which these factors are organized is called risk assessment. Risk assessment as first set forth by the National Research Council (NRC) in its 1983 report, and as affirmed by another NRC committee in 1994 (NRC, 1994), is a systematic means of evaluating the probability of occurrence of adverse health effects in humans from excess exposure to an environmental agent (in this case, a nutrient) (FAO/WHO, 1995; Health Canada, 1993). The hallmark of risk assessment is the requirement to be explicit in all of the evaluations and judgments that must be made to document conclusions.

Risk assessment is a scientific undertaking having as its objective a characterization of the nature and likelihood of harm resulting from human exposure to agents in the environment. The characterization of risk typically contains both qualitative and quantitative information and includes a discussion of the significant scientific uncertainties in that information. In the present context, the agents of interest are nutrients, and the environmental media are food, water, and nonfood sources such as nutrient supplements and over-the-counter pharmaceutical preparations. Additional human exposure to some dietary agents, including nutrients, sometimes occurs through other media, such as air. For example, inhaling zinc oxide in an industrial setting is associated with metal fume fever (Hodgson et al., 1988). The applications of risk assessment to nutrients and other food components in general are the subject of this section, although the principles and methods discussed are more broadly applicable.

Performing a risk assessment results in a characterization, with due attention to scientific uncertainties, of the relationships between exposure(s) to an agent and the likelihood that adverse health effects will occur in members of exposed populations. Scientific uncertainties are an inherent part of the risk assessment process and are discussed below. Deciding whether the magnitude of exposure is “acceptable” or “tolerable” in specific circumstances is not a component of risk assessment; this activity falls within the domain of what is called risk management. Risk management decisions depend on the results of risk assessments but may involve additional considerations, such as the public health significance of the risk, the technical feasibility of achieving various degrees of risk control, and the economic and social costs of this control. Because