RADIATION STANDARDS, INCLUDING FALLOUT
49
cases of leukemia in them in the last few years. This is why the
academy report talks about so many cases in the first 10 or 15 years.
So muchfor those.
Then there is the data that Dr. Upton and Firth and a numberof
people developed on 7,000-odd greenhouse mice which were subjected
to acute whole-body radiation in which he found there seemed to be an
optimal dose for each type of leukemia and cancer that was induced.
The minute you varied from that dose you got into a much lowerin-
cidence of that particular effect. The group at Argonne have just
finished and are reporting on an experiment involving about the same
number of mice showing that in terms of lifespan the time you get
down below 5 roentgens per day, which is still a fairly high dose rate,
other factors seem to be more important in effecting the lifespan than
the radiation itself, except in particularly rugged creatures.
Representative Hosmer. You mean by other factors, unrelated to
radioactivity ?
Dr. Dunuam. General health of the animal] and that sort of thing.
Then one other very interesting group of experiments was done by
Dr. Mole at Harwell in England. He has by varying the dose and
using fairly high dose rates and giving a total dose of 700 roentgens
over a period of 6 or 7 weeks obtained the maximum cases of leukemia
in his mice. If he uses a continuous low level exposure up to the
same dose over the same period of time it is very much lower. All
of these things point in that direction. They do not necessarily prove
or indicate that there is a threshold but certainly the effects, as the
FRCsaid, are very much lower from low dose rate continuous chronic
rate of exposure.
Chairman Honirreto. With a massive dose you have a destruction
of the red corpuscles where in the gradual dose you have the regenerative effect in the blood of replacing the corpuscles that have been damaged or killed.
Dr. Dunuam. Thisis certainly one of the factors.
Another thing I might mention. Davies, a British plant geneticist,
has shownthereis a big dose rate effect in somatic mutations in plants.
It is hard to get at somatic mutations in humans. But in plants you
can do this. He has found a factor of 10 between 85,000 roentgens
per hour and 25 roentgens per hour in somatic effects. This I think
is important because much of the proportionality hypothesis was
based on the idea that maybe these effects were due to somatic mutations.
Representative Price. Mr. Ramey.
_ Mr. Ramny. Dr. Dunham,I think each session we have on this subject we always inquire as to the status of research generally in the
field of fallout. Are you getting enough financial support these days?
Dr. Dunuam. I ought to ask Mr. Holland about that if you are
talking about the sampling program. I think we will get enough
support.
Mr. Ramey. Not just sampling but research on low level effects.
Dr. Dunuam. I think we are moving as fast as the available manpowerwill let us. Perhaps not completely optimal. We have the
facilities now, thanks to your committee. JI think we are moving
ahead with this program all right now.
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