incidence in the exposed Rongelap people than in the unexposed group andthe low-level exposed Uurik group. Whetheror not this 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 malignancy is not certain in all cases because ofthe dif- ficulty of obtaining autopsies for verification, and (d) the types of malignancy were not those that have been correlated 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 ex- posed 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 finding of detectable levels of 137Cs and ®Zn (higher in the Utiriks) indicated the feasibility of using this technique in the islands. When the Rongelap peopie returned to their home island in 1957, the low levels of en- vironmental contamination were soonreflected in increased body burdens of some radionuclides.’ A numberofradiological surveys}5&-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 movements of radionuclides from the soil through the marine and plant food chain to man andshould proveusefulin predicting future body-burden patterns of people returning to Bikini and Eniwetok. Theprincipal residual radioactive elements on Rongelap and Utirik were 137Cs, 99Sr, 65Zn, and 55Fe, with small but measur- able amounts ofotherfission products and neutron- Figure 53. Steel room used for whole-body gammaspectroscopy.” Figure 54. Arrangementoflead bricks used for whole-body counting.