The Medical Peocearch Conte


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Brookhaven National Laboraiy-y

Upton, L. L, New York

nepositony —SV4L RECORDS


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BWt43 iba
Radiation Carcinogenesis: Epidemiology

and Biological Significance, edited by
J. D. Boice, Jr. and J. F. Fraumeni, Jr.

40. BSQ

Raven Press, New York 1984.

Late Radiation Effects in Marshall Islanders
Exposed to Fallout 28 Years Ago
Robert A. Conard
Brookhaven National Laboratory, 32 Ivy Lane, Setauket, New York 11733

In 1954, following detonation of a megaton nuclear device at Bikini, an unfor-

tunate accident occurred owing to an unpredicted shift in winds resulting in
exposure to radioactive fallout of 250 Marshallese people, 28 American servicemen on atolls to the east, and 23 Japanese fishermen on their fishing vessel.
In this presentation, medical findings in the exposed Marshallese noted over
the past 28 years will be briefly reviewed with particular emphasis onlate effects

on the thyroid gland. Details of the accident, evacuation of the people, and
medical surveys and findings can be found elsewhere (10—14,37,55).

The exposure of the Marshallese differs from the exposure of the Japanese

at Hiroshima and Nagasaki. The Japanese were exposed directly to the detonating
bombs, and this resulted in gammaand neutron radiation, and blast and thermal
trauma, with considerable early mortality. The Marshallese on the other hand
were too far distant from the detonation for any direct effects, and their exposure
was due entirely to fallout radiation during the 2 days prior to evacuation.

This consisted of penetrating whole-body gammaradiation, irradiation of the

skin (principally beta radiation) from fallout deposited on the skin, and internal
absorption of radionuclides from ingestion of contaminated food and water.

The most serious internal exposure was that to the thyroid from radioiodines,
which wererelatively abundant in the fallout.

Table 1 shows the estimated doses (whole body and thyroid) received by

the Marshallese on the three atolls (at approximate distances from Bikini of

100 miles on Rongelap, 90 to 100 miles on Ailingnae, and 300 miles on Utirik).
It should be emphasized that these are only rough dose estimates, since many
uncertainties were involved in the dose calculations (13,33). On the basis of
the degree of hematological depressions in the different groups, the whole-body
gammadose estimates do not appearto be far out of line. There is much greater
uncertainty regarding the thyroid doses, which is unfortunate because dose-

effect relationships for these findings are of considerable interest. The thyroid

Select target paragraph3