The Relative Hazards of Strontium 90 and Radium 226

Abstract

A study has been made of the concentrations and linear dimensions of radium deposits in the skeleton of a man exposed to the risk of radium ingestion over a long period of adult life, and having a terminal body burden of 0·48 μg of Ra. Assuming deposits of ⁹⁰Sr of the same sizes and relative concentrations as in the radium case, calculations have been made of the dose to soft tissues embedded in bone. Comparison has then been made of the dose from α and β particles under the same conditions of deposition. For the sites considered, the radiation dose non-uniformity factor for ⁹⁰Sr varies from 0·9 to 3·1, while that for Ra varies from 1 to 16. A critical examination has then been made of the maximum permissible burden for ⁹⁰Sr, at present based on a comparison with radium, using data from certain animal experiments. It is considered that this comparison is open to serious objection. It is also shown that a comparison of the maximum permissible burdens for those two isotopes on the basis of radiation dose presents many difficulties. It is suggested that the maximum permissible burden for ⁹⁰Sr should be determined on a dosimetric basis without reference to radium.