Comparison of different digestive tract models for estimating bioaccessibility of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) from red slag 'Kieselrot'

'Kieselrot' (red slag), a highly PCDD/F-contaminated leaching residue from a copper production process, has been used as surface layer for more than 1 .000 sports fields, playgrounds and pavements in Germany and neighbouring c ountries. Children can ingest this material directly by hand-to-mouth activ ities or soil-pica behaviour. Furthermore secondary contamination of farm l and or kitchen gardens by drift of red slag dust may lead to an enrichment of PCDD/F within the food chain. PCDD/F can be mobilized from contaminated materials by digestive juices and thus become bioaccessible for intestinal absorption. Two different digesti ve tract models were used to estimate the bioaccessibility of PCDD/F from r ed slag and to study the influence of food material on the mobilization of the contaminants. The bioaccessibility of PCDD/F from red slag depends on the charge of red s lag material used, the bile content of the intestinal juice and on the pres ence of lipophilic foodstuffs. A low bioaccessibility of less than 5 % was found when using a digestive tract model with a low bile content and in abs ence of food material. The bioaccessibility was estimated to be more than 6 0 % when using a model with a higher bile content and in the presence of wh ole milk powder. A low bioaccessibility of PCDD/F from red slag in general - as assumed until now and mentioned in legal provision was not confirmed b y our study. Considering observations for the different homologue groups it is obvious t hat bioaccessibility is the first of several important steps to estimate hu man health risks arising from contaminated materials. In case red slag cont aminated with PCDD/F their absorption rare in the digestive tract and/or me tabolism might be at least just like important.