• Discussion of health-risk reductions obtained by encouraging people to reduce radon concentrations in indoor air with methods already developed and comparison of them with the risk reductions associated with mitigation of radon in water.

Composition of the Report

Chapter 2 presents baseline data regarding concentrations of radon in water and indoor air. It includes a discussion of radon concentrations measured in outdoor air throughout the United States and an estimate of a national annual average concentration of ambient radon.

Chapter 3 describes the transfer coefficient that expresses the increase in indoor airborne radon in reference to the concentration of radon in water. It includes a survey of measurements and theoretical considerations.

Chapter 4 discusses the dosimetry of ingested radon. It describes patterns of consumption of water directly from the tap or faucet. The calculations make extensive use of physiologically-based pharmacokinetic (PBPK) models that have been developed for dosimetry of internal radioactivity. The chapter includes computations of equivalent dose and risk to individual tissues and organs. A special model was developed to estimate the concentration of radon and the alpha-particle radiation dose produced by decay of radon and its decay products occurring next to sensitive cells in the stomach wall.

Chapter 5 discusses the risk associated with inhalation of radon and radon decay products. It includes a summary of the methods used to form risk-projection models that were developed by the National Research Council's committees on Biological Effects of Ionizing Radiation (BEIR).

Chapter 6 discusses the basic mechanisms that are believed to be responsible for radiation-induced carcinogenesis.

Chapter 7 presents an analysis of the uncertainty and precision associated with the risk estimates obtained in the previous chapters.

Chapter 8 discusses the methods and efficiencies of radon mitigation in both indoor air and water. It includes an examination of techniques for reducing radon concentrations in existing buildings and procedures for reducing radon in new construction.

Chapter 9 analyzes the concepts associated with a multimedia approach to risk reduction. Several scenarios illustrate various ways to evaluate gains in risk reduction by using an alternative AMCL for water with other indirect approaches that encourage or even enforce mitigation in indoor air.

The committee's research recommendations are summarized in chapter 10.

A glossary and six appendixes present specific details and methods that were incorporated in the various chapters.

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