ABSTRACT
Thefirst instance of exposure of human beings to mixed fission products occurred as a
result of the contaminating detonation of 1 March 1954. Beta activity in the urine of these
exposed human beings indicated significant internal contamination from the ingestion and inhalation of fallout material. The body burden of the group of human beings with the greatest
internal contamination was of the order of the maximum permissible concentrations for the
individual radionuclides.
Few of the fission products present in the environment were readily absorbed by the
bloodstream from the lungs and the gastrointestinal tract. Most of those radioelements that
gained entry into the body had short radiological and biological lives, and thus the levels of
activity in the tissues of the body were relatively low. The concentration of radioisotopes at
6 months postdetonation was barely detectable in the urine of most of the exposed individuals.
The human body burden of individual radionuclides was estimated from radiochemical
analysis of the human urine and of the tissues and urine of animals from Rongelap. The mean
body burdens of the radionuclides in the Ailinginae group were approximately one-half those
of the Rongelap group, and the mean body burdensof the American group were about onefourth those of the Rongelap group.
Radioiodine is probably the most hazardousinternal radioemitter at early times after
exposure. Of the longer lived fission products Sr® is the most abundant and presents the
greatest potential hazard in this particular group.
Oral administration of calcium EDTA, beginning seven weeks postdetonation, to a representative group of individuals from Rongelap increased the rate of excretion of activity. However, the decrease of the body burden was insignificant since the excretion rate was very low
at this late time.
High levels of activity were found in water and on the external surfaces of plants. The
contamination of the internal portions of fruits and vegetables was small; however, high levels
of contamination were found in the coconut tree sap. Of the individual radionuclides, Sr®,
because of its high solubility and relatively long radioactive half life, was probably the isotope
of greatest potential hazard in the environment.
Gross beta activity of urine and tissue samples of animals indicates significant internal
contamination of all the animals. The level of internally deposited radioisotopes in the pigs
from Rongelap was ten times the amount in human beings from the same area.
Studies of animals provided direct data on the nature and distribution of the contamination
in the tissues of the body. Over 90 per cent of the activity in the body of animals was localized
in the skeleton. The pattern of deposition of the fission products in the skeleton seen in auto-
radiographs was similarto that of alkaline earths. The fish and clam had a much lower concentration of the alkaline and rare earths and a body burden considerably higher than that of
the land animals. Since fish form a large staple item in the diet of the island populations, this
high level of contamination is of considerable importance.
Studies made on egg production of contaminated hens gave no evidence of any radiation
effect. The production rate for eggs was normal, and the eggs produced were also normal.
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