- li -
among those who apparently received a heavy gamma radiation exposure, there has been a significant increase in
myelogenous leukemia.
Because of the rarity of this
disease, even the increase in frequency of from 10 to
20 times over the Japanese normal would not have been
recognized if these studies had not been made over the
entire surviving popuiation of the two cities.
A third possible delayed effect of radiation
exposure which has been demonstrated in animals is a
statistical shortening of Life expectancy.
This
phenomenon does not result from any specific cause of
death but apparently from a general acceleration of the
aging process.
Whether this factor can be recognized in
a human population is as yet unknown.
For it to be-=
come a significant conseauence of sublethal radiation
exposure, it wouid seem necessary that all causes of death
operating in earlier years would have to be sharply suppressed.
As stated previously, within the region of the
detonation and the associated early fallout in the case of
surface bursts, the evidence has been overwhelming that
the hazard from inhaled or ingested radioactive material is
inconsequential compared to the external gamma dose to the
whole body and beta-gamma dose to the skin.
More remotely,
however, after decay of the isotopes of ¥Ery short half
lives, some of radio-elements such as qi
become of
significance.
Because of the surface contamination of
foliage and the high rate of assimilation of iodine from
the gastrointestinal tract, it is not difficult to
demonstrate the presence of such radioactive material in
the thyroids of grazing animals for several weeks after a
detonation.
The amounts acquired by man are in general
much smaller than by sheep and cattle in the same areas.
The radioactive iodine decays rapidly and the actual
radiation exposure, even to the thyroid where the material is concentrated, is only a minute fraction of that
capable of producing recognizable damage.
The average exposure from this cause to the people of the United States
from the fallout cf the entire series of tests this past
spring was substantially less than 10% of that accepted as
permissible for continuous exposure over an entire year.
Somewhat more complicated is the subject of radioisotopes of long haif life that enter into biological
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