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4.2.2 Dermal Contact with Soil Some soil contaminants may be absorbed across the skin into the bloodstream. Absorption will depend upon the amount of soil in contact with the skin, the concentration of chemicals in soil, the skin surface area exposed, and the potential for the chemical to be absorbed across the skin. Note, USEPA assumes that benzene and ethylbenzene will not be on the skin long enough (due to volatilization) to absorb through the skin. 4.2.3 Inhalation of Volatile and Particulate Emissions in Outdoor Air The inhalation exposure route includes the inhalation of both volatile and particulate emissions. The inhalation slope factors and noncarcinogenic inhalation reference doses are presented in Table 7. 4.3 Chemical Parameter and Toxicity Values Used The default chemical parameter values came from the RWQCB 2 Environmental Screening Levels (2007). The toxicity values for noncarcinogenic toxicity came from USEPA's On-line Risk Information System (IRIS, 2011). The carcinogenic toxicity values for benzene, ethylbenzene, and naphthalene came from OEHHA's list of cancer potency factors (OEHHA 2009). The carcinogenic oral slope factor for benzo(a)pyrene came from OEHHA's Public Health Goals for Chemicals in Drinking Water for Benzo(a)pyrene (OEHHA 2010). 5 SOIL SCREENING LEVELS Table 8 shows the soil screening levels calculated for each exposure scenario. Table 8: Summary of Soil Screening Levels for different Exposure Scenarios and Receptors Chemical Residential Commercial/ Industrial Utility Worker 0 to 5 feet bgs mg/kg Volatilization to outdoor air (5 to 10 feet bgs) mg/kg 0 to 5 feet bgs mg/kg Volatilization to outdoor air (5 to 10 feet bgs) mg/kg 0 to 10 feet bgs mg/kg Benzene 1.9 2.8 8.2 12 14 Ethylbenzene 21 32 89 134 314 Naphthalene 9.7 9.7 45 45 219 PAH* 0.063** NA 0.68 NA 4.5 Notes; * Based on the seven carcinogenic PAHs as benzo(a)pyrene toxicity equivalent [BaPe]. The PAH screening level (applicable to total BaPe) is only applicable where soil was affected by either waste oil and/or Bunker C fuel. ** DTSC (2009) reports average ambient PAH concentrations (as BaPe) in California ranging from 0.16 to 0.21 mg/kg, and upper tolerance limits (UTLs) ranging from 0.9 to 1.5 mg/kg. The screening level shown in this table is "risk-based" and is far below the average ambient concentrations for PAHs in California. It is suggested that DTSC citation (2009) be consulted for sites with PAH contamination. 8