Long Term Retention of Radium in Man

Abstract

THE late biological effects of skeletally deposited radium in man have long been used as a basis for setting maximum permissible body contents of both radium itself and other long lived bone-seeking radio-elements such as plutonium¹. Knowledge of the retention pattern is a fundamental requirement in the relation of the body content of radium at the time of observation of a bone neoplasm to the amount of radium initially in the blood. Much effort is being devoted to a determination of this, chiefly in the United States^1–3 where a number of persons who received radium by injection or occupationally have been studied at intervals for many years. These people have radium-226 contents in the approximate range 0.02–2.0 µCi, levels which are easily measured by whole body gamma ray spectrometry. Only relatively few measurements have been made, however, and the accuracy of the estimated biological elimination rate for an individual is poor. Keane and Evans² reported an average biological half life of 28 ± 8 yr for a group of twenty subjects, 30–40 yr after acquisition, while Miller and Finkel³ found an average of 15 yr (range 9.6–21.7 yr) for the biological half life in eight patients for the period 19–33 yr after injection.