Radon Progeny Deposition in the Nasal and Tracheobronchial Regions of the Respiratory Tract

Abstract

The assessment of the radiation dose to the respiratory system from 222Rn progeny requires knowledge of the radioactivity deposited in the tracheobronchial region. To determine the amount of radioactivity deposited, a sampling system that simulates the collection characteristics of the human nose and tracheobronchial regions was used. Deposition measurements were made at different conditions of exposure for aerosol types, concentrations, and sizes encountered in residential buildings. Test aerosols included ordinary room air particles, cigarette smoke, wax aerosol, electric heater and methane cooking gas particles. For comparison, the fraction expected to deposit in the tracheobronchial region was also computed from diffusion battery measurements of particle size distribution. The latter measurements also yielded the activity median diameter and the unattached fraction of the test aerosol. The results indicate high nasal and tracheobronchial deposition of 222Rn progeny that were attached to the smaller carrier aerosol. With the electric heater and cooking gas particles, tracheobronchial deposition ranged from 13.2 to 26.3%. For all other particle sizes and conditions of exposure, both nasal and tracheobronchial depositions were lower. For ordinary room conditions, the tracheobronchial deposition averaged 4.7%.