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Health Physics
corrected for fractionation, (3) estimation of the deposi-
tion density of '’Cs followmg each of 20 tests on all
inhabitedatolls, (4) estrmation ofthe mtake of "Csatall
August 2010, Volume 99, Number 2
uptake and, to a lesser degree, madvertent consumption
of soil (Stmon 1998, Simon et al 2010) A previous
assessment (Lessard et al 1984) showedthat five radio-
mhabited atolls assummg that the ratio of mtake to
nuchdes account for essentially all the mternal dose from
intakes of all radionuchdes considered at all mhabited
The available historical whole-body counting and
bioassay measurements were used as a basis to estimate
the chronic mtakes smce a suitable dietary model coverimg the many yearsafter the tests, when lifestyles became
deposition was the same at all atolls, (5) estrmation of
atolls following each nuclear test, and (6) estmation of
annual and cumulative radiation absorbed doses to four
organs (RBM, thyroid, stomach, colon) of representative
persons for all relevant birth years
Detailed mformation on the acute mtakes and resultimg doses, as well as the estrmated uncertamty in these
dose estimates, 1s presented m Simon et al (2010) The
population of the southern atolls had acute mtakes
estimated to be much smaller than those experienced by
the more highly exposed Rongelap and Utrik populatons For example, adult Mayuro residents had imtakes of
about 6% and 9% of the "I and '’Cs (cumulative over
all tests), respectively, of adult Utmk commumty mem-
bers, and about 1%, and 2%, respectively, of the mtakes
of Rongelap community members exposed to Castle
Bravo fallout on Rongelap Island (see Table 8, S1monet
al 2010)
Doses to the thyroid gland were much greater than
those to the other organs and tissues, and were much
greater for the Marshallese who resided on Rongelap and
Utnik Atolls at the tme of the Castle Bravo test than for
the residents of any other atoll (Table 10, Simon etal
2010) The southern atolls, where about 73% of the
population resided durmg the testing years, recerved the
lowest organ doses The population of mid-latitudeatolls
(Kwayalein and others, see Fig 2), home to about 23% of
the total Marshall Islands population durmg the testing
years, received organ doses that were about three times
greater than at the southern atolls The population of
Utnkreceived doses intermediate m magnitude between the
mid-latitude atolls and Rongelap, with thyroid doses about
35 timesgreater than the southern atolls (Table 10, Simon et
al 2010) The Rongelap Island communtty received the
Inghest doses, with thyroid doses about 350 to 400 umes
greater than those received m the southern atolls
Internal doses from chronic intakes of radionuclides. Following the deposition of radionuchdes on the
ground, chromc (1, protracted) mtakes took place at
rates much lower than those due to the acute mtakes
While both acute and chronic intakes were primarily a
result of mgestion, the environmental transport processes
leading to chrome mtakes were substantially different
from those that gave rise to acute mtakes Chrome
intakes were primarily a function of the consumption of
seafood and oflocally grown terrestrial foodstuffs imternally contammated with long-hved radionuchdes via root
chrome mtake “Fe, Co, “Zn, Sr, and '’Cs
more westermzed, does not exist Those whole-body and
bioassay measurements were made on the Rongelap and
Utrik evacuees for years after they returned to their
respective home atolls (Lessard et al
1984)
The
Rongelap and Utrk populations, who were evacuated
withm about two days followmg the detonation of the
Castle Bravo test on 1 March 1954, were retumedto their
home atolls m June 1957 and June 1954, respectively
(Table 3) Durmg the first few weeks after ther return
and until the 1980's, a Brookhaven National Laboratory
team regularly conducted measurements of whole-body
activity of “Cs, “Co and “Zn, as well as urmary
concentrations of “Sr Measurements of *Fe m blood
were also performed, but only once (Lessard et al 1984)
The steps used to estrmate the doses from chromic
mtakes of radionuchdes were
(1) estimation of the
chromc mtakes by Rongelap and Utrk adult evacuees
due to the Bravo test, (2) estmmation of the chromc
intakes resultmg from the Bravo test by adults ofall other
atolls, based on the relative ‘Cs deposition, (3) estrmation ofthe chronic intakes by adults resultmg from tests
other than Bravo, agam based on relative *’Cs depost-
tion, (4) estimation of the chromc mtakes by children,
and (5) estrmation of the doses from chromic intakes from
all tests and all population groups usmg International
Commission on Radiogical Protection recommended
dose coefficients
Detailed mformation on the estimation of chromc
imtakes and resulting doses 1s presented m Simonet al
(2010) The doses from chronic intakes show the same
geographical pattern as the doses resultmg from acute
intakes and '*’Cs deposition (Fig 2) However, because
of the absence of short-hved iodine isotopes which
dommiated the thyroid dose from the acute mtakes, the
thyroid doses from chromc intakes were not much
greater than the doses to other organs and tissues Similar
to the situation for acute mtakes (Simonet al 2010), only
a few radionuchdes contributed most of the organ absorbed dose For all organs and for all four of the atoll
and population groups discussed, Cs was either the
first or second most rmportant contributor to imternal
dose from chromic mtakes For the evacuated Rongelap
Island commumity, °’Cs was the most important contrib-
utor to the chromic dose, whereas Zn was the largest