67 incidence in the exposed Rongelap peopie than in the unexposed group and the low-level exposed Utirik group. Whetheror notthis is correlated with radiation exposure cannot be ascertained. The data must be interpreted with considerable caution since (a) the populations are smail, (b) the unexposed population was not examinedbefore 1957 and has undergone changes dueto both at- trition and addition, (c) the diagnosis of malig- nancyis not certain in all cases because of the dif- ficulty of obtaining autopsies for verification, and (d) the types of malignancy were not those that have been correlated with radiation exposure in the Japanese exposed at Hiroshima and Nagasaki.177 Vi. Radiological Monitoring of Personnel and Environment A. GENERAL During their 3-year sojourn on Majuro (1954- 1957), the Rongelap people’s body burdens of radionuclides decreased rapidly, as shown by radiochemicai analyses of urine. By 6 months radionuclides in the urine were barely detectabie.* The Utirik peopie were moved back to their home island after the initial examinations and were exposed to very low levels of residual radioactivity there. In 1957 (3 years after the accident) gamma spectrographic analyses were carried out on 4 Rongelap and 2 Udrik people at Argonne National Laboratory in Chicago.455 The finding of detect- able levels of 87Cs and §5Zn (higherin the Utiriks) indicated thefeasibility of using this technique in the islands. When the Rongelap people returned to their homeisland in 1957, the low levels of environmental contamination were soon reflected in increased body burdens of some radionuclides.?7 A number of radiological surveys!56-164 ar Rongelap and Utirik have been carried out in conjunction with personnel monitoring, largely by University of Washington staff and morerecently also by a group from the BNL Health Physics and Safety Division. These studies have provided important information on the movements of radionuclides from thesoil through the marine and plant food chain to man and should prove useful in predicting future body-burden pattems of people returning to Bikini and Eniwetok. The principal residual radioactive elements on Rongelap and Utirik were 137Cs, 90Sr, 65Zn, and 55Fe, with small but measurable amounts ofotherfission products and neutron- — S005 tot Figure 53. Steel room used for whole-body gammaspectroscopy.” Figure 54. Arrangementof lead bricks used for whole-body counting. ay ne emt ete ag