MEASUREMENT OF THE BIOTRANSFER AND TIME CONSTANT OF RADON FROM INGESTED WATER BY HUMAN BREATH ANALYSIS

Forty-one tests were performed on 38 volunteers to measure elimination rates of Rn-222 in expired breath. Participants ranged from ages 9 to 85 y, with 16 males and 22 females. The levels of physical activity of the subjects ranged from very inactive to marathon level. Calibration of our flow-through scintillation cell was accomplished using a medical ventilator and Rn-222 reservoir for 5-15 L min-1 flow rates. We found a wide range of percent elimination (12-68%) in 30 min. The percent elimination has a mild correlation with the predicted forced expiratory volume in 1 s and with time passed since eating. Our observations of bio-retention half-times range from 17-400 min. The whole-body dose calculations yield a mean of 2.70 +/- 3.43 nGy Bq-1, and the stomach dose calculations yield a mean of 276 +/- 186 nGy Bq-1. These means range beyond those previously reported.