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i Closure Report 31 Golden Grain Manteca Bean Facility,299 Moffat Boulevard,Manteca,California July 16,19% ' For carcinogens, it is assumed that no threshold exists, and that any dose may result in cancer induction The probability of cancer development is described by the slope of the dose response ' curve The doses from the various known or suspected carcinogens are assumed to be additive The cancer slope factor(SF) is the toxicity value used to quantitatively express the carcinogenic tisk ' of cancer-causing constituents The slope factor is expressed in units of(mg/kg/day)t The SF is the upper 95 percentile confidence limit of the linear term of the dose response curve The product of the lifetime average daily dose and the SF Is the incremental risk,above background, of developing cancer over a lifetime The lower limit of the SF is often zero and therefore lifetime incremental cancer risk is most appropriately reported as ranging from zero to the reported upper bound value For noncarcinogens, A is assumed that a dose exists below which no adverse health effects will be ' seen(i e,threshold dose) Compounds that affect reproduction are also considered to have threshold doses unless the mechanism of action of the compound has been confirmed as one for which no threshold exists Compounds with short-term,acute effects are generally considered to have a threshold dose The RfD is the toxicity value used to quantitatively express the hazard of noncarclnogenic constituents The RfD is expressed In units of mg/kg/day and represents a daily intake of chemical per kilogram of body weight that is not sufficient to cause the threshold effect for the chemical The RfD is the toxicity value used to quantitatively express the hazard of noncarcmogenic constituents The RfD is expressed In units of mg/kg/day and represents a daily intake of contaminant per kilogram of body weight that is not sufficient to cause the threshold effect for the chemical The ' ratio of exposure to the RfD is called the hazard quotient The primary sources of toxicity values are the Integrated Risk Information System compiled by USEPA and the Health Effects Assessment Summary Tables (USEPA 1994a) ' 6 3 5 Proposed Target Risk and Target Hazard Index As mentioned earlier, the USEPA considers a cumulative site risk of 1 in 10,000 as the upper end estimate that will warrant remedial action For Golden Grain's Manteca Bean Facility, a chemical-specific target nsk of 1 in 100,000 and target hazard quotient of 0 1 were assumed in the ' calculation of cleanup goals The number of COPCs at the site could potentially be at a maximum of five, thus, the cumulative site risk would still be below the upper end estimate of 1 in 10,000 ' Risk is mathematically expressed in the following equation as ' 42020-213 CR FLUOR DANIEL GTI