where the reductions in the estimated ingestion
doses in this paper are shown asa function of the
environmental half-life.
For example, if the
environmental half-life of 137Cs is equal to its
radiological half-life of 30 y, then the
estimated ingestion.doses would be 50% of what
wepresentin this paper.
The problem, of course, is in determining
Aenvironmental)
people), or both.
To charactefize such
uncertainty and variability in estima
each input variate (Bogen and S
Nazaroff et al., 1987; IAEA, 1989;
We are in the process of
evaluating data from Enewetak and Bikini
Atolls that we have accumulated since 1978. We
also have data from samples collected at
Rongelap Atoll from 1986 to 1993 from specific
trees first sampled in 1959 and 1961. These data
will provide at least a limited retrospective
look at the environmental half-life over this
30-y period.
Although we have not completed our
analysis of these data and cannotat this time
incorporate an actual environmental half-life in
our dose assessment, the net result must be to
reduce the total dose received from internal and
external exposures.
as a function of ingested 137Cs (L
ICRP, 1990, 1991a) was replacef@
following single-compartment model:
qi{t;) = FBR); eA
Uncertainty and Interindividual
Variability in Estimated Rongelap
Doses
atany time t, 0 st; St,
qi (u) = 4BK + A) ilu)
for any time u, fj; Su St,
The doses presented above were calculated
using arithmetic mean values for each of the
parameters in the dose models, such as body
weight, residence time of radionuclides in the
body, radionuclide concentrations in food and
soil, dietary intake (in g d-!), and fractional
deposition of radionuclides in body
compartments. The distributions for some of
these parameters are shown in the following
figures; both log and linear probabilityplots are
given on each graph. Figures 6 and 7 show the
distribution of body weights for Marshallese
females and males, respectively; Figures 8 and 9
thedietary intakes; Figures 10, 11, 12, and 13 the
Pu and Am concentrations in soil; and, Figures 14
and 15 the 137Cs concentrations in drinking
coconut meat and fluid. Most of these data are
lognormally distributed.
|
Estimated dose is a function of distributed
quantities reflecting either uncertainty (i.e.,
lack of knowledge concerning “the true” value) or
interindividual variability (which hereafter
will be referred to simply as “variability,” i.e.,
heterogeneity in values pertaining to different
gij(u) = FBRy e44i e(BK +A )u
for any time u, tj; <u St,
by the
(1)
(2)
(3)
in which: q;;(u) is the activity, in Bqfkg-! body
weight, of 187Cs ij n the whole body at Any time u
following ingestion of an activity Rj Jin Bq kg"!
body weight) of 137Cs contained in a f
type j at time t,, prime © denotes dif
with respect
i
rate of 137Cs, K = Ln(2)H-! is the bio
rate of 137Cs from the dominagt
“slow
dose-estimation uncertainty factor) [associated
' with Rij and B is a factor re
uncertainty associated with H.
angle brackets ({ }) denote ma
expectation only with respect to un
an overbar denotes expectation only
to interindividual variability.
Daily intakes Rj in Bq kg! d-! bf 137Cs in
local food items of type j were ass
37