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THE SHORT TERM BIOLOGICAL FATE AND PERSISTENCE OF
RADIOACTIVE FALLOUT AS MEASURED AT VARIOUS
LOCATIONS WITUIN FALLOUT PATTERNS
By BR. G. lanprera and K. H. Larson
Radio-Ecology Division, Atomic Energy Project, University of California at Los Angeles
The
problem
of assessing
the biological
hazards of radioactive fallout may be arbi-
trarily divided into two parts; one, the acute or
immediate hazard arising primarily fram ex-
ternal radiation and secondarily from the
metabolism of certain fission products; and
two, the chronic or long term hazards arising
primarily from the metabolizedfission products,
and secondarily from external radiation. The
division of the problem is real. The exact
duration of each phase is not.
The Alamagordo Section and the succeeding
Radio-Ecology Division at the Atomic Energy
natural environments relatively unaffected by
human exploitations. Jn these native, stable
communities the occurrence of fission products
originating from fallout have been documented
as they oecur in the various components of the
environment. The
particular
components
studied during weapons testing programs have
been air, soil, plants, native rodents, andfallout,
Fromthesedata, collected serially over a period
of time, the cycling of bomb debris may be
followed as the contamination passes from one
A reasonably continuous record is available of
the fate of plutonium contamination near the
New Mexico TestSite from 1947 tu the present,
componentof the environmentto another.
The kangaroo rat, genus Dipodomys, and the
jack rabbit, genus Lepus, have been used as
indicators of the biological availability of radioactive fallout to other mammals. These
animals are abundant in most areas and are
easily collected by trapping or shooting. The
’ kangaroo ratis of particular interest because of
its sedentary nature. In other words, the body
contamination in several areas adjacent to the
Nevada Test Site from 1951 to the present. is
within one or two hundredfeet of the point of
Project, Universityof California at Los Angeles,
has been engaged in part in studying the fate
and persistence of radioactive fallout in areas
adjacent to continental test sites since 1947,
A record of the fate of repeated fission product
also available. Lest we stray from the “short
term’' objectives of the symposium, the data
presented below will emphasize data collected
during weapons testing programs and up to
one year following fallout contamination of an
environment.
During the course of these studies many
kinds of environments have been sampled
varying from the semiarid desert valleys, to
juniper and pifiion pine covered slopes, to
relativelyrich agricultural areas. Byandlarge
the sampling has emphasized the study of
burdenof fission products in any particular rat
is the result of that animal living its entire life
collection. Therefore, knowledge of the conditions of contamination within this area provides
us with parameters for estimating the biological
significance of any particular fallout condition.
The plant species and plant parts which go to
make up the primary forage of the kangaroo rat
and jack rabbit in any particular area are the
ones chosen fer documenting the oceurrence of
fallout materials in or on plants.
Experience has shown that radioactive fallout
originating from continental weapons tests tends
to remain in the surface inch or two of soil in
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