DILEMMA OF LUNG DOSIMETRY

A legitimate criticism of health physics arises from the derivation of quite complex relationships for the permissible deposition of radionuclides in the body, in the absence of valid experience in man. It has to be accepted that inhalation of substantial amounts of radon and daughter products has a finite probability of causing cancer in the bronchial epithelium. Establishment of a quantitative dose-effect relationship has a formidable array of impediments. The radioactive nuclides in mine air comprise a short-lived chain existing in physical forms from free ions through small nuclei to large dust particles. Intake and primary retention of these media has to be calculated from models. Subsequent translocation up the bronchial tree is a significant factor in exposure. If the nucleus of a basal cell of bronchial epithelium is assumed to be the biological target, the penetration of alpha particles to it can be modeled in various degrees of sophistication. This leads to a numerical relationship between nature and concentration of the ambient radioactivity and the relevant tissue dose or dose-rate. The quoted number may be high or low by a factor of about three. This is essentially a permissible dose type of calculation. It is not a demonstrated dose-effect relationship. The feasibility of programs to progressively eliminate these uncertainties will be discussed in terms of refined study of mine exposees, relevance of data from radium or other human cases, and animal experimentation. © 1969 Health Physics Society.