There was a consensus that modeling for retrospective and prospective analysis will likely play a more important role in ecological exposure assessment than it normally does in human health risk assessment. Direct measurements with personal monitors or tissue-fluid analysis, the preferred methods of human exposure assessment, usually are not feasible or are prohibitively expensive in ecological assessments. Modeling was at least an underlying concept in all the case studies.
Test of the Definition
The group tested its proposed definition by attempting to fit it to the case studies and the 13 issues addressed by the EPA Science Advisory Board (SAB) Relative Risk Reduction Project (EPA, 1990). The group concluded that the new definition fit all six case studies, but that the definition provided in the Red Book fit only the three chemical case studies. Similarly, the new definition fit all 13 of the issues addressed by SAB, but the Red Book definition fit only about half. Two of the six case studies (on species introductions and harvesting) were related to issues not addressed by SAB.
G. W. Suter II and W. A. Farland
This group first developed a definition of risk characterization for ecological assessment and then applied the definition to the six case studies. As in health risk assessment, the principal objectives of risk characterization are to integrate information on exposure and effects and organize the results for presentation to risk managers, stake-holders, and the public.
Definition of Risk Characterization
The group determined that integration of exposure and exposure-response assessments is a complex process that requires a great deal of expert judgment. For the relatively straightforward case of predictive