Radiation Dose to the Respiratory System Due to Radon and Its Daughter Products

Abstract

Annual radiation doses to the respiratory system due to radon and its daughter products have been calculated in various working environments of London (U.K.) area. The method is based on an accurate calculation of the energy dissipation of alpha-particles in the vulnerable tissue, 1 μ-diameter and located at various depths, from the daughter activity deposited on the walls of the respiratory system; the equilibrium daughter activity has been calculated from the deposition rates and the mucous movement. The proportions of the daughter activity present as free ions in air have been calculated from extensive published theoretical and experimental results. As a more realistic lung model, an extensive set of experimental data on aerosols and a more precise calculation of energy dissipation, among others, have been employed in the present study; it is claimed that the method is an advance on those of ALTSHULER, NELSON arid KUSCHNER and JACOBI. The radiation dose is found to be highest in segmental bronchi; in comparison with ALTSHULER et al.'s results, the present calculation almost always gives higher values. The annual radiation dose at a depth of 30 μ from the top of mucous layer in segmental bronchi is 13.8 rad for the highest radon concentration met in our study viz. 10.1 × 10−12 Ci/l. curies/liter (c/l.) (dealer in luminescent clocks). In view of the findings of the present study, it is felt that the present MPC value for radon should be revised downwards.