[ RadSafe ] pyrophoric uranium considered nonessential

[Franta, Jaroslav]

>From the ANL Fact Sheet on uranium....  
Note especially the inhalation exposures of dogs to soluble uranium
compounds.

Jaro 
^^^^^^^^^^^^^^^^^^^


Human Health Fact Sheet 
ANL, October 2001
Uranium

What's in the Environment? 
Uranium is naturally present in all environmental media at very low
concentrations (a few parts per million). Higher levels are present in
certain areas, including those with natural uranium ores such as in the
southwestern United States. In its natural state uranium occurs as an oxide
ore, U3O8. Additional compounds that may be present include other oxides
(UO2, UO3) as well as fluorides, carbides or carbonates, silicates,
vanadates, and phosphates.
<SNIP>

.....and for DU:

Depleted uranium penetrators have a "sharpening effect" upon impact that
allows greater penetration through armor. Weapon testing shows that when a
depleted uranium round penetrates an armored vehicle, it may pass completely
through the vehicle or ricochet around and fragment inside the vehicle.
Metal fragments from the penetrator and the vehicle's hull can scatter
inside the vehicle, killing and injuring personnel, destroying equipment,
and causing secondary explosions and fires. As much as 70% of a depleted
uranium penetrator can be aerosolized when it strikes a tank. Aerosols
containing uranium oxides may contaminate the area downwind. Uranium metal
and oxide fragments may also contaminate the soil around the struck vehicle.
Tests of depleted uranium penetrators striking depleted uranium armored
vehicles have shown that most of the contamination will occur within 5 to 7
meters (16 to 23 feet) of the vehicle.
<SNIP>
On the battlefield, exposure to depleted uranium can occur several ways.
After impact with an armored vehicle, depleted uranium in the form of oxide
and metal fragments will contaminate the struck vehicle and the surrounding
area, especially if an explosion or fire occurs. Depleted uranium oxide can
be aerosolized, presenting an inhalation hazard to soldiers in the vicinity
or downwind of the struck vehicle. In addition, depleted uranium dust can be
resuspended in the air from soil contamination around the vehicle. Soil
contamination also can be ingested inadvertently from hand to mouth contact.
In another example of battlefield exposure, at least 36 soldiers in
Operation Desert Storm were reported to have wounds involving imbedded
depleted uranium fragments. (Many of these fragments were not removed
because the risk of surgery was judged to be too great.) Following combat,
maintenance and recovery personnel can be exposed to equipment contaminated
with depleted uranium. Dust containing depleted uranium can be resuspended
during recovery operations, posing an inhalation hazard. Spent depleted
uranium rounds and penetrators that were fired but missed their targets may
be scattered on the battlefield and can thus potentially lead to additional
exposures.
<SNIP>
The extent of chemical damage from exposure to a depleted uranium compound
depends on its solubility and the route of exposure. In most assessments,
only inhalation and ingestion are considered because although dermal
absorption of some soluble compounds (e.g., uranyl nitrate) is possible,
these exposures generally are not significant in association with industrial
emissions or environmental exposures. When soluble or moderately soluble
compounds such as uranyl fluoride (UO2F2) or uranium tetrafluoride (UF4) are
inhaled or ingested, some of the uranium enters the bloodstream and reaches
the kidney and other internal organs; thus, chemical toxicity is of primary
importance.
When insoluble compounds such as UO2 and U3O8 are inhaled, the uranium is
generally deposited in the lungs and can remain there for long periods of
time (months or years). The main concern from exposure to these insoluble
compounds is increased cancer risk from the internal exposure to
radioactivity. Ingested insoluble compounds are poorly absorbed from the
gastrointestinal tract, and so generally have low toxicity.
Available health effect criteria for acute and chronic uranium exposures are
provided in Tables 1 and 2, respectively, derived from animal studies. Only
limited data exist for human exposures.
<SNIP>

TABLE 2. Reference Levels for Chemical Effects of Chronic Uranium Exposures
<SNIP>
Inhalation 
Soluble compounds

(1) Reference Level 0.011 mg/m^3                
Derived - Based on route-to-route extrapolation of ingestion value (EPA
1996).

(2) Reference Level 0.0012 mg/m^3
Derived - Based on adjustments to occupational exposure limit (EPA 1992).

(3) Reference Level 0.0004 or 0.0003 mg/m^3
ATSDR (1999) - Based on intermediate duration (5 weeks) and chronic (1 year)
inhalation exposures of dogs to soluble uranium compounds.
----------

Soluble compounds include uranyl fluoride (UO2F2), uranyl nitrate
hexahydrate (UO2(NO3)2 x 6H2O), and uranium
tetrachloride (UCl4). Some insoluble compounds are uranium metal, uranium
dioxide (UO2), uranium trioxide (UO3),
and triuranium octaoxide (U3O8). Uranium hexafluoride (UF6) decomposes to
UO2F2 and HF in the presence of
moisture. Uranium tetrafluoride (UF4) is very slightly soluble. 
Source: ATSDR (1999).

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