Use of Bioavailability Data for the Establishment of Alternate Cleanup Levels for Environmental Media. J. A. Bland, E. V. Sargent, and L. Tyls, Merck and Co., Inc., P.O. Box 100, WS2F-45, Whitehouse Station, NJ 08889; M. V. Ruby, Exponent, 4940 Pearl East Circle, Suite 300, Boulder, CO 80301; P. Chrostowski, The Weinberg Group Inc., 1220 Nineteenth Street, NW, Suite 300, Washington, DC 20036-2400; and T. Bingman, E. I. du Pont Chemicals, 894 Beaver Grade Road, Coraopolis, PA 15108
Sound science dictates that additional data are often necessary in order to reduce uncertainty in risk assessment. Identifying and reducing uncertainty are critical to the refinement of risk estimates and to the ultimate improvement of risk-based decision making. Acceptable cleanup levels for soil are generally established using an assumption that contaminants are 100% bioavailable. Bioavailability, or the fraction of a substance that is absorbed into the body, is known to vary according to the specific form of the contaminant and conditions of the environmental media in which it is found. While properly conducted bioavailability studies can lead to more accurate estimates of chemical exposure and help drive more appropriate and cost effective clean-up decisions, they can be expensive and time consuming. For this reason in vitro bioaccessibility systems which use the solubility of contaminants in physiological fluids as a surrogate for bioavailability have been developed. Use of bioavailability and bioaccessibility data require greater knowledge of the chemical form of the contaminants of concern, i.e., speciation. Remedial decisions where bioavailability has been considered will be reviewed as will limitations to the universal application of bioavailability to the establishment of alternate clean-up levels. The need for policy and guidance on the development and application of bioavailability data will also be discussed.
This work was supported by the American Industrial Health Council Environmental Health Risk Assessment Committee.
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