The new ICRP model for the respiratory tract

The International Commission on Radiological Protection (ICRP) has recently adopted a new dosimetric model of the human respiratory tract, to be issued as ICRP Publication 66. A summary of the new model is presented. The model is a general update of that in Publication 30, but is of wider scope. It applies explicitly to: workers and all members of the public; inhalation of gases, vapours and particles; evaluation of dose per unit intake or exposure; and bioassay interpretation. The fundamental difference in approach is that whereas the Publication 30 model calculates only the average dose to the lungs, the new model takes account of the presumed differences in radiosensitivity of respiratory tract tissues, and the wide range of doses they may receive, and calculates specific tissue doses. The model can readily incorporate information related to the subject (age, activity, health status) or the exposure (particle size, chemical form). The assessment of clearance parameters for specific compounds is discussed.