Hawaii Health officer Dr. Lorin Pang (US Army Medical Corps retired) testifying as a citizen before the 2007 Hawaii Senate said this about Depleted Uranium: (This guy is a medical doctor, not a metallurgist. In most of this he is not testifying about the medical effects, he is testifying about the metallurgy.)
The health effects of depleted uranium (DU) weaponry are complex and at best unknown. (He is saying that he doesnt know anything about the health effects of DU. He should leave it at that.) . When DU is fired at high velocity the metal burns when traveling and on impact with metal targets. (DU does not catch on fire when traveling through the air. The melting temperature is over 2000F)(It melts as it passes through dense target material)The explosive burning is at very high temperatures creating a variety of chemical compounds as well as elemental metal particles. (He learned this at medical school?) In general the heavier metal particles settled quickly around the target zone but the finer, lighter uranium oxides (produced by burning) and molecular uranium nanoparticles can become airborne and travel for miles from the site. (This is pure speculation with no basis in fact.)These compounds can be inhaled by those exposed to the plume. (Those exposed to the plume are dead because they have been incinerated. This is a weapon. My guess is that that they are not worried about exposure to Uranium Oxides.) During site clean-up settled particles can again become airborne. The binding to soil components and leaching into ground water is complex and not well understood. (The only thing that is clear from this explanation is that he does not understand the interaction between a projectile and a target.)(He also offers not understanding about the corrosion process of any of these metals or alloys left exposed to the environment over time.) (If he does, it is not clear here.)
Since he is doing plenty of speculation, I think that I will do a little of my own. Tracers are pyrotechnic rounds that have a hollow base on the end of the round that is filled with something like Mg. The external metal parts of any rounds do not catch on fire. The light is produced by the pyrotechnic parts that are added to the rounds. DU does not burn on the way to a target as the good doctor imagines. DU, upon impact with a dense material such as steel, melts its way through the target. It sluffs off material as it passes through the target material and is said to be self sharpening—hence the penetration power. Similar rounds that are alloys of Nickel, Cobalt, Tungsten and other things, just go through this alloying process as they crunch their way through the target. DU, however, has the interesting property of being pyrophoric. This is the only reason that people who are opposing the DU rounds have any credibility, however small. For the millionth of a second or so that it is inside the target material, I doubt if anyone understands the metallurgy, but it is clear when it exist the material on the inside of the vehicle, the small Uranium particles in the melt catch on fire as they hit the air and ignites anything burnable in the vehicle. The projectile is most likely used up in the process and all the products formed by the round and the metal in the target are going to be contained in the vehicle. That is, it probably will not penetrate the other side. My guess is that most or all of this will be solidified droplets or splatters will be contained inside the vehicle. If the round ignites ammunition in the vehicle and the vehicle explodes, that will scatter some of the solidified droplets around the site. Test vehicles are not loaded with explosives, so what goes in should stay in the vehicle. A DU round is not just Uranium. It is an alloy of other elements such as Mo, W, Ti and who knows what else. The alloy is probably proprietary to some company. The droplets are going to be all those elements mixed with Fe and whatever alloying elements in the vehicle that gets melted into the mix. A lot, if not all, of the DU is probably encapsulated by the process which is an alloy generating process. There is a possibility that the pyrophoric flash that ignites the fire will produce oxides. There are probably test results from that by the pound.
This is not the fairy tale that Dr Pang imagines, where from the moment of firing a flaming round streaks across the sky emitting radioactive products which are immediately carried to the nearest population center by the winds of fate. Well, maybe that is too critical. Lets just say, if the thousand tons that was used in the Iraq war was matched by testing at PTA, they would have an argument. Some oxides are going to be formed, and some will probably get into the environment. The quantity is the issue. Things that they are not considering is the fact that what goes into an armored vehicle will stay in the vehicle. That can be towed off and properly disposed of in a controlled test. In that case probably nothing would go into the environment. Also, though the military tend to lie about everythingthey are probably not using DU at PTA. Cost is the reason. In test firings, the aiming part is the concern. If the gunner can hit the target, that is all that they need for training. They dont want to blow up the target, because they just have to go get another one.
While all the uranium compounds share a common risk of uranium radiation, each compound also has specific toxicity, distribution, metabolism and clearance within the body depending on its chemical composition and size. Inhaled uranium oxides can bind to the lung for years while nanosized particles can penetrate and affect many tissues on a cellular level. While alpha particles are relatively safe outside of the body (lack of penetrating power) when internalized they are the most dangerous form of radiation.
Uranium miners run this sort of risk. Like coal miners, they develop some serious health problems over time. Coal is not radioactive, but coal dust is dangerous when it collects in the lungs. Any kind of dust is dangerous when it collects in the lungs. The DU round is probably 99%+ U238 and other alloying elements. When you include those materials from the target which will be the lions share of materials, it would be difficult to find anything radioactive from a DU strike. The amount of U234 and U235 is miniscule and will be alloyed with all of the other materials on the site. U238 is probably less radioactive than naturally occurring Uranium in a mine. Having worked with DU in laboratories and knowing the metallurgy of the material, I would say that detecting radiation by flying over the site where a tank had been recently hit with DU rounds would be impossible. Anything metal found on the site of a strike will not be dangerous. Most oxides left over from the fires started by DU will not be a problem either since most of the products will be from burned things that came with the vehicle. The small amount of Uranium Oxides are toxic and radioactive. But like I say they will probably stay in the vehicle. Only massive use would be a problem and I doubt if they have been used at all.