Assessing Oral Human Bioavailability of Arsenic in Soil with in Vitro Gastrointestinal Methods.

Ingestion of contaminated soil is an important exposure pathway in human and ecological risk assessment and often is the “risk-driver” for trace element contaminated soil.  Trace element exposure from soil ingestion depends on the bioaccessibility of the trace element (e.g., the amount dissolved in the gastrointestinal tract) and the subsequent absorption of the trace element across the gut epithelium.  Novel research efforts focusing on development and application of methods to measure contaminant bioaccessibility in contaminated soils have advanced on several continents.  The sustained increase in research publications, especially in the last 2 years, shows research in this area is past emergence and is maturing science.  However, the ability of in vitro methods to predict As bioavailability is very limited.  The main objective of this study was to determine the ability of in vitro gastro(intestinal) methods (i.e., bioaccessibility methods) to predict arsenic bioavailability in soils. Bioaccessible As was determined by a variety of in vitro gastro(intestinal) methods.  Relative bioavailable (RBA) As was determined from dosing trials using juvenile swine.  Limited results support that the IVG methods can accurately predict in vivo RBA As.   Soil properties were poor predictors of RBA As across all soils.  However, excellent agreement between measured and predicted values using soil property models was found for a narrower subset of soils. Results clearly show the ability of soil properties to predictive IVBA As is contaminant source dependent.  Further research on the effect of contaminant speciation of different contaminant sources on the ability of various in vitro methods to predict RBA As is needed.