Validation of the Predictive Capabilities of the Sbrc-G in Vitro Assay for Estimating Arsenic Relative Bioavailability in Contaminated Soils

A number of bioaccessibility methodologies have the potential to act as surrogate measures of arsenic (As) relative bioavailability (RBA), however, validation of the in vivo-in vitro relationship is yet to be established. Validation is important for human health risk assessment in order to ensure robust models for predicting As RBA for refining exposure via incidental soil ingestion. In this study, 13 As-contaminated soils were assessed for As RBA (in vivo swine model) and As bioaccessibility (Solubility Bioaccessibility Research Consortium gastric phase extraction; SBRC-G). In vivo and in vitro data were used to assess the validity of the As RBA-bioaccessibility correlation previously described by Juhasz et al. (2009). Arsenic RBA and bioaccessibility in the 13 soils ranged from 6.8 +/- 2.4% to 70.5 +/- 6.8% and 5.7 +/- 0.3% to 78.4 +/- 0.8% respectively with a strong linear relationship (R-2 = 0.75) between in vivo and in vitro assays. When the As in vivo-in vitro correlation was compared that of Juhasz et al. (2009), there was no significant difference (P > 0.05) indicating that the relationship between As RBA and As bioaccessibility was consistent thereby demonstrating its validation. For these data, a grouped linear regression model was developed (R-2 = 0.82) with a slope and y-intercept of 0.84 and 3.56 respectively. A number of cross validation methodologies (2-fold, repeat random subsampling, leave one out) were utilized to determine the performance of the linear regression model. Residuals and prediction errors ranged from 5.4 to 9.4 and 6.9-12.2 respectively illustrating the capacity of the SBRC-G to accurately predict As RBA in contaminated soil.