164
Health Physics
August 2010, Volume 99, Number 2
variation of the intake rates with time. Assuming implicitly that fallout from the Bravotest at Rongelap and Utrik
was much more important than the fallout from all other
tests, Lessard et al. (1984) used a single exponential
relationship to model the decline of dietary activity intake
during the entire period of time in which whole-body and
intakes and are primarily related to the consumption of
seafood and oflocally grownterrestrial foodstuffs internally
contaminated with long-lived radionuclides as a result of
root uptake, and, to a lesser degree, to the inadvertent
consumption of soil (Simon 1998; NCRP 1999).
The available whole-body counting and bioassay
measurements were used as a basis to estimate the
chronic intakes. Those whole-body and bioassay measurements were made on the Rongelap and Utrik evacuees for years after they returned to their respective home
bioassay measurements were made, 1.e., from 1957 to 1981.
The variation with time of the dietary intake rate, g, of
radionuclide, Z, from test Bravo, at atoll, 7, with time, f,
(assuming no additional fallout) can, thus, be expressedas:
atolls (Lessard et al. 1984). Those two atolls had been
q(Z, Bravo, j, t) = q(Z, Bravo,j, 7)
evacuated within about two days following the detonation
of the Castle Bravo test on 1 March 1954. Rongelap and
Utrik inhabitants were returned to their homeatolls in June
1957 and June 1954, respectively (Simonetal. 2010, Table
3). During the first few weeksafter their return and until the
1980’s, a Brookhaven National Laboratory team regularly
% I+EZAIXU-ME (5)
where
q(Z, Bravo, j, T) =the dietary intake rate (Bq d')
of radionuclide Z from the
conducted measurements of whole-body activity of '°’Cs,
Co and ®Zn, as well as urinary concentrations of ”’Sr.
Measurements of *Fe in blood were also performed but
Bravo test on the day of return
to the atoll /;
T =is the time (d) elapsed between
the Bravo test and the return to
the atoll, and ¢ is greater than, or
equalto, 7;
A(Z) =the radioactive decay constant
only once (Lessard et al. 1984).
The steps used to estimate the chronic intakes of
radionuclides were: (1) estimation of the chronic
intakes by Rongelap and Utrik adult evacuees due to
the Bravo test, (2) estimation of the chronic intakes
(d') of radionuclide Z; and
resulting from the Bravo test by adults of all other
k(Z,j) =the dietary removal constant
atolls, (3) estimation of the chronic intakes by adults
resulting from tests other than Bravo, and (4) estima-
(d_') of radionuclide Z at atoll j.
The values of g(Z, Bravo, j, 7) and k(Z, 7) obtained by
Lessard et al. (1984) are presented in Table 3. It is
tion of the chronic intakes by children.
worthwhile noting that the uncertainties are large and the
Estimation of the chronic intakes by Rongelap
and Utrik adult evacuees due to the Bravo test.
Lessard et al. (1984) summarized the findings of the
values of k for °Co and °Zn obtained for Rongelap were
used for Utrik by Lessard et al. (1984), as well as in this work
Brookhaven whole-body counting and bioassay program
and estimated the ingestion rates of Fe, °°Co, ®Zn, °°Sr,
because of the paucity of relevant measurements on the Utrik
residents. In fact, because many more measurements were
and '°’Cs for the adult populations monitored when they
made on the Rongelap evacuees than on the Utrik evacuees,
only the results obtained for the Rongelap evacuees were used
returned to their atolls, and also provided data on the
Table 3. Values used to estimate chronic intakes for the populations of Rongelap and Utrik. Uncertainties correspond
to one standard deviation (based on Lessardet al. 1984).
Ingestion rate on day
Radionuclide,
Z
Atoll, j
Fe
Rongelap
Sr
Rongelap
Co
Zn
BCs
Fe
Co
Zn
Sr
BICs
Rongelap
Rongelap
Rongelap
Utrik
Utrik
Utrik
Utrik
Utrik
of return to the atoll,
q(Z, Bravo, j, T)
(Bq d-')
1,700 + 930
95 + 32
1,300 + 940
21+ 1.1
390 + 130
1,300
130
21,000
0.40
210
+
+
+
+
+
* Assumed value.
> Assumed to be the same as in Rongelap.
710
44
16,000
0.30
110
Effective half-time of
dietary removal,
Radioactive decay
Dietary removal rate,
7.1 x 104
0°
constant, A(Z, j) (d7')
K(Z, j) (d-')
3.6 X 107*
2.8 x 1073
2.0 x 1073
1.3 x 1073
6.3 X 107
2.0 x 107"
6.6 X 10°
7.1
3.6
2.8
6.6
6.3
xX
x
X
X
X
1074
10-4
107
10°
10°
1.7 x 10+
2.0
1.3
1.6
1.8
0
x 107
xX 107%
x 1074
x 1074
In 2/[A(Z, )+k(Z,/)]
(d)
980
290
170
2,900
2,600
980
290
170
3,100
2,900