Chromium Oral Bioavailability in 16 Contaminated Soils from Different Sources: Mouse Model Development and Cr Speciation in Soil and Mouse Tissues

Soil contamination by chromium (Cr) has attracted much public attention due to its ubiquity in the environment and toxicity to humans, with hexavalent CrVI being more toxic and mobile than trivalent CrIII. In this study, 16 soils contaminated from different sources were chosen to determine their Cr accumulation in mouse tissues and changes in Cr speciation in soils, and mouse intestinal contents, organs and excreta based on a steady-state mouse model. The Cr accumulation in mouse organs after exposing to CrVI was 1.6-2.6 fold greater than those exposing to CrIII. Further, Cr relative bioavailability (RBA) was measured using a mouse urinary excretion bioassay. Results show that Cr via oral digestion was mainly accumulated in the kidneys, with Cr-RBA in soils being 5.12-50.0%, averaging 15.6%. Besides soil properties, variation in Cr-RBA also depended on its contamination sources, with soils near electronic waste dismantling and tannery sites showing greater values. Further, instead of the CrVI contents in contaminated soils, Cr-RBA was closely related to the unreduced CrVI contents in mouse intestines, with 90.1% of CrVI being reduced before its absorption. This study helps to evaluate the health risks associated with Cr-contaminated soils by measuring Cr-RBA via a newly developed mouse model and its influence by Cr speciation. Our data suggest a potential risk associated with incidental exposure to Cr-contaminated soils via an oral pathway.