PARENT SESSION
39 - Appraising and Quantifying Bioavailable Pollutant Fractions
7:50 AM to 6:30 PM, Tuesday, 14 May 2002
Exhibition Area

(39-11) Comparison of five in vitro digestion models to study bioaccessibility of soil contaminants .

Oomen, A.^*,1, Hack, A.², Minekus, M.³, Zeijdner, E.³, Cornelis, C.⁴, Schoeters, G.⁴, Verstraete, W.⁵, Van de Wiele, T.⁵, Wragg, J.⁶, Rompelberg, C.¹, Sips, A.¹, Van Wijnen, J.⁷, ¹ RIVM, Bilthoven, The Netherlands² Ruhr-Universitaet, Bochum, Germany³ TNO Nutrition, Zeist, The Netherlands⁴ VITO, Mol, Belgium⁵ LabMET, Ghent University, Ghent, Belgium⁶ British Geological Survey, Nottingham, United Kingdom⁷ GG&GD, Amsterdam, The Netherlands

ABSTRACT- Soil ingestion can be a major exposure route for humans to many immobile soil contaminants. Exposure to soil contaminants can be overestimated if oral bioavailability is not accounted for. Recently, several in vitro digestion models simulating the human gastro-intestinal tract have been developed to assess mobilisation of contaminants from soil during digestion, i.e. bioaccessibility. Bioaccessibility is a crucial step of oral bioavailability for soil contaminants. Presently, a multilaboratory comparison and evaluation of five in vitro digestion models is performed. Their experimental design and results of a round robin of three soils, each contaminated with arsenic, cadmium and lead, are discussed. A wide bioaccessibility range was determined for the three soils, for As 6 - 95%, 1 - 19%, 10 - 59%, for Cd 7 - 92%, 5 - 92%, 6 - 99%, and for Pb 4 - 91%, 1 - 56%, 3 - 90%. Bioaccessibility was often <50%, indicating that accounting for bioavailability can have implications for risk assessment. Although the experimental design of the digestion systems is very distinct, the main differences in bioaccessibility can be explained by the applied gastric pH. High values are typically observed for a method that measures bioaccessibility in the gastric compartment at low pH (pH 1.5). Other methods that also apply a low gastric pH, and include intestinal conditions, produce lower bioaccessibility values. The lowest bioaccessibility values are observed for a method employing high gastric pH of 4.0.

Key words: oral bioavailability, bioaccessibility, in vitro digestion models, metals