Comparison of in vitro models in a mice model and investigation of the changes in Pb speciation during Pb bioavailability assessments.

In this study, the predominant Pb minerals prior to and after Pb relative bioavailability (Pb-RBA) and Pb bioaccessibility (Pb-BAc) tests were identified using SEM (scanning electron microscopy), XANES (X-ray absorption near edge structure) and XRD (X-ray diffraction). The correlations between in vitro Pb-BAc (using the UBM (Unified BARGE Method) and RBALP (Relative BioAccessibility Leaching Procedure) models) and in vivo Pb-RBA (using endpoints of kidney and liver in an mice model) were determined. The results demonstrated that both RBALP and UBM (gastric phase) reliably indicate Pb-RBA (Pb-RBA). However, raising the solid:liquid ratio of the gastric phase of UBM is necessary to determine Pb-BAc if the soils contain total Pb >10,000 mg/kg. The comparison of Pb minerals prior to and after in vitro extractions demonstrated that the relatively soluble forms of Pb (PbSO, PbO and MgO Pb) start to dissolve than other forms of Pb minerals, suggesting there was no difference in Pb release between chemical-based (RBALP) and physiologically-based (UBM) models. The identification of the Pb minerals of Pb(PO)Cl and organically-complexed Pb in mice excreta demonstrated that a portion of Pb combined with food and humic acid to generate organically-complexed Pb in mice excreta, and that Pb(PO)Cl is not bioavailable.