Emergency Standards for Alpha Emiitters

[Joyce Davis <JOYCED@DNFSB.GOV>]

The recent news about the Cassini mission controversy reminded me of
an issue that has bothered me for quite a while.
  
What standards should be used for accident safety, emergency
guidance, etc. when the hazard is a pure (or almost pure) alpha emitter
like Pu-238 with a long biological half life ?  Many of the current
standards and guidance values, e.g., 25 rem for public accident analysis
dose (10 CFR PArt 100), and 100 rem guidance for lifesaving dose,
developed from consideration of external radiation, mainly gama.  As I
understand it, the main basis for these  numbers originally was the
prevention of clinical symptoms or severe illness, respectively.  I think
they were best expressed in units of rads of gamma.  Once the idea of
effective dose came into vogue, these numbers were translated into
effective dose equivalent in rem.  They thereby acquired a correlation
with fatal cancer induction and appeared applicable to all types of
radiation.
Should we be using such numbers for Pu-238 ?  25 CEDE averages
approximately 500 mrem per year for 50 years--  Not much more than a
doubling of background -- is that a reasonable criterion for emergencies
?  Would it be better to set the criterion  on organ doses ? For example,
maybe the analogue to 25 rad external WB is the alpha dose to the lung
(in rads, alpha) that is just below the threshold for functional impairment; 
maybe the analogue for 100 rem is the threshold for clinically observable
illnesss or tissue damage ?  Or do we need 2 sets of standards, one for
prompt effects and one for cancers ?

Is there somewhere in the literature where these issues have been
discussed ?  Is there someone who is the "expert" on this ?  

Your thoughts on this would be appreciated. ( Maybe we can collectively
put together something for publication on the Net or in HPS News ?)        
( Please answer either directly or on radsafe as appropriate)

J P Davis
(Of course I speak only for J P Davis)
joyced@dnfsb.gov