Blood Findings in Cyclotron Workers

Abstract

With the increasing number of cyclotrons in operation and the wider use of radioactive compounds in quantities larger than for tracer work, the problem of possible dangers to the workers from radiation must be considered. The sources of danger are the neutrons themselves and the alpha, beta, or gamma radiation given off by the different targets used or by parts of the apparatus. Two large groups of workers—those associated with the Harvard University cyclotron and those associated with the cyclotron and the electrostatic generator at the Massachusetts Institute of Technology—were studied; the Harvard University group through the co-operation of Drs. K. T. Bainbridge and Roger Hickman, and the Massachusetts Institute of Technology group through the co-operation of Prof. Robley D. Evans and Doctor Van der Graaf. Every effort has been made since the first to protect those working with these two cyclotrons and the generator. From time to time, however, certain almost unavoidable exposures arose in the handling of targets and in carrying out chemical manipulations on radioactive isotopes, as well as in the course of necessary repairs to the cyclotrons. From our knowledge of the effects of radium and of x-rays, changes in the blood or damage to the skin or gonads were to be expected before damage to other tissues if radiation exceeded the limit of safety. Damage to the skin is usually obvious because of the acute response. It has not been encountered among these workers. Skin changes are most readily produced by beta radiation. For practical reasons gonadal changes could not be checked. Evans (2) has called attention to the danger that may exist in the air from radioactive material and has investigated particularly the alpha radiation of radon and thorium B. Lung cancer may be induced by inhalation of radioactive substances. The safe limit is regarded as 10−11 curies per liter of air. Pulmonary exposure is not a hazard in cyclotron workers unless through the inhalation of particles such as might occur in sanding the dees (or electrodes).An attempt has been made to extrapolate alpha ray data to neutrons (Third International Cancer Congress, Atlantic City, N. J., 1939, Section on Biophysics). Damage to the constituents of the blood may be very insidious. It has been long known that radium, radioactive substances, and x-rays will produce profound alterations in the blood, ranging from moderate anemia to leukemia (1). Moreover, repeated small exposures to radiation may cause more lasting damage in bone marrow than does a single large exposure (5). Regenerative hyperplasia of the marrow elements, reflected by elevated cell counts in the blood, is rarely seen except as a late result of repeated exposure to low intensity radiation (1).