More on DU

[David W Lee <lee_david_w@lanl.gov>]

Keith Bradshaw wrote (in part):

"I calculated an Annual Limit of Intake (inhalation) of 32Bq, which
corresponds to 2100microgram of DU for members of the public (1mSv/yr
limit). At 2000 hr per year and a breathing rate of 1.2m3/hr, you obtain a
Derived Air Concentration (DAC) of 0.013 Bq/m3 which corresponds to
0.88microgram/m3. This is a factor of 227 times more restrictive than the
ACGIH limit."

"I think calculating the amount of U in x tonnes of surface soil etc is
missing the point. It's clearly impossible to inhale several kg of dirt."

"Perhaps, but exposure limits have been set and it's our statutory duty to
both keep below them AND to clearly demonstrate that we are keeping below
them. From the sound of things, this has not been done in the Gulf War."

A few comments, although I've been trying to stay out of this thread:

        a.  I know of no occupational radiation dose limit that has ever been
formulated presuming anything other than peacetime, steady-state, "calm"
working conditions.  For "out of the ordinary," even extraordinary conditions,
the NRC and EPA have larger planned special exposure/protective action guides
(episodic) dose limits/guides, e.g., 250 mSv and up.

        b.  As Keith has acknowledged, the Gulf War was a WAR.  To me this 
means soldier's exposure to DU, pesticides, bullets et al. (the whole gambit of
things on the battlefield that can injure a person in War) occurred under decidedly
non-peacetime, non-university laboratory, non-steady-state exposure conditions
to which peacetime occupational radiation, pesticide, and lead limits should NOT
be presumed to apply.  I am unable to discern the logic by which Keith ends up
presuming public and occupational dose limits apply to a rare, "bullets flying past
your ear" situation.

        c.  But irrespective of the magnitude of any DU dose limit applicable in
a wartime situation, it was the soldier's government that asked the soldier to
fight and take on the additional risk of injury/exposure in the battlefield, if need be.
Therefore, such governments should endeavor to provide the appropriate
health care to those soldiers injured under such a soldier/government contract.
The generic problem that the U.S. government (and US Army) faces in this
DU issue is that while there appears to be no shortage of soldiers who have some
sort of clinically manifest injury/illness that they directly attribute to the Gulf War, the
biological mechanism of action by which inhaled DU may have caused their illnesses has yet
to be properly documented/proven.  The field of medicine must first attain a decent
understanding of the mechanism by which inhaled DU ends up causing clinically
manifest health difficulties in order to then estimate whether the specific
clinically manifest heath difficulties experienced by certain Gulf War soldiers are
directly attributable to DU exposure, with its sometimes overriding chemical effects
or its sometimes overriding radiological effects. 

        d.  As Colonel Daxon wrote:  "The measured airborne concentrations
from resuspension inside struck vehicles (worst case because of the confined areas)
were below the OSHA limits and NRC limits for continuous occupancy."  This implies
that IF the soldiers' clinically manifest health difficulties are due to DU exposure in
WARTIME, then our peacetime, occupational DU limits are way too high.

        e.  I would suggest that Keith try to aid in the resolution of this
Gulf War syndrome issue by endeavoring to determine, for example, whether
or not Dr. Rokke's clinically manifest health problems are directly attributable to DU
exposure.  Does exposure to even peacetime air concentrations of DU dust produce
lung scarring with consequent breathing difficulty (decrease in tidal volume, etc)?
Have similar problems become clinically manifest in UK uranium workers, etc.?

        f.  This whole Gulf War DU situation, in my opinion, can only hope to be resolved
when the medical community feels it understands the clinical signs/symptomology
associated with exposure to DU-laden dusts.  Making putative calculations of estimated
cancer mortality based on estimated internal dose does not meaningfully assist the medical
clinician who is confronted with Gulf War soldiers manifesting clinically real (non-cancer)
health difficulties.  Whether or not the soldier's difficulties are due to DU exposure hinges
almost totally on understanding and documenting the clinical signs/symptomology of
exposure to DU dusts.

Best regards  David  

DAVID W. LEE
Los Alamos National Laboratory
Radiation Protection Services, ESH-12
X-Ray/Source Control Team Leader
PO Box 1663, MS K483
Los Alamos, NM  87545
PH:   (505) 667-8085
FAX:  (505) 667-9726
lee_david_w@lanl.gov