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Hazard:
Hazard:
The potential for causing harm; that which is a potential cause of harm. With respect to chemicals which are capable of causing harm, "hazard" is about equivalent in meaning to "toxicity"; measuring the hazard or toxicity of a chemical is to measure its potency in producing harm: the lower the dose required to produce harm, the greater the hazard or toxicity, the more hazardous or toxic is the substance.
Since the time of Paracelsus, in the early 16th century, it has been recognized that all chemicals, given in sufficient doses, are capable of producing harm. Therefore, it is not very meaningful simply to call a chemical a hazard, or to speak of a chemical as hazardous, without qualification or definition. Three categories of information are needed to define a hazard: specific descriptions of the harms it can produce, specific identification of the species or kinds of subjects that can be harmed, and specification of the kinds of exposure to the chemical (including dose) which can result in the respective harms.
Observe that hazard is the potential for causing harm. However hazardous a chemical might be, it may present no risk if potential victims are not exposed to it! Risk management is the effort to limit the likelihood that the hazard of a chemical will be realized or manifested.
For chemicals, such as drugs, it is frequently more informative to consider their hazards relative to their potential for producing benefit, rather than relative to the hazards of other chemicals. An extremely potent therapeutic agent may also be potent in producing harm, but it may be a useful drug because of its large therapeutic index or standardized safety margin.
Cf. Risk, Potency, Therapeutic Index, Standardized Safety Margin, CT Index, Toxic Effects
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