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URANIUM
Summary
Natural ly occurring, uranium has an exceedingly long half Jife and anits
alpha particles.
It is concentrated in kidney and bone.
Uranium has been the
subject of toxicological study for many years, and its nephrotoxic properties
were known a century prior to work on its radiobiological significance.
The
chemical toxicity to the kidneys of natural uranium overrides any potential
for radiobiologic toxicity.
Only with high specific activity fsotopes of
uranium is the skeleton at risk for subsequent radiation-related cancer
_ development.
Environmental Pathways
Uranium (238u, 234, and 235u) is naturally occurring and is
distributed ubiquitously but variably throughout the earth's surface.
It is
present in water and in foods, so that small quantities are ingested daily.
The NCRP (1975), fran data of Welford and Baird (1967), reported an average
Approximately equai amounts (about
22 percent) of dietary uranium were derived from each of four food groups:
cereals and grains; meat, fish, and eggs; green vegetables and fruits; and
root vegetables.
About 7 percent was fron dairy products, and 2 percent was
fran drinking water.
Inhalation was considered to be a very minor route of
assimilation.
%s eg
Peta ea, Spethat oe a tee
The dose rate to bone fran natural uranium was calculated to he about
12 mrem/yr (NCRP, 1975).
Thts value amounted to only about one-tenth of the
total for skeletal tissues fran naturally occurring radioact tvity.
Any urantum that {s released into the environment sich as that which dnes
not undergo fission in a nuclear weapon detonation would be restored to the
whee
s
see
daily intake of 0.9 picocuries of uranium.