Evaluation of the intake of radon through skin from thermal water

Abstract

The biokinetics of radon in the body has previously been studied with the assumption that its absorption through the skin is negligibly small. This assumption would be acceptable except in specific situations, such as bathing in a radon hot spring where the radon concentration in thermal water is far higher than that in air. The present study focused on such a situation in order to better understand the biokinetics of radon. To mathematically express the entry of radon through the skin into the body, we first modified the latest sophisticated biokinetic model for noble gases. Values of an important parameter for the model—the skin permeability coefficient K (m s−1)—were derived using data from previous human studies. The analysis of such empirical data, which corresponded to radon concentrations in the air exhaled by subjects during and following bathing in radon-rich thermal water, revealed that the estimated K values had a log-normal distribution. The validity of the K values and the characteristics of the present model are then discussed. Furthermore, the impact of the intake of radon or its progeny via inhalation or skin absorption on radiation dose was also assessed for possible exposure scenarios in a radon hot spring. It was concluded that, depending on the radon concentration in thermal water, there might be situations in which the dose contribution resulting from skin absorption of radon is comparable to that resulting from inhalation of radon and its progeny. This conclusion can also apply to other therapeutic situations (e.g. staying in the pool for a longer period).

Radon transfer from thermal water to human organs in radon therapy: exhalation measurements and model simulations

“…Since the Leggett et al (2013) model considers only radon inhalation and ingestion but does not consider radon transfer through the skin, Sakoda et al (2016) extended this model by an additional skin compartment, which transports radon from the water to the skin and further to the venous blood compartment. For comparison, in the earlier modeling study of Hofmann and Winkler-Heil (2010) radon was, based on the Peterman and Perkins (1988) model, directly transferred to the subcutaneous fat (fat 1) compartment without invoking a separate skin compartment.…”

“…Because of its much higher blood flow and fat content, the radon transfer from water to blood in the skin takes place primarily in the adipose subcutaneous tissue layer. The diffusional transport of radon from water to the dermal skin compartment is characterized by a permeability coefficient and the surface area of the skin (Sakoda et al 2016), with the stratum corneum as the rate-limiting outermost layer for the permeability (Potts and Francoeur 1990). The transfer rate from the DS to the SS compartment was adopted from the earlier modeling effort which was based on the Peterman and Perkins (1988) model (Hofmann and Winkler-Heil 2010).…”

“…In a previous modeling attempt, the Peterman and Perkins (1988) model had been extended to incorporate the water-skin-blood transfer of radon for the simulation of the radon activity concentrations in exhaled breath and in various organs and tissues of the human body (Hofmann and Winkler-Heil 2010). More recently, Sakoda et al (2016) evaluated the uptake of radon through the skin from thermal water by incorporating an additional skin compartment to the biokinetic model for noble gases proposed by Leggett et al (2013) specifically for radon inhalation.…”

Internal Dosimetry

“…It included an enhanced photon dosimetry model, as well as models to account for air gap and cover materials for photon dosimetry and predicts beta dosimetry in shallow skin targets. 68) Recently, the uptake of radon through skin was evaluated by SAKODA et al 69) They added to the latest biokinetic model for noble gases an uptake path via the skin using the skin permeability coef cient as parameter.…”

“…Similar calculation procedure for thoron progeny can be referred to BI et al 123) The study on comparison of skin dose and inhalation is recently studied by SAKODA et al 69) The calculated dose conversion factors for radon and thoron progeny are practically used to assess the annual dose contributions for dwellings with earthen architecture in Germany. 124) For example in one house, it is shown the annual dose of 1 to 2 mSv from radon progeny in the upper oor and 3 to 6 mSv in the ground oor and additional 1 to 2 mSv from thoron progeny with slightly smaller values in the adjacent rooms without thoron-exhaling building material.…”