ABSTRACT
A risk assessment methodology should include variables which clearly represent the hazard level, exposure level, and the level of risk at a particular site. The toxicities of contaminants at a site are determined during the hazard analysis. Animal studies and human studies, when available, are used to derive toxicity values based on dose-response relationships and statistical models. The manner in which toxicity values are derived should be compared among the different methodologies. Chemicals at a site can have diverse short-term and long-term effects. Pharmacokinetic factors, when available, can account for differences in absorption and metabolism due to different exposure routes. A standard procedure in a risk assessment methodology would aid in identification of the most toxic chemicals, which can then represent the overall toxicity of a mixture. Environmental fate analyses may include variables such as air transport, surface water or groundwater transport, and bioconcentration of chemicals in plants, fish, and livestock.
