PRINCIPLES OF TOXICOLOGY

19.4 PETROLEUM HYDROCARBONS: ASSESSING EXPOSURE AND RISK TO MIXTURES 485
TABLE 19.2 Example—Worker Exposure to Diesel Fuel Hydrocarbons in Soil, Typical Reasonable
Maximum Exposure Soil Exposure Parameters
Exposure Parameter Value Reference
ABSgi 1 Default
ABSsk 0.05 Professional judgment
AF 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 to
calculate 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 Table
19.3. These ADIs were calculated using the soil concentrations in Table 19.1, the exposure assumptions
presented 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 are
calculated by dividing the calculated ingestion and dermal intake by RfD for the appropriate petroleum
hydrocarbon fraction. The calculated HQs for the six petroleum hydrocarbon fractions are presented
in Table 19.4.
Several petroleum fractions may affect the same target organ or have similar critical effects. In the
absence of strong evidence indicating another type of interaction (an antagonistic effect or a synergistic
effect), 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 the
HQs for a particular target organ is termed the HI. The calculated HIs for liver toxicity, decreased body
weight, and kidney toxicity are presented below.
HI for liver toxicity = sum of the oral and dermal HQs for aliphatic petroleum fractions C>12–C16,
C>16–C21, and C>21–C35 = 0.024
TABLE 19.3 Example—Worker Exposure to Diesel Fuel Hydrocarbons in Soil, Calculated Average
Daily Intakes of Diesel Fuel Hydrocarbons
Average Daily Intake
Petroleum Hydrocarbon Fraction Ingestion (mg/kg) Dermal (mg/kg)
C>12–C16
C>16–C21
C>21–C35
C>12–C16
C>16–C21
C>21–C35
Aliphatic
1.08 × 10 –3
8.81 × 10 –3
3.23 × 10 –3
Aromatic
7.34 × 10 –4
4.55 × 10 –3
4.45 × 10 –3
4.31 × 10 –4
3.52 × 10 –3
1.29 × 10 –3
2.94 × 10 –4
1.82 × 10 –3
1.78 × 10 –3