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ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts

How Can Information on Oral Bioavailability Improve Human Health Risk Assessment for Lead-contaminated Soils? Implementation and Scientific Basis

Oomen, Agnes G.; Brandon, Esther F. A.; Swartjes, Frank A.; Lijzen, Johannes P. A.; Sips, Adrienne J. A. M.

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In The Netherlands, in present human health risk assessment of contaminated soils, a relative bioavailability factor of “1” is used. This means that it is assumed that there is no difference in the bioavailability of a contaminant from soil compared with the bioavailability from the matrix used in the studies underlying the intervention value for remediation, which is typically a food or water matrix. However, there is ample evidence demonstrating that the bioavailability of a contaminant from a soil matrix can be considerably lower than from food or water. This presentation addresses how the assessment of human health risks due to exposure to lead through soil ingestion can be improved by using specific information on oral bioavailability of lead in the human body. The research focused on the contaminant lead, because lead is frequently encountered in soil at high concentrations. Furthermore, soil ingestion is an important pathway of exposure for lead, especially for children, leading to potential adverse effects. Therefore, the need for a realistic but still protective risk assessment for human health is high.

RIVM has developed a simple experimental tool, an in vitro digestion model, to supply information on the bioavailability of a contaminant in the human body after ingestion of contaminated soil. In this presentation, a concrete proposal is given for using information on oral bioavailability obtained with the in vitro digestion model into procedures to assess the soil quality according to the Dutch Soil Protection Act. To this purpose, a tiered approach is used.

In addition to the approach to implement specific information on oral bioavailability into risk assessment, also the scientific basis of the RIVM in vitro digestion model is addressed. The relationship between the results of the digestion model and the relative bioavailability factor are described. Furthermore, the results of the in vitro digestion model are compared with bioavailability data obtained in in vivo studies with juvenile swine (soils and bioavailability data kindly provided by Dr. Casteel [University of Missouri]). Together this provides a state-of-the-art overview of the proposal for application of information on oral bioavailability of soil contaminants into risk assessment in The Netherlands.

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