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' DRAFT <br /> Calculated volatilization factors for the residential and commercial, construction, and <br /> landscape maintenance receptors are presented in Tables 11 and 12 for soil and <br /> ' groundwater, respectively. <br /> ' 1.3 Toxicity Assessment <br /> Toxicity values used in the risk evaluation included cancer potency slope factors (SFs) <br /> for carcinogens or chronic reference doses (RfDs) for non-carcinogens. The most recent <br /> ' version of the California Cancer Potency Factors prepared by the Standards and Criteria <br /> Workgroup of the California Environmental Protection Agency(CalEPA, 1994)were <br /> ' given higher prioritization over other available values. It should be noted that RfDs are <br /> not included in the California Cancer Potency Factors list. If not listed in the California <br /> ' Cancer Potency Factors list,the U.S. EPA's Integrated Risk Information System (IRIS) <br /> values were used for the SFs and RfDs. If toxicity criteria were not available from either <br /> ' source, the U.S. EPA Health Effects Summary Tables (HEAST) were used. <br /> All of the chemicals of concern included in the risk evaluation were evaluated for <br /> noncarcinogenic hazard and carcinogenic risk, as appropriate. Although no carcinogenic <br /> ' assessment was available for PCE(EPA, 1998c) and the carcinogenic assessment for <br /> TCE was withdrawn (EPA, 1998e),PCE and TCE were considered to be carcinogens for <br /> this risk evaluation. Tables 12 through 15 present the SFs and RfDs used in this <br /> evaluation. <br /> ' 1.4 Risk Characterization <br /> ' In order to assess the potential adverse health effects associated with the chemicals <br /> detected in soil and groundwater, noncarcinogenic hazard quotients and excess cancer <br /> ' risk estimates were calculated separately for each investigation area. Details of the risk <br /> characterization are presented in the following sections. <br /> ' SOMA 99-2218 11 12/10/99 <br />