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## Risk Assessment of Radon in Drinking Water (1999) Commission on Life Sciences (CLS)

### Citation Manager

. "F EPA Approach to Analyzing Uncertainty and Variability." Risk Assessment of Radon in Drinking Water. Washington, DC: The National Academies Press, 1999.

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 Page 262

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Table F.1

Probability Density Functions Used in the Calculation of Risk of Cancer Posed by Ingestion of Radon Gas in Water (following notation of EPA 1995)

 Variability Uncertainty Parameter Distribution Type Distribution Values Distribution Type Distribution Values C (concentration of radon in water, pCi/L[water]) Lognormal distribution, LN(µ) C = LN(µ,σ) 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) V (volume of water ingested, L/d) Lognormal distribution, LN(µ,σ) V = LN(µ,σ) 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=100 m = ln(0.526) s = ln(1.922) F (fraction remaining) Beta distribution, B(m,md,min,max) F=B(m,md,min,max) min=0.5 max=1 m=U(a,b) md=U(m,max) or U(min,m) Uniform distributions U(a,b) U(m,max) a=0.7 b=0.9 min = 0.5 max=1 RF (risk factor, cancer-death risk per person per pCi ingested) This factor has uncertainty only RF=LN(µ,σ) µ= ln(1.24 × 10-11 σ = ln(2.42) Calculated individual risk Uncertainty==> Variability 5th percentile mean 95th percentile 5th percentile 1.7 × 10-8 1.3 × 10-7 4.0 × 10-7 median 8.3 × 10-8 6.2 × 10-7 1.9 × 10-6 95th percentile 3.4 × 10-7 2.6 × 10-6 7.9 × 10-6 m=mean value derived from a sample s=standard deviation of a sample n=sample size md=mode of a sample µ=mean value of ln(x) in a lognormal distribution µ=standard deviation of ln(x) in a lognormal distribution
 Page 262
 Front Matter (R1-R14) Public Summary (1-7) Executive Summary (8-22) 1 Introduction (23-31) 2 Baseline Information on Indoor Radon and Radon in Water in the United States (32-49) 3 Transfer of Radon from Water to Indoor Air (50-58) 4 Dosimetry of Ingested Radon and its Associated Risk (59-81) 5 Dosimetry of Inhaled Radon and its Associated Risks (82-104) 6 Molecular and Cellular Mechanisms of Radon Induced Carcinogenesis (105-123) 7 Defining Key Variabilities and Uncertainties (124-140) 8 Mitigation (141-179) 9 Multimedia Approach to Risk Reduction (180-197) 10 Research Recommendations (198-199) References (200-222) Glossary (223-230) A Behavior of Radon and Its Decay Products in the Body (231-240) B A Model for Diffusion of Radon Through the Stomach Wall (241-248) C Water-Mitigation Techniques (249-253) D Risks Associated with Disinfection By-products Formed by Water Chlorination Related to Trihalomethanes (THMs) (254-256) E Gamma Radiation Dose from Granular-Activated Carbon (GAC) Water Treatment Units (257-259) F EPA Approach to Analyzing Uncertainty and Variability (260-268) Index (269-279)