The Safe Drinking Water Act directs the U.S. Environmental Protection Agency (EPA) to regulate the quality of drinking water, including its concentration of radon, an acknowledged carcinogen.

This book presents a valuable synthesis of information about the total inhalation and ingestion risks posed by radon in public drinking water, including comprehensive reviews of data on the transfer of radon from water to indoor air and on outdoor levels of radon in the United States. It also presents a new analysis of a biokinetic model developed to determine the risks posed by ingestion of radon and reviews inhalation risks and the carcinogenesis process. The volume includes scenarios for quantifying the reduction in health risk that might be achieved by a program to reduce public exposure to radon.

Risk Assessment of Radon in Drinking Water, reflecting research and analysis mandated by 1996 amendments to the Safe Drinking Water Act, provides comment on a variety of methods to reduce radon entry into homes and to reduce the concentrations of radon in indoor air and in water. The models, analysis, and reviews of literature contained in this book are intended to provide information that EPA will need to set a new maximum contaminant level, as it is required to do in 2000.

Contents

• COMMITTEE ON RISK ASSESSMENT OF EXPOSURE TO RADON IN DRINKING WATER
• BOARD ON RADIATION EFFECTS RESEARCH
• COMMISSION ON LIFE SCIENCES
• [The National Academies]
• Preface
• Public Summary
• Executive Summary
• 1. Introduction
  • The Origins of Radon
  • Migration of Radon
  • Exposure to Indoor Radon
  • Absorbed Dose from Indoor Radon
  • Health Risks Posed by Indoor Radon
  • Legislation and Regulations Regarding Indoor Radon
  • Charge to the Committee
  • Composition of the Report
• 2. Baseline Information on Indoor Radon and Radon in Water in the United States
  • Indoor Radon
  • Radon in Groundwater and Public Water Supplies
  • Ambient Radon
• 3. Transfer of Radon from Water to Indoor Air
  • Measurements Of Transfer Coefficients
  • Modeling Of Transfer Coefficient
  • Conclusions
• 4. Dosimetry of Ingested Radon and its Associated Risk
  • Intakes And Consumption Of Water
  • Physicochemical Properties Of Radon
  • Fate of Radon Decay Products in the Body
  • Cancer Risk Per Unit ²²²RN Concentration in Drinking Water
  • Special Populations At Risk
• 5. Dosimetry of Inhaled Radon and its Associated Risk
  • Inhalation Of Radon And Its Short-lived Decay Products
  • Risk Posed By Inhalation Of ²²²Rn Decay Products
  • Lung Dose From ²²²Rn Gas
  • Dose to Organs Other than the Lung from Inhaled ²²²Rn
  • ²²²Rn Decay-Product Dose During Showering
  • Lung-Cancer Risk Posed by Inhalation of ²²²Rn Decay Products
  • Epidemiology of Childhood Exposure and Lung-Cancer Risk
  • Environmental and Domestic Epidemiology
  • Epidemiology Of Cancer Of Organs Other Than Lung
  • Evaluation Of Risk Per Unit Exposure From Inhaled ²²²RN in Air
• 6. Molecular and Cellular Mechanisms of Radon-Induced Carcinogenesis
  • Cells at Risk
  • Cellular Damage Induced by Radon Alpha Particles
  • Transformation of Cells by Alpha Particles in Vitro
  • DNA Damage and its Repair—The Caretaker Genes
  • Deletion Mutagenesis and Chromosomal Changes Caused by Densely Ionizing Radiation
  • Control of Cellular Responses to Damage—The Arbitrator Gene
  • Apoptosis—The Undertaker Genes
  • Initial Genetic Changes in Carcinogenesis—The Gatekeeper Genes
  • Tumor Growth and Nutrition—The Caterers
  • Genetic Instability in Irradiated Cell Populations—The Diversifiers
  • Mutations In α-Particle-Induced Tumors—The Fingerprints
  • Epidemiologic, Biophysical, And Cell-Based Models Of Radon-Induced Carcinogenesis
• 7. Defining Key Variabilities and Uncertainties
  • Reliability Of A Health-Risk Assessment
  • Environmental Protection Agency Process For Assessing And Evaluating Uncertainties In Radon Risk
  • Issues In Uncertainty Analysis For Radon
  • The Committee's Evaluation Of Uncertainties In Risk Assessment Of Radon In Drinking Water
  • Communication Of Uncertain Risk Information
  • Discussion And Recommendations
• 8. Mitigation
  • Mitigation Of Radon In Indoor Air
  • Mitigation of Radon in Water
  • Conclusions
• 9. Multimedia Approach to Risk Reduction
  • Derivation of the Alternative Maximum Contaminant Level (AMCL)
  • Equivalent Risk-Reduction Scenarios
  • Equity and Implementation Issues and Risk Reduction
  • Summary
• 10. Research Recommendations
• References
• Glossary
• Appendixes
  • A Behavior of Radon and its Decay Product in the Body
  • B A Model for Diffusion of Radon Through the Stomach Wall
  • C Water-Mitigation Techniques
  • D Risks Associated with Disinfection By-products Formed by Water Chlorination Related to Trihalomethanes (THMs)
  • E Gamma Radiation Dose From Granular-Activated Carbon (GAC) Water Treatment Units
  • F EPA Approach to Analyzing Uncertainty and Variability

This report was prepared under EPA Contract EPA X825492-01-0 between the National Academy of Sciences and the Environmental Protection Agency.

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard to appropriate balance.