UD prof to testify on toxics before congressional subcomittee

1:56 p.m., Sept. 24, 2003--Herbert Allen, a professor of civil and environmental engineering at UD, is slated to testify before a subcommittee of the U.S. House of Representatives on Thursday, Sept. 25, on the toxicity of mining wastes. Allen is director of UD's Center for the Study of Metals in the Environment and a recognized expert on the fate and effects of metals in water, sediment and soils.

“Mining waste materials often contain metals, such as copper and lead and metalloids, such as arsenic, that are commonly regarded as having the potential to be toxic to humans and to organisms in the environment,” Allen states in written testimony prepared for the Subcommittee on Energy and Mineral Resources of the House Resources Committee. “Whether toxicity occurs depends critically on the physical and chemical composition of the waste material and on the chemical conditions in the environment receiving the waste material,” he adds.

In his testimony, Allen argues that bioavailability—rather than the total volume of a discharged material—is the critical criterion to use in predicting toxic effects because “only the bioavailable fraction causes a toxic response.” Both the chemical form of a substance and interactions of the contaminant and organisms with other substances affect the bioavailability of the contaminant.

Allen further notes in his written testimony that the U.S. Environmental Protection Agency is developing a “Framework for Assessing Hazards and Risks of Metals and Metal Compounds,” and he adds that “the agency should be encouraged to apply the best science available as they complete the framework. This would emphasize the key roles of incorporating exposure and bioavailability in the assessment of risk of metals.”

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