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



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

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