Results adult and child activity based asbestos air

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Results Adult and child activity-based asbestos air sampling, conducted on September 27 through 29, 2005, included off highway vehicle riding (OHV) (motorcycles, ATVs and SUVs), hiking, camping, vehicle washing and vacuuming, post-decontamination driving, and fence building/repairing (Table 1). Adult OHV riders in trailing positions were exposed to airborne asbestos concentrations, in their breathing zone, that frequently exceeded the OSHA PEL of 0.1 fiber/cc (Table 2A). However, most exposures for lead adult OHV riders did not exceed the PEL. It should be noted that the OSHA PEL is an 8-hour time weighted average (TWA) and the exposure scenarios in this study were run for less than 8 hours. One trailing adult motorcyclist was exposed to a concentration (1.3 PCMe fibers/cc) which is greater than OSHA’s 30-minute “not to exceed” excursion level of 1.0 fiber/cc. Adult hiking and camping exposures did not exceed OSHA’s PEL except for the maximum asbestos concentration for the camper. Child maximum measured asbestos air concentrations for the motorcycle rider, ATV rider, and SUV passenger exceeded adult maximum measured air concentrations for most riding activities (Table 2C). The highest asbestos air concentration was for a trailing child motorcyclist air sample which had a concentration of 1.2 PCMe fibers/cc. Additionally, child minimum asbestos air concentrations exceeded or equaled adult values for trailing motorcyclists and trailing ATV rider positions. In this memorandum, risks are evaluated for both child and adult recreational exposures assuming exposure durations of 12 years and both 18 and 30 years, respectively. Two adult exposure durations are evaluated so the risks to the receptor that starts exposure as an adult can be compared with the risks to the receptor that begins exposure as a child and continues to be exposed as an adult. Risks are estimated using both the U.S. EPA IRIS and the Cal/EPA OEHHA unit risk values. Then, only for results based on the IRIS unit risk value, the risks are summed for a child plus adult recreational exposure duration of 30 years at the CCMA.
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9 For both adult and child exposures, ELCRs are calculated from exposure parameters for 1- day per year, 5-day per year (Reasonable Maximum Exposure [RME]) and 12-days per year (high estimate) exposure frequencies (Table 3A [adult – 30 year exposure duration], Table 3B [child – 12 year exposure duration] and Table 3C [adult – 18 year exposure duration]). For both adult and child exposures, ELCRs are calculated using both the IRIS and OEHHA unit risk factors. Calculations for individual adult activities (30 year exposures) are shown in Tables 9 to 18, and ELCR values are presented based on the IRIS and OEHHA unit risks in Tables 4A through 4D. These values indicate that, for maximum asbestos air concentrations, trailing OHV riders always exceeded the upper limit (1E-04) of EPA Superfund Program’s risk management range (1E-06 to 1E-04), when 12 or more riding days per year are assumed (Tables 4B and 4D).
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