However, data indicate that Pu bound to soil
probably has a much lower gut-transfer factor of
about 10-4 to 10-5 (Gilbert et al., 1989; Harrison et
al., 1989). ICRP also recognizes a different gut
transfer factor for Pu that is not organically
bound (ICRP, 1990). Consequently, we used a gut
transfer factor of 10 for Pu bound to soil. All
Am was assumed to have a gut transfer factor of
10-3. It is noted that the 10-3 gut transfer factor
is considered to have a considerable margin of
safety built in (ICRP, 1986, 1990).
The estimated effective dose from Pu based
on the concentrations in food, soil, and air are
very similar to those calculated by BNL based on
the analysis of Pu in urine of the Rongelap
people (Sun, 1992). These two very independent
methods are in excellent agreement on the
Magnitude of the dose from the transuranic
radionuclides as shown in Table 17. The
estimated average committed effective dose for
30-y residence from Pu based on environmental
data and models is 0.26 mSv (26 mrem), or 0.10
mSv (10 mrem), for the 50-y integral effective
dose. We have assumed that a person is in a
high-resuspension condition (1 h d-! ) everyday
of his life, which is probably excessive, and that
a person consumes 100 mg of soil every day. The
value of 40 mrem committed effective dose from
urine analyses is based on the detection limit of
the analytical method used for analyzing Pu in
urine. The median value for Pu in the urine ofall
the people analyzed is below this detection
limit value. In other words, the actual median
committed effective dose people receive is below
_the detection limit value of 40 mrem committed
effective dose. People have been living on
Rongelap Island for about 28 y subsequent to the
fallout from BRAVO. Consequently, both
for residence between 30 and 50 y.
In the long term, of course, as
and 69Co disappear, the
radionuclides will be the only sourcg
The total estimated effective dose
fransuranic
of exposure.
fgom 239+240Py
and 241Am radionuclides, baged on the
inhalation and imported food afailable diet
scenario discussed previously, is alfout 0.08 mSv
(8 mrem) over 30 y, 0.18 mSv (18
} over 50 y,
and about 0.33 mSv (33 mrem) over
y.
From the marine pathway,
reef fish in
particular, and the pelagic fist, are a key
source, and a favorite source, of grotein in the
Marshallese diet. It is fortunate
and 99Sr concentrations are very
marine foods (Tables 5 and 6). Co
that the 137Cs
low in the
ently, the
marine pathway is a minor contgibutor to the
total estimated dose from} man-made
radionuclides, but not necessarily
for naturally
because there is more 137Cs and
in the ground
occurring radionuclides.
The roof-catchment water [(i.e., cistern
water) contributes in a very minpr way to the
estimated dose listed in Table
If ground
water is consumed, then the d
will go up
water than in the cistern water;
ever, ground
water generally is used only in c
of extreme
drought. In our dose calculations, we assume 40%
this.
The maximum annual intake
9067, 239+240Py and 241Am for Ron
Table 17. The average committed effective dose from Pu and Am at RongelapIsland in
Method
Environmental (LLNL)*
Committed effective dose__50-y integral effective dose
njSv (mrem)
|
Urine Analysis (BNL)
Committell effective dose
Pu
.
0.26 (26)
0.10 (10)
0.49
(40)
Am
0.23 (23)
0.078 (7.8)
Nqd estimate
a Twosignificant figures are given only to showthe slight difference between Pu and
b Based on the detection limit. The actual mean dose is something below this number.