Radiation doses and cancerrisks in the Marshall Islands @ S. L. Simon ET AL.
the doses from acute intakes. However, doses from
chronic intakes were small and refinements to the esti-
mation of the uncertainty associated with them would
contribute little to the overall dose uncertainty.
Projected cancer risks
The annual doses from external irradiation and from
internal irradiation that were estimated for the 25 Marshallese population groups according to birth year were
combined with the population sizes and with agedependent organ-specific risk coefficients to derive the
corresponding cancerrisk projections presented in Land
et al. (2010). Risk estimates were presented in terms of
the number of cancers by organ site projected to occur
among Marshallese as a consequence of exposure to
fallout from regional nuclear tests. The cancer risks were
based on an estimated population of 12,175 residents of
the Marshall Islands born before 1948 and another
12,608 born in the years 1948 through 1970, giving a
total potentially exposed population of 24,783. Projected
lifetime numbers of baseline and radiation-related (ex-
cess) cancers are shown in Table 10 by cancer type:
occurred or will occur and that can be attributed to
exposure to radioactive fallout, expressed as a percentage, is about 20% for thyroid and about 5% for leukemia.
These percentages can be comparedto all other cancers,
for which the attributable fractions are on the order of
1%. The attributable fractions, as expected, were much
higher among the most heavily exposed population
groups (Landet al. 2010). A breakdown of the estimated
number of cancer attributable to exposure to fallout
radiation according to population group and time period,
as well as estimation of the uncertainties in the projected
numberof cancers, is discussed in detail by Land etal.
(2010). The attributable fractions (%) of all cancers from
exposure to fallout radiation within each of the four atoll
groups with 90% uncertainty ranges are presented in
Table 11 and have the same geographic pattern as for
'S"Cs deposition illustrated in Fig. 2. Because of the small
numbers of projected cases on someatolls (resulting in
highly uncertain estimates), the cancer risk projections
are shown only for groups of atolls rather than for
individual atolls.
leukemia, thyroid, stomach, and colon. In addition, the
numbersof “all other solid cancers” has been estimated
using the colon dose as representative of the dose to most
other organs and tissues of the body. The projected
number of baseline (non-radiation related) cancers
among the 24,783 Marshallese in all organs totals
10,600, while the projected numberof excess (radiationrelated) cancers is 170, including 65 that have yet to
occur (Land et al. 2010). In comparison to our 2004
estimates, which also are presented in Table 10, the
numbers of projected radiation-related thyroid and colon
cancers are much smaller as a result of a much more
realistic dose assessment.
Whenthe entire population of the Marshall Islands
is considered, the estimated fraction of cancers that has
121
CONCLUSIONS
The methods and findings described in this paper
and the seven companion papers represent the most
comprehensive retrospective evaluation ever conducted
of exposure of Marshallese and the related cancer risks
from regional nuclear testing. This effort, in response to
a Congressional request, will provide information useful
to U.S. Congressional committees as well as to health
authorities both in the U.S. and in the Marshall Islands.
However, the methods are also illustrative of methods
that may be useful in broader circumstances, some of
which might occur in the future. Though nuclear testing
in the atmosphere is not likely to be revived, nuclear
detonations that would result in exposure of the public
Table 10. Projected numberoflifetime baseline and excess cancers for the entire population of the Marshall Islands by
cancer type and comparison with the results of the NCI preliminary study (DCEG 2004).
This study (Landet al. 2010)
Preliminary study (DCEG 2004)
Cancer type
Leukemia
Thyroid
Stomach
Colon
Baseline
number of
cancers*
123
127
326
470
Excess
number of
cancers
Total
number of
cancers
5
262
15
157
128
389
341
627
Baseline
number of
cancers*
140
190
570
930
Projected
Projected
excess number
excess number
of cancers
of cancers
from 2009
1948-2008
onwards
6.0
35
3.1
7.2
1.4
15
3.6
9.3
Rounded total
number of
cancers
147
240
577
946
All other solid cancers
4,550
93
4,643
8,800
54
36
8,890
Rounded total number of
5,600
530
6,100
10,600
105
65
10,800
cancers
“The 2004 preliminary analysis assumed the population size obtained by the 1958 census, while the present study is based upon the
total number of people exposed anytime between 1948 and 1970, which is projected to be about twice the size of the 1958 population.