ARCHIVED REPORTS XR0000211 - Laserfiche WebLink

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SECTIONFIVE UnIcKwAssessmenR that for at least some chenucals, there is a threshold below which the contaminant will not Increase the risk of cancer The EPA uses an evaluation process in winch the substance is assigned a weight-of- evidence classification Tins describes the likelihood, based on scientific evidence, that the substance is a human carcinogen A SF is then calculated that defines quantitauvely the relationship between average lifetime dose and carcinogenic risk(EPA, 1989b) The SFs are usually based on the results of animal studies There is uncertainty whether animal carcinogens are also caremogensc in humans While many contaminant substances are carcinogenic in one or more animal species, only a small number of contartmant substances are known to be human carcinogens The EPA assumes that humans are as sensitive to all animal carcinogens as the most r sensitive animal species Tins policy decision is designed to prevent underestimating risk and introduces the potential to overestimate carcinogenic risk(EPA, 1989b) Oral RIDS and SFs were used to evaluate both the oral and dermal exposure routes Data on oral absorption efficiency may be used to convert an administered-dose (oral) RID or SF to an absorbed- dose (dermal) RID or SF for use in calculation of risk from dermal absorption However, because of the limited information on oral absorption efficiencies, conversion of administered-dose oral toxicity values to absorbed-dose values was not attempted This approach could somewhat underestimate potential risk associated with dermal absorption of chenucals of concern if oral absorption efficiencies are significantly lower than 100 percent(e g, 50 percent or less) r r r r 7119971973009NAWOCKTON REPORT%SHOREP#1 D0CkS_FEBBB1B7300BNA%SNA 5-3 r