Exposure of volunteers to a radon progeny enriched atmosphere

For an improvement of dose estimation of the exposure by inhalation of radon progeny in the domestic environment human volunteers were exposed to precisely determined radon progeny atmospheres in the walk-in radon chamber at the Paul Scherrer Institut (PSI). One of the major targets of the experiments consists of the determination of the transport rare of the short-lived radon progeny from the respiratory tract into the blood circuit. The question is, if this transport may be fast enough compared to the physical half-life of the radon progeny to have a significant influence on dose considerations. The experimental set-up consisting of measurement devices for the size distribution of the unattached radon progeny during the exposure and for the activity of the radon progeny in the blood circuit is described. First volunteers have been exposed to atmospheres with a large fraction of unattached radon progeny. From these measurements, a larger transfer rate of the unattached radon progeny from respiratory tract to the blood circuit than reported in the literature can be derived, but without reaching values significantly influencing dose estimations.