~ 34 There is no definitive information at low dose rates, 1,05, 0.1 r
per day or 0.3 r pex week, which is in the range of the permissible
levels as recomended by the International Camisasion on Radiation Pro-
tection,
A few experixents at these levels have been done in wice and
rats. In each instance the avewage life span of the irradiated group
was slightly higher than that of the control.
It appears, however, that
the sparing effect is during middle life and perhaps chronie lev level
exposure has seme sort of nonspecific effect by permitting survival
of experimental snimales in the presence of certain ectoparasites.
In
any event, the longer-lived animals in the irradiated group do not live
any longer than the longer~lived animals in the control group, The
causes of death in these low dese level experiments are not noteworthy
though in one experiment there was an increase in the momber of cases
of leukemia.
However, there was not a sufficient musber of cases appear~
ing early in life to swing the ever~all statistics one way or another.
A dose rate of 0.13 r per 36-year period would reduce the average life
span by at the most a few days.
Leukemia
The present, heukeada rate in the United States is epprorisately
11,00 eases per year,
It is an established fact in many axperiments
done on animals that large doses af radiation induce Jevkeala.
In
some experiments, although the total mumber of cases was not increased,
the oneat was vreatly accelerated by the radiation expomre.
Though
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