ARCHIVED REPORTS HUMAN HEALTH SCREENING EVALUATION

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' Human Health Screening Evaluation Surland Homes—Bridle Creek February 12,2009 incremental lifetime cancer risk; EPA, 1989). The potential carcinogenic health risks for each individual chemical in an exposure pathway were summed to estimate an overall cancer risk for each exposure pathway. Cancer risks across all evaluated exposure pathways were then summed to estimate incremental lifetime cancer risk for the individual. Potential future non-cancer health hazards were likewise calculated for on-site residential child ' receptors. Hazards were estimated by comparing estimated potential on-site doses to an acceptable reference-dose exposure. The calculated ratio of the potential estimated dose to the reference dose (the hazard quotient) was calculated for potential exposure to each COPC. The potential health hazards for each chemical in an exposure pathway were summed to estimate the total heath hazard for each exposure pathway. Health hazards across all evaluated exposure pathways were then summed to estimate the total hazard index for the receptor. In accordance with the National Contingency Plan, an incremental lifetime cancer risk of 1E-06 was used as a point of departure, and an excess cancer risk equal to or below this threshold was ' considered to be insignificant. If the excess cancer risk is within the acceptable range between 1E-04 and 1E-06, DTSC will make risk management decisions on a site-specific basis. For non- carcinogenic hazard indices, a hazard index of 1 or less is considered to be an acceptable health ' hazard level. If the regulatory criteria are exceeded based on the screening evaluation, this evaluation identifies the chemical and the exposure pathways contributing to the elevated risks or hazards, which can be more precisely assessed in a site-specific refined health risk assessment, if ' warranted. 5.1 RESIDENTIAL CANCER RISKS For potential on-site residential receptors, the oral and dermal cancer risks and inhalation cancer risks for exposure to on-site soils were calculated using the following equations: Oral and Dermal Cancer Risks for Direct Contact with Soil (PEA Guidance Manual, Figure 2.3): Risksoii = (SFo x Cs x [1.57E-06]) + (SFo x Cs x [1.87E-05] x ABS) Where: Risksoit = oral and dermal cancer risks from direct soil exposure SFo =oral cancer slope factor, (mg/kg-day)-1 Cs = concentration in soil, mg/kg ABS = dermal absorption fraction, dimensionless ' Table 8 shows the oral and dermal cancer risk calculations for potential residential exposures to soil at the site. Potential cancer risks were estimated for BTEX, PAHs, and metals, and then summed among chemicals for oral and dermal exposures. Inhalation Cancer Risks for Air (PEA Guidance Manual, Figure 2.4): Riskeir = SFi x Ca x 0.1.49 Where: 7 '-__ MENOMW`® From Science!o Solutions