Radon Progeny Particle Growth in the Simulated Environment of the Respiratory Tract

Abstract

To determine the magnitude of induced particle growth of radon progeny, a simulator was constructed to create and maintain conditions similar to those prevailing in the respiratory tract. During testing, the conditioned metal simulator was connected to a radon chamber in which different test aerosols were mixed with radon progeny. The exhaust rate from the radon chamber and through the simulator test chamber ranged from 0.1 to 0.15 m³ / min. The residence time of the radon progeny attached to the test aerosol in the air space of the simulator ranged from 1.0 to 1.5 min. To measure particle growth, alternate tests were made in the simulator and in a second test chamber identical to the simulator but without the water. Particle size was measured with diffusion batteries and growth was determined from the difference in the activity median diameters of the radon progeny measured in the two test chambers. The results from tests using different aerosols showed average particle growth factors of 1.5 for room air, 1.8 when an electrical heater is operating, 1.7 when a methane gas burner is on, 2.0 while a kerosene lamp is lit, 1.6 while a candle is burning, 1.2 during cigar smoking, 2.8 when a NaCl generator is on, 1.0 in the presence of wax aerosol, and 1.05 in the presence of very young radon progeny from freshly filtered radon gas. This study shows that, as a result of particle growth, deposition in the tracheobronchial region of the respiratory tract and the radiation dose from radon progeny attached to ordinary room air aerosol is reduced by an average value of 25%