Inhaled aerosol transport and deposition calculations for the ICRP task group

J. Aerosol Scl., Vol. 20, No. 8, pp. 1301-1304, 1989. Printed in Great Brltaln. Pergamon Press plc I N H A L E D A E R O S O L T R A N S P O R T AND D E P O S I T I O N C A L C U L A T I O N S F O R T H E ICRP T A S K G R O U P M. J. Egan, % W. Nixon, % N.I. Robinson, % A.C. James ~ and R.F. Phalen ~ # AEA Technology. Safety and R e l i a b i l i t y Directorate. Wigshaw Lane Culcheth. Warrington WA3 4NE. UK ¶ Paciflc Northwest Laboratory. Richland. Washington 99352. USA § Air Pollution Health Effects Laboratory. Department of Co~r, unity and Environmental Medicine. University of California. Irvine. California 92717. USA Introduction Important advances in understanding the fate of inhaled aerosols have been achieved since publication of the conclusions of the original ICRP Task Group on Lung Dynamics (TGLD, 1966). In particular, increasingly sophisticated experimental work with volunteer subjects has augmented the range of particle sizes and breathing conditions for which deposition data are now available. Meanwhile, there has been a similar expansion in the development of theoretical models to study inhaled aerosol behaviour. Such models can play an important part in efforts to assess the ultimate consequences of aerosol inhalation, both as aids in the interpretation of measurements and as tools for making predictions beyond the range covered by experimental data. An ICRP Task Group is currently revising existing dosimetric models for the inhalation pathway. Part of this work includes the use of a theoretical model to estimate regional aerosol deposition under conditions where experimental measurements are sparse and where such knowledge is required in order to perform adequate assessments. Specifically, the model has been used: (i) to calculate deposition within a representative lung geometry for conditions chosen to simulate spontaneous breathing at different activity levels; and (ii) to estimate inhaled aerosol deposition for children of different ages. Prior to performing the required simulations, a preparatory review was made of recent information related to the behaviour of inhaled aerosol, so bringing the theoretical framework of the model up to date. Subsequently, a number of controlled experimental inhalation studies were simulated, in order to validate the predictive capabilities of the model against data over as wide as possible a range of circumstances. Finally, aerosol deposition profiles in the lung have been predicted for each of the required inhalation conditions. Aerosol Transport Model The theoretical model used for the simulations has been mathematical framework originally derived for the study transport. A brief outline only of the basic methodology however, details of the model have been described elsewhere et al., 1977, Egan and Nixon, 1985, 1987). developed from a of pulmonary gas is possible here; (Nixon, 1977; Pack Aerosol transport a n d d e p o s i t i o n within the lung airways is represented by: a (ATe) a (AAuc) a ac (AAD-Fx) -L (I) Within the model, A A is the cross-sectional area for aerosol transport, summed over all airways at distance x from the origin of the trachea. A T represents