by CKR
This post is based on an e-mail exchange. I thought the information might be worth sharing more generally.
Q: This is a piece about the military use of DU in Afghanistan and Iraq. I've read two or three articles about it, but am no position to verify the accuracy of the claims made in this article…help me better understand the accuracy or inaccuracy of the claims in this article.
A: The article is an example of what is getting to be the standard case against depleted uranium (DU). It's a mixture of some truth with a lot of exaggeration. Well done as rhetoric, less so as fact.
DU is a heavy-metal poison, dangerous in the same ways that, say, lead and cadmium from mining waste are dangerous.It is particularly damaging to kidneys and has some affinity for bones that puts it into the body to continue its toxic effects. It's not something you want to ingest.
However, DU is NOT radiologically dangerous. The long half-life means that there are very few disintegrations per minute. A half-life represents a constant number of atomic disintegrations. A very long half-life means that relatively few disintegrations take place per unit time and therefore there is not much radiation. The chemical dangers, on the other hand, persist forever.
There is a certain amount of natural radioactivity on earth, and there was more while humans were evolving. Because humans evolved in a radioactive world, they probably have some innate defenses against cell damage from radioactivity. At low doses, the effects of radiation are not well known. The reason for this is that the effects are so small that impractically enormous numbers of people or animals would have to be studied.
It’s best to minimize exposure to radiation, but we can’t always do that. Our houses may be built on soil and rock that contain natural uranium, which is more radioactive than DU. We are constantly subject to cosmic rays, those of us at high altitude more so than those at sea level. Bananas and the human body contain potassium-40. If you sleep with someone, you are getting a higher dose of radiation than if you sleep alone!
DU is attractive for ammunition for several reasons. The US government owns a lot of it. It’s what is left over after the uranium-235 has been removed for reactors and nuclear weapons. It’s much denser than lead (18.7 grams/cc versus 11.4) and therefore hits harder. It also tends to burst into flame when it fragments in air, particularly when it can react with steel, so it’s good for piercing armor.
Lead is also a heavy-metal poison and an undesirable element of soil. The big differences between the two are the tendency of uranium to burst into flame and that it becomes more soluble in soil. Breathing the vapor from flaming uranium ammunition brings it into the body in a way that allows it to be absorbed readily. The fine particles probably settle out quickly, but they are probably in a form that allows the uranium to be mobilized by water and taken up by plants.
The focus on DU detracts from the more basic issues. We might consider the damage done by a doctrine of preventive war, for example. Spreading DU around isn’t a good idea. Spreading lead around isn't much better. But many, many more people are killed and maimed directly by the actions of war.
Many thanks to JW and LS for asking the questions.