Managing Global Resources for a Secure Future

Arsenic, Pb and Cd in soils are of great environmental concern due to its extensive contamination and toxicity. Anthropogenic activities including mining, smelting, and industrial uses are the main sources of their contamination. When considering As, Pb, and Cd risks via incidental soil ingestion, human exposure is greatly influenced by their bioavailability in soils (i.e., the proportion of metals that are absorbed into the systemic circulation). Animal models including mouse and swine have been used to estimate metal relative bioavailability (RBA; relative to the adsorption of soluble references). To measure metal RBA, different endpoints (metal concentration in blood, kidneys, liver, or urine) have been used to determine metal absorption following a single gavaged dose or multiple repeated doses of contaminated soil via diet. The objectives of this study were to develop and compare mouse models to determine the RBA of As, Pb or Cd in contaminated soils. Metal-RBA varied greatly with soils and metals. The As-RBA in 12 As-contaminated soils was 6.4-73% based on a mouse blood model via a single dose, while the Pb-RBA in 12 Pb-contaminated soils was 7.0-84%, and Cd-RBA in 12 Cd-contaminated soils was 37-84% based on a mouse kidney model via steady state dosing. As expected, soils impacted by mining and smelting showed lower RBA due to the presence of higher Fe oxides and/or insoluble metals. Based on the data, it is important to determine metal bioavailability to proper assess their risks to humans.