-5so for this fraction of the fallout the protective f.
tor
may be reduced to 14.
Since milk is the source of m: 2%
of our calcium, this means that the actual ratio of ridiostrontiun concentration in new human bones relative to
that in the top soil should approach these numbers.
It must be realized that though only a small part
of the calcium is derived from vegetables and meat, a similar
calculation must be made for this portion and the total
average ratio obtained.
It seems that the meat-—vegevtable
overall discrimination factor is about 10 so if 20 percent
of the calcium is derived from such sources on the average
the average overall factor will be between 1/13-and 1/30.
The experinental data on new human bone in children appear
to give a smaller figure, 1/60, as mentioned later.
£ matter of importance in connection with the
amount of strontium-90 which one would expect to be de-~
posited in human bone as a result of atomic weapon detona~
tions is the calcium concentration in the top soil.
Since
calciun is so similar to strontium, it seems very likely,
and the evidence confirms this, that high available c.icium
content of the soil will reduce the probability of strontium-
90 being taken up into the plants.
Of course this probably
does not have nearly as great an effect on the uptake of the
material which is picked up directly on the leaves.
‘ie might
expect therefore that soils which are particularly low in
calcium might show higher strontium-90 contents for tne
grasses grown cn them. This is, in fact, so, and shecp and
goats and cattle feeding on such pasture display a higher
strontium-90 bone content.
How such calcium deficiencies in the soil should
affect the strontium-90 uptake by the human population is a
most important question.
One sees immediately that food
distribution systems are such that the food supply is derived from large areas, and that there is consequently a
sharp reduction in the sensitivity of the human population
to calciun deficiencies in local soils.
This is brouzht
out particulariy well by the data on the radium contents of
human bones and their obvious lack of strong dependence on
the radium contents of local waters.
But for people who
consistently drink miik from cows grazing on such ground
there should be a definite effect on the amount of rediostrontium uptaxe and the effect should be proportion~ . to
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