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Thursday, May 1, 2003



Radioactive fallout courtesy of U.S.

In 1789, a German chemist, Martin Heinrich Klaproth, announced that he had discovered a new element in the dull black mineral pitchblende. He named it after the planet Uranus, itself discovered only eight years earlier.

Little interest was shown in uranium for more than 100 years, until in 1896 the French physicist Antoine Becquerel found that it caused a sealed photographic plate to become exposed, a phenomenon that Marie Curie, a young doctoral student from Poland working in Paris, named "radioactivity."

Curie found that pitchblende contained two further new elements. Working with her husband, Pierre, the Curies announced the discovery of polonium in 1898 ("from the name," they wrote in their paper, "of the original country of one of us."). Showing dedication to match anything seen in science, the Curies spent a further four years isolating another new, radioactive element from pitchblende: radium. But it was the element discovered by Klaproth, the dense metal uranium, that would become the most sought after and have the greatest historical impact.

The uranium found naturally in pitchblende is in two forms: uranium-235 and uranium-238 (the different numbers refer to the number of neutrons in each atom). Uranium-235 is far more radioactive. It is the one that the governments of the United States and Germany raced to extract during World War II, and is the one that was used to make the nuclear bombs that were dropped on Japan. It's what fuels nuclear power stations and what terrorists around the world would love to get their hands on. When the metal is composed of mainly uranium-235, it is said to be "enriched."

The other isotope, uranium-238, is what is left over, and is known as "depleted" uranium (though it still contains small amounts of uranium-235).

Despite its derogatory-sounding name, depleted uranium is no namby-pamby element. It is nearly 2.5 times more dense than steel and 1.7 times more dense than lead. It is this immense hardness that makes it attractive to the military: Shells tipped with uranium make short work of Iraqi tanks.

But its use is controversial. On impact, the uranium tips of shells disintegrate and ignite. DU shrapnel becomes embedded in anything nearby: people, buildings, soil; uranium oxide dust is spread into the air. The bombs dropped on a restaurant in Baghdad where Saddam Hussein was thought to be contained several tons of DU.

In the first Gulf War, in 1991, the U.S. and Britain fired around 350 tons of DU at Iraqi tanks. This time around, an estimated 1,000 to 2,000 tons has been used. But since 1991 there has been an increase in cancers and birth defects in Iraq, and many doctors put the blame on DU-contaminated farmland.

There is also a growing suspicion among scientists that DU is more dangerous than it would appear to be in theory. DU is only weakly radioactive, but it is genotoxic, meaning that it chemically damages DNA, and it causes genes to be switched on that shouldn't be. DU dust that is inhaled increases the danger from radiation. The chemical toxicity combined with radioactivity might be the reason for the rise in cancers in Iraq.

A recent study on the possible effects of DU by The Royal Society, the U.K. national academy of science, concluded: " There is a possibility of damage to DNA due to the chemical effects being enhanced by the effects of the alpha-particle irradiation."

The report also stated that some soldiers might suffer kidney damage and an increased risk of lung cancer if they breathe in substantial amounts of DU dust.

Last month the British defense secretary, Geoff Hoon, denied that DU was a health risk, but last week The Royal Society challenged that view and urged the Ministry of Defense to publish details of where and how much DU was used.

"It is highly unsatisfactory to deploy a large amount of a material that is weakly radioactive and chemically toxic without knowing how much soldiers and civilians have been exposed to it," said Brian Spratt, chairman of the society's working group on DU.

"It is only by measuring the levels of DU in the urine of soldiers that we can understand the intakes of DU that occur on the battlefield, which is a requirement for a better assessment of any hazards to health. It is vital that this monitoring takes place and that it takes place within a matter of months."

The Royal Society recommended that milk and water samples in Iraq should be monitored for DU.

"The question of who carries out the initial monitoring and clean-up is a political rather than scientific question," Spratt said. "Monitoring, however, is likely to be a long-term task, spanning many years, so it is vital that Iraq acquires the capabilities to undertake this itself.

"The coalition needs to acknowledge that depleted uranium is a potential hazard and make inroads into tackling it by being open about where and how much depleted uranium has been deployed."

Spratt added: "We also need to know the exposures of Iraqis living in any residential areas where DU munitions were deployed. We believe that exposures to DU will be low for most individuals, but we need to take measurements.

"Fragments of DU penetrators are potentially hazardous, and a recent Royal Society study recommended that they should be removed, and areas of contamination around impact sites identified, and where necessary made safe."

Uranium-238 has a half-life of 4.46 billion years. This isn't a problem that's going to go away soon.

Rowan Hooper welcomes comments at rowan.hooper@tcd.ie

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