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Issues in Risk Assessment (1993)

Chapter: Analysis of Case Studies

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Suggested Citation:"Analysis of Case Studies." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.

identification in the case studies are as important in the presentation of hazard data as they are for health risk assessment.

Discussion of other questions suggested that the scope and definition of ecological risk assessment might be broader than the scope and definition of human health risk assessment in the Red Book. For example, risk management considerations (management and political pressures, social costs, economic considerations, and regulatory outcomes) were ingredients in all case studies and related discussions. Much attention was paid to the influence of management on the scope and design of assessment. Such considerations are absent from discussions of health risk assessment. Some participants also felt that generation of new data should be treated as an aspect of risk assessment, rather than restricting risk assessment to evaluation of data that are already in hand.

Discussion leaders questioned the role of valuation in hazard identification, but this issue was not discussed in detail. In view of repeated references to the question of end point selection as a valuation decision, additional examination on this point is needed.

The case studies illustrated the importance of a systematic presentation and evaluation of data used to identify hazard. Discussion leaders noted that presentation of hazard data was highly variable in the case studies and suggested that some of the hazard identification principles that guide health hazard evaluation might be useful, including emphasis on a complete and balanced picture of relevant hazard information. Specific criteria and questions that are critical to identifying ecological risk are needed to develop an operational definition of complete and balanced.

Analysis of Case Studies

Examination of the case studies revealed a variety of approaches to ecological hazard identification.

For the tributyltin study, hazard identification was based initially on field studies. Retrospective epidemiological studies included a monitoring program (both biological and chemical) and laboratory investigation of cause-effect relationships.

In pesticide risk assessments, as exemplified by the agricultural chemicals case study, neither laboratory nor field studies are required to establish a hazard. Instead, there is a regulatory presumption of hazard.

Suggested Citation:"Analysis of Case Studies." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
Page 310
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The scientific basis, inference assumptions, regulatory uses, and research needs in risk assessment are considered in this two-part volume.

The first part, Use of Maximum Tolerated Dose in Animal Bioassays for Carcinogenicity, focuses on whether the maximum tolerated dose should continue to be used in carcinogenesis bioassays. The committee considers several options for modifying current bioassay procedures.

The second part, Two-Stage Models of Carcinogenesis, stems from efforts to identify improved means of cancer risk assessment that have resulted in the development of a mathematical dose-response model based on a paradigm for the biologic phenomena thought to be associated with carcinogenesis.

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