955 is the grams of food i ingested on day j by this particular female,
and Ci; is the pCi/g in that ingested food. The g's and c's have been
generated as described above.
By summing the pCi/day intakes of Sr-90
over all foods over the entire year, we get the daily dietary intake
for the year (D,) needed in Bennett's bone model.
B,
where
B.
n
and
=
His model for adults is
(c+g)D +e -h (BL - cD.)
concentration of Sr-90 in bone for year n (n = 1,2,...),
dietary intake of Sr-90 for year n,
c, g and A are parameters as defined by Bennett.
Thus, going through the above scheme we can generate a value for Dy, to use
in this model for a given individual.
What about the parameters c, g and A?
Bennett obtained estimates for these based on a multiple regression analysis.
We might generate values for c, g and A in the same way as we did for dietary
intakes.
For example, consider c.
Let the value of c used in Bennett's model
be drawn from a normal distribution with a mean equal to the value published
by Bennett and a standard deviation approximated by (b-a)/6, where a and b
might be plus and minus, say 20 percent on either side of Bennett's value.
Again, the correct percentage to use is open to question.
This same approach
could be used to obtain computer generated values for g and i.
At this point we have generated values for Do» d, g, and » so that By
can be computed for a given female individual.
We also have an estimate of the
amount of calcium (Ca) in her bones since the diet survey also gives estimated body
weights.
We could also generate a value of Ca to use from a normal distribution
to take into account measurement error.
Hence, for this individual we can
calculate B/Ca, j.e., the estimated concentration of Sr-90 per gram of calcium
in her bones.
This is then multiplied by 4.5 to obtain Down? the estimated dose
rate (mrem/yr) to a small tissue-filled cavity in bone (Spiers approach).
Also,
Den = 0.444 Doin and Dan = 0.315 Doan’
The above scheme would be followed for each of the 36 females resulting
in an estimated dose DS n for each.
Hence, a distribution (histogram) of doses
to these 36 individuals could be generated.
We could compute x and 3x for this
distribution and see if 3x is in fact a reasonable estimate of the maximum
individual dose.