For what it's worth, I wrote letters to the editors of both the Seattle P-I and the Tacoma News Tribune in response to articles that ran in each paper last week decrying the use of depleted uranium in military munitions. Now the great Instapundit has heard of the P-I story.

Here's my letter, sent last Friday:

To the Editor,

I agree with the article's implication that contamination of the ocean with radioactive material would alarm fishermen and consumers alike. However, I hope you will take the time to do further research on the actual level of danger to the public.

The article correctly states that depleted uranium remains radioactive for approximately 4.5 billion years. Basically, the time period you refer to is the radioactive half-life of the material. The half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay. After two half-lives, there will be one fourth the original sample, after three half-lives one eighth the original sample, and so on.

For example, Plutonium is one of the most highly radioactive materials on earth--so much so that it is not normally found in nature, but is created by man through atomic fission. Plutonium's half-life is approximately 24,000 years (Knapp, Brian, Nuclear Physics, 1996). The end of the decay process results in a material that is stable, like lead.

In fact, depleted uranium's long half life makes it useful for radiation shielding! Some DU applications include use in medical isotope casks, radioactive source shields, tank armor, and ammunition for the CIWS (AKA Phalanx) and the A-10 aircraft used by the Air Force and National Guard.

The real "danger" of DU is not radioactivity, but toxicity. Uranium is a heavy metal, like arsenic, cadmium, barium, zinc, lead and mercury. Given the small number of rounds fired during the tests you reported, the level of toxic exposure in a given area of the sea is virtually statistically insignificant. Ironically, the lead weights that fishermen use to hold down their baited hooks and nets are much more commonly deposited in the ocean environment than DU. Perhaps your next story can sensationalize that danger?

One of the best articles on the risks of exposure to DU is a recent study by the British Royal Society--the summary is all you need to read.