V7
IV,
RADIONUCLIDES OF SIGNIFICANCE
Isotopes of iodine, strontium, and cesium have received the greatest
attention as canponents of radioactive fallout.
Although other radionuclides
are fission products as well, few of them have the characteristics to make
them as important biologically (Sternberg, 1968).
To be of radfobfological significance, a radionuclide released into the
environnent first must have a physical half-life of sufficient duration so
that {t will continue to be radtoactive during the time required to enter into
biological systens and to traverse food chains to reach the individual who
consumes {t.
Jodine-13), with its 8-day half life, exists long enough to move
through the atmosphere-vegetatton-cowmilk-people pathway.
Strontium-90 and
cesium-137 have half-lives of 29 and 30 years, respectively, and can eastly
enter the same pathways for human exposure.
Their longer lives also enable
them to use other pathways as well, such as sofl*vegetation tow for 205r,
and vegetation-cow-meat for 137Cs (Comar and Lengemann, 1967).
The significant radionuclide should also be able to be effectively
lodine-13] has easy access, Oeceuse isdin
mw
aessiaflated into the body.
te
'?
required for norma) thyroid gland function and the body does not distinguish
between fsotopes of the element.
Stronttum-90 and cesium-137 cap enter the
body because they behave generally like calctum and potassium, respect tvely,
which are important canponents of biological systens.
Jt is the specific
metabolism of each radionuclide that determines its potential for direct toric
effect.
Other fissfon products tent not to have the ease of entry into the
dfet or into tissues that these three do.
Research on the radinecoloyy ant blological effects of rther fission
products has heen done, though mot on such an
tntense hasis.
for esacrie,
Hamilton (1987), Im work on tre Pryutaniusn Profect, studvet the frgtetth pt toe