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

Ingestion of Non-carcinogenic Contaminants
Eq. 16
where:
THQ BW AT 365 days/year
mg/kg =
1
10
RfD -6 kg/mg EF ED IRS
THQ = Target hazard quotient of 1
BW = Body weight of adult (70 kg)
AT = Averaging time (25 years)
RfDo = Oral reference dose (chemical-specific) (mg/kg-day)
EF = Exposure frequency (225 days/year)
ED = exposure duration (25 years)
IRS = Soil ingestion rate for adult (100 mg/day)
Inhalation of Carcinogenic Contaminants
Eq. 17
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 (225 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)
16