Widespread use of depleted uranium weaponry by U.S. and British forces in Iraq could pose serious health and environmental risks to troops and residents, nuclear and medical experts warned.

Dr. Helen Caldicott, president of the Nuclear Policy Research Institute, an anti-nuclear research group, said the hazards of using the radioactive material included pollution and severe consequences for kidney function.

"They didn't blow up cities, but they polluted them forever," Caldicott said of U.S. and British forces in Iraq. "They have absolutely no right to be using radioactive weapons."

Some experts at the one-day conference on depleted uranium's health risks called for it to be banned in weapons.

Others seconded assurances by U.S. defense officials that the weapons do not pose an "unacceptable health risk" to U.S. troops.

Most of the scientists, physicians and specialists called for more study on the materials, and demanded a full accounting of its use, not only in the recent war in Iraq but also in the 1991 Persian Gulf War and in the NATO bombing of the former Yugoslavia in the 1990s.

Depleted uranium is left over from enriching uranium for use as nuclear fuel. It is used in weapons because its superior strength and density can stop conventional armor-piercing shells.

Ammunition with needle-like depleted uranium penetrators can punch through conventional armor.

It is far less radioactive than natural uranium and, at temperatures above 315 degrees Celsius, ignites on impact.

U.S. Defense Department officials and many experts contend that depleted uranium, because of its low radioactivity, poses no risk to the health of soldiers handling munitions made from it, or to civilians living in areas where those shells were used.

Thomas Cochran, of the environmental group Natural Resources Defense Council, said although the radiation danger was low, exposure should be kept to a minimum and sites should be cleaned up.

Hari Sharma, a retired chemistry professor from the University of Waterloo, Ontario, said studies of urine specimens from Gulf War soldiers showed evidence that depleted uranium had lodged in human tissue.

"As long as something is radioactive, you are going to do harm to human health," Sharma said.

Physicians in southern Iraq have documented a threefold increase in childhood cancers, and fivefold increase in birth defects since 1990, said Dr Thomas Fasy, of New York's Mt. Sinai School of Medicine, who met with Iraqi physicians and presented the research to the symposium.