Table F.4

Probability Density Functions Developed by EPA (1995) in Calculation of Risk, Unit Risk and Variation of Individual Risk Posed by Radon Progeny Inhaled after Transfer from Water (following notation of EPA 1995)

RF (risk factor, lifetime risk of cancer death per person-WLM)

This factor has uncertainty only

 

RF=LN(µ,σ

µ= ln(2.83 × 10-4) σ = ln(1.53)

UR (unit risk factor, lifetime risk of cancer death per pCi/L)

Uncertainty = => Variability 5th percentile mean 95th percentile

5th percentile 1.3 × 10-10 2.1 × 10-9 7.2 × 10-8

median 3.4 × l0-10 5.1 × l0-9 1.8 × l0-8

95th percentile 8.9 × 10-10 1.2 × 10-8 4.2 × 10-8

C (concentration of radon in the water, pCi/L [water])

Lognormal distribution LN(µ,σ)

C = LN(µl,σl,) µ = TS(m,s,n) (σ)2=IChi(s,n)

Student t distribution, TS(m,s,n) Inverse chi-squared distribution, IChi(s,n)

n= 10 m = ln(200) s = ln(1.85)

IR (individual risk, lifetime risk of cancers per person-year)

Uncertainty==> Variability 5th percentile mean 95th percentile

5th percentile 1.8 × 10-8 5.2 × 10-7 1.9 × 10-6

median 5.4 × 10-8 1.3 × 10-6 5.0 × 10-6

95th percentile 1.5 × 10-7 3.2 × 10-6 1.3 × 10-5



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