2005 年 40 巻 3 号 p. 285-294
Indoor radon has been determined to be the second leading cause of lung cancer after tobacco smoking. There is an increasing need among radiation practitioners to have numerical values of lung cancer risks for men and women, smokers and non-smokers exposed to radon in homes. This study evaluates individual risks for the Japanese population exposed to indoor radon at different radon concentrations and for different periods of their lives. Based on the risk model recently developed by U. S. Environmental Protection Agency (EPA), individual risks of radon induced lung cancers are calculated with Japanese age-specific rates for overall and lung cancer mortalities (1996-2000) as well as the Japanese smoking prevalence data in 2002. Convenient tables of lifetime relative risks are constructed for lifetime exposures and short exposures between any two age intervals from 0 to 110, and for various radon concentrations found in homes from 25 to 600Bq/m3. The risk of developing lung cancer from residential radon exposure increases with radon concentration and exposure duration. For short exposure periods, such as 10 or 20 years, risks are higher in middle age groups (30-50) compared especially to the later years. Individuals could lower their risks significantly by reducing their radon exposure levels earlier in life. The tables can help radiation protection practitioners to better communicate indoor radon risks to members of the public.