RADIATION TOLERANCE FROM FALLOUT IN
PROTECTIVE STRUCTURES*
Robert A. Conard
Medical Research Center
Brookhaven National Laboratory, Upton, New York
whole-body dose of 175 rads of gammaradiation,
and sufficient contamination of the skin to result
later in widespread beta burns and loss of hair. In
addition, measurable amounts of radionuclides were
detected in their urine from internal absorption of fallout materials. Gamma radiation caused a reduction in their blood cells to about half-normallevels
This paper is concerned with the protective role of
shelters as related primarily to the hazards of closein fallout radiation associated with nuclear detonations. The formation of such fallout occurs in the
following manner. The intense heat of the fireball,
as it touches the surface of the ground, incinerates
earthen material to an ash-like state, drawing it into
the cloud where it becomes mixed withradioactive
and proved to be the most serious of the hazards to
which they were exposed. Fortunately, the dose was
just short of lethal, and no deaths or serious consequences (such as bleeding or infections from lowering of their blood levels) were apparent. The return
of blood levels toward normal was evident within
one year. Beta burns and epilation began to appear
about two weeks after exposure in about 90 per cent
of the people. They occurred largely on areas that
were not covered by clothing at the time of exposure.
Most burns were superficial and healed within a few
weeks, though there were a few that were moreserious, resulting in painful ulcerations and requiring
longer healing time. Loss of hair on the head was
spotty and temporary with regrowth occurring within
residue from the bomb detonation. Because of the
heavy particulate nature of the material it is deposited within an area of several hundred miles. The
hazards associated with fallout are due primarily to
gamma and beta irradiations associated with the
fission products in the fallout material. In some
cases alpha-emitting isotopes may be present, but
these are likely to be present only in small amounts.
Neutron radiation is not associated with fallout but
is emitted with gamma radiation at the time of deto-
nation, and, as is true with blast and thermal effects,
is of concern only in the immediate area of the
detonation.
six months. Based on radiochemical urine analyses
Effects of Fallout in an Open Field
it was estimated that during the two days prior to
evacuation, the average individual body burdens for
the principal isotopes were as follows: sr89, 1.6-
When an individual is exposed to fallout in an open
field, there are three types of hazards to which he
is subjected: first, that of penetrating whole-body
2.2 uc; Bal40, 0,34-2.7 wc; Rare Earth Group, 0-1.2
uc; 1231 (in thyroid gland), 6.4-11.2 uc; Ru! z
0-0.013 ue; Cat), 0-0.19 uc; and Fessile Material
0-0.16 2 gm. (1) Absorbed material radioiodines
were the most hazardous isotopes, and it was
calculated that the dose to the adult's gland was
150 rads and to the child's gland approximately
1,000 rads. The rapidity of isotope elimination from
the body was noteworthy: no acute effects associated
with the presence of these isotopes were detected.
gamma radiation; second, that due to irradiation of
the skin from deposit of fallout material on the body;
and third, that of internal absorption of radioactive
materials from air breathed and food and water
consumed. Our experience with 82 Marshallese
people who were accidentally exposed to such fallout on Rongelap Island in the Pacific in 1954, following the experimental detonation of a thermonuclear
device, exemplifies these three types of hazards{1,2)
The findings of subsequent surveys suggest that
possibly somelate radiation effects are evident in
The island was dusted with white ashen material
which fell for a time estimated at up to 16 hours
the Marshallese.(2) These include slight retardation
following the detonation. Since their flimsy, thached
palm huts offered little protection, the natives lived
under the most extreme conditions of fallout contamination for the two-day period before evacuation
*Research supported by the U.S. Atomic Energy
Commission.
was possible. The majority received an estimated
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