A generic biokinetic model for noble gases with application to radon

Abstract

To facilitate the estimation of radiation doses from intake of radionuclides, the International Commission on Radiological Protection (ICRP) publishes dose coefficients (dose per unit intake) based on reference biokinetic and dosimetric models. The ICRP generally has not provided biokinetic models or dose coefficients for intake of noble gases, but plans to provide such information for (222)Rn and other important radioisotopes of noble gases in a forthcoming series of reports on occupational intake of radionuclides (OIR). This paper proposes a generic biokinetic model framework for noble gases and develops parameter values for radon. The framework is tailored to applications in radiation protection and is consistent with a physiologically based biokinetic modelling scheme adopted for the OIR series. Parameter values for a noble gas are based largely on a blood flow model and physical laws governing transfer of a non-reactive and soluble gas between materials. Model predictions for radon are shown to be consistent with results of controlled studies of its biokinetics in human subjects.

Evaluation of the intake of radon through skin from thermal water

“…This model was developed by incorporating skin compartments into the model previously published by Leggett et al . [ 3 ]. In their original model, the only routes of radon intake that were considered were inhalation and ingestion, because the purpose of their study was to develop a generic model from the viewpoint of radiation protection from inert gas exposure by inhalation and ingestion.…”

“…This results in a dose of radiation to the tissues, although the effective dose from radon gas inhalation is generally about 20 times less than that resulting from radon progeny inhalation [ 1 , 2 ]. The biokinetics of inhaled radon has been studied both numerically [ 3 – 8 ] and experimentally [ 9 , 10 ]. Different biokinetic models for radon have been developed with regard to the systemic compartments and relevant parameters such as a tissue/blood partition coefficient.…”

“…The latest model, which was developed as a generic biokinetic model framework for inhaled (and ingested) noble gases, was reported by Leggett et al . [ 3 ]. The predictions generated when this model was applied to radon were shown to be consistent with measured data from earlier human studies.…”

“…The aim of the present study was to evaluate quantitatively the skin absorption of radon that takes place during taking a bath using published data from human subjects. The most recent biokinetic model for radon was first modified to account for skin absorption as an intake route [ 3 ]. Values of the unknown parameter, i.e.…”

Internal Dosimetry

“…For gases and vapours a model is provided, three classes of gases uptake pattern; insoluble and non-reaction gases SR-0, soluble or reaction gases and vapours (SR-1) and soluble and reaction gases and vapours (SR-2) were recommended, so that the deposition of radon gas and other gases can be calculated. Based on this model for gases and vapours, LEGGETT et al 64) proposed a new model for radon and other noble gases. In the OIR series, the general defaults for gases and vapours are 100% total deposition in the respiratory tract (regional deposition: 20% ET2, 10% BB, 20% bb, and 50% AI) with Type F absorption.…”