databases, NOAELs and LOAELs, and UFs. In cases where no data exist with regard to NOAELs or LOAELs for the group under consideration, extrapolations from data in other age groups and/or animal data are made on the basis of known differences in body size, physiology, metabolism, absorption, and excretion of the nutrient.

If the data review reveals the existence of subpopulations having distinct and exceptional sensitivities to a nutrient's toxicity, these subpopulations are considered under the heading “Special Considerations. ”



The accessibility of a nutrient to participate in metabolic and/or physiological processes.

Dose-Response Assessment:

The second step in a risk assessment in which the relationship between nutrient intake and adverse effect (in terms of incidence and/or severity of the effect) is determined.

Hazard Identification:

The first step in a risk assessment, which is concerned with the collection, organization, and evaluation of all information pertaining to the toxic properties of a nutrient.

Lowest-Observed-Adverse-Effect Level (LOAEL):

The lowest intake (or experimental dose) of a nutrient at which an adverse effect has been identified.

No-Observed-Adverse-Effect Level (NOAEL):

The highest intake (or experimental dose) of a nutrient at which no adverse effects have been observed.


Within the context of nutrient toxicity, the probability or likelihood that some adverse effect will result from a specified excess intake of a nutrient.

Risk Assessment:

An organized framework for evaluating scientific information, which has as its objective a characterization of the nature and likelihood of harm resulting from excess human exposure to an environmental agent (in this case, a dietary nutrient). It includes the development of both qualitative and quantitative expressions of risk. The process of risk assessment can be divided into four major steps: hazard identification, dose-response assessment, exposure assessment, and risk characterization.

Risk Characterization:

The final step in a risk assessment, which summarizes the conclusions from Steps 1 through 3 of the risk assessment and evaluates the risk. This step also includes a char-

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