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s <br /> Human Health Risk Assessment <br /> Former Mobil Oil Bulk Plant 04-343 <br /> 540 East Grant Line Road <br /> i Tracy, California <br /> 5.3.3 Exposure Parameters for Inhalation of BTEX in Indt•.1r Air <br /> This exposure scenario evaluates potential exposure to BTEX through inhalation. Only the <br /> Reasonable Maximum Exposure is presented for a quantitative estimate; of potential exposure. <br /> The exposure parameters associated with the Reasonable Maximum Ext-osure is presented next. <br /> 5.3.3.1 Reasonable Maximum Exposure <br /> The Reasonable Maximum Exposure represents continuous exposure for a 20-year period of a <br />' worker onsite. The exposure frequency is assumed to be 8 hours per day, 240 days per year <br /> for 20 years (EPA, 1989b). An average adult body weight of 70 kilograms is assumed <br /> (EPA, 1989b). For this scenario, the length of a potential receptor's ISetime is 75 years, and <br />' a human inhalation rate of 10 m3 per 24-hour day were assumed (EPA, 1989b). The <br /> bioavailability of inhaled BTEX is conservatively assumed to be 100 )ercent. A summary of <br />' exposure parameters for the Reasonable Maximum Exposure is pres:.rted in Table 5-2. The <br /> potential inhalation exposure for carcinogenic chemicals is calculated es follows: <br /> LADD = CA x RR x ED x EY x BI <br /> BW x L <br /> Where: CA = Concentration of chemical in air (mg/ma) <br /> RR = Human respiration rate (m3/day) <br /> ED = Exposure duration (days/year) <br /> EY = Exposure duration (years/lifetime) <br />' BI = Bioavailability of chemical (dimensionless) <br /> BW = Average human body weight (kg) <br /> L = Lifetime (days) <br /> LADD = Lifetime Average Daily Dose through inhalation (mg/kg-day) <br />' Actual calculations of this exposure scenario are presented in Appendix D. <br /> 30-0136-1 1 <br /> s-lo <br /> 1 <br />