<4
name wee
UNCLASSIFIED
Part V!
Biology and Medicine
Whole-body gamma radiation measurements were made during the sixth annual medical
survey of the Rongelap people, which was carried out in March. Examination of these people
for internal levels of radioisotopes revealed low levels (one to two percent of maximum permissible levels) of cesium 137 and zinc 65. These levels were not appreciably greater than
levels found in the previous year, indicating that the body burden of these isotopes in the
people has about reached equilibrium with their slightly contaminated environment. Radiochemical urinalyses for strontium 90 have not been completed. No additional medical surveys
are planned until approximately the spring of 1961, subject to review and approval by the
Trust Territory of the Pacific.
ECOLOGY STUDIES AT RONGELAP ATOLL
This program was begun in March 1958. Expeditions to the atoll were made in March and
August, 1958, and in February, March, and September, 1959. However, at the request of the
Trust Territory of the Pacific, the next study has been postponed until 1961, Meanwhile, samples and data already collected will be analyzed, and laboratory experiments with large soil
samples will be conducted by the University of Washington.
Atypical plants have been observed on someof the islands of the atoll but whether these
are the result of radiation exposureis still in question. Since radiation effects upon biota are
too elusive to be followed profitably in the field, the emphasis has been upon mineral transport
through the biota, which requires evaluation of the stable isotopes as well as the radioisotopes
Efforts during the first year were concentrated on land forms. In September extensive sampling of the lagoon bottom and plankton was accomplished. Some of the points that stand out
most clearly thus far are as follows:
.
In general, cesium 137 and strontium 90 are the principal radioisotopes (half life
of about 28 years) found in the land organisms, while discrimination against these
fission products is noted in marine organisms which selectively absorb the nonfission
produced relatively short lived radioisotopes, such as zinc 65, ‘cobalt 60, manganese 54,
and iron 55 (half lives ranging from 260 days to 2.9 years).
Gamma dose rates have declined as expected from theoretical decay curves for
mixed fission products. The average and maximum values at Rongelap Island in Sep-
tember 1959 were 0.03 milliroentgen per hour (mr/hr) and 0.04 mr/hr, However, the
UNCLASSIFIED
4
o BA aTt
1 ehee
okare
ot
MEDICAL SURVEY OF RONGELAP PEOPLE, MARCH 1959 (UNCLASSIFIED)