Comparison of Old and New ICRP Models for Respiratory Tract Dosimetry

The historical development and application of respiratory tract dosimetry models by the International Commission for Radiological Protection, ICRP, for health protection from inhaled radioactive aerosols is examined. Three different models are discussed, those that were included in ICRP recommendations published in 1960 and 1979, and the new ICRP Publication 66. Basic features of these models are compared and contrasted. These features include model structure, sites and frequencies of particle deposition, processes and rates of clearance of the deposited material from the respiratory tract, and consideration of the parameters involved in these processes and how various factors can influence these parameters. All three models lead to the calculation of absorbed radiation doses with differing degrees of regional and local specificity. These calculations are achieved using different tools ranging from quick hand calculations to sophisticated computerised modelling approaches. A side-by-side review of these models indicates several important trends in respiratory track dosimetry models that reflect both the increasing size of the knowledge base derived from studies in laboratory animals and in human subjects and the need for models more broadly applicable for both occupational and environmental exposures. The detailed design of the new model and its associated software provide excellent means of identifying useful research areas and using the resulting new information in organised and productive ways.