Within the past few years several situations have been brought to light which indicate an increased radiation exposure of certain segments of the general population caused by human activities. The most widely publicized activities are those associated with the mining and milling of uranium in the western United States, the phosphate industry in Florida, and those potential problems represented by former Manhattan Engineer District sites. One of the primary problems involves exposure to radon and radon daughters which are released from large waste piles or, in some cases, evolve from backfill and construction materials used in homes, schools, and other buildings. This report presents a review of the available data on radon and radon daughter concentrations in dwellings and other structures. The primary objectives were to compile and tabulate pertinent radon exposure data and to prepare a statistical summary of the data which will be useful in the prediction of normal levels of radon and radon daughter concentrations in these structures. In addition, other parameters associated with radon exposure conditions are presented and discussed.

In view of the well-known urban-rural difference in lung cancer rates, remaining also after standardization for smoking, it is suggested that low levels of radon and its daughters in dwellings might be of etiologic importance to this disease. To test this hypothesis, a case-referent (case-control) study was undertaken in a rural area; it considered residency in wooden houses (assumed to be associated with low-level exposure to radon and its daughters), "mixed type" houses (medium expos ure) and stone houses (high-level exposure) among cases of lung cancer and referents (controls). The results indicate an increased risk of lung cancer among residents in "mixed type" and stone houses. Additional studies are highly desirable to confirm or refute these findings, which, if valid, mean increasing lung cancer hazards caused by a decrease in ventilation in future energy saving unless special measures are undertaken to reduce radon daughters in dwellings.

This book describes hazards from radon progeny and other alpha-emitters that humans may inhale or ingest from their environment. In their analysis, the authors summarize in one document clinical and epidemiological evidence, the results of animal studies, research on alpha-particle damage at the cellular level, metabolic pathways for internal alpha-emitters, dosimetry and microdosimetry of radionuclides deposited in specific tissues, and the chemical toxicity of some low-specific-activity alpha-emitters. Techniques for estimating the risks to humans posed by radon and other internally deposited alpha-emitters are offered, along with a discussion of formulas, models, methods, and the level of uncertainty inherent in the risk estimates.

The factors used to assess the radiation dose and health risks from human exposure to radon in dwellings are critically reviewed in this summary. Sources of indoor radon and determinants of air concentrations and exposure levels are given as well as the uncertainties that exist in their formulation. Methods of assessing health effects from inhalation of radon and its progeny are discussed with emphasis on dosimetry of radon daughters and formulation of risk per dose values. Finally, methods of assessing risks for general population exposures to indoor radon concentrations are treated.