1330 . FALLOUT FROM NUCLEAR WEAPONS TESTS DeTRODUCTION. Pollowing the detonation of a thermonuclear device at the Pacific Test Site on 1 March 1954, 239 Marshallese people were exposed to significant levels of’ : gemua radiation from fallout. Estimated total exposures ranged from 175r on Rongelep to dir on Utirdk (1). These populations were evacuated to Kwajalein for decontamination and care. During the ‘two days of fallout exposure before evacuation was completed, the Marshallese also received some radioactive naterials internally by ingestion and inhalation. Estimates of the internal body burden from fallout vere obtained from the analysis (1) of urine samples collected soon after exposure. These data indicated that the acute hazard from internally deposited fission ' fragments was quite small es canpared to the whole body gamma radiation exposure. Although the radioactivity levels in the urine were low, the activity was sufficient to obtain reasonable precision and to warrant additional long tern studies of the activity levels and excretion patterns of this rather large and well isolated population. The people from Alinginse and Utirik vere returned to their home islands in June 1954. Radiation intensities on Rongelap, hovever, precluded an early return to this atoll and the Rongelap people lived on Majuro from June 1954 until duly 1957. ” Basic data on the food crops of theMarshallese indicated that after resettlement on the contaminated atollsintake of etrontium? would be increased considerably, andthat cesiun!37, 2inc®5, and eobalt®© vere dietary constituents of island and ocean foodstuffs, and also would be assimilated (2). ‘The expected increases in the trace enounts of radionuclides in the food supply of a large population would afford an opportunity to investigate the rate of equilibration end the discrimination factors operating between food supply and man. Urinary