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["Maclellan, Jay A" <jay.a.maclellan@pnl.gov>]

	Is Pu more hazardous toxically or radiologically? Which is it??

	I believe an honest question deserves an honest answer.  Therefore I
quote from Chapter 8 "Biomedical Aspects of Plutonium" (J.N. Stannard) in
Uranium, Plutonium, Transplutonic Elemets (Hodge, Stannard and Hursh Editors). 

	Plutonium has often been called "the most toxic element known to man".
While not quite true it is indeed a most effective agent in producing g
long-term effects in the body.  Its general toxicology is that of a
"bone-seeker" superficially like radium, uranium, or strontium but with many
significant differences.  Because of its tendency to be a "surface seeker"
rather than a "volume seeker" it is markedly more effective than radium on a
activity basis in producing damage such as the induction of osteogenic sarcoma.
Also the contrast in behavior between inhaled plutonium and that entering by
other routes is so large that bone may not be a "critical organ" under
conditions of inhalation exposure, and the component of deposition in and damage
to soft tissue is much larger than with radium no matter want the route of
administration.

	The fact that the plutonium isotopes of most interest in biology and
medicine are almost exclusively alpha emitters (in terms of internal
contamination problems) puts them in a class with many other radionuclides in
that effects occur a concentrations far below those associated with conventional
"chemical" toxicity.  Thus it is commonly assumed that the radiation dose is the
prime if not the only cause of biological effect and that this is the more
likely because of the high relative effectiveness (RBE) of alpha particles,
Chemical properties affect primarily metabolism of the isotopes (absorption,
distribution and excretion).  Such properties include not only basic chemistry
of the element but valence state, compound, complexes, etc.  However, it cannot
be proven beyond doubt that there is absolutely no chemical toxicity since there
is no stable isotope for comparison and actually many inconsistencies persist.

	Jay A. MacLellan, CHP
	Manager, Radiation Records
	Radiation and Health Technology
	Pacific Northwest National Laboratory
	Phone:  509-376-7247
	Fax:      509-376-2906
Email:   jay.a.maclellan@pnl.gov <mailto:jay.a.maclellan@pnl.gov> 
	 
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