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Section 4 <br />Potential for Rock to be Toxic-Forming <br />Further, inputs to the calculatio <br />correspondence (CDM 2009a), i <br />ingest 114 mg of fine material fi <br />rate is high compared to a typic <br />thus accounts for increased ingi <br />with soil during weed or fire cc <br />BLM RMCs is presented in Attz <br />based on cancer risk can reason <br />of one (1) for number of media. <br />recalculated as: <br />S <br />RVIC= CS = <br />EF <br />Where: <br />Cs = Chemical Risk <br />TR = Target Excess Individual L <br />AT = Carcinogenic Averaging T <br />EF = Exposure Frequency <br />SFo = Oral Carcinogenic Potenc, <br />CF = Conversion Factor (kg/mg <br />MN = Number of Media <br />IRs = Age Adjusted Soil Ingestic <br />SFi = Inhalation Carcinogenic Pc <br />IR = Inhalation Rate <br />PEF = Particulate Emission Facti <br />as provided by Dr. Ford in telephone <br />ply that a worker visiting the site will accidentally <br />n the development rock piles per day. This ingestion <br />commercial/ industrial worker (50 mg/day) and <br />:ion during short-term, relatively intense contact <br />rol activities. Additional information regarding <br />iment 4. Overall, a site-specific RMC for arsenic <br />rly be recalculated using Dr. Ford's suggested input <br />site specific RMC for arsenic RBCs was therefore <br />FR• 4F• 365 <br />• (SF • CF. IRS ) + SF, . IR• UEO) <br />MN Criteria in Soil (mg/ kg) <br />etime Cancer Risk (unit less) 1 <br />ne 25,550 days <br />40 days/year <br />Slope 1.5 (mg/kg-day)-i <br />1x10-6 kg/mg <br />Rate 114 (mg-yr/kg-day) <br />ncy Slope 15 (mg/kg-day)-1 <br />2.5 m3/ day <br />4.63 x10-9 m3/kg <br />This equation, when used with the above exposure assumptions for workers, yields a <br />criterion for arsenic of 37 mg/kg for protection from carcinogenic health effects; an <br />upwards revision from the guidance document criteria of 12 mg/kg. <br />Bioavailability: Past and ongoing studies at mine sites throughout the American west <br />have repeatedly shown that arsenic in mine wastes is less bioavailable than is <br />typically assumed in calculations for exposure and risk (EPA 1997). BLM RMCs do <br />not consider relative bioavailabi4ty (RBA); instead the RMC values are based on a <br />toxicity study using exposure vi <br />where arsenic is nearly complete <br />arsenic assume that all arsenic it <br />body; this is not consistent with <br />discussed in the BLM guidance I <br />screening value upwards for ars <br />into the body from development <br />. dissolved arsenic in drinking water; an exposure <br />ly absorbed into the body. Accordingly, RMCs for <br />development rock is available for uptake into the <br />;tudies of arsenic exposure at mine sites. As <br />BLM 2004, p.13), RBA can be used to adjust the RMC <br />nic to account for differences in arsenic absorption <br />rock. <br />• <br />• <br />0 <br />4-4