ARCHIVED REPORTS XR0000211 - Laserfiche WebLink

Home Browse Search

SECTIONFOUR The 95% UCL soil concentrations for surface soil listed on Table 3-1 were used for the soil concentration Co Details on intake factors for the occupational receptors are provide in Section 4 5 4.5 EXPOSURE ASSUMPTIONS The potential intake amount received through the various exposure pathways is estimated using EPA [ and DTSC guidance, site-specific inforination, and professional judgment It is not possible to estunate �j the exact level of exposure for specific individuals due to uncertainties in behavior patterns and incomplete knowledge of exposure variable values A primary objective of this risk assessment was to use conservative parameters so as to not underestimate potential human and groundwater exposures This risk assessment evaluates exposures to carcmogeruc and noncarcinogemc chemicals of concern The EPA recommends that when evaluating exposure to noncarcmogenic chemicals, the intake should be calculated by averaging the intake over the duration of exposure(referred to here as averaging time or AT) (EPA 1989b) For the carcinogenic endpoint, lifetime average daily intakes are calculated by averaging the total chemical exposures during the exposure period over an average lifetime of 70 years The use of different averaging times for estimating intakes for carcinogenic and noncarcinogenic endpoints is based on currently held scientific opinion that the mechanism of action of carcinogens and noncarcmogens is different, namely that the potential for toxic effects from exposure to noncarcinogens ceases when the exposure ceases, but the potential for carcinogenic effects exists even after exposure ceases 4.5.9 Exposure f=requency, Duration, Body Weigh Several exposure parameters, such as exposure duration, body weight, and averaging tunes, have general application in all intake estimations, regardless of exposure pathway These general assumptions are detailed below a Occupational frequency of exposure was estimated to be 5 days/week for 50 weeks (250 days per year)for the RME exposure(EPA, 1989 and DTSC, 1993) o Residential frequency of exposure for RUE was assumed to have a high-end exposure frequency of 350 days/year(allowing 15 days per year for vacations and holidays, etc) (EPA, 1989 and DTSC, 1993) 0 Exposure duration refers to the number of years spent on or near the site The occupational exposure duration used was 25 years(EPA, 1989 and DTSC, 1993) o Residential receptor exposure duration was assumed to 30 years For child residents, a 6-year exposure duration was evaluated(EPA, 1989 and DTSC, 1993) o The body weight was 70 Kg for adult residents and occupational employees, and 15 Kg for children(EPA, 1989 and DTSC, 1993) " 7° ® T%1997%97300®MAWMCKTON4REPORTI-SHOREP#10ocw-m�73oommmA 4-14