Bio-kinetics of radon ingested from drinking water.

Previous studies have identified the stomach as the most significant organ for the dose from ingested radon. An important factor in dosimetric modelling is the rate of radon loss from the stomach. In the present study, two subjects who ingested radon-rich water were measured using a NaI(Tl) detector fixed over the stomach. The counting rates for 214Pb and 214Bi peak regions were plotted as a function of time after ingestion. These data were interpreted using a compartment model that expressed biokinetics of radon and its progeny. The model was fitted to the experimental data by changing biokinetic parameters such as the rate of radon loss from the stomach. Previous models for dosimetric purposes often assumed that the half-time for radon loss from the stomach is below 20 min. The present results, however, suggest that a part of radon stayed longer in the stomach than expected in the previous models.