. "Appendix C Options for Dealing with Uncertainties." Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: The National Academies Press, 1997.
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DRI DIETARY REFERENCE INTAKES FOR Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride
sults. Although presenting a number of plausible risk estimates has clear advantages in that it would seem to reflect more faithfully the true state of scientific understanding, there are no well-established criteria for using such complex results in risk management.
The various approaches to dealing with uncertainties inherent to risk assessment, and discussed in the foregoing sections, are summarized in Table C-1.
As will be seen in the chapters on each nutrient, specific default assumptions for assessing nutrient risks have not been recommended. Rather, the approach calls for case-by-case judgments, with the recommendation that the basis for the choices made be explicitly stated. Some general guidelines for making these choices will, however, be offered.
TABLE C-1 Approaches for Dealing with Uncertainties in a Risk-Assessment Program
Program Model
Advantages
Disadvantages
Case-by-case judgments by experts
Flexibility High potential to maximize use of most relevant scientific information bearing on specific issues
Potential for inconsistent treatment of different issues
Difficulty in achieving consensus
Need to agree on defaults
Written guidelines specifying defaults for data and model uncertainties (with allowance for departures in specific cases)
Consistent treatment of different issues
Maximize transparency of process
Allow resolution of scientific disagreements by resort to defaults
May be difficult to justify departure, or to achieve consensus among scientists that departures are justified in specific cases
Danger that uncertainties will be overlooked
Assessors asked to present full array of estimates, using all scientifically plausible models
Maximize use of scientific information
Reasonably reliable portrayal of true state of scientific understanding
Highly complex characterization of risk, with no easy way to discriminate among estimates
Size of required effort may not be commensurate with utility of the outcome
