2007 年 42 巻 3 号 p. 221-226
The bio-kinetics of radon ingested from drinking water was investigated for eight Japanese subjects. A whole-body counter at National Institute of Radiological Sciences (NIRS) was used for the measurement of the 214Bi transfer half-life from the stomach to the small intestine. The transfer half-life seemed to be affected by water quality (chemical/physical properties) as well as the meal ingested before the experiments. The shortest transfer half-life among the subjects was about 50 minutes. During the whole-body counting, the air expired by the subjects was sampled and its radon concentration was measured using two ionization chambers. The changes in radon concentration in the expired air could be classified into three patterns. (1) It decreased with time after ingestion. (2) A peak appeared at the 15 minutes after ingestion. (3) A peak appeared at the 25 minutes after ingestion. These patterns seemed to be related to the 214Bi transfer half-life and the amount of ingested water.