Units will not cause a detectable increase in bone
eukenia.
This fits well with the laboratory data c
incer or
animals
and the limited experience on humans with radium. ‘.1av is,
1 microcurie being 1000 Sunshine Units, is still cc:. sidered
to be pretty safe on tne dasis of the laboratory daca.
It
is set as a tolerance for occupational workers and it is
therefore reascnable that eight Sunshine Units should give
an effect so small as to be very, very difficult to detect.
It is, I think, helpful for us, however, to realize that the
present tcedy burden of strontium-90 in new bone from the
weapons tests that have occurred in the past is equal to
the increase in cosmic ray intensity that goes with an in-
crease of some 400 feet in altitude, a very small fraction
‘of the difference in cosmic radiation intensity between
Denver and sea level. Therefore, at the same time that we
consider the possible effects of strontvium-90 from such concentrations, we may deduce from our everyday ordinary experience limits on the effects to be expected.
None of the
evidence on the occurrence of bone cancer or leukemia as a
function of aititude has given us any reason to believe that
the present tolerance limits are in any way in error.
The
‘present body ourdens in new bones are small comparec to these
limits.
Separate from the strontiun-90 effects are the effects of general gamma radiation, the radiation that is ree
ceived mainly from outside the human body, and which cones
mainly from the very young fission products in the local
fallout area, but which can come in smallest part from radiocesium accumulating on the ground in the case of the strato-~
spheric fallout, or more importantly, from the shorter-lived
fission products deposited sy the tropospheric fallout.
Of
course, weapons tests are so conducted as to avoid exposures
to local fallout, so our present discussion of the effects of
weapons Wliil oe restricted to the much smaller gamma ray
doses from the offsite troposoheric and stratosdheric types
of fallout.
In time of war, of course, it would be the
local fallout which would be of more cirect concern, next to
blast and thermal effects, and it is to this aspect of fallout
which FCDA acdresses itself in the main.
In regard <o nu-
clear tests, we have to study the ef
effects on human genevics
and the possibie effects of sucn doses of radiation on health.
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