- ‘ -3- The hematological surveys continue to show considerable fluctuation in the year-to-year mean levels of leukocytes in both the exposed and unexposed groups. The mean leukocyte level of the exposed group showed a decrease at the 1960 survey compared to 1959 (no unexposed people were exemined). The reasons for these fluctuations are not apparent. At five years post-exposure (1959), the exposed people still had mean platelet levels 10 to 15% below those of the unexposed group, but in 1960 the lymphocyte levels for the first time equaled those of the unexposed group. The mean erythrocyte levels were slightly lower in the exposed people but a general anemic tendency exists in all Marshallese, both exposed and unexposed. The fact that some of the blood elements in the exposed group have not yet returned to the levels of the unexposed group raises the possibility that a residual radiation effect on the bone marrow persists, but other, not immediately apparent, factors may be involved. Radiomelide body burdens of Cs37, 25 and sr9 were evaluated by measurement in a whole-body analyses ofthe urine. counter or by estimation from radiochemical The mean body burdens for 1959 were: Cs137 = oO. 0-57 Gk mm65 = O.4bac; and Sr90 = 6.0we. The body burdens of 265 gr90 continue to rise but at decreasing rates, whereas the level for Cel37 appears to have reached equilibrium and now to be diminishing. Little or none of the body burdens of the exposed group appear to be due to the initial exposure, since at present there is little difference between the levels of the exposed and unexposed populations living on Rongelap Island. This may be explained by the fact that additional weapon tests held in the area have deposited additional fission products into the enviroment, and the fact that certain staples of diet are imported and, hence, the people are not living in a "closed enviroment." Consequently, it may never be possible to equate body burdens with envirommental contaminations. In any case, the body burdens are now and will be of small significance in terms of radiation hazards. Judging from the Japanese populations being studied by the Atomic Bomb Casualty Commission at Hiroshima and Nagasaki, the next five years will pe the critical period for the development of leukemia in the Marshallese. Since animal experiments indicate that still other late effects may occur in man such as premature ageing, shortening of life span, increase in degenerative diseases, genetic changes, etc., continued careful examination of these populations is in order; all effects should be documented and therapeutic procedures instituted wherever possible, should such effects develop. In addition, the relation of the enviromental contamination on Rongelap to the body burdens of radiomelides of the people living there, imperfect though it is, warrants close study. The United Nations Selentific Committee on the Effects of Atomic Radiations now reviews these yearly surveys. bi82017