Contamination from Local Fallout ing low Jevel of Cs?37 from stratospheric fallout during 1956 while they were living on Majuro. By contrast. the Cs}37 mean body burden of the Utirik people iwho were returned to their atoll in 1954) was 340 myc, 30 times higher than that of the Rongelap people residing on Majuro (Woodward et al, 1959). This higher burden can be attributed to the higher level of Cs?* contamination in the environment of the Utirik people during this period of time. The level of Cs?87 in the bodvhas fluctuated over the vears since the original contaminating event. Unlike S186, which is firmly fixed in the skcletal tissue, Csi8* has a relatives short biological half-life and thus readily reflects the en- vironmental level. The slightly increased level of Cs?8* during the 1956 and 1955 periods of weapon testing was'thus rapidly reflected in an increased body burden in the Marshallese. A very marked increase in Cs?87 was also observed in the Rongelap people after they returned to their original island in 1957. The Cs!#? level in the Rongelap people in 1958 was about 0.6Syuc. about 60 umes greater than the 1957 level, while the urinary Cs!87 level rose 140 times. The mean Zn™ body burden of the Marshallese, according to preliminary anan sis of the 1959 whole-bod, counting data, is 0.44 uc. S per cent higher than the 1955 value (Cohn. 19593. These data would also appear to indi- cate that Zndeposition in the Rongelap people has not as vet reached equi- hbrium. SUMMARY AND CONCLUSIONS Since the nuclear fallout-producing detonation of 1954, in which a large lanc mass in the Marshall Islands and an isolated group of people were accidentalix contaminated, studies have been in progress to determine the movement of fission products in the environment and in man himself, While a large number of fission products are produced by a nuclear detonation, the majority have short half-lives, of the order of minutes or days. Still fewer gain entry into humantissues, as a result of the protective filtering mechanisms in the inhalation and ingestion systems of man. At early times following the contaminating accident. Sr89, Ba!4#9, 1131 and the shorter-lived iodine isotopes and some of the rare earth elements contribute the major por- tion of the internal dose. After a period of } vear, the Sr®° contributes the greatest dose (to the skeletal tissue} and is the most critical fission product from the point of view of internal hazard. Cs!87 and Zn* have also been de- tected in tissucs. These are present in small amounts, but are of intcrest be- cause they yicld information on the movement of the fission products from the environment to man. The dose from the internally deposited emitters was sma}] compared to the concomitant external dose. Other than transitory changes in blood-cell levels, no pathological cffects have as vet appeared as a result of this radiation. Considerable data have been collected on the amount and kind of fission products in the soil, in various plants and numerous land animals and marine specimens. Radiochemical assays of specimens collected in yearly surveys have 327 3012801