ABSTRACT
As described in Chapter 1, one of the most important goals of toxicology is to protect humans and ecosystems from hazardous substances. Toxic substances such as biological agents (e.g., microorganisms), chemicals, and physical agents (e.g., radiation, temperature, sound) differ greatly in the nature and potency of their toxicity. Because human exposure to these agents (individual or mixture) is not always avoidable, risk assessments need to be carried out to determine the allowable safe level of exposure under which no risk is likely to occur. Comprehensive reviews evaluating the procedure and methodology of risk assessments are available (Paustenbach, 2000; Song et al., 2013). In principle, the critical point for the safety and risk assessment of chemicals is the protection of human and ecosystem health, and therefore conservative approaches or options need to be considered because of gaps in our toxicological knowledge. However, when undue caution or emotional factors are incorporated into the process, chemicals of great value may be willfully ignored under public pressure and society may be burdened with unnecessary economic costs resulting from pollution prevention measures and environmental cleanups. Therefore, the most important function of toxicology is to establish the scientific basis for regulating the use (and disposal) of chemicals without undue human health hazards or undue cost based on risk assessment.
