INTERNAL DOSE FROM SHORT-LIVED RADIONUCLIDES
By Karu Z. Monaan
Oak Ridge National Laboratory, Oak Rulye, Tennessee
INTERNAL DOSE FROM STFORT-LIVED
RADIONUCLIDES
The National Committce on Radiation Pro-
tection (NCRP) and the International Commission on Radiological Protection (ICRP) set.
the national and international standards for
radiation protection. One of the important
assignments of these organizations has been
the establishment. of the maximumpermissible
body burden, q, and the maximum permissible
concentrations, MPC, of the radionuclides in
air, water, and food. To the present time only
q and MPC values for continuous exposure to
the radionuclides have been published in the
values for inhalation. The GJ. tract was not
included as a critical body organ in Handbook
52 because at the time of the publication of
Handbook 52 radiation damage per roentgen
to the GI. tract was considered less significant
thanthatto the other body organs and because
insufficient data were available to estimate
the absorbed dose and corresponding hazard
to various portions of the GJ. tract. When
Dr. E. E. Pochin® furnished to the ICRP
Committee data on the mass and timedistribution of material in the G.I. tract, it became
evident that the GI. tract receives the greatest
absorbed dose from manyof the radionuclides.
Values
The lowerlarge intestine is the critical portion
of the G.T. tract for all radionuclides considered
will probably be several years before final
agreement is reached on a set of values.
Mn® and F*, in which cases the upper large
intestine and stomach are the critical portions
NCRP? and the ICRP? Handbooks.
for single exposure are being considered but it
The ICRP Handbook, which was published
abouttwo years after the NCRP Handbook 52,
differs in some respects from the earlier pub-
lication.
Perhaps the most important change
was the incorporation of MPC values based
on the G.I. tract as the critical body organ.
The importance of this is emphasized by the
fact that of the 355 MPC values listed in the
ICRP Handbook, 71 percent for ingestion and
41 percent for inhalation refer to the G.T. tract
as the critical body organ.
The bone is the
second most important body organ and is the
critical body organ for 11 percent of the MPC
values for ingestion and 28 percent of the MPC
in the ICRP Handbook with the exception of
of the G.I. tract, respectively.
The lower
large intestine is usually the critical portion
of the G.I. tract for three reasons:
1, Only radionuclides with a radioactive
half-life greater than 1 hour were considered
in the preparation of the ICRP Handbook.
2. The contaminates} material remains in
the lowerlarge intestine 18 of the 31 hours
that it is in the GL tract.
3. The mass of material in which the radionuclide is diluted and to whichtheradiation
dose is delivered is relatively small, i. e.,
150 g in the lowerlarge intestine, 250 g in
the stomach, 1100 g in the small intestine,
and 135 g in the upper largeintestine.
t Handbook 52, “Maximum Permissible Amounts of Radivisntopes
in the Homan Body ond
Permissible C
i
in Alr
and Water," by Natlonal Cammittec on Radiation Protechon, National
Bureau of Standards, Washington, 13, C. (1953)
2TCRP Handbook, “Recommendations of the International Com-
i}rivate Communication from BE. BE. Paehin, Director, Department
uf Clinical Research, University College Hoxpital, Medieal School,
British Institute of Radiology, London (1955).
dutedOctober o, 1B5%
mission on Radiological Protection,” 4. Jr. of Radiotogy, Supplement 6,
University Street, London, W. C. 1., Great Britain, to K. Z. Morgan,
149