Quantification of radon-progeny deposition on the skin in underwater radon-therapy

Despite all the theories and discussions about the (negative) effects of radioactivity, radon is applied for therapeutic purposes in many places in the World. In Badgastein/Austria, one of the leading radon therapy sites worldwide, radon, alongside inhalation, is also applied as underwater radon therapy. For 20 to 30 minutes patients are bathing in the "Best'sche Wanne", a bathtub filled with 600 litters of water, with concentrations of approximately 1000 Bq L-1. During the exposure phase in the bath, radon decay products deposit on the skin of the patients. Results currently under consideration indicate that the activity on the skin depends on the chemical behaviour of the decay products. For the theoretical calculation of the deposition dynamics, reliable and quantifiable results of progeny measurements on the skin are of fundamental importance. Immediately after leaving the bath tub, the skin of the patients was gently dried by dabbing it with towels and alpha detectors were fixed to the skin by elastic bands. For radon decay product (Rnp) measurements, we used surface barrier detectors directly in contact with the skin, only protected by a mylar foil. The activity decay curve and the alpha spectrum were measured for a period of 30 minutes after the exposure phase, starting approximately 3 minutes after leaving the bath tub. Though the detectors are almost in direct contact with the skin, on which the alpha particles are deposited, a strong distortion of the spectra could be observed. We assume this effect to be a combination of absorption and migration of the progeny into the skin. With model assumptions on the migration behaviour and the production of sweat during the measurement, we tried to interpret the shape of the spectra, in order to obtain quantitative measurements of the radon progeny on, and in, the skin.