Evaluation of SBRC-gastric and SBRC-intestinal methods for the prediction of in vivo relative lead bioavailability in contaminated soils

In this study, lead (Pb) bioaccessibility in contaminated soils was assessed using an in vitro method (SBRC) encompassing gastric (SBRC-G) and intestinal (SBRC-I) phases. Initially, bioaccessibility studies were performed with a Pb reference material (Pb acetate, 1-10 mg L^-1) in order to determine the influence of pH on Pb solubility. In the gastric phase (pH 1.5), Pb solubility was 100% (100 ± 2.9%, n = 16) irrespective of the Pb concentration added, however, when the pH of the intestinal phase was increased to near neutral, Pb solubility decreased to 14.3 ± 7.2%. In contaminated soils, Pb bioaccessibility varied from 35.7 to 64.1% and 1.2 to 2.7% for SBRC-G and SBRC-I phases, respectively. When relative bioaccessibility (Rel-SBRC-I) was calculated by adjusting the dissolution of Pb from contaminated soils by the solubility of Pb acetate at pH 6.5 (intestinal phase pH), Rel-SBRC-I values ranged from 11.7-26.1%. A stepwise regression model based on Pearson correlation factors was used to determine the suitability of in vitro assays for predicting in vivo (swine assay) relative Pb bioavailability. Rel-SBRC-I provided the best estimate of in vivo relative Pb bioavailability for soils used in this study (in vivo relative Pb bioavailability [%] = Rel-SBRC-I [pH 6.5%] x 0.58 + 1.98, r²) 0.53). The versatility of Rel-SBRC-I was demonstrated by accurately predicting relative Pb bioavailability from other reported in vivo studies.