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FORMER MOBIL BULK TERMINAL 04343, TRACY, CALIFORNIA <br /> CALCULATION OF INCREMENTAL CANCER RISKS AND HAZARD INDICES <br /> VAPOR PATHWAY ANALYSIS Page 3 of 3 <br /> EXPOSURE: POTENTIAL EXPOSURE TO CHEMICALS IN SUBSURFACE SOIL <br /> RECEPTOR: POTENTIAL FUTURE EMPLOYEE <br /> SITE CONDITION: PAVED AND DEVELOPED COMMERCIAL AREA <br /> EXPOSURE SCENARIO: REASONABLE MAXIMUM EXPOSURE <br /> ENDPOINT:INCREMENTAL CANCER RISK <br /> EQUATIONS: <br /> LADD = Ci(s)* RR*ED*EY f l/L* l/BW* BI <br /> RISK = LADD*CSF <br /> HI = Ci(s)/RfC <br /> SYMBOLS AND DESCRIPTIONS UMTS VALUES RATIONALE <br /> Ci(s) = Concentration of Chemical in Indoor Air <br /> mg/m3 see below (by previous equation) <br /> RR = Human Respiration Rate m3/day 10 (by previous equation) <br /> ED = Exposure Duration days/year 240 (work days per year) <br /> EY = Exposure Duration years 20 (professional judgement) <br /> L = Days in Average Lifetime days 27375 (based on 75 years; EPA, 1989a) <br /> ' BW = Average Human Body Weight kg 70 (adult average; EPA, 1989b) <br /> BI = Bioavailability of Benzene through Inhalation dimensionless 1 (maximum value) <br /> LADD = Lifetime Average Daily Dose mg/kg-day see below (by equation) <br /> RfC = Reference Concentration mg/m3 see below (EPA, 1991) <br /> CSP = Cancer Slope Factor for Benzene 1/(mg/kg-day) 2-90E-02 (EPA, 199 1) <br /> Risk = Upper-Bound Incremental Cancer Risk dimensionless see below (by equation) <br /> III = Hazard Index dimensionless see below (by equation) <br /> 1 <br /> Chemical Cis LADD RIC Risk HI <br /> Benzene 2.61E-04 6.53E-06 NA 1.89E-07 NA <br /> Toluene 1.05E-04 NA 2E+00 NA 5.24E-05 <br /> Ethylbenzene 6.65E-04 NA IE+00 NA 6.65E-04 <br /> Xylenes 2.47E-04 NA 3E-01 NA 8.23E-04 <br /> s <br /> s <br /> RSKCALC4 <br />