products in many industrial processes which involve chlorine or chlorinated compounds. Additionally both groups of compounds were found to be formed in a broad range of combustion processes, including accidental fires. Municipal waste incineration is particularly considered to be a very important, if not the most important, of the identified source of environmental dibenzo-p-dioxin and dibenzofuran contamination. As a consequence, the evaluation and close control of new and existing installations for their dioxin releases has become a major concern. Based on this relative importance of municipal waste incinerators, and taking into account the relative toxicity data actually available for PCDD and PCDF, it was decided to prepare and certify a crude fly ash extract (CRM 429) for the twelve more toxic PCDD and PCDF [18,19]. 

About 40 kg of fly ash was collected from an average municipal waste incinerator. Three samples, taken randomly from the bulk material, were analysed, using validated laboratory procedures, in order to ensure that the levels of the twelve target congeners were adequate for certification (i.e. at least three times the limits of detection of MS). The collected material fulfilled these requirements it was treated in separate batches of 330 g which were transferred into 2 L erlenmeyer flasks and suspended in a mixture of 1 L bidistilled water and 100 mL of 12.5 mol L hydrochloric acid. The suspension was stirred magnetically for 2 h. The bulk of the fly ash was separated from the supernatant after centrifugation. The precipitate was then re-suspended several times 

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