LONDON, Jan 9, 2001 -- (Reuters) Scientists backed calls for more research into the health effects of uranium-tipped weapons on Tuesday but said it is unlikely they are the cause of poor health and leukemia among Balkan peacekeepers.

European members of NATO are demanding an investigation into depleted uranium (DU) ammunition and a possible link to so-called "Balkan Syndrome" after six Italian soldiers died of leukemia following exposure to the spent weapons while serving in the former Yugoslavia.

Cases of cancer have also been reported among soldiers from France, the Netherlands, Spain and Belgium.

"The diagnosis of leukemia in many of these people is very soon after the alleged exposure. Whilst you can never say never in science this does seems extraordinarily unlikely to be causal," Professor Eric Wright, an expert on radiation-induced leukemia at the University of Dundee, told Reuters.

SYMPTOMS CAN TAKE 10 YEARS TO SHOW UP

Leukaemia is a relatively rare cancer of the white blood cells. Like most cancers, scientists suspect people may have a genetic predisposition to the disease that makes them vulnerable to exposure to cancer-causing agents. The period between exposure to the development of symptoms is two to 10 years. According to Wright, all the scientific evidence for leukemia that has definitely been caused by radiation shows it needs a similar period of time to develop.

"My initial reaction is driven by biology. It is unlikely that one would see high numbers of leukemia one to two years after exposure to radiation."

Wright also said the Italian cluster of leukemia cases could be a statistical fluke that may not be due to any particular cause.

NATO and the World Health Organization insist there is no scientific evidence to link the illnesses to the controversial weapons, but Wright said there have not been many studies.

"I am not aware of any real radiobiological research in depleted uranium," he added.

MORE INFORMATION NEEDED ON EXPOSURE AND RISKS

Depleted uranium is a dense waste product of the natural uranium enrichment process. It is used to enhance the ability of the weapons to pierce armored vehicles.

When a uranium-tipped weapon hits an object it produces a vapor that is weakly radioactive but can be dangerous depending on the amount of exposure.

The United Nations says it has found evidence of radioactivity at eight of 11 sights tested in Kosovo after they were struck by NATO ammunitions with depleted uranium.

According to a preliminary assessment by the United Nations Environmental Program (UNEP) of the potential dangers of depleted uranium during the 1999 Kosovo conflict, kidney dysfunction is the main chemically induced effect of oral exposure to uranium in humans.

But the report added that soluble uranium could have contaminated the soil or migrated to the surface of ground water which could lead to human exposure.

"One of the problems is we don't know how high the exposures might be and whether the risks are incredibly small or just modest," said Professor Brian Spratt, chairman of the working group on depleted uranium of the Royal Society of British scientists.

"There is not a lot of evidence that these low levels of radiation that troops are likely to be exposed to cause leukemia," he added.

The academy of scientists announced plans on Monday to conduct an independent study into the possible health effects of depleted uranium. It also supported calls for further research and testing soldiers who had served in the Balkan and Gulf Wars.

"It is not impossible that there is a cause and effect relationship," said Wright.

"But if there is, the potential mechanism that underlies that relationship is one that we are not yet familiar with or could extrapolate from any of our existing knowledge."