SO
WL Robison
SS
BW Wachholz
mi
vei
OV
Date
July 9, 1979
To
North Marshall Islands Advisory Group
from
R. 0. Gilbert
subject’
An Approach for Assessing the Validity of the 3xRule for
Estimating the Maximum Individual Dose. Should the Method be
Used for the Enewetak Dose Assessment?
0.0. Cetbeat
NS
No
409836
nae in
FOLOER
BOX No.
COLLECTION Marshal!
estimate of the “maximum individual" dose, where x is the estimated maximum
annual dose as computed using average values for the diet and food
j
pate “29/7 2
concentrations.
LLL argues that 3x may be equal to the 95th percentile or so
of the dose distribution over individuals, so that the probability of an
individual receiving an annual dose greater than 3x is very small.
The
validity of this approach is open to question, of course, since we don't know
what the actual distribution of doses will be for any given year following
the return of the Enewetak people to the Enewetak Atoll], if that return
KECTE
should take place.
Reviewed by
REPOSITORY
Internal Oistibaten
Pacific Northwest Laboratories
I have been thinking about LLL's proposed procedure of using 3x aS an
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Entwtlak June-July “79
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Personally, I would feel more confident about the 3x approach if LLL
could demonstrate via computer simulations that this factor of 3 is reasonable.
These simulations could be based on the diet information from Michael Pritchard's
recent survey of the Enewetak people, and upon the soil and plant/soil ratio
data now available.
The basic idea would be to generate the projected dose by specifying
distributions for each of the input parameters of the model, e.g., Bennett's
model for Sr-90 in bone.
The model itself would be assumed to be correct,
If
the resulting variability of the generated dose distribution was such that, say,
20 or 30 percent of the distribution was greater than 3x, then we might
consider using 4x or some other factor that did reach out into the 99 percentile
or so.
On the other hand, if the value 3x was greater than 99 percent of the
distribution under worst case conditions, I would feel more comfortable with
the factor 3.
Of course, the simulation results would prove nothing since we
don't have a very good handle on the distributions of the various parameters
involved.
But, by going through the simulation process and generating the dose