National Academies Press: OpenBook

Issues in Risk Assessment (1993)


Suggested Citation:"VALIDATION OF PREDICTIVE TOOLS." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.

be reduced, but often they can be quantified using empirical regression techniques (Suter et al., 1983), time series analysis (Jassby and Powell, 1990), or formal model uncertainty analysis (Bartell et al., 1992). Di Toro and Fogarty et al. provided examples of model uncertainty analyses in their case study papers (Appendix E). Uncertainties related to inadequacies of models (or scientific ignorance in general) are much more difficult to quantify.

Choices between risk assessment methodologies often involve tradeoffs between different types of uncertainty. For example, decisions about the need for pesticide testing are now based on qualitative evaluation of toxicity and exposure data (Urban and Cook, 1986). Explicit models of the effects of toxicant exposure on the abundance and persistence of bird populations have been developed (Grier, 1980; Tipton et al., 1980; Samuels and Ladino, 1983) and could be used to quantify uncertainties related to variability in exposures or extrapolation from field plots to natural landscapes. Relying on expert judgment avoids the need to postulate particular mechanisms of exposure or complex population dynamics but prevents risk assessors from providing information on the value of collecting additional information to reduce uncertainties or providing information on the ecological costs and benefits of regulatory decisions. Using a model to quantify uncertainties would in principle permit more useful risk assessments, but if the model itself is a poor representation of reality, the results might be totally meaningless.

The committee believes that improvements are needed in techniques for qualitative and quantitative analysis of uncertainty for ecological risk assessment. Techniques for model uncertainty analyses developed by systems engineers have been used by ecologists for more than a decade (Gardner et al., 1981; Bartell et al., 1992; Di Toro, Appendix E). The large and growing technical literature on decision analysis (Raiffa, 1970; Lindley, 1985; Von Winterfeldt and Edwards, 1986) has been much less thoroughly exploited (see Walters (1986) and Reckhow (1990) for examples of ecological applications of Bayesian decision theory) and should be surveyed for potentially useful approaches.


Improvements in the mathematical models, qualitative and quantitative

Suggested Citation:"VALIDATION OF PREDICTIVE TOOLS." National Research Council. 1993. Issues in Risk Assessment. Washington, DC: The National Academies Press. doi: 10.17226/2078.
Page 262
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,'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!