Assessment, Correlation and Validation of Bioaccessibility Methods for Predicting As and Pb Relative Bioavailability in Contaminated Soil.

In order to refine risk calculations by adjusting the default bioavailability value, reliable assays are required that can quantitatively measure site specific bioavailability.  In vivo assays are considered the most reliable method for refining exposure models.  However, given the time and cost requirements, in addition to ethical issues, there is great demand for appropriate in vitro assays for estimating contaminant relative bioavailability.  In vitro assays that simulate gastrointestinal conditions are simple, rapid and inexpensive and numerous methods (e.g. SBRC, RBALP, PBET, SBET, IVG, DIN, RIVM, UBM, TIM, SHIME) have been developed over the past 20 years as potential surrogate measures of contaminant relative bioavailability.  While in vitro assays overcome the aforementioned shortfalls of in vivo methods, the development and assessment of bioaccessibility assays for predicting contaminant relative bioavailability is still an ongoing research endeavour.  Although considerable information is available regarding the bioaccessibility of priority contaminants (e.g. As and Pb) in mine impacted soils, limited information is available on the suitability of in vitro assays for predicting As and Pb relative bioavailability in non-mine impacted soils.  This is due in part by the limited number of soils which have been evaluated by in vivo assays, the reference point for determining which in vitro method most closely approximates relative bioavailability results.  This paper discusses the assessment, correlation and validation of bioaccessibility methods for predicting As and Pb relative bioavailability in contaminated soil.  The bioaccessibility of As and Pb in a variety of source dependent contaminated soils  is compared using a number of commonly utilised in vitro assays (SBRC, RBALP, PBET, IVG, DIN and UBM) while in vivo-in vitro correlations are presented using As and Pb relative bioavailability data derived using swine and mouse assays.