Chemical and hygienic studies on natural radioactive spa, 4

Dose rates of external radiation were measured with an ionization chamber equiped with ivibrating reed electrometer at some spots in Misasa and Masutomi spa areas which are called strong radioactive fountains in Japan. At Misasa spa area, the maximum value of 25.0 μR/hr was recorded in a bath room, and the minimum value was 13.0 μR/hr in field. The maximum value recorded at Masutomi spa area was 24.5 μR/hr in a bath room, and minimum one recorded in a garden of hotel was 5 μR/hr, which was equal to the average value measured in Tokyo. If the habitants in these spa area are assumed to take a bath every day and stay in the bath room for 30 minutes, it can be said that their radiation dose rates might amount to 116 mR/year at Misasa and 48 mR/year at Masutomi.