Abstract
The transfer of radon from thermal water via the skin to different human organs in radon therapy can experimentally be determined by measuring the radon activity concentration in the exhaled air. In this study, six volunteers were exposed to radon-rich thermal water in a bathtub, comprising eleven measurements. Exhaled activity concentrations were measured intermittently during the 20 min bathing and 20 min resting phases. Upon entering the bathtub, the radon activity concentration in the exhaled breath increased almost linearly with time, reaching its maximum value at the end of the exposure, and then decreased exponentially with time in the subsequent resting phase. Although for all individuals the time-dependence of exhaled radon activity was similar during bathing and resting, significant inter-subject variations could be observed, which may be attributed to individual respiratory parameters and body characteristics. The simulation of the transport of radon through the skin, its distribution among the organs, and the subsequent exhalation via the lungs were based on the biokinetic model of Leggett and co-workers, extended by a skin and a subcutaneous fat compartment. The coupled linear differential equations describing the radon activity concentrations in different organs as a function of time were solved numerically with the program package Mathcad. An agreement between model simulations and experimental results could only be achieved by expressing the skin permeability coefficient and the arterial blood flow rates as a function of the water temperature and the swelling of the skin.
Highlights
In the Gastein valley, Austria, natural radon-rich water in springs and radon vapor in the thermal gallery have been successfully used in the past for the treatment of various rheumatic diseases, most notably ankylosing spondylitis (Shehata et al 2006; van Tubergen et al 2001)
Individual exhalation curves as a function of time for seven measurements are plotted in Fig. 2, normalized to the corresponding radon activity concentrations in thermal water
The apparent variations of the measured exhalation curves among the six volunteers, consisting of four female and two male subjects, normalized to the corresponding radon activity concentration in thermal water (Fig. 2), illustrate the effects of female-male differences and inter-subject variations among the test persons. This inter-subject variability of the exhaled radon activity concentrations is caused by variations of individual body characteristics and respiratory parameters, such as body surface area, the content of body fat, respiratory tract volume, and respiratory minute volume
Summary
In the Gastein valley, Austria, natural radon-rich water in springs and radon vapor in the thermal gallery have been successfully used in the past for the treatment of various rheumatic diseases, most notably ankylosing spondylitis (Shehata et al 2006; van Tubergen et al 2001). The physiological and cellular mechanisms triggered by very (1) In the thermal bath, patients are sitting in a bathtub (37–40 °C) for a period of 20 min (on average ten treatments) with a radon activity concentration in water of about 900 kBq m−3. (2) In the thermal gallery, patients are exposed to radon and radon progeny for 60 min (on average ten treatments) at an average radon activity concentration in air of about 45 kBq m−3 (37–41.5 °C and 70–99% RH). (37 °C) in a small exposure chamber for a period of 20 min (on average ten treatments) with radon activity concentrations in air ranging from 30 to 300 kBq m−3 (average value: 90 kBq m−3). Tempfer et al (2010) proposed an immune response caused by irradiation of the deeper layers of the skin by radon progeny adsorbed to the skin as an alternative explanation for the therapeutic effectiveness of the thermal water treatment
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