407936
RADIOACTIVITY IN FOODS
Cyril L. Comar, Ph.D., Ithaca, N. Y.
There is little doubt that atomic energy will as-
sume an importantrole in our civilization, andit is
appropriate that future possible hazards should be
evaluated. At the present time, it can be concluded that there is no reason for any change in
our nutritional habits or food technology as a result of fall-out contamination. Research must continue, however, so that recommendations can be
made to minimize the intake of radioactive contamination should this ever become necessary.
Although environmental contamination now existing is due almost entirely to fall-out from nuclear weapons, peacetime operations may become
physica] half lives, they can be dangerous only
during certain periods, depending on the frequency
and the nature of production of contamination.
Experience has indicated that iodine-131 transmitted in milk mav be important at short times after
releases such as in reactor accidents, Strontium-89,
which is produced in higheractivities than strontium-90, may be more hazardous shortly after production, while strontium-90, with a much longer
half life, becomes more dominant with time. The
strontium radioisotopes, of course, are cumulative
Atmosphere
(A}
increasingly important as sources of radioactive
contamination. In addition to’ fall-out, small quantities of radioactive materials may be released into
the environment as a result of such operations as
mining of uranium and thorium ore and fuel processing; reactor installations in power plants, submarines, ships, and aircraft (normal operations and
accidents}; and radioisotope applications in medicine, industry, and agriculture.
Determining Factors in Hazard of Radioisotopes
The relative hazard of radioactive materials will
be governed by the amount released into the environment, physical half life, efficiency of transfer
through the food chain to the humandiet, degree
of absorption by the body, and length of time retained in the body. By these criteria, the radioisotopes from fall-out of the greatest concern are
iodine, barium, strontium, and cesium. Extensive
data are available on the passage of these radioactive materials through food chains and subsequent implications.' Table 1 summarizes their
characteristics from the standpoint of environmental contamination.
The radioisotopes of iodine collect in the thyroid
gland and those of barium concentrate in bone.
Since isotopes of both. of these elements have short
Director of the Laboratory of Radiation Biology, Department of
Physiology, New York State Veterinary College, Comell University.
Vegetation
(V) === Soil (S)
Cattte (C)
Meat
Milk
Products (Mp)
(M)
Diagram of main terrestrial food chains by means of which
environmental radioactive contaminants reach the human
population.
in bone. Cesium-137, which follows potassium in
metabolism, is considered less of a hazard than
strontium-90 because it is turned over relatively
rapidly in the body, it is not selectively concentrated in any one part of the body, and it does not
pass appreciably from soil to plant in the food
chain.
Radioactive contaminants are transferred to man
by means of specific pathways through the main
terrestrial food chains. These food chains are ilhustrated diagrammatically in the figure and the primary pathways of barium, iodine, strontium, and
cesium are shown in table 1. As an example, strontium-90 is deposited from the atmosphere on the
foliage of plants and on the soil. Transfer between
soil and plant proceeds in both directions by normal
root uptake and by washing from leaves or death