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SECTIONTFMEE T®chnlcal Approach <br /> • addition potential carcinogens are classified according to the "weight of evidence" that these <br /> substances are carcinogenic in humans For non-carcinogens, toxicity is quantified based upon a RfD, <br /> which represents a safe dose for humans <br /> 3A.7 Risk Characterization <br /> The risk characterization will combine the results of the exposure assessment and toxicity assessment <br /> to quantify potential health risks Conservative RM[E risks will be determined, in accordance with <br /> agency guidance, in addition to average or typical risks The purpose of the risk characterization <br /> process is to quantitatively estimate the magnitude of potential health hazards(i e, non-carcinogenic or <br /> toxic effects) and carcinogenic risks posed by the proposed future use at the site <br /> Potential carcinogenic risks are calculated using the following equation <br /> IPoten9W Cancer Risk= C(x)x llntake Factor x SF(x) <br /> where <br /> C(x) = Concentration of chemical x at a point of human exposure <br /> Intake Factor = A quantitative estimate of the extent of human exposure based on <br /> factors such as duration and frequency of chemical exposure <br /> SF(x) = Slope factor,which reflects the relative potency of the chemical <br /> to produce carcinogenic effects <br /> Potential cancer risks are typically estimated for each chemical in each exposure pathway for each <br /> exposed population, and are then summed to yield an overall potential cancer risk. Potential cancer <br /> risks are expressed as a unitless probability (e g, one in a million or 10') of an individual developing <br /> cancer over a lifetime as a result of the exposure above his "background" risk of developing cancer <br /> This risk is referred to as the lifetime incremental excess cancer risk <br /> Potential health hazards C e, potential non-carcinogenic effects of chemicals) are evaluated by <br /> estimating a value known as the hazard quotient The hazard quotient is calculated as follows <br /> c(x) x Intake Factor <br /> Hazard Quotient = RfD(x) <br /> • C(x) = Chemical concentration as described for equation 1 <br /> Intake Factor -- A quantitative estimate of exposure as described for equation 1 <br /> ® Tome a Dote.ALo4mA%sNa 3-8 <br />