-~ 14 -
one another in general shape and that the magnitude « ° the
distribution o7 the strontium-90 contents of the Chic igo
stillborn babies was not in any way anomalous. There ore,
we shall take the distribution curve for radiostrontium
to be the same as for the normal strontium data.
The
occurrence of non-radioactive normal ordinary strontium
in the bones should certainly tell us what the equilibrium
distribution will be for radioactive strontium, and from
it we should be able to learn the points about distribu-
tion which we cannot yet learn in any detail from the
radioactive strontium itself.
Turekian and Kulp noted
in their study of normal strontium in human bone that in
a given region the deviation from the average was about
34h percent of the average, that is, for human bone from
the regions Colorado, Texas, Cologne, Bonn, Venezuela,
Chile, Vancouver, China and India.
in each instance the
ratio of the standard deviation from the mean itself was
taken and the average calculated to obtain 34 percent.
Therefore, we take 34 percent as the expected standard
deviation from the mean for a given locality for the
eventual strontium-90 equilibrium burden in human bones.
With this result we can, assuming a normal errcecr
curve shape of the distribution of probabilities, answer
the immediate question: What is the probability of an
individual exceeding the tolerance even though the mean
does not? On the basis of this analysis we find that at
steady state and in equilibrium the variation from the
mean will constitute an error curve with a shape corres-
ponding to the standard deviation, being 1/3 of the mean.
Therefore, at steady state among people living in a given
locality, only one person in about 700 will have more than
twice the average strontium-90 burden, and the chances of
anyone having as much as three times the normal burden will
be about one in twenty million.
Now what about the non-equilibrium distribution,
when the strontium-90 is finding its way into the biological
system?
Obviously, the burden will be much lower here, but
the deviation from the mean will probably be much higher
percentagewise, particularly in adults where most of tne
bone has been deposited before strontium-90 was produced.
The present strontium-90 content of adults depends very
much on the growth rate and the metabolic activity of the
(more)
om
EB
RF
F
££
tf
nh
é@
ho
oe
eB
EE
OY
FE