Gt
Question 12A
. Do you, or any of your colleagues, have any reason to think that the
acceptably safe?
~
*
‘b
..
~ “acceptable,” "safe," "permissible" doses of radiation may not be
‘Answer 12A
No.
Question 12B
A study by Warren A. Brill at the National Center for Radiological Health
concludes that an acceptable dose of iron-55 to the spleen probably re-
sults in a dose two times higher to the red blood cells, and 800 times _
higher to the blood ferritins.
experts?
Is this conclusion accepted by other
Answer 12B
The conclusion was drawn by Warren A. Brill, although the information
is primarily a summary of work done by other investigators.
It is interesting
to notethat problems related to iron-55 dosimetry in various biological
entities have been under study for about a decade.
Various organs such as
the spleen, tissues such as blood and tissue components such as erythrocytes
or ferritin aggregates have been investigated.
The conclusion stated in
the question is generally accepted by those knowledgeable in the field of
dosimetry.
We should be aware, however, of exactly
the energy is absorbed,
by what biological entity
For itron-55 the energy available for deposition
in biological systems averages about 6 keV (the ICRP uses a more conservative
value of 6.5 keV).
Auger electrons.
The energy is emitted either as X-rays or as short-ranged
The Auger electrons account for about 80% of the available
energy so that, for cells containing high concentrations of iron-55, most of
the decay energy is deposited within the cell.
Because of this short range