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The oral reference doses (subscript "o") for trivalent and hexavalent chromium are from the <br /> Integrated Risk Information System ("IRIS", USEPA, 11/00) and the oral reference dose for <br /> copper is from the Health Effects Assessment Summary Tables ("HEAST", USEPA, 1997). The <br /> inhalation reference dose (subscript "i") for hexavalent chromium is from IRIS. Published <br /> inhalation Rfds were not found for trivalent chromium and copper. Consequently the oral Rfd <br /> values were also utilized for the inhalation exposure route. The values are tabulated below: <br /> COPC SFo SH Rfdo Rfdi <br /> Cu (non-carc.) -- - 4.0 E-2 4.0 E-2 <br /> ' Cr" (non-carc.) -- -- 1.5 E+0 1.5 E+0 <br /> Cr 6+ (carc.) 4.2 E-1 5.1 E+2 3.0 E-3 2.2 E-6 <br /> Pb N/A (exposure and risk evaluated using "Lead Spread") <br /> ) <br /> 5.3 Exposure Assessment <br /> In order to be conservative, for purposes of this risk evaluation it was assumed that human <br /> exposure would occur to unpaved soil under a residential use scenario. Potential routes of <br /> exposure include ingestion, dermal absorption and dust inhalation. Inhalation of vapors was not <br /> considered since all the COPCs are non-volatile. <br /> 5.4 Risk/Hazard Quantification for COPCs other than Lead <br /> The quantification of potential adverse health effects due to soil exposure was calculated using the <br /> formulae presented in the PEA Guidance Manual. In accordance with the manual, the skin <br /> absorption fraction ("ABS") used for the metals was 1% except for the cancer risk calculation via <br /> the dermal contact pathway for hexavalent chromium where 0% was utilized. <br /> The incremental lifetime probability of contracting cancer from exposure to the soil is expressed <br /> as Cancer Risk (Risk). For this evaluation, significant risk is considered to be a probability <br /> greater than or equal to one-in-one-million (1 E-6). For non-cancer toxic effects, the Hazard <br /> Quotient compares the exposure dosage for each COPC to the dosage at which adverse health <br /> effects might be expected. The Hazard Index is the sum of the individual Hazard Quotients. A <br /> Hazard Index of 1 is the level at which adverse effects could be anticipated and is considered the <br /> ' level of significance in this evaluation. The equations are presented below: <br /> 7 <br />