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' DRAFT <br /> 2.0 RESULTS <br /> Results of the noncarcinogenic and carcinogenic evaluations for each investigation area <br /> areP resented in this section and Appendix A through D. <br /> Noncarcinogenic hazards are evaluated by summing the hazard quotients calculated for <br /> each COC to yield a hazard index as described in Section 1.4.1. For noncarcinogenic <br /> hazard evaluation, a hazard index greater than a value of one would be considered to <br /> represent a potential threat to human health warranting additional evaluation. <br /> In the carcinogenic risk evaluation, the individual risk estimates calculated for each COC <br /> ' are summed to yield an estimated excess carcinogenic risk, as described in Section 1.4.2. <br /> For the residential exposure scenario, the summed estimated total lifetime excess cancer <br /> risk of less than 1 E-06 is considered by Cal EPA to be an acceptable excess cancer risk to <br /> human health from carcinogens for the residential scenario. A summed estimated total <br /> ' lifetime excess cancer risk in the range of 1E-04 to 1E-06 is generally considered to <br /> ' represent an acceptable excess cancer risk for a non-residential site use. <br /> Lead in soil was evaluated using the CaIEPA LeadSpread Pb6 model, a one-compartment <br /> bio-uptake and kinetic model which adopts a health criterion for blood lead level as its <br /> target level. The Pb6 model is based on blood lead concentrations because of the <br /> extensive human epidemiological data supporting the relationship between blood lead <br /> concentrations and adverse health effects. Dose-response curves for these endpoints <br /> appear to extend down through 10µg Pb/dL or less (CaIEPA, 1992). The target blood <br /> lead level of 10 gg/dL for the human receptor has been identified by both U.S. EPA and <br /> ' CaIEPA as an acceptable health criterion. <br /> For the area-specific evaluations, a lead concentration in soil equal to a blood level of <br /> 10µg Pb/dL for the 95th percentile of the industrial and residential (child) scenarios was <br /> developed. The child receptor-based lead in soil target concentration is 485 mg/kg. The <br /> industrial receptor-based lead in soil target concentration is 5,486 mg/kg. These values <br /> SOMA 99-2218 14 12/10/99 <br />