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Abstract
A regional workgroup comprised of individuals from regulatory agencies, uni versities, and consulting companies was formed to develop an approach for incor porating information on chemical availability in soils into risk assessment and risk based decision making. The approach consists of the following decision framework for including information on chemical availability: (1) Determine the usefulness of incorporating information on bioavailability; (2) Identify information needs from a conceptual model of exposure for the site and from exposure pathways judged critical to the assessment; (3) Identify soil factors that affect bioavailability; (4) Determine the type or form of information (measures and/or models) that can be used within the risk assessment and risk management process; (5) Select methods (measures and/or models) based on the “weight of evidence” or strength of the bioavailability information they will provide and how that information will be used for risk assessment and risk based decision making; (6) Incorporate information into the risk assessment and risk based decision making. These fac tors can be integrated into existing risk based approaches for site management such as Superfund, state approaches, and the ASTM Risk Based Corrective Action Process (RBCA). Consistent with risk assessment guidance, an assessment of chemical availability in soils must consider current as well as reasonably foresee able conditions. The approach recognizes that information on chemical availabil ity is contextual and depends on the receptor and pathway. Further, the value of information depends on how well it is accepted and/or validated for use in regulatory decision making. The workgroup identified four principles for select ing methods (measures and/or models) for obtaining information on chemical availability and for evaluating information on chemical availability for use in risk assessments: (1) soil chemical relevance, (2) pathway relevance, (3) receptor relevance, and (4) acceptance of the method.