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�.t <br /> 6.0 <br /> RISK CHARACTERIZATION <br /> 6.1 INTRODUCTION <br /> Risk characterization is the final step of the risk assessment process. In this step, the <br /> toxicity factors (RfDs and cancer slope factors from Section 5.0) for the chemicals of <br /> concern are applied in conjunction with estimatedchemical intakes to evaluate potential <br /> noncarcinogenic and carcinogenic health risks to exposed individuals. <br /> The potential for noncarcinogenic effects is characterized by comparing estimated <br /> chemical intakes with chemical-specific RfDs. Potential carcinogenic effects are <br /> characterized in terms of the incremental or excess probability that an individual will �--r <br /> develop cancer in his or her lifetime due to the modeled exposure. Excess cancer risk � <br /> is estimated from the projected lifetime intakes and 'the cancer slope factor, which <br /> represents an upper-bound estimate of the dose-response relationship. <br /> Potential health risks associated with the chemical exposures are presented in Section l <br /> 6.3. Uncertainties inherent in the risk assessment process are presented in Section 7. <br /> 6.2 METHODOLOGY FOR QUANTITATIVE RISK ESTIMATION <br /> 6.2.1 Hazard Index for Noncarcinogenic Effects -= <br /> The potential for adverse noncarcinogenic effects resulting from exposure to a chemical <br /> of concern is evaluated by comparing the average daily intake of the chemical (expressed <br /> as mg/kg-day) to a reference dose (expressed as mg/kg-day). The resulting ratio is <br /> called a hazard quotient (EPA 1989b). It is derived in the following manner: f-y <br /> l <br /> Noncancer Hazard Quotient = Chemical Intake (mg/kg-days <br /> RfD (mg/kg-day) <br /> rJ <br /> S:\LDC\YELLO.RPT May 4,1995 6-1 ,-. <br />