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New Testing Methods for Arsenic and Lead in Soil

EPA's innovative soil-testing methods could save millions in cleanup costs at Superfund sites across the nation.

Karen Bradham, Ph.D.

Karen Bradham, Ph.D., researching bioavailability methods.

Cleaning up arsenic and lead at Superfund sites can be an expensive proposition. Currently, if the levels of contaminants are high, the top layer of soil is removed and transported to a hazardous materials landfill for careful treatment to isolate and remove the toxic metals. The price tag for such remediation activities can reach into the millions of dollars per acre.

Developing rapid, reliable, and inexpensive tools for guiding remediation activities that effectively protect human health could have a big impact on the way Superfund and other contaminated sites are managed. When every acre spared from soil removal and treatment means a million less dollars spent, the savings add up fast.

EPA scientist Karen Bradham, Ph.D., and her research partners are working on just those kinds of tools. She and her collaborators are evaluating new and inexpensive methods for assessing arsenic levels as a means to improve human exposure estimates for soil arsenic and lead.

"Not all toxic metals present in soil are in a form that can harm humans or animals," Bradham explains. "Certain forms of arsenic and lead are not fully available or absorbed by the human body."

The amount that is absorbed is referred to as "bioavailable," meaning it is in a form that can enter the bloodstream and affect human health.

Bradham, along with EPA scientists Drs. David Thomas, Kirk Scheckel, and Mike Hughes are focusing their efforts on new methods of assessing bioavailability of arsenic and lead in contaminated soils.

One of the new methods they developed uses laboratory analyses that mimic the way the human digestive system absorbs arsenic to illuminate the amount of bioavailable arsenic in a given sample of contaminated soil.

Preliminary results have been encouraging. When researchers evaluated arsenic-contaminated soil samples from a Superfund site using the newly developed bioavailability methods, they found that only about half the arsenic was bioavailable. In this example, approximately 90 acres of soil would need to be removed, as opposed to the 117 acres that would have been slated for removal using cruder, more traditional tests. Those more traditional tests are based on measurements of total arsenic levels instead of that which is truly problematic for human exposure.

Science to Support
Superfund Clean Up

Each of EPA's 10 regional offices has a Superfund Technical Liaison (STL) who assists the regional Superfund staff with formulating cleanup decisions. STLs provide an important link between the "on the ground" work at the cleanup sites and the expertise of EPA's researchers by coordinating technical support through EPA's Technical Support Centers (TSCs). The TSCs are specialized resource centers dedicated to providing high-quality, quick-response technical expertise on hazardous waste issues to the regions.

For more information on the STL program and the TSCs, go to http://epa.gov/osp/hstl.htm.

The potential cost savings of the above example: $9 million.

Elizabeth Southerland, Ph.D., former director of the Assessment and Remediation Division in EPA's Office of Superfund Remediation and Technology Innovation, underscored the importance of this work. "The use of site-specific bioavailability information will lead to more accurate risk assessments and customized cleanup levels," she said.

With the new methods, EPA can better evaluate human exposure to toxic soil contaminants at a greatly reduced cost. Further, when a new chemical extraction lab method that's under development is complete, researchers will be able to determine the bioavailability of contaminants without the use of animal studies, greatly reducing testing costs as well.

Roseanne Lorenzana, D.V.M., Ph.D., a scientist in EPA's Pacific Northwest regional office, notes that results from this bioavailability research have already provided information and protocols for assessing large-area contaminations sites. "This research really shows the impact of EPA science on improving environmental decision-making," Lorenzana said.

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