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8. B. - Page 181 <br /> I�� basic terms, ca�lcer risks are calculated as the prodL�ct of a�1 exposL�re dose, a ca�lcer rislc <br /> adjL�stment factor to accoL�nt for age sensitivity, a�ld a ca�lcer potency factor�. For the case <br /> where the TAC concentration is consta�lt over tlie 70 yea� e�osure period, this is expressed <br /> as: <br /> Cancer Risk =(Dose x CRAF x Ca�lcer Potency Factor) <br /> Where: <br /> Ca�lcer Risk = rislc (potential cha��ces per nullion) <br /> Dose = e�osure does through ii�llalation (mg/kg-day) <br /> CRAF = Ca�lcer Risk Adjustment Factor (for residential receptors with constant <br /> concentrations over 70 years the CRAFis 1.7) <br /> Ca��cer Potency Factor = toxicity factor (mg/lcg-day <br /> For TAC exposure through inhalation, the exposure dose is calculated as the TAC <br /> concentration multiplied by u�halation dose pa�ameters, incli�ding the daily breathing rate, <br /> frequency of exposL�re, e�osure duration, a�1d averagu�g time (70 years). <br /> li7 evall�ating ca�icer risks from roadways a�l added complication u1 the a�lalysis is that not <br /> only do the velucle nules tra�eled a�ld enussions va�y per yea�, bL�t the BAAQMD's ASFs <br /> vary depending on yea� of e�posi�re�. Since flie number of vehicles on the roadway a�ld the <br /> associated enussions vaiy from year to year, the modeled concentrations affectulg sensitive <br /> receptors will not be constant, bL�t will also va�y. Therefore, a consta��t CRAF caiu�ot be used <br /> a��d the effect of the vaiying ASFs needs to be accoL�nted for, along with the effect of varying <br /> concentrations used to calculate the exposure dose, when calcL�lating cancer risks. <br /> I�� order to account for the variations in the exposL�re dose and the ASF over time the <br /> BAAQNID developed a method i�sing SWFs to compi�te the total 70 year ca��cer risk based <br /> on calcL�lating a 70 year tiine weighted average TAC concentration and exposL�re dose�. <br /> Functionally, in using this method the vehicle emissions are estimated on a grams per mile <br /> basis for each year, from the first year of e�osL�re to flie last year of exposi�re (70 year). <br /> Also, for each year a SWF is calcL�lated usulg the appropriate ASF for fliat year and dividing <br /> by the e�posi�re period associated with the emission estimate. Then, for each year the <br /> enussion rate is mL�ltiplied by the corresponding SWF to get a�1 a�ulual SWF weighted <br /> enussion rate. The SWF weighted einission rates for each yea� are then sununed to get a total <br /> 70 year average SWF weighted TAC enussion rate that ca�� be used with the air quality <br /> dispersion modeling to calculate a 70 year average concentration. This concentration <br /> incoiporates both the year to year variation in emissions a��d ASFs. This concentration is <br /> then i�sed in calculating a 70 year exposure dose that incorporates the cancer risk adjustment <br /> factor and finally to calculate the expected ca��cer risk. <br /> ` BAAQNID. 2011. Recommended Methods for Screeiuna and Modelin� Local Rislis and Hazards. Ba� Area Air <br /> Qualin-• Management Disriict. Ma��, 2011, page 87. <br /> BAAQNID. 2011. Recommended Methods for Screeiuna and Modelin� Local Risks and Hazards. Bay Area Air <br /> Qualin-• Management Disriict. Ma��, 2011, page 65. <br /> 8 BAAQNID. 2011. Recoinmended Methods for Screeiuna and Modelin� Local Rislis and Hazards. Ba�• Area Air <br /> Qualin-• Management Disriict. MaS�, 2011, pages 67 - 71. <br /> 2580 El Cainino Real Residenrial Project 13 Response to Conmients Recei��ed on Final EIR <br /> Cin� of Red��ood Cin� Jannai� 2012 <br />