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5.9 PUBLIC HEALTH <br /> calculated as the maximum product of any potential carcinogenic risk greater than 1 in one <br /> million and the number of individuals at that risk level. Because the MICR is less than 1 in <br /> one million,the potential cancer burden is zero. If the potential MICR had substantially <br /> exceeded 1 in one million,then the worst-case estimate of cancer burden would have been <br /> calculated based on the assumptions described below. <br /> The MICR concentration would have been applied to all affected portions of identified <br /> census tracts within the radius area defined by the distance to the 1st high (MIR) <br /> concentration. A detailed listing and map of affected census tracts and year 2000 population <br /> estimates would then have been provided. Figures would then have been presented to show <br /> the 1-,2-, and 3-mile radius plots in relationship to the census tract locations and site.This <br /> procedure,if it had been needed,would have resulted in a conservatively high estimate of <br /> cancer burden. However,as described above,because the calculated MICR for the project is <br /> less than 1 in one million,this procedure is not required. <br /> By definition,human health risks associated with emissions from the project cannot be <br /> higher elsewhere than at the location of the MICR. Therefore,the potential cancer risk <br /> elsewhere also would be lower than the maximum listed in Table 5.9-6. Because the <br /> potential cancer burden listed in Table 5.9-6 is less than one, the emissions from the project <br /> would not be associated with any increase in cancer cases in the previously defined <br /> population. <br /> The maximum potential acute non-cancer health hazard index associated with <br /> concentrations in air is shown in Table 5.9-6. The acute non-cancer health hazard index for <br /> all target organs falls below 1.0,the threshold of significance. <br /> Similarly,the maximum potential chronic non-cancer health hazard index associated with <br /> concentrations in air is shown in Table 5.9-6. The chronic non-cancer health hazard index <br /> falls below 1.0,the threshold of significance. <br /> The estimates of cancer and non-cancer risks associated with chronic or acute exposures fall <br /> below thresholds used for regulating emissions of toxic air contaminants to the air. <br /> Historically, exposure to any level of a carcinogen has been considered to have a finite risk <br /> of inducing cancer. In other words,there is no threshold for carcinogenicity. Because risks at <br /> low levels of exposure cannot be quantified directly by either animal or epidemiological <br /> studies,mathematical models have estimated such risks by extrapolation from high to low <br /> doses. This modeling procedure is designed to provide a highly conservative estimate of <br /> cancer risks based on the most sensitive species of laboratory animal for extrapolation to <br /> humans (i.e.,the assumption being that humans are as sensitive as the most sensitive animal <br /> species). Therefore,the true risk is not likely to be higher than risks estimated using <br /> inhalation cancer potency factors and is most likely lower, and could even be zero <br /> (EPA, 1986;EPA,1996). <br /> The analysis of potential cancer risk described in this section employs methods and <br /> assumptions generally applied by regulatory agencies for this purpose. Given the <br /> importance of assuring public health,these methods and assumptions are highly <br /> conservative. Conservative methodology and assumptions are outlined below. <br /> 5.9-18 SAC/371322/082340007(LEC_5.9_PUBLIC_HEALTH.DOC) <br />