2007 年 42 巻 4 号 p. 341-348
Internal exposure to alpha particles emitted from 222Rn (radon) and its daughters is the second leading cause of lung cancer. As a source of indoor radon in home, there are interior building materials that contain radioactive minerals. These radioactive consumer products have been claimed by distributors to have effect of “minus-ion” or “radon spring” for healthy promotion. We analyzed radioactive nuclides contained in the interior building materials, and measured radon levels released from them. The results of gamma-ray spectrometry revealed that these interior building materials contain U- and Th-series nuclides. The densities of some radioactive nuclides in the tile used for a bathroom exceeded the exempt limits of International Basic Safety Standards. However, the radon densities released from the the was lower than detectable limit. In contrast, one of the wallpaper released 34Bq·m-3 of radon gas in a 50-liter container. This value is two times higher than the average radon level in Japanese homes.
The “minus-ion effect” wallpapers are thought to be a cause of residential exposure to radon.