-~ 14 In obtaining the derived values in Tables I and Il,
MPLB and MPC, for Pu~239, a QF=10 was employed.
implies,
as menticrcd above,
This QF
that the particles cf Pu-239,
which emit alpha particle radiation, are 10 times more effective
in inducing cancer
than X-rays.
Although the irradiation of
tissue by insoluble plutonium particles is highly nonuniform,
no DF value has beer assigned to these particies and hence,
a
DF=l1 was empleycd in determining the derived values in Tables I
and II.
Ideally,
the DF should be determined by the ratio
of the observed effects
in an organ following uniform and
nonuniform radiation of the tissue with the same radionuclide;
for example:
«
DF = Number of cancers
Number of cancers
(nonuniform irradiation)
(uniform irradiation)
Since direct experimental data are not available,
it is
necessary to derive the DF for insoluble Pu-239 particles from
collateral data.
In a subsequent section, we shall present
the biologics: cVicencle
that strongly suggests that a DF=1
grossly underestimates the DE for insoluble particulates of
“
r
Pu-239 and, consequently, that the derived standards, MPLB
and MPC, for this radionuclide,
In fact,
are greatly in error. *?
it will be shown that the biological data strongly
suggests that for such particles one should use a DF=115,000.
20/
This applies as well to other alpha-emitting actinides
in insoluble particulate form.
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