UC Irvine

While evaluating respiratory tract kinetic models, we have encountered a number of problems with the recently published ICRP Dosimetric Model for the Respiratory System. Some of those to be discussed are the following.The assumption that the nasopharyngeal (N-P) region can be ignored, despite considerable evidence of significant retention in the N-P region and of pathological effects.Treatment of the tracheobronchial tree (T-B), the pulmonary (P) region and the pulmonary lymph nodes (PLN) as one combined organ for calculating dose.The lack of deposition estimates for very small particles (<0.1 μm dia.) and the use of a probit scale for percentage deposition.Use of the aerodynamic equivalent diameter of particles beyond the range of applicability of the model and the desirability of defining an appropriate 'equivalent deposition diameter' suitable for the whole range of particle sizes of interest.Treatment of components of inhaled mixtures as if they are independent in regard to both deposition and clearance characteristics.Limitations of the currently used rigid solubility classifications (D, W or Y) of inorganic compounds in estimating retention and disposition of deposited particles. © 1982 British Occupational Hygiene Society.