Dear Sarah,
I think it is very important to ask several questions about DU exposures when talking with those who say no danger exists.
1. Is there evidence of inhalation of ceramic particles? The chemical and radiological danger from insoluble ceramic particles is quite different from that of soluble particles. Insoluble particles can stay in the lung and then elsewhere in the body for many years. Soluble particles can be expelled by the body within 1-2 days. Also, inhalation is the primary danger; if insoluble particles are ingested they go through the intestinal tract without being absorbed. You recall that when a DU round burns, between 40-70% is oxidised at such a high temperature that it becomes a glass or ceramic.
2. In fact the toxicology of inhaled ceramic particles is incomplete. There is no evidence, in other words, that it is NOT capable of damaging lungs, lymph nodes, brain tissue, etc. Further epidemiological studies need to be done. What is known is that it stays in the body for many years, and that during this time particles irradiate surrounding cells.
3. Ask your friend whether he was referring to internal or external doses. Externally, one could hold a DU round for quite a while before experiencing a skin burn - I have heard estimates from scientists of several weeks. Internally, the alpha emissions are extremely damaging to cells and cellular structures. The difference is an easy one to comprehend. If you sit next to a fire, the burning coal puts out an amount of energy which is comfortable; if you pick up a red coal and eat it, the same amount of energy will have a markedly different effect. Often radiological authorities confuse the public by making specious comparisons to external radiation, e.g., "it's no more dangerous than a long trip on an airplane" which exposes you to external cosmic radiation. However, internal exposures are another matter altogether. The ICRP has created mathematical estimates for the added risk factor from internal exposures, called the RBE, or the Relative Biological Effect. This is the number by which external risks are to be multiplied to give an idea of internal risks. However, these mathematical estimates are based upon a limited number of studies, some of which are not at all relevant to long-term internal exposures.
4. Ask your friend if he/she is aware that the DoE has admitted that some DU stores are contaminated by minute amounts of plutonium and other transuranics; this can change the expected dose.
5. Ask your friend if they are aware of the current controversy about low dose exposures. I have spoken to scientists who believe that current risk estimates being promulgated by the ICRP, IAEA, NRPB, etc. are between 100-10,000 times too low. The whole history of the development of these radiation risk estimates is suspect, yet internationally the nuclear industry and radiological protection officers rely upon them. The scientists I spoke to were extremely skeptical of the way they have been developed. They say that if you use several recent empirical studies, the risk estimates for cancer and opther radiological effects are too low. One said by a factor of 100x and the other said by a factor of 10,000x. Either way, a simplistic statement that "DU is not dangerous radiologically" needs to be picked apart. Futhermore, some studies suggest that exposure to low levels of radiation may actualy be more dangerous than medium exposures, as the cells and cellular structures, like DNA, are damaged, but still able to reproduce in a damaged state; with higher exposures, the cells are simply killed outright.
5. The traditional response from both the DoD and MoD is that the radiological effect of soluble uranium is less dangerous than the heavy metal effect. This is true. The heavy metal effect is similar to that from lead or mercury or other toxic metals, and can damage kidneys, liver, etc. [Lead paint and leaded petrol were banned because of their effects on those exposed.] Even on this count DU may be considered a kind of chemical weapon. However, the effect for insoluble uranium is different, as it stays in the body several years, thus dramatically increasing the overall radiological exposure.
Cat
CADU