Health Physics

exposure to 157 members of the Utrik community.
Lesser exposures of different degrees affected approxi-

mately 13,000 other Marshallese then living elsewhere in

the archipelago, including the major population centers
of Majuro and Kwajalein.
The purpose of the present paper is to update and
replace the cancer risk estimates of an earlier report

(DCEG 2004)titled “Estimation of the Baseline Number

of Cancers among Marshallese and the Number of
Cancers Attributable to Exposure to Fallout from Nuclear Weapons Testing Conducted in the Marshall
Islands” and to provide thorough documentation of the
methods used to estimate cancer risks. Presented here,

for the first time, is a comprehensive assessment of
cancer risks from exposure to fallout from all nuclear
tests for all Marshallese alive during the years 1948
through 1970.
Ionizing radiation exposure is a known cancerrisk
factor and, because it is often possible to estimate
tissue-specific radiation doses with reasonable precision,
the relationship between dose and subsequent cancerrisk
is probably better quantified than for any other common
environmental carcinogen. In the companion papers,
estimates of organ-specific radiation absorbed doses
from fallout-related internal (ingested) and external ra-

dioactive materials are derived for residents of different
atolls affected by different test explosions, by year and
age. These values have been summarized to provide
yearly radiation doses correspondingto all calendar years
from 1948 through 1970,all historically inhabited atolls,
and all ages when exposures occurred.
Although small-scale medical studies have been
reported describing early and late health effects among
residents of Rongelap and Utrik in particular (Conard et
al. 1970; Hamilton et al. 1987; Cronkite et al. 1997;
Takahashi et al. 1997, 2001), and records are available

concerning compensation claims awarded to RMIresidents who developed cancers and other health problems

subsequent to fallout-related events (NCT 2004), the

infrastructure of medical reporting and records in the
RMIis not sufficient to support detailed epidemiological
studies such as those carried out among survivors of the
atomic bombings of Hiroshima and Nagasaki, Japan
(Preston et al. 2003, 2007). Fortunately, however, much

of the dose-response information provided by studies of
the atomic bomb survivors and of other populations
exposed to medical, occupational, and other sources of

radiation, is summarized in the recent report of the U.S.
National Research Council’s Committee to Assess

August 2010, Volume 99, Number 2

Health Risks from Exposure to Low Levels of Ionizing
Radiation, otherwise known as BEIR VII (NRC 2006).

The goal of the present investigation is to estimate the
likely consequences of the nuclear tests in terms of
cancer risk to the MI population from fallout-related
radiation exposures, and to that end we have used the
BEIR VII dose-response models, with a few modifica-

tions which are noted in the text. Cancer risk projections
are provided for post-1948 lifetime baseline? and
radiation-related numbers of leukemias and cancers of
the thyroid, stomach, colon, and all remaining solid

cancer sites considered as a group. Lifetime risk is

further divided into “past” (from 1948 through 2008) and
“future” (after 2008) periods.

Table 1 showstotal MI population numbers bysex,

as determined by censuses carried out in 1935, 1958,
1967, and 1973 (RMI 1987, Tables 1.1 and 1.7). These

data indicate that the MI population increased by about
33% over the 1935 value between 1935 and 1958, by
36% of the 1958 value between 1958 and 1967, and by
another 28% between 1967 and 1973, and that the

male/female ratio decreased from 1.10 in 1935 to 1.06 in
1958 and to a little over 1.04 in 1967 and 1973. Fig. 1
shows estimated sex-specific MI population sizes by
year, obtained by interpolation using the standard fitted
Bezier cubic spline curve algorithm (Foley et al. 1992) as
implemented in the Microsoft Excel’ spreadsheet command for XY scatter plot with data points connected by
smoothed lines.
The census reports of 1958, 1967, and 1973 also

gavetotal population numbers byatoll (RMI 1987, Table
1.2), which weused to apportion the total populations for
these and other years by atoll. As a general rule, for
yearly apportioning of the interpolated yearly total numbers amongthe various atolls, we used the 1958 proportional allocation for each of the years 1948-1957, and
interpolated linearly between 1958 and 1967 for 19591966 and between 1967 and 1973 for 1968-1970.
Estimated numbers are plotted by year in Fig. 2 for the
combined populations of the northern atolls of Rongelap
and Utrik, the mid-latitude population center Kwajalein,
a group of six other mid-latitude atolls (Ailuk, Likiep,
Mejit, Ujelang, Wotho, and Wotje), the southern population center Majuro, and the remaining 13 southern
atolls (Ailinglaplap, Arno, Aur, Ebon, Jaluit, Kili, Lae,
Lib, Maloelap, Mili, Namorik, Namu, and Ujae). Fig. 2

* Cancers that presumably would have occurred in the absence of
exposure to radioactive fallout.
* Provided for information purposes only. Identification of software does not imply any endorsement.

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