Mouse Assay for Determination of Arsenic Bioavailability in Contaminated Soils

Abstract

A mouse assay for measuring the relative bioavailability (RBA) of arsenic (As) in soil was developed. In this study, results are presented of RBA assays of 16 soils, including multiple assays of the same soils, which provide a quantitative assessment of reproducibility of mouse assay results, as well as a comparison of results from the mouse assay with results from a swine and monkey assay applied to the same test soils. The mouse assay is highly reproducible; three repeated assays on the same soils yielded RBA estimates that ranged from 1 to 3% of the group mean. The mouse, monkey, and swine models yielded similar results for some, but not all, test materials. RBA estimates for identical soils (nine test soils and three standard reference materials [SRM]) assayed in mice and swine were significantly correlated (r = 0.70). Swine RBA estimates for 6 of the 12 test materials were higher than those from the mouse assay. RBA estimates for three standard reference materials (SRM) were not statistically different (mouse/swine ratio ranged from 0.86–1). When four test soils from the same orchard were assessed in the mouse, monkey, and swine assays, the mean soil As RBA were not statistically different. Mouse and swine models predicted similar steady state urinary excretion fractions (UEF) for As of 62 and 74%, respectively, during repeated ingestion doses of sodium arsenate, the water-soluble As form used as the reference in the calculation of RBA. In the mouse assay, the UEF for water soluble As^V (sodium arsenate) and As^III (sodium [meta] arsenite) were 62% and 66%, respectively, suggesting similar absolute bioavailabilities for the two As species. The mouse assay can serve as a highly cost-effective alternative or supplement to monkey and swine assays for improving As risk assessments by providing site-specific assessments of RBA of As in soils.

Acknowledgments

The U.S. Environmental Protection Agency funded and managed the research described here. It has been subjected to agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Portions of this work were funded by the U.S. Environmental Protection Agency Office of Superfund Remediation and Technology Innovation, under General Services Administration Contract GS 00F 0019L. The authors gratefully acknowledge advice and assistance from the following people who contributed to the planning and execution of this work: Michele Burgess and James Konz, Office of Superfund Remediation and Technology Innovation, Science Policy Branch. The authors appreciate materials provided by Sophia Serda, U.S. EPA Region 9. MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. The authors appreciate review and comments on the article provided by William Brattin of SRC, Inc. Arsenic RBA estimates from monkey assays were generously provided to the U.S. EPA by Dr. Steve Roberts of University of Florida.