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FIGURE 3-3 Illustration of the population at risk from excessive nutrient intakes. The fraction of the population consistently consuming a nutrient at intake levels in excess of the Tolerable Upper Intake Level (UL) is potentially at risk of adverse health effects. See text for a discussion of additional factors necessary to judge the significance of the risk. LOAEL = lowest-observed-adverse-effect level, NOAEL = no-observed-adverse-effect level.

  1. the fraction of the population consistently consuming the nutrient at intake levels in excess of the UL;

  2. the seriousness of the adverse effects associated with the nutrient;

  3. the extent to which the effect is reversible when intakes are reduced to levels less than the UL; and

  4. the fraction of the population with consistent intakes above the NOAEL or even the LOAEL.

The significance of the risk of excessive nutrient intake cannot, therefore, be judged only by reference to Figure 3-3, but requires careful consideration of all of the above factors. Information on these factors is contained in this report’s sections describing the bases for each of the ULs.


Dourson ML, Stara JF. 1983. Regulatory history and experimental support of uncertainty (safety) factors. Regul Toxicol Pharmacol 3:224–238.

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