PRINCIPLES OF TOXICOLOGY - Biology East Borneo

19.4 PETROLEUM HYDROCARBONS: ASSESSING EXPOSURE AND RISK TO MIXTURES 485TABLE 19.2 Example—Worker Exposure to Diesel Fuel Hydrocarbons in Soil, Typical ReasonableMaximum Exposure Soil Exposure ParametersExposure Parameter Value ReferenceABSgi 1 DefaultABSsk 0.05 Professional judgmentAF 0.2 mg/cm 2 USEPA (1997)ATnc 9125 days USEPA (1991)BW 70 kg USEPA (1991)ED 25 years USEPA (1991)EF 250 days/year USEPA (1991)IR 50 mg/day USEPA (1991)SA 2000 cm 2 USEPA (1992)HQ or HI exceeds one, there may be a concern for adverse effects. Exposure assumptions used tocalculate exposure to petroleum hydrocarbons in soil are presented in Table 19.2.The average daily intakes (ADIs) of the six petroleum hydrocarbon fractions are presented in Table19.3. These ADIs were calculated using the soil concentrations in Table 19.1, the exposure assumptionspresented in Table 19.2, and the equations presented later in this chapter (see Table 19.10).HQs associated with the calculated levels of exposure to petroleum hydrocarbons in soil arecalculated by dividing the calculated ingestion and dermal intake by RfD for the appropriate petroleumhydrocarbon fraction. The calculated HQs for the six petroleum hydrocarbon fractions are presentedin Table 19.4.Several petroleum fractions may affect the same target organ or have similar critical effects. In theabsence of strong evidence indicating another type of interaction (an antagonistic effect or a synergisticeffect), the USEPA assumes that the effects of chemicals affecting the same target organ are additive.Thus, the hazard quotients for chemicals affecting the same target organ are summed. The sum of theHQs for a particular target organ is termed the HI. The calculated HIs for liver toxicity, decreased bodyweight, and kidney toxicity are presented below.HI for liver toxicity = sum of the oral and dermal HQs for aliphatic petroleum fractions C >12–C 16,C >16–C 21, and C >21–C 35 = 0.024TABLE 19.3 Example—Worker Exposure to Diesel Fuel Hydrocarbons in Soil, Calculated AverageDaily Intakes of Diesel Fuel HydrocarbonsAverage Daily IntakePetroleum Hydrocarbon Fraction Ingestion (mg/kg) Dermal (mg/kg)AliphaticC>12–C16 1.08 × 10 –3 4.31 × 10 –4C>16–C21 8.81 × 10 –3 3.52 × 10 –3C>21–C35 3.23 × 10 –3 1.29 × 10 –3AromaticC>12–C16 7.34 × 10 –4 2.94 × 10 –4C>16–C21 4.55 × 10 –3 1.82 × 10 –3C>21–C35 4.45 × 10 –3 1.78 × 10 –3