user's guide and background technical document for the nevada ...

ED = Exposure duration (25 years)
IRS = Ingestion rate for soil (50 mg/day)
Inhalation of Carcinogenic Contaminants
Eq. 11
where:
mg/kg =
TR AT
EF ED ET CF [( 1 1
) or (
PEF VF ]
TR = Target risk of 10 -6
AT = Averaging time (70 years x 365 days/year x 24 hours/day)
IURi = Inhalation unit risk (chemical-specific) (μg/m 3 ) -1
EF = Exposure frequency (250 days/year)
ED = Exposure duration (25 years)
ET = Exposure time (8 hours/day)
CF = Conversion Factor (1,000 μg/mg)
PEF = Particulate emission factor used for dusts (1.2×10 9 m 3 /kg)
VF = Volatilization factor used for volatile organic chemicals (m 3 /kg)
Inhalation of Non-carcinogenic Contaminants
Eq. 12
where:
mg/kg =
THQ x AT
EF ED ET ( 1
) x [(
RfC 1 1
) or (
PEF VF )]
THQ = Target hazard quotient of 1
AT = Averaging time (25 years x 365 days/year x 24 hours/day)
EF = Exposure frequency (250 days/year)
ED = Exposure duration (25 years)
ET = Exposure time (8 hours/day)
RfCi = Inhalation reference concentration in (chemical specific) (mg/m 3 )
PEF = Particulate emission factor used for dusts (1.2×10 9 m 3 /kg)
VF = Volatilization factor used for volatile organic chemicals (m 3 /kg)
Dermal contact pathway is not quantitatively evaluated as per USEPA (2002a, 2004).
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