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Risk:
Risk:
The likelihood that harm will result from exposure to a hazard. More generally, the probability that an event has occurred, or will occur, in members of a population under specified conditions, e.g., of exposure to a hazardous chemical; the "population at risk" consists of the subjects who could experience the event, e.g., who were exposed to the chemical. Risk is calculated by dividing the number of subjects who experience an event by the number of subjects in the population at risk. The risk, so calculated, is one of the bases used to estimate the likelihood that the event will occur in the future, the predicted risk. Risk, calculated as described, also indicates the probability that any individual subject in the population at risk experienced the event. (Formally, the idea of "risk" is applicable to the study of both desirable and undesirable events.)
For a meaningful estimate of risk (following exposure of subjects to some hazard), it is necessary to have carefully defined the harm that was done, to have characterized the population at risk, and to have specified the conditions of exposure. Interpreting an estimate of risk requires comparing the data with those from a "control" population, ideally one never exposed to the hazard. The statistical techniques used to estimate risks and to compare them are, generally, the techniques used in epidemiology.
Perceived risk is the subjective assessment of the importance of a hazard to individuals or to groups of individuals, For example, hazards that affect children generally have higher perceived risks than those that tend to affect adults. Hazards viewed as under a person's control (e.g., driving a car) generally have lower perceived risks than those viewed as not under such control (e.g., riding in a aircraft piloted by someone else). Hazards that produce fatalities grouped in time and space (e.g., airplane crashes) generally have higher perceived risks than those which produce fatalities scattered in time and space (e.g., automobile accidents), etc. Perceived risks are not necessarily correlated with the risks, for the same hazards, measures by epidemiologic techniques.
Risk management is the effort to reduce the likelihood that a hazard will produce harm. Risk management may involve decreasing the size of the population at risk (e.g., by prohibiting the use of a chemical as a food additive), altering the conditions of exposure (e.g., requiring adequate ventilation in an industrial environment), developing and using therapeutic regimens to minimize the consequences of exposure, etc.
Cf. Hazard, Toxicology
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