bone., The figure of 0.7 grams for the "Standard Man" is being borne
out by more recent studies.
Thus theonly really important correction to the SUNSHINE
model which can be madeate this time, then, relates to the first paramoe,
ofuniform @istribution.
Calculations indicative of howthis cen
“affect the results have been given above.
It is important to recognize,
however, that the SUNSHINE model deliberately strove to make the most
"pessimistic" assumption possible; i.e., where a parameter value was
in doubt, the value which led to the lowest possible estimate of
fission yield was chosen.
‘The range of uncertainty involved is such
‘that had the upper limit been sought instead, it would have been greater
than the lower limit of 25,000 MI by as much as a factor of a thousand.
Evaluation of the Strontium-90 MPC.
As indicated previously,
the 1.0 microcurie of strontium-90 maximum permissible concentration
_
in man is based essentially on the following relationship:
groo Mouse _ (sr?y
Human ) eK (sr? Human )
ee
Mouse "
Ra
Human
Ra
Human
The non-bracketed values are observed and the others are calculated.
The factor K is introduced to convert the strontium-89 experience to
the strontium-90 equivalent.
The data leading to the establishment of 1.0 microcurie as the
MFC for strontium-90 in man derive from the mouse experiments at the
Argonne National Leboratory and the acceptance of 0.1 pgm of radium as
being 0.1 of the lowest amount of that element in humans that has been
found to be associated with tumor formation.
The strontiwn-90 MFC
value, therefore, is critically dependent upon the strontium-89 effects
data originating from one laboratory and on the strontium-89/radium
effects ratio derived from one species of lower animal and the extrapo-
lation of this ratio to strontium-90 equivalent in man.
This is
obviously a rather tenuous basis for establishment of such an important
standard.
able.
In addition, the radium experience in man
is far from reli-
The clinical data are sparse; the collection of cases is not
120