Mechanisms and Permanence of Sequestered Lead and Arsenic in Soils: Impact on Human Bioavailability

ER-1742

Objective

Lead (Pb) and arsenic (As) are the most common metals exceeding risk criteria because soil ingestion is the primary human health risk driver at many Department of Defense (DoD) sites contaminated with toxic metals. Many studies have shown that Pb or As bioavailability and not total content determines human risk from soil ingestion. However, the current regulatory paradigm for human health risk assessment (HHRA) of contaminated soils does not include the use of bioavailability measures. Use of contaminant total content instead of bioavailability is often overly conservative and can result in costly and unnecessary soil remedial action. By comprehensively linking soil Pb and As contaminant speciation with human bioavailability and determining the permanence of future human bioavailability of sequestered Pb and As in untreated and treated soils, this project seeks to provide science and technology transfer to increase the confidence level of site managers to incorporate site-specific bioavailability measures into site management decisions based on technically defensible cleanup goals while ensuring protection of human health and the environment.

The overall objective of this project is to provide basic research on the propensity of soils and soil amendments to decrease toxic metal bioavailability and increase long-term metal sequestration. Several novel aspects of this research include (1) a selection of soils from U.S. Environmental Protection Agency (USEPA), SERDP, and ESTCP projects focused on DoD sites to provide Pb and As binding mechanisms common to many soil types; (2) use of the inexpensive adult mouse model recently developed by EPA to estimate human bioavailability; (3) use of human Caco-2 cell lines coupled with in vitro gastrointestinal (IVG) methods to estimate human bioavailability; (4) evaluation of coupled chemical and biological processes on the permanency of sequestered metal in soil remediated by commonly accepted soil amendments; and (5) technology transfer from the EPA research team (via its Bioavailability Committee) to EPA regional offices.

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Technical Approach

In this project, researchers will determine the fundamental relationships between Pb or As soil binding mechanisms with surrogate methods used to estimate human bioavailability for unamended and amended soils. Binding mechanisms of Pb or As will be determined using advanced spectroscopy. Human bioavailability of Pb and As will be estimated using an in vivo model and IVG models. Additional studies will determine the impact of chemical and biological processes on the long-term permanency of the metal-soil binding mechanism and their impact on potential future bioavailability to humans. Results from metal-soil speciation studies will be cross-correlated with bioavailability studies to clearly link the binding mechanism or Pb or As in soil with human bioavailability surrogate endpoints.

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Benefits

A primary impediment to the use of bioavailability data in risk assessment and decision making by site managers is the absence of rapid and inexpensive tools for reliable human bioavailability estimates. This project will comprehensively evaluate tools for human bioavailability measures. Results from this study will lead to adoption of tools to provide reliable estimates of human bioavailability by DoD site managers, risk assessors, and the scientific community at large. A simple decision-based framework will enable use of information from this study to be put into practice. At the simplest level, this project will identify which soil types are most likely to result in a significant reduction in contaminant bioavailability and should be considered in an HHRA by site managers. (Anticipated Project Completion - 2013)

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Points of Contact

Principal Investigator

Dr. Nicholas Basta

The Ohio State University

Phone: 614-292-6282

Fax: 614-292-7432

Program Manager

Environmental Restoration

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
  • Technical Report - Additional interim reports, laboratory reports, demonstration reports, and technology survey reports.
  • Guidance - Instructional information on technical topics such as protocols and user’s guides.
  • Workshop Report - Summary of workshop discussion and findings.
  • Multimedia - On demand videos, animations, and webcasts highlighting featured initiatives or technologies.
  • Model/Software - Computer programs and applications available for download.
  • Database - Digitally organized collection of data available to search and access.