Residential radon and lung cancer: end of the story?

The earliest evidence of increased lung cancer risk associated with radon came largely from studies of highly exposed underground miners. In the United States, concerns about residential exposures became prominent in the early 1980s with the identification of the Watras home, which had remarkably elevated radon concentrations. By then, the problem of indoor radon was already recognized in Europe and the first epidemiological studies on indoor radon had been reported. The concern about the risk of indoor radon motivated a series of case-control studies of residential radon and lung cancer in the United States, Canada, China, and a number of European countries. In 1999, the U.S. National Research Council Committee on the Biological Effects of Ionizing Radiation (BEIR VI) weighed the scientific evidence available at that time on this issue and concluded that residential radon was an important contributor to the lung cancer burden and that risks were appropriately estimated by a linear nonthreshold model. Since individual case-control studies have not provided consistent direct evidence of excess lung cancer risk at residential exposure levels, combined analyses of residential radon studies have been undertaken in both North America and Europe. These combined analyses, including the North American pooled analysis described in this issue, represent an important complement to the findings of the miner studies and further support the linear no-threshold model for cancer risk adopted by the BEIR VI Committee and other groups.