-6The general tissue doses from fallout are of the order of one to two per
cent of that which is ordinarily received at sea level from the natural
radioactivity.
We do not know even approximately the biological effects,
if any, of this natural background radiation which is delivered at the
slow rate of approximately 100 millirads per year.
We do know that all
life has evolved in this radioactive environment and that there has not
been a single living cell since the beginning of life on earth that has
not been constantly subjected to radiation originating both from without
and from within its substance.
We are aware that in the United States
there is a considerable fraction of our population that lives in regions
of background external radiation 100% greater than that normally at sea
oy
galt
‘
level.
There are some heavily populated regions of the world where
inhabitants have been subjected to levels of radioactivity at least
10 times that considered usual. Final conclusions as to the possible
biological effects of these exposures must await future studies, but it
can be said that there are no obvious manifestations of radiation injyry
in these’-situations.
Our conclusions are that until we have knowledge cf the biological
effects of natural. radioactivity it is impossible to make a precise '
estimate of the significance of a small increment in the exposure.
We
assume, in accordance with the present state of knowledge of radiobiology,
that such changes as may occur are to some extent injurious rather than
beneficial. In any case, the degree of enhanced risk is so minute that
detection has not been possible by any method,
The report stresses the irregularities in intensity and the maximum values
for the fallout activities with special emphasis on the radioisotopes of
short half-lives.
Respectfully submitted,
Cie)
A
ab fughow-
24,
“Ai ae
c?
(
v
John C, Bugher, Acting Chairman
H. Bentley Glass
Fred J. Hodges
James G. Horsfall
Robert F. Loeb
Leonidas D, Marinelli
Carl V. Moore
James H. Sterner
Harland G. Wood
Mr. John A. McCone, Chairman
U. S. Atomic Energy Commission
Washington 25, D. C.
Enclosure