Measurement of the deposited activity of the short-lived radon progeny in the human respiratory tract

Volunteers were exposed in the radon chamber at Paul Scherrer Institut to an atmosphere enriched with highly unattached radon progeny. The deposited radon progeny activity in the respiratory tract of the volunteers was determined using a low level in-vivo counter. The detector arrangement and its calibration for the measurement of deposited radon progeny activity is described and the results for a mouth and a nose breathing volunteer are presented. For the nose breathing volunteer 55% of the deposited radon progeny activity was located in the head and the remaining 45% in the chest whereas for the mouth breathing volunteer 25% was located in the head and the remaining 75% in the chest. A mean clearance half-life fur the deposited radon progeny from the respiratory tract of (2 +/- 1) h was obtained from the analyses of the temporal behaviour of the deposited radon progeny activity in the head.