Radon daughter products (Po-210, Pb-214, Bi-214) are main components of naturally occurring radioactive aerosols in air and are considered to be important elements initiating lung cancer. They are classified for size into two groups: attached atoms and unattached atoms (free atoms). In this study, we have developed a measuring method with a screen-type diffusion battery for the size distribution of radon daughter products and have carried out measurements in some outdoor and indoor airs. Deposition of radon daughter products to the human respiratory tract has been calculated using the observed size distribution in every generation. The onversion factor from exposure to absorbed dose is also discussed.
