Dames & Moore, 1999 - USDA Forest Service

where:
PEF = Particulate emission factor (m3Ikg)
QIC
= Inverse of mean concentration at center of source (@m2-s per kdm3)
V = Fraction of vegetative cover
Um = Mean annual windspeed (mls)
Ut = Equivalent threshold value of windspeed at 7 m (mls)
F(x) = Function dependent on Um/Ut (unitless)
Q/C was selected from the Soil Screening Guidance (USEPA, 1996) for the closest geographical area
(Seattle).
7.1.4.4 Risk Characterization
Risk characterization involves estimating the magnitude of the potential adverse health effects of the
hazardous chemicals under study and making summary judgements about the nature of the health threat to
the defined receptor populations. It combines the results of the toxicity assessment and exposure
assessment.
Exposure Concentrations vs. Method C Levels
Table 7.1-41 compares exposure concentrations for each exposure pathway to the corresponding Method C
levels. Exposure concentrations for all lHSs for each exposure pathway are below their corresponding
Method C levels.
Human Health Risk Estimates
The site-specific risks and hazard quotients for each IHS ,and each exposure pathway are detailed in Table
7.1-42. Cancer risk was evaluated by comparing the exposure point concentration to the Method C criteria
based on carcinogenic effects, as follows:
Exposure Concentration
Cancer Risk = Method C Criteria (cancer) x(lx10")
Noncancer hazard quotients were evaluated by comparing the exposure point concentration to the Method C
criteria based on noncarcinogenic effects, as follows:
Exposure Concentration
Hazard Quotient = 7-14
Method C Criteria (noncancer)
The results shown in Table 7.1 -42 indicate that.carcinogenic risk and noncarcinogenic hazard to receptors is
acceptable (i.e., the cancer risk is less than 1 x 10'' and the hazard quotient is below one). Risks and hazard
quotients for each exposure media are summarized below:
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