S epa iris unit risk tables 35 through 38 those

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to the CCMA, based on risks evaluated using only the U.S. EPA IRIS unit risk (Tables 35 through 38). Those combined activities include driving to the vehicle staging areas in an SUV, motorcycling (or hiking/hunting), camping, and camping overnight. The summed risks for combined activities are significantly greater than that for any single activity. These values indicate that, for combined activities including an adult motorcyclist and hiker exposed to maximum asbestos concentration, cancer risks exceeded the upper value (1E-04) of EPA Superfund Program’s risk management range (1E-06 to 1E-04), when 3 or more riding days per year combined with overnight camping are assumed (Tables 35B and 36B). The adult motorcyclist and hiker exposed to minimum concentrations had cancer risks within EPA’s risk management range (Tables 35A and 36A). All of the combined activities for the child motorcyclist and hiker scenarios were either well below or within EPA’s risk management range (Tables 37 and 38). These results indicate that motorcycling, SUV driving to a staging area, camping, and hiking/hunting all can contribute significantly to risks during recreational visits to the CCMA. Uncertainty Analysis : This risk assessment presents quantitative estimates of some potential current and future cancer risks for recreational users of the CCMA. However, it is important to note that these numbers do not predict individual exposures, or actual health outcomes. Specific uncertainties should be considered when interpreting the results for this risk assessment, as follows: SAMPLING UNCERTAINTY Seasonal Variability Soil moisture is likely to affect dust generation and asbestos exposure during recreational activities, such that dry season samples are likely to over-estimate exposure during the wet season and wet season samples are likely to underestimate exposure during other times of the year. This uncertainty is addressed in this study by sampling during different seasons, ranging from very dry to very wet. Three activity-based asbestos sampling events were completed at the CCMA during November 2004, February 2005, and September 2005. The sampling event that occurred in September 2005 represents climate conditions during the dry season while the November 2004 and February 2005 represent the wet season. The dry season is assumed to contribute more asbestos fiber-containing dust to air which may overestimate the risk results, while the wet season is assumed to have comparably less asbestos containing dust in air. More motorcycle riders use the CCMA during cooler weather. Seasonal asbestos air concentrations will be compared in a future report. In addition, soil samples were collected along all routes traveled during activity-based sampling, and analyzed for soil moisture (soil data will be presented and interpreted in a future report).
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11 Within Season Variability ° Time of Day, Style of Riding, Vehicle Type, Window Position, Other Non- seasonal Factors. Exposure concentrations may vary due to time of day, style of riding, vehicle type, if the vehicle windows are open or closed, distance from preceding rider, height of rider, etc.
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