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DRI DIETARY REFERENCE INTAKES FOR Vitamin C, Vitamin E, Selenium, and Carotenoids
degree of scientific support. Indeed, appropriate analysis of uncertainties seems to require such a presentation of risk results. Although presenting a number of plausible risk estimates has the advantage that it would seem to more faithfully reflect 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 in risk assessment are summarized in Table G-1.
As can 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 are, however, offered.
TABLE G-1 Approaches for Dealing with Uncertainties in a Risk Assessment Program
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; maximization of transparency of process; resolution of scientific disagreements possible by resort to defaults
Possible difficulty in justifying departure or achieving consensus among scientists that departures are justified in specific cases; danger that uncertainties will be overlooked
Presentation of full array of estimates from all scientifically plausible models by assessors
Maximization of 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