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dread diseases by moving to a higher altitude or by moving
from a sedimentary soil, where the uranium content is low,
to an igneous or granitic surface, where the uranium content is very much higher, or by moving from a wooden to a
brick or concrete house.
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Another way of evaluating the possible risk from
strontium-90 in fallow& is through comparison with the permissible cencentration of strontium-90 recommended by
authoritative groups. The permissible amount of strontium90 for atomic energy workers in the United States is about
2,000 times the present strontium-90 content of new bone
in the United States resulting from fallout.
(Strontium-90
concentrations in the rest of the world are generally lower
than those in the United States.) Authoritative groups have
ae
recommended that, on grounds of general prudence, the per-=
missible limit for whole populations be one-tenth of that
for atomic energy workers.
On this basis, the present level
for new bone, that is, in children, in the United States is
somewhat less than one percent of the maximum permissible
concentration for the population.
Perhaps a word of explanation should be given regarding these maximum permissible concentrations.
As you
know, scientists do not speak of "risks" or "hazards" in the
sense that the words ordinarily are used.
They try to measure possibilities almost to the limits of the finite;
therefore, "risk" includes the possibility of effects far
beyond the range of the probable or detectable.
The maximum
permissible concentrations are not safety limits, rather,
they indicate that at considerably larger concentrations,
perhaps tenfold greater, there would be definitely detectable
effects.
So far, I have been discussing principally the
possible risks from radioactive strontium.
Radioactive fallout intludes other materials which dco not accumulate inside
the body, but do emit penetrating radiation which can irradiate the sex organs and other parts of the whole body from
the outside.
Such radiations can produce genetic mutations.
Again, in evaluating the possibility of genetic
effects from fallout, we should try to compare it with normal
experience.
The external dosages from fallout, that is, those
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