National Academies Press: OpenBook

Issues in Risk Assessment (1993)

Chapter: Appendix H Workshop Summary

« Previous: Appendix G Contemplations on Ecological Risk Assessment
Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×

Appendix H
Workshop Summary

The workshop lasted only 3 days, and it was impossible to achieve consensus on every issue. There was general agreement on the need for ecological risk assessment to be broadly defined. As noted in the plenary presentations by Drs. Yosie, Lovejoy, and North, the policy needs that must be served are broad. Despite the diversity of environmental problems and the complexity of the science needed to address them, decision-makers need common frameworks for comparison and common procedures to ensure credibility.

Retrospective studies, such as those of TBT and the spotted owl controversy, which involve identification and resolution of existing problems, and predictive studies, such as those of agricultural chemical regulation and biological control, which are aimed at preventing new problems, involve different scientific approaches and rest on different information bases. The technical issues discussed at the workshop include the following:

  • Selecting among numerous possible end points at different levels of biological organization;

  • Extrapolating effects from one species or level of organization to others;

  • Discontinuities and nonlinear responses;

  • Spatiotemporal scaling;

  • Accounting for background variability;

  • Evaluating both quantitative and qualitative uncertainties.

Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×

Despite the complexities, there was a clear consensus that it is feasible to talk about assessing ecological risks in a manner analogous to human health risk assessment and that most, and perhaps all, types of ecological risk assessment can be accommodated within a single conceptual framework.

There was also a consensus that the health risk assessment framework presented in the NRC's 1983 report, although useful as a point of departure, is too narrowly defined for ecological risk assessment. Its most obvious weakness is its orientation toward toxic chemicals. Ecological risk assessment must be applicable to a much broader array of stresses. The discussion groups on exposure assessment and dose-response assessment agreed, however, that the concepts of exposure and dose-response could be generalized in a straightforward way to accommodate nonchemical stresses.

A clear theme running through nearly all the case studies and discussion groups was that the links between management and risk assessment are much stronger and more pervasive in ecological risk assessment than is indicated in the 1983 report. Subjects of particular importance include the role of policy, in the form of legal mandates and regulatory procedures, in defining an ecological hazard, the kinds of information to be used to assess risks, and the complexity of risk characterization in ecological risk assessment. Ecological risk assessment must include evaluations of kinds of uncertainty usually absent from health risk assessment, expression of risks in terms useful for decision-making (including economic valuations), and communication between risk assessors and risk managers, many of whom are not trained as ecologists. Several groups discussed possible modifications of the Red Book paradigm, but workshop participants as a whole were divided over whether to modify the paradigm or to develop a new one that is explicitly ecological.

A number of research needs themes surfaced at the workshop. These are too numerous to list here and are noted in the summaries of individual discussion groups. However, we note several common themes, some of which were discussed in more than one group:

  • Extrapolation across scales. Effects of interest to risk managers usually involve changes in populations or ecosystems. However, many stressors (including toxic chemicals and exploitation) act through direct

Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×

effects on individual organisms. Alternatively, risk managers might be interested in effects of large-scale regional change over long periods (e.g., logging of old-growth forest), but individual studies are restricted to relatively short periods and small areas. Some form of modeling appears generally necessary to make these extrapolations, but few models have been used.

  • Quantitative and qualitative analysis of uncertainty. It was amply noted that uncertainty in ecological risk assessment extends far beyond uncertainty in individual parameter values. Many of the uncertainties are related to extrapolations across scales and other kinds of qualitative gaps in knowledge. Those knowledge-based uncertainties result in many assessments being based principally on professional judgment, rather than on quantitative analysis. Evaluating the uncertainty inherent in professional judgments is as important as quantifying the uncertainty in model-based assessments.

  • Validation of predictive tools: Needs for validation were mentioned specifically in the risk characterization, uncertainty, and modeling groups and by plenary session speakers (Yosie and North). Validation could include both designed experiments and retrospective monitoring of the outcome of risk management decisions.

  • Expression of risks in policy-relevant terms. This topic was debated at length in discussions of risk characterization, the regulatory process, and valuation and was mentioned in plenary session presentations (by North, Yosie, and Slimak). Many difficulties were noted. Terms used by ecologists (such as ecosystem, stability, and resilience) are unfamiliar to decision-makers and the public, and their value is not immediately obvious. Expression in economic terms is attractive and is favored by decision-makers. However, the valuation discussion made it clear that many aspects of valuing ecological resources—especially nonuse values, such as biodiversity—involve economic theories and measurement methods that themselves are highly uncertain.

Some of the above issues might never be fully resolved. However, workshop participants familiar with health risk assessment often noted that the same or similar difficulties also affect health risk assessment, and the existence of difficulties has not precluded health risk assessments. In his closing statement, Dr. Barnthouse noted that the terms of discussion about ecological risk assessment have changed. In past years, the discussion was about whether the concept of risk and the methods of

Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×

quantitative risk assessment were even applicable to ecological problems. Future discussions will concern conceptual form, technical development, and implementation in specific circumstances. The reality of ecological risk assessment is now beyond dispute.

Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 343
Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 344
Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 345
Suggested Citation:"Appendix H Workshop Summary ." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 346
Next: Appendix I References for Appendixes »
Issues in Risk Assessment Get This Book
×
Buy Paperback | $65.00
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

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.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!