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goals described above was the development of a hierarchical information package that would contain all relevant information arrayed in increasing complexity of description. That approach would allow the characterization to be understood as deeply as deemed necessary by various clients. Discussants characterized the product as ''simple words to complex graphs and charts," meaning that a good risk characterization should consist of a concise summary supported by detailed appendices.

The risk characterization should convey the nature of the uncertainties, so that clients understand that uncertainties arise from both a lack of specific knowledge and from the character of the available information (i.e., both what we do not know and what we do know contribute to our uncertainties). Finally, the characterization should convey perceived needs for information. It should clearly identify research or management practices that could reduce uncertainties or improve our ability to assess risk in the future.

Differences from and Similarities To the 1983 Report

Discussants considered the definition of risk characterization presented in the 1983 report (p. 20): "Risk characterization is the process of estimating the incidence of a health effect under the various conditions of human exposure described in exposure assessment. It is performed by combining the exposure and dose-response assessments. The summary effects of the uncertainties in the preceding steps are described in this step." It was generally felt that this aspect of risk assessment was the least well-developed component of the process. Discussants were particularly concerned that the characterization not only describe the incidence of potential ecological effects, but also consider types and levels of hazard and communicate what is known about the temporal aspects of a risk. Although it was not mentioned in the 1983 report, discussants stressed the importance of having the risk characterization represent an iterative process involving collaboration between the assessors and their clients.

All those points led to a consensus that risk characterization for ecological risk assessment should not be constrained by the 1983 report. It must represent a broader perspective on the nature of potential effects.



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APPENDIX F 321 original typesetting files. Page breaks are true to the original; line lengths, word breaks, heading styles, and other typesetting-specific formatting, however, cannot be About this PDF file: This new digital representation of the original work has been recomposed from XML files created from the original paper book, not from the retained, and some typographic errors may have been accidentally inserted. Please use the print version of this publication as the authoritative version for attribution. goals described above was the development of a hierarchical information package that would contain all relevant information arrayed in increasing complexity of description. That approach would allow the characterization to be understood as deeply as deemed necessary by various clients. Discussants characterized the product as ''simple words to complex graphs and charts," meaning that a good risk characterization should consist of a concise summary supported by detailed appendices. The risk characterization should convey the nature of the uncertainties, so that clients understand that uncertainties arise from both a lack of specific knowledge and from the character of the available information (i.e., both what we do not know and what we do know contribute to our uncertainties). Finally, the characterization should convey perceived needs for information. It should clearly identify research or management practices that could reduce uncertainties or improve our ability to assess risk in the future. Differences from and Similarities To the 1983 Report Discussants considered the definition of risk characterization presented in the 1983 report (p. 20): "Risk characterization is the process of estimating the incidence of a health effect under the various conditions of human exposure described in exposure assessment. It is performed by combining the exposure and dose-response assessments. The summary effects of the uncertainties in the preceding steps are described in this step." It was generally felt that this aspect of risk assessment was the least well-developed component of the process. Discussants were particularly concerned that the characterization not only describe the incidence of potential ecological effects, but also consider types and levels of hazard and communicate what is known about the temporal aspects of a risk. Although it was not mentioned in the 1983 report, discussants stressed the importance of having the risk characterization represent an iterative process involving collaboration between the assessors and their clients. All those points led to a consensus that risk characterization for ecological risk assessment should not be constrained by the 1983 report. It must represent a broader perspective on the nature of potential effects.