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Preliminary Assessment of a Unified Bioaccessibility Method for Potentially Harmful Elements in Soils

Cave, Mark*; Wragg, Joanna*; Klinck, Ben*; Gron, Cristian; Oomen, Agnes; van de Wiele, Tom§; Ollson, Cris; Koch, Iris; Reimer, Ken; Basta, Nick; Tack, Karine**

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

*British Geological Survey; †DHI Soil and Water, Denmark; ‡RIVM, The Netherlands; §University of Ghent, Belgium; ¶Royal Military College of Canada; ∥Ohio State University; and **INERIS, France


Symposium Title: Childhood Exposures to Bioavailable Metals in Soil and Household Dust in Residential Environments

Symposium Organizers: Pat Rasmussen, Joanna Wragg, and Mark Cave


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When considering the direct ingestion of soil in risk assessment, total concentrations of potentially harmful substances (PHS) are often considered to be a gross overestimate of the amount of PHS entering the body. The human gastrointestinal tract only makes a fraction of the PHS accessible for absorption. U.K. technical guidance, however, permits the use of site-specific estimates of oral bioaccessibility.

This presentation describes 2 initiatives being undertaken by the BGS and the Bioaccessibility Research Group of Europe (BARGE) for standardized and validated procedures for measuring bioaccessibility by: 1) preparation of a reference soil to allow testing laboratories to monitor the QA of bioaccessibility measurement; and 2) development of a unified and validated in vitro bioaccessibility test.

Reference Soil Description and Methodology:

A total of 0.5 tonne of soil, of a similar type to the Banbury series (ferritic brown earth), was collected from North Lincolnshire. The sample was dried, ground, homogenized, and characterized and the total As concentration was found to be 87.1 ± 4.7 mg kg-1 with the bioaccessible As c.5 mg kg-1.

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The proposed unified procedure has been derived from the RIVM physiologically based in vitro extraction test.1 The performance of the method has been tested on 9 soils for which in vivo arsenic bioavailability data has been obtained using a swine model.2 The soils have been provided by Professor Nick Basta of the Ohio State University, Columbus, Ohio. The soils are calcine and iron slag soils with total As concentrations ranging from approximately 400 to 18000 mg kg-1 and relative bioavailabilities from approximately 4% to 40%. Initial studies have shown that the gastric phase bioaccessibility values from the unified procedure have a correlation coefficient of 0.907 and a regression line slope of 1.2 with the absolute bioavailability data.

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1. Oomen AG. Bioavailability of Soil Borne Contaminants. University of Utrecht; 2000.
2. Rodriguez RR, Basta NT. Casteel SW, Armstrong FP, Ward DC. Chemical extraction methods to assess bioavailable arsenic in soil and solid media. Journal of Environmental Quality. 2003;32:876–884.
© 2006 Lippincott Williams & Wilkins, Inc.