Laserfiche WebLink
Section 4 <br />Potential for Rock to be Toxic-Forming <br />noncancer health effects, BLM RMCs have been divided by 11 metals and "n" medial to account <br />for multiple chemical and media exposures. Such a calculation is conservative for the Sunday <br />Mines Group because most metals are present only at concentrations well below their respective <br />RMCs indicating little if any potential for adverse health effects. Even so, all arsenic <br />concentrations are below the noncancer "RMC" of 65 mg/kg. From a non-cancer viewpoint, <br />development rock at the Sunday Group mines is not toxic-forming for direct contact. <br />RMCs based on cancer risk assume possible exposure to arsenic in groundwater, soil and air <br />and the number of media included in the calculations is therefore three (3). Thus, the RMC for <br />arsenic in soil is about one third of the value that would be calculated assuming exposure to soil <br />alone. In telephone correspondence with Dr. Karl Ford of the BLM (author of the BLM RMC <br />document), (CDM 2009a), Dr. Ford indicated that the appropriate number of media for the <br />worker scenario was one (1). This input to the calculations is appropriate because: <br />1. Groundwater is present only at depth and no contact with groundwater is possible for a <br />worker or camper that visits the site. <br />2. Possible exposure to arsenic suspended as dust in ambient air is estimated in the <br />equation for calculation of the RMC based on cancer risk, and <br />3. Possible exposure to other carcinogens observed in development rock (cadmium and <br />nickel) is accounted for in the calculations <br />Further, inputs to the calculations, as provided by Dr. Ford in telephone correspondence <br />• (CDM 2009a), imply that a worker visiting the site will accidentally ingest 114 mg of fine <br />material from the development rock piles per day. This ingestion rate is high compared to a <br />typical commercial/ industrial worker (50 mg/day) and thus accounts for increased ingestion <br />during short-term, relatively intense contact with soil during weed or fire control activities. <br />Additional information regarding BLM RMCs is presented in Attachment 4. Overall, a site- <br />specific RMC for arsenic based on cancer risk can reasonably be recalculated using Dr. Ford's <br />suggested input of one (1) for number of media. A site specific RMC for arsenic RBCs was <br />therefore recalculated as: <br />R9if? s TR x AT X $65 <br />Where: <br />Cs = Chemical Risk Management Criteria in Soil (mg/kg) <br />TR = Target Excess Individual Lifetime Cancer Risk (unitless) 1 <br />AT = Carcinogenic Averaging Time 25,550 days <br />EF = Exposure Frequency 40 days/ year <br />SFo = Oral Carcinogenic Potency Slope 1.5 (mg/kg-day)-1 <br />CF = Conversion Factor (kg/mg) 1x10-6kg/mg <br />Nco = Number of COCs with Oral Cancer Slope Factor 1 <br />MN= Number of Media 1 <br />' Media include soil, air, groundwater, sediment and surface water. Only soil and air are relevant to the Sunday <br />Group mines, as discussed in the text. <br />Cm 4-3 <br />T:164986-Denison Mines%Task Ortler 3 - DMO Sampling and Analysis Plan%Task 3.12 - Soil. Ore. Rock Data Assessment Report%Sunday Rack Report\final reportlReporOFinal Sunday Mines Group Soil Ore Rock <br />Data Assessmenl Report_051509.doe