Assessment of cadmium bioaccessibility to predict its bioavailability in contaminated soils

In vitro assays have been developed to determine metal bioaccessibility in contaminated soils; however, their application to Cd is limited. To assess their suitability to determine Cd relative bioavailability (RBA), Cd-RBA in 12 contaminated soils containing 3.00-296mgkg(-1) Cd were determined using a mouse model and compared with Cd bioaccessibility data based on four assays including the UBM, SBRC, IVG, and PBET. After being administered feed amended with soil or CdCl2 for 10-day, the Cd concentrations in the mouse liver and/or kidneys were used as biomarkers to estimate Cd-RBA. Cd-RBA was comparable at 34-90% and 40-78% based on mouse liver and kidneys with RSD of 7.10-8.99%, and 37-84% based on mouse liver plus kidneys with lower RSD of 5.8%. Cadmium bioaccessibility in soils varied with assays, with 61-99, 59-103, 54-107, and 35-97% in the gastric phase and 20-56, 38-77, 42-88, and 19-64% in the intestinal phase of the UBM, SBRC, IVG and PBET assays. Based on the combined biomarker of liver plus kidneys, better correlation was observed for PBET (r(2)=0.61-0.70) than those for IVG, UBM and SBRC assays (0.12-0.52). The monthly Cd intake in children was 0.24-23.9μgkg(-1) using total Cd concentration in soils, which was reduced by 43% to 0.18-12.3μgkg(-1) using bioavailable Cd. Our data suggest it is important to consider Cd-RBA to assess risk associated with contaminated soils and the PBET may have potential to predict Cd-RBA in contaminated soils.