At least 17 countries already have in their arsenals bullets made from depleted uranium (DU). Many - such as Israel, Turkey, Saudi Arabia, Kuwait, Taiwan - get them from the United States. England and France buy DU wholesale from the US. Russia now sells DU rounds on the open market.
Such proliferation has raised unanswered questions about the long-term health effects of the hard-hitting and controversial ordnance.
Is there a continuing health risk from DU fragments and particles for civilians in Iraq and Kuwait? And if the degree of danger to human health can't be nailed down, how should future use of DU be dealt with?
Several official bodies already take serious precautions. The United States Nuclear Regulatory Commission (NRC), for example, requires a license to handle or test-fire DU munitions. The US Army has 14 separate NRC licenses related to the substance. The Navy and Air Force each have one NRC "master materials" license.
Workers handling DU in the US must treat it as low-level radioactive waste. Disposal typically means the substance is locked into a 30-gallon canister, sealed with plastic, then sealed again inside a 55-gallon drum and, by law, buried in licensed underground dumps. Fine particles are mixed into concrete and locked into drums.
Definitive statements about DU's health risks to humans are not easy to make, scientists say.
"We don't know everything we'd like to know," says Ron Kathren, a physics professor and director of the US Transuranium and Uranium Registries in Richland, Wash. Attached to Washington State University, the registry has studied uranium and its effect on industry workers for 30 years.
"The reason people get panicky is because DU is radioactive, but [the battlefield dose] is so small that it never approaches chemical hazard," says Mr. Kathren.
Part of the problem with DU is public misperception, says John Russell, the associate director of the registries: "You say 'uranium,' and people think of the bomb. That's not the case here."
At the heart of the health debate is this question: Do small DU particles trapped in the body emit enough radiation over time - in the form of alpha particles - to cause physical harm?
Most of the concern is focused on dust particles left after a bullet is incinerated upon impact.
Carried aloft by the wind, the small particles can work their way into the human body, where the emission of alpha particles can be extremely damaging to cells, says Douglas Collins, a health physicist for 20 years and an NRC division director of nuclear material safety in Atlanta.
A 1990 study commissioned by the Army links DU with cancer and states that "no dose is so low that the probability of effect is zero." Dr. Asaf Durakovic, who was chief of nuclear medicine at the US Department of Veterans Affairs' medical center in Wilmington, Del., from 1989 until 1997, takes that a step further. Even the smallest internal alpha dose, he says, "is a high radioactive risk."
One safety memo, written by the US Army in 1991, says a single charred DU bullet found by US forces was emitting 260 to 270 millirads of radiation per hour. (A rad is a measurement of ionizing radiation absorbed into material.)
"The current [NRC] limit for non-radiation workers is 100 millirads per year," it noted. The limit for radiation workers would be some 30 times more.
DU's critics cite incidents to bolster their case against its use.
In 1992, for instance, a German scientist found a spent DU bullet in the Iraqi desert and was later arrested and fined by a Berlin court for "releasing ionizing radiation upon the public" when he brought it home.
"You're not playing with anything innocuous," says Leonard Dietz, a nuclear scientist who worked for 28 years at the Knolls Atomic Power Laboratory in New York.
In 1979, DU particles escaped from the National Lead Industries factory near Albany, N.Y., which manufactured DU penetrators. The particles traveled 26 miles and were noticed in a laboratory filter by Mr. Dietz. The factory was shut down in 1980 for releasing more than 0.85 pounds of DU dust into the atmosphere every month - a fraction of the 320 tons fired during the Gulf War.
"It's still hot forever," says Doug Rokke, a Pentagon DU expert until last year. "It doesn't go away, it only disperses and blows around in the wind."
THE British Atomic Energy Agency, at the behest of the Ministry of Defense in 1991, tried to quantify the risk. Based on an early estimate of just 40 tons of DU used during the Gulf War, it said that that amount could cause "500,000 potential deaths."
Recently declassified, its report says this purely theoretical calculation is "obviously not realistic" because it would require every single person to inhale similar quantities. But the sheer volume does "indicate a significant problem."
The Pentagon rejects that. "The problem is that all of that stuff has to be put into people. It physically can't happen," says Col. Eric Daxon, the radiological staff officer for the Armed Forces Radiobiology Research Institute. The possibility of DU causing serious health problems in Iraq, he says, is "exceptionally small, to the point where it should be absolutely at the bottom of the list."
Bernard Rostker, the Pentagon's special assistant for Gulf War illness, also sounds an all-clear. The Gulf War "is not an extraordinary nuclear event," he said. "This area [where DU was used], we would say, is free for any agricultural, industrial use, any personal use."
But Dr. Durakovic says those areas are still dangerous. Widespread use of DU, he told Congress in 1997, means that "the battlefields of the future will be unlike any ... in history."
The result is that "injury and death will remain lingering threats to 'survivors' of the battle for years and decades into the future," he testified. "The battlefield will remain a killing zone long after the cessation of hostilities."