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Health Physics
August 2010, Volume 99, Number 2
Table 21. A comparison of the birth-cohort averaged dose (BCAD) with the dose to infants who are assumed to have
been born on Jan. | in the same year as the tests (1948, 1951, 1953, 1954, 1956, 1958). All estimated doses (mGy) are
from acute intakes of radionuclides, are truncated to the end of the year, and are rounded to two significant digits.*
Birth year
and year
of tests
1948
1948
1951
1951
1952
1952
1954
1954
1956
1956
1958
1958
Assumption
for dose
calculation
BCAD
Born Jan.1
BCAD
Born Jan.1
BCAD
Born Jan.1
BCAD
Born Jan.1
BCAD
Born Jan.1
BCAD
Born Jan.1
Majuro residents
Kwajalein residents
RBM
Thyroid
Stomach
Colon
RBM
Thyroid
Stomach
Colon
0.00028
0.00080
—
—
0.025
0.030
0.10
0.42
0.017
0.036
0.0025
0.0068
0.046
0.13
—
—
6.3
7.3
16
66
2.5
5.4
0.37
0.99
0.00027
0.00076
—
—
0.058
0.067
0.13
0.53
0.020
0.044
0.0025
0.0066
0.0022
0.0063
—
—
0.30
0.35
0.82
3.5
0.13
0.29
0.021
0.055
0.063
0.19
0.00056
0.0020
0.027
0.031
0.20
0.67
0.032
0.072
0.0036
0.0094
18
53
0.11
0.38
7.7
9.0
54
180
6.0
13
0.50
1.3
0.17
0.51
0.00089
0.0032
0.076
0.088
0.52
1.7
0.053
0.12
0.0030
0.0080
0.98
2.9
0.0054
0.020
0.34
0.39
2.5
8.3
0.30
0.67
0.026
0.068
“Note: Table entries with a dash (—) were doses estimated to have been less than 0.001 mGy.
Utrik population group. As is the case for the
Rongelap Island community and as shown in Tables 11
and 19, the internal thyroid doses received by the Utrik
community in 1954 were, for the most part, due to acute
intakes of radioiodines ('*'I and '**1) resulting from the
Bravo test. However, no samples for bioassay of '*'I were
Q('3'1, Bravo)
Dep('*'I, Bravo)
Dep('*’Cs, Bravo) — Dep('*’Cs, Bravo)
O('3'T, Bravo)
Dep('*'I, Bravo)|’
(16)
collected from the members of the Utrik community.
The first term is derived from the tables provided in
densities provided in Becket al. (2010) for all tests with
that the deposition ratios have relatively small error
Those intakes were estimated from the '*’Cs deposition
measurable fallout. Taking only into consideration the
intakes of ''I and ‘I from Bravo, the thyroid dose
received in 1954 by representative adults of the Utrik
community is expressed as:
D(adults) = Dep('*’Cs, Bravo)
O(}341, Bravo)
D331)
Dep('*'Cs, Bravo)
OCD)
O('?71, Bravo)
D331)
(15)
epic Bravo) ~ af
Uncertainties in Dep(’*’Cs): As discussed in Becket
al. (2010), an uncertainty estimate was assigned to each
estimate of the '°’Cs deposition density at each atoll from
each test. These uncertainties, expressed in terms of
GSDs, ranged from 1.3 to 3.0, depending on the availability and number of measurements of exposure rates
and long-lived radionuclidesat the atoll for the test under
consideration. In the case of Utrik, the '*’Cs deposition
density resulting from the Bravo test was estimated to be
21 kBq m~ with an uncertainty (GSD)of1.5.
Uncertainties in OCT, Bravo)/Dep(’*’Cs, Bravo)
and Q('I, Bravo)/Dep(""’Cs, Bravo): Taking '*'I as an
example, O('*'I, Bravo)/Dep('*’Cs, Bravo)is, in fact, the
product of two terms:
Hicks (1984) for discrete times of fallout. It is assumed
(Hicks 1982) and, thus, that the uncertainty in the first
term is due primarily to the uncertainty in the TOI
estimate of 31 h for Utrik after the Bravo detonation.
Estimates of TOI that depend on TOAclearly influence
the estimates of intake for short-lived radionuclides due
to differences in physical decay. In a simple analysis
where TOA(h) wasallowed to take on values of the best
estimate minus 20% and the best estimate plus 20%, we
compared the organ doses at the four atolls discussed.
We found that organ doses from acute intakes were 7%
to 25% greater at the earlier TOAs (best estimate minus
20%) compared to the best estimates, depending on the
organ and population group. Conversely, we found that
organ doses were 7% to 17% lowerat longer TOAs(best
estimate plus 20%) compared to the best estimates
depending on the organ and population group. Table 22
presents a summary of the outcomeof these calculations
and leads to the general conclusion that errors in TOA or
TOI potentially lead to errors in dose that are, for the
most part, less than 25% and, more often than not,
about +15%. Considering that the overall uncertainty in
internal doses is characterized by a GSD ofat least 2, the
uncertainty in TOI and, thus, in the first term, is a small
component of the overall uncertainty and can be ignored
for practical reasons.