Measurements of radiation dose due to radon and its daughters in Oku-Hida hot spring area and its health physical consideration

In view of health physics aspect, in the Oku-Hida hot spring area in Gifu Prefecture, the radon-222 concentrations in hot spring waters and in bathrooms were determined with a liquid scintillation counter. The scintillation counter method with Rn dissolved in toluene is convenient because of small sample quantity, sample preparation at the sites and measurement at several positions. In the hot spring areas, the content of radon-222 in Shinhodaka hot spring water was higher than that in other three hot spring waters, Hirayu, Gamada and Hitoegane. The radon-222 concentration in the air in bathrooms was 5.3 pCi per liter. Since radon-222 decay products are deposited on the surfaces of respiratory system by inhalation, the exposure dose to bronchus epithelium is an important problem. The annual dose due to radon-222 and its daughters was estimated by the method of Haque. (J.P.N.)