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Human Health Risk Assessment <br /> Former Mobil Oil Bulk Plant 04-343 <br /> 500 East Grant Line Road <br /> Tracy, California <br /> 4.0 DOSE-RESPONSE ASSESSMENT <br /> This section provides a brief discussion of the dose-response assesst,-ient component of risk <br /> assessment. Dose-response assessment is the process of characterizing the quantitative relation- <br /> ship between the dose of a chemical or agent and the anticipated incidence of an adverse health <br /> effect in an exposed population. The end result of the dose-response a.-sessment is a quantitative <br /> estimate of the incidence of the adverse effect as a function of human exposure to the chemical. <br /> ' The dose-response assessment also provides the quantitative basis for setting allowable chemical <br /> exposures. <br /> ' The majority of information available on the dose-response relationship is based on data <br /> collected from animal studies. Mathematical models are often used to estimate the possible <br /> human response to chemical exposure. Since the predicted dose-response values used in risk <br /> assessment are 1) primarily based on animal studies and 2) rely on extrap:)lation or mathematical <br /> ' modeling to predict human dose-response values, uncertainty exists is the final dose-response <br /> value. <br /> Typically, animal research involves administration of high doses. Conversely, human exposure <br /> to environmental contaminants occurs at concentrations that are order. of magnitude less than <br /> ' the lowest doses administered to animals. Therefore, it is uncertain whether human exposure <br /> to low concentrations of chemicals in the environment would cause the same effects observed <br /> ' in experimental animals. The limitations of the dose-response estimate should be considered <br /> when the final risk estimates are evaluated. <br /> ' A comprehensive evaluation of the dose-response literature and criteria was not completed for <br /> this risk assessment. Instead, dose-response criteria (e.g., Cancer Slope Factors and Reference <br /> Concentrations) derived by the Environmental Protection Agency (EPA) are presented. <br /> Generally, the EPA-established dose-response criteria have been reviewed by a number of <br /> E authorities and the values are representative of conservative estimates of human response to the <br /> ' indicator chemicals. <br /> 30-0136-11 4-1 <br />