Steven L. Simon,* André Bouville,* Charles E. Land,* and Harold L. Beck’
doses to the stomach wall and red bone marrow were similar
in magnitude, about 1 mGy to 7 mGy for permanentresidents
of the southern and mid-latitude atolls. However, adult residents of Utrik and Rongelap Island, which are part of the
northern atolls, received much higherinternal doses because of
intakes of short-lived radionuclides leading to doses from 20
mGy to more than 500 mGyto red bone marrow and stomach
wall. In general, internal doses to the colon wall were four to
ten times greater than those to the red bone marrow and
internal doses to the thyroid gland were 20 to 30 times greater
than to the red bone marrow. Adult internal thyroid doses for
the Utrik community and for the Rongelap Island community
were about 760 mGy and 7,600 mGy,respectively. The highest
doses were to the thyroid glands of young children exposed on
Rongelap at the time of the Castle Bravo test of 1 March 1954
and were about three times higher than for adults. Internal
doses from chronic intakes, related to residual activities of
long-lived radionuclides in the environment, were, in general,
low in comparison with acute exposure resulting from the
intakes of radionuclides immediately or soon after the deposition of fallout. The annual doses and the population sizes at
each atoll in each year were used to develop estimates of cancer
risks for the permanent residents of all atolls that were
inhabited during the testing period as well as for the Marshallese population groups that were relocated prior to the testing
or after it had begun. About 170 excess cancers (radiationrelated cases) are projected to occur among more than 25,000
Marshallese, half of whom were born before 1948. All but
about 65 of those cancers are estimated to have already been
expressed. The 170 excess cancers are in comparison to about
10,600 cancers that would spontaneously arise, unrelated to
radioactive fallout, among the same cohort of Marshallese
Health Phys. 99(2):105-123; 2010

Abstract—Nuclear weapons testing conducted at Bikini and
Enewetak Atolls during 1946-1958 resulted in exposuresof the
resident population of the present-day Republic of the Marshall Islands to radioactive fallout. This paper summarizes the
results of a thorough and systematic reconstruction of radiation doses to that population, by year, age at exposure, and
atoll of residence, and the related cancer risks. Detailed
methods and results are presented in a series of companion
papersin this volume. From ouranalysis, we concluded that 20
of the 66 nuclear tests conducted in or near the Marshall
Islands resulted in measurable fallout deposition on one or
more of the inhabited atolls of the Marshall Islands. In this
work, we estimated deposition densities (kBq m™’) of all
important dose-contributing radionuclides at each of the 32
atolls and separate reef islands of the Marshall Islands.
Quantitative deposition estimates were made for 63 radionuclides from each test at each atoll. Those estimates along with
reported measurements of exposure rates at various times
after fallout were used to estimate radiation absorbed doses to
the red bone marrow,thyroid gland, stomach wall, and colon
wall of atoll residents from both external and internal exposure. Annual doses were estimated for six age groups ranging
from newbornsto adults. We found that the total deposition of

7Cs, external dose, internal organ doses, and cancer risks

followed the same geographic pattern with the large population of the southern atolls receiving the lowest doses. Permanent residents of the southern atolls who were of adult age at
the beginning of the testing period received external doses
ranging from 5 to 12 mGy on average; the external doses to
adults at the mid-latitude atolls ranged from 22 to 59 mGy on
average, while the residents of the northern atolls received
external doses in the hundreds to over 1,000 mGy. Internal
doses varied significantly by age at exposure, location, and
organ. Except for internal doses to the thyroid gland, external
exposure was generally the major contributor to organ doses,
particularly for red bone marrow and stomach wall. Internal

Key words: cancer; fallout; Marshall Islands; nuclear weapons


* Division of Cancer Epidemiology and Genetics, National

THE MarsHa.i Islands atolls were administered by the
United States as a United Nations Trust Territory from 1947
until 1986 when the Republic of the Marshall Islands was
established as a sovereign nation in free association with the

CancerInstitute, National Institutes of Health, Bethesda, MD 20892;

* New York City, NY.

For correspondence contact: Steven L. Simon, National Cancer
Institute, National Institutes of Health, 6120 Executive Blvd., Bethesda, MD 20892, or email at

(Manuscript accepted 5 March 2010)

United States. Previous to those years, the Marshall Islands

Copyright © 2010 Health Physics Society

were administered by Japan under a League of Nations
mandate, and were the site of many important battles of the

DOI: 10.1097/HP.0b013e3 18 1de523c

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