67 incidence in the exposed Rongelap people than in the unexposed group and the low-level exposed Utirik group. Whether or notthis is correlated with radiation exposure cannot be ascertained. The data must be interpreted with considerable caution since (a) the populations are small, (b)} the unexposed population was not examined before 1957 and has undergone changes due to both attrition and addition, (c) the diagnosis of mailignancyis not certain in all cases because ofthe difficulty of obtaining autopsies for verification. and (d) the types of malignancy were not those that have beencorrelated with radiation exposurein the Japanese exposed at Hiroshima and Nagasaki.!77 Vi. Radiological Monitoring of Personnel and Environment A. GENERAL During their 3-year sojourn on Majuro (19541957), the Rongelap people’s body burdens of radionuclides decreased rapidly, as shown by radiochemical analyses of urine. By 6 months radionuclides in the urine were barely detectable.? The Utirik people 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 Utirik people at Argonne National Laboratory in Chicago.!55 The findingofdetect- able levels of 137Cs and ®5Zn (higher in the Utiriks) indicated thefeasibility of using this technique in the islands. When the Rongelap people returned to their home island in 1957, the low levels of en- vironmental contamination were soon reflected in increased body burdens of some radionuclides.” A numberof radiological surveys!56-164 at Rongelap and Utirik have been carried out in conjunction with personnel monitoring, largely by University of Washington staff and more recently also by a group from the BNL Health Physics and Safety Division. These studies have provided important information on the movementsof radionuclides from the soil through the marine andplantfood chain to man and should proveuseful in predicting future body-burden patterns of people returning to Bikini and Eniwetok. The principal residual radioactive elements on Rongelap and Utirik were 137Cs, 99Sr, 65Zn, and *5Fe, with small but measur- able amounts of otherfission products and neutron- Figure 53. Steel room used for whole-body gammaspectroscopy.’ Figure 54. Arrangement of lead bricks used for whole-body counting.