DEPOSITION OF INHALED CHARGED ULTRAFINE PARTICLES IN A SIMPLE TRACHEAL MODEL

The deposition of ultrafine (d less than or equal to 200 nm) particles on airway surfaces is an important determinant of the radiation dose that results from inhalation of radon progeny. Diffusion is the domina nt deposition mechanism for radon progeny since most of the alpha part icle activity is on ultrafine particles. Freshly formed Po-218 is rapi dly neutralized but, there remains some charged fraction of each short -lived decay product. Theoretical predictions suggest that a measurabl e increase in airway deposition may result from particle charge. We ha ve measured and compared the deposition (eta) of monodisperse singly c harged, and charge neutralized, particles with diameters from 15 to 95 nm in simple tracheal models. Differences in deposition were detectab le for particles < 30 nm in diameter in 10, 23 and 30 cm long tubes, a nd for particles up to 95 nm for the longest (30 cm) tube tested. Vari ations in the magnitude of electrostatic deposition with particle and flow parameters is consistent with theoretical predictions.