January 13, 2001
By GINA KOLATA
A furor has been growing in Europe for weeks over contentions that
some allied troops contracted leukemia from exposure to depleted
uranium used in NATO ammunition in the Balkans, and that civilians
were put at risk by military testing.
But physicists and medical experts say it is biologically
impossible for depleted uranium to have caused the leukemia, and
they doubt that the metal caused any illnesses in Europe.
If the uranium was causing leukemia, it would presumably do so by
emitting radioactive particles that would damage the bone marrow.
But Dr. Frank von Hippel, a physicist who is a professor of public
and international affairs at Princeton University, said depleted
uranium was not much of a radioactivity hazard. It is what its name
implies depleted. It is what is left when the more highly
radioactive uranium 235 has been removed from its more abundant
atomic cousin, uranium 238.
Uranium 235 is used to fuel nuclear reactors and nuclear weapons.
But uranium 238 "is very weakly radioactive," Dr. von Hippel said.
Even if one assumes that there is a ton of depleted uranium dust
for every square kilometer in Kosovo, he said, its radiation would
be just one one-hundredth, or 1 percent, of the naturally occurring
level of radiation in the environment. "So this is not a very
significant hazard," he said.
Moreover, uranium 238 emits alpha radiation, said Dr. Michael
Thun, who directs epidemiological research for the American Cancer
Society, and that radiation does not even penetrate the skin. The
radiation that is known to cause leukemia, gamma rays and X-rays,
passes through the body and reaches the marrow, damaging cells and
giving rise to disease.
Uranium is a heavy metal, and as with all heavy metals it can be
toxic. When it enters the body, it lodges in the kidney, which it
can damage. But studies of a handful of gulf war soldiers who were
hit by friendly fire and left with fragments of uranium 238 in
their bodies have been reassuring, said Dr. Charles Phelps, the
provost at the University of Rochester and a member of an Institute
of Medicine committee that reported on the problem last year.
Uranium 238 clearly was leaching into the soldiers' kidneys, he
said. "They had very high levels of uranium salts in their urine,"
Dr. Phelps said. "But there is no evidence of kidney disease."
Depleted uranium has long been used to strengthen weapons because
it is extremely dense, 65 percent denser than lead. A weapon made
with depleted uranium can penetrate even steel-armored tanks. It
also ignites when it hits.
"When you fire into or through steel, it actually vaporizes the
steel," said Dr. Bruce Kelman, a toxicologist who is a president of
GlobalTox, a business in Seattle that studies industrial hygiene
and toxicology for governments and industry. "You get a mist of
depleted uranium and steel."
Dr. von Hippel said that although the metal was radioactive, "its
half- life is 4.5 billion years, which is, by coincidence, the age
of the solar system." That means that it would take 4.5 billion
years for half the uranium 238 atoms in a chunk of the metal to
decay by emitting radioactive particles.
Because the radiation does not go to the marrow, it is
biologically impossible for depleted uranium to cause leukemia,
said Dr. John Boice, scientific director of the International
Epidemiology Institute, a research concern in Rockville, Md., and
an expert on radiation and cancer.
"To get leukemia," Dr. Boice said, "you need to get the radiation
to the bone marrow. And uranium 238 will not get to the bone
marrow."
Dr. Bruce Boecker, a radiation biologist at the Lovelace
Respiratory Research Institute in Albuquerque, said, "I don't think
it causes leukemia at all."
If a person inhales uranium 238, it lodges in the lungs where, in
theory at least, it might cause lung cancer or it might travel to
the lymph nodes and theoretically cause lymphoma.
But Dr. Boice said extensive studies of workers who processed
uranium, some exposed to high levels by breathing uranium dust, did
not find any association between inhaling uranium 238 and
developing lung cancer or lymphomas.
Lymphomas do not seem to be caused by radiation in any case, Dr.
Boice said. But lung cancer can be, although the study of uranium
workers did not find that.
"We would not have been surprised at these high levels to find a
link with lung cancer," he said. "But there was none."
Dr. Thun of the cancer society said even though science might not
support the idea that depleted uranium is causing health problems
in Europe, that does not mean that scientists should turn their
backs on the concern. People think they have leukemia because they
were exposed to depleted uranium, and those fears will not easily
go away.
"What I've been telling people," Dr. Thun said, "is that we need a
systematic, open and prompt evaluation of the situation, which
would involve determining the cases of leukemia, determining the
age of the patients, the diagnosis, and the type of leukemia.
"In most cases, one of the major reasons for doing a systematic
evaluation is to determine what is actually going on and to provide
some real information, rather than rumors."
Copyright 2000 The New York Times Company