Sunday, September 07, 2003

U and you

A day or so ago Glenn Reynolds posted about depleted uranium (U), which has been a bee in many bonnets for some time. I'm not naive enough to think that the issue will go away, because too many professional liars find it convenient. But I've cast pearls before swine before, so what follows is some information about uranium in the environment, from Nature's Building Blocks by John Emsley.

The fact is that uranium really isn't that uncommon. It's alleged to be the reason for the continuing heat in the earth's core, which may in fact be a huge reactor. Its decay is the source of radon which can concentrate in homes (you know, the ones that are too tightly sealed because they're trying to save energy so we'll quit building nuclear power plants). Just ask this guy, whose house was so full of radon that he was contaminating his work site at the Limerick nuclear power plant in PA (the link is a PDF several pages long, but it's informative and probably contrary to your expectations).

And this uranium is primordial - it was there long before there were bomb tests or any other anthropic means of mass distribution of radioactive isotopes. Every life form on the planet has been exposed to it from day 1, so every life form inherently can deal with radiological impacts to greater or lesser degrees. And the variance is such that tree-huggers in Colorado will get more dose in their lifetimes just from living there than I ever did in a 10 year career working at nuclear power plants (and that includes trips into the drywells dressed up in rubber sucking air through a tube).

OK, just how common is it? In seawater it's about 3 parts per billion, and in the earth's crust it's about 2 ppb. It's more common than silver and mercury combined.

Is uranium toxic? Sure, if you get enough of it in the right places. But a little doesn't hurt, and you're already eating 1-2 micrograms of it daily. In excess it can mess up your kidneys by forming salts that will block its tubules. The soluble forms can be absorbed through the skin but are also readily excreted. If inhaled it is bad for your lungs, but then it's so dense that it's hard to get the stuff airborne.

So if you're around the dust for a while you might suffer the above? Not necessarily. You don't have to look far for examples - consider Nobel laureate Marie Curie and her husband Pierre. This woman worked with radioactive substances long before there was any concept of industrial hygiene:
Sometimes they could not do their processing outdoors, so the noxious gases had to be let out through the open windows. The only furniture were old, worn pine tables where Marie worked with her costly radium fractions. Since they did not have any shelter in which to store their precious products the latter were arranged on tables and boards. Marie could remember the joy they felt when they came into the shed at night, seeing "from all sides the feebly luminous silhouettes" of the products of their work. The dangerous gases of which Marie speaks contained, among other things, radon - the radioactive gas which is a matter of concern to us today since small amounts are emitted from certain kinds of building materials. Wilhelm Ostwald, the highly respected German chemist, who was one of the first to realize the importance of the Curies' research, traveled from Berlin to Paris to see how they worked. Neither Pierre nor Marie was at home. He wrote: "At my earnest request, I was shown the laboratory where radium had been discovered shortly before.... It was a cross between a stable and a potato shed, and if I had not seen the worktable and items of chemical apparatus, I would have thought that I was been played a practical joke."

They did suffer health effects:
In actual fact Pierre was ill. His legs shook so that at times he found it hard to stand upright. He was in much pain. He consulted a doctor who diagnosed neurasthenia and prescribed strychnine. And the skin on Marie's fingers was cracked and scarred. Both of them constantly suffered from fatigue. They evidently had no idea that radiation could have a detrimental effect on their general state of health. Pierre, who liked to say that radium had a million times stronger radioactivity than uranium, often carried a sample in his waistcoat pocket to show his friends. Marie liked to have a little radium salt by her bed that shone in the darkness. The papers they left behind them give off pronounced radioactivity. If today at the Bibliothèque Nationale you want to consult the three black notebooks in which their work from December 1897 and the three following years is recorded, you have to sign a certificate that you do so at your own risk.
The dose rates she received had to have been astronomical. And as a bonus, she was hounded by the French press for an alleged affair and she suffered from anti-Semitism without even being Jewish. But this frail woman later had a healthy child and died in 1934 at age 67.

There's no question that having the DU around increases the amount of radiation in the vicinity. But it's interesting to note that the complaints never mention actual dose rates - they just say the rates are X% greater than "background". It makes the numbers look more impressive to be sure, but IMO those truly concerned with dose rates would present the impact in those terms instead rather than just "increases in background". It makes quite a difference - the two are related, but much more loosely than you might suspect, and in a way that makes the DU sound thousands of times worse than it is.

So forget about the DU already. And for extra credit, smack the next guy who tries to make an issue out of it.

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