Bow
BSA EG
aa
.
a
“|
Sr™ and Pu*. The occurrence of epidermoid carcinoma in the lungs of mice after exposure
to plutonium particles suggests that accumulations of such materials may present a similar
hazard to man,
Finally, the results of thorough studies of animals and humans accidentally exposed to
radiation from fall-out during the Pacific fleld tests in the spring of 1954 demonstrate’! that;
4. External gamma radiation ts by far the most serious hazard in the fall-out area.
2, Beta radtation of the skin can be a problem even in the absence of lethal doses of associated gammz- radiation exposure.
,
3. Some degree of internal contamination will occur in persons exposed to fall-out, but
the amounts deposited in the body will be relatively small. It appears certain that no contribu-
tion to the acute medical picture will result from this cause and furthermorethat, although
data are incomplete, little or no long-term hazard is likely, particularly tf reasonable precautions are taken to avoid excessive Inhalation ind ingestion of contaminated materials during
and after the fall-out period.
4.2
CONCLUSIONS
From careful analysis of field studies made following the Apple Il tower detonation and
possible acute hazard from inhaling radtoactive fall-out materials:
t. There is no apparent situation in nuclear warfare in which it would be possible, during
the first few days following a detonation, to inhale amounts of fall-out materials sufficient to
cause acute radiation injury to the lungs or intestinal tract without simultaneously receiving
supralethal external doses of beta-gamma radiation.
2. From consideration of physical factors alone (such as strength and type of detonation,
particle-size distribution, decay rates, meteorological conditions, air-borne radioactivity
levels, and percentage of radioactivity in the 0.1- to 5.0-p size range), the acute external beta‘gamma radiation hazard is at least 1000 times greater than tha: from inhalation,
3. When phystological phenomenaare also considered, the defense mechanisms of the
respiratory organs effectively reduce the pulmonary hazard by at least another factor of 10,
4. The possibility of inducing bronchial or pulmonary carcinoma by the {nhalation and
long-term retention of a single radivactive particle (20 » in size) appears remote on the basis
of both physical and physiological considerations,
5. From the results of repeated (60) 6-hr inhalation exposures of rats and rabbits to
radioactive insoluble particles (0.1 to 5.0 y) under controlled conditions in the laboratory, it is
estimated that, because of lung clearance mechanisms, similar dally exposures would have to
be continued for 5 to 20 years in order to accumulate sufficient quantitles of such matertals to
induce pathological lesions in the lungs.
6. Under field conditions and in laboratory studies designed to permit acute exposure by
inhalation, and to prevent simultaneous ingestion of radioactive fall-out particulate materials,
the radiation exposure to the intestinal organs exceeded that to the organs of respiration by
factors of 10 to 150. Direct ingestion of such materials would further increase the intestinal
and internal hazard.
4.3
RECOMMENDATIONS
In future investigations emphasis should be shifted to the long-term (years, pulmonary
neoplastic effecta {rom acute and chronic inhalation exposure to long-lived alpha-emitting
radioisotopes, especially Pu**, and to the chronic effects in the intestines and bones from
acute and chronic ingestion of Srand Pu’”*,
24
m
yaad
SOI
SrSt (Fo
PS Bre pte2aee
eM AOees
apieGE
Ae leeet nt8
RS
46
*
PE
Ey onan“
eI
EE
re
=
n
ee
mee be
from extensive inhalation studies performed during the past 6 years in the !aboratories of the
atomic Energy Project, UCLA, six important conclusions have been reached regarding the
the th
vA
3. Little information ts available on the poten:.al haza_ to the fesptratory system and
other organs fotlowing chronic exposure to email amounts of tong-ilved radioisotopes: such as