National Academies Press: OpenBook

Issues in Risk Assessment (1993)

Chapter: Application to the Case Studies

« Previous: Differences from and Similarities To the 1983 Report
Suggested Citation:"Application to the Case Studies." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×

Specific protocols for ecological risk characterization will likely be developed only through practice.

Application to the Case Studies

The ecotoxicological case studies were sufficiently similar that common lessons could be drawn from them. The population-management case studies were diverse and are discussed separately.

Lessons learned from the ecotoxicological case studies regarding risk characterization are summarized as follows:

  • There was no attempt to carry out a risk characterization. None of these case studies included an actual risk assessment, and none contained attempts to convey the science in a risk perspective.

  • Ecotoxicological assessments are as amenable to the development of a risk characterization as health risk assessments.

  • Case study end points were not well characterized in general. Sentinel species were used in most cases. End points need to be put into perspective, so that the scope of the assessment and the relevance of measured versus predicted responses can be appreciated.

  • The quality of the data was not made explicit in the case studies.

  • Any inferences drawn on the basis of extrapolation across species or levels of organizations need to be carefully articulated, and uncertainties in them need to be explicit.

  • Each case needs a statement as to how the acquired data will affect future assessment. Not all data gaps represent data needs for ecological assessment.

  • Exposure-based partitioning was suggested as a means to put the scope of case assessments into perspective. It will help to determine whether a defined case represents a major or a minor route of environmental contamination or exposure.

The Georges Bank fishery study is the nearest of the population-management case studies to the conventional scheme of integrating exposure estimates (harvest) with exposure-response (fish population and community dynamics) models. Good features of this case study include development of alternative lines of evidence, acknowledgment of uncertainty,

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

and recommendations to resource managers for management experiments. The major unresolved problem in risk characterization is communication with managers. It was clear, both from the case study paper and from the discussion after the case study presentation, that fishery managers are resistant to ecological risk as a decision-driver, have a short time horizon, and have difficulty in appreciating the assumptions that underlie alternative models.

As described in the case study, the northern spotted owl assessment was not formulated in terms of risks, and the decision apparently was not based on analysis of the relationship of exposure (to logging) to effects (population reduction). Literal application of the risk characterization scheme developed by the group would require that spotted owl population characteristics be quantitatively related to habitat characteristics. Decisions concerning spotted owl management appear to have been based principally on qualitative habitat evaluation. Demographic models, such as the one presented in the case study, have been used principally as supporting lines of evidence. Uncertainty, especially concerning the link between spotted owl population dynamics and distribution patterns of old-growth forest, has not been systematically addressed.

The species introduction case study is not a risk assessment, as defined for this workshop. There is no scale of exposure (the species is successfully introduced or not), and the effects are qualitative (the species is effective or not; it becomes a pest or not). The risk assessment is intuitive and based on expertise, rather than on explicit assumptions and models. Because the regulatory approach used by USDA is not open, it is not subject to review and scrutiny, and no attempts are made to communicate the results beyond regulatory decision-makers. There is no acknowledgment of uncertainty, even though the number of alternative hosts tested is small relative to the diversity of potentially exposed species. The case study reminded the session participants of the space-shuttle program, which relied on intuitive risk assessments until catastrophic failure occurred. To outsiders, it is not clear whether the success of USDA's species introduction program in avoiding ecological catastrophes is due to luck or to the rigor of the evaluation program.

Suggested Citation:"Application to the Case Studies." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 322
Suggested Citation:"Application to the Case Studies." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
×
Page 323
Next: Agricultural Chemicals »
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!