Answer to Question #746 Submitted to "Ask the Experts"

Q

How are bullets made by depleted uranium, and what reactions do they cause when they enter into contact with the ground and with humans?

A

Because of its very high density—nearly twice that of lead—and certain
other properties, depleted uranium is used in certain kinds of
munitions because of its ability to penetrate heavily armored vehicles
such as tanks and armored personnel carriers. Depleted uranium (DU) is
not used in small cartridges or bullets for rifles or machines guns but
alloyed DU is used in the 25, 105, and 120 millimeter (mm) kinetic
energy cartridges used primarily as antitank munitions. DU is also a
component in some tank armor and sometimes used as a catalyst for land
mine systems.



Since depleted uranium is weakly radioactive, the public has been
concerned about the possiblility of adverse health effects from DU. DU
is a heavy metal, and like all heavy metals such as mercury and lead,
is toxic. However, except in certain very unusual situations, it is the
chemical toxicity and not the radioactivity that is of concern. And,
from a chemical toxicity standpoint, uranium is on the same order of
toxicity as lead. Largely from work with animals along with a few
instances in which humans inhaled very large amounts of uranium, the
chemical toxicity of uranium is known to produce minor effects on the
kidney, which in humans who have suffered large acute exposures have
been transitory and wholly reversible. Because depleted and natural
uranium are only weakly radioactive, radiological effects from ingested
or inhaled uranium have not been detected in humans.



Human experience with uranium has spanned more than 200 years. In the
early part of the twentieth century, uranium was used therapeutically
as a treatment for diabetes, and persons so treated were administered
relatively large amounts of uranium by mouth. Tens of thousands of
persons have worked in the uranium industry over the past several
decades, and have been followed up and studied extensively as have
populations in Canada and elsewhere who have high levels of uranium in
their drinking water. Results of these studies have not revealed any
ill health in these populations that is attributable to the intake of
uranium. This is not surprising, as the risk from the radiation dose
from uranium is far overshadowed by its potential chemical toxicity,
and intakes of uranium of sufficient magnitude to produce chemotoxic
effects are unlikely in and of themselves. Any such effects from
ingestion or inhalation of uranium would likely manifest themselves
first in the form of minor effects associated with the kidneys.
That military personnel and others who may have had contact with
depleted uranium from munitions are suffering from various illnesses is
not in dispute. That their illnesses are attributable to their exposure
to uranium is very, very unlikely.
Health physicists are deeply concerned with the public health and
welfare, and as experts in radiation and its effects on people and the
environment, are quite aware that something other than exposure to
uranium is the cause of the illnesses suffered by those who have had
contact with depleted uranium from munitions. A truly enormous body of
scientific data shows that it is virtually impossible for uranium to be
the cause of their illnesses. Despite this body of scientific data to
the contrary, misguided or unknowing people continue to allege that the
depleted uranium, and specifically the radioactivity associated with
the depleted uranium is the cause of these illness. This is indeed
unfortunate, for health physicists and other scientists and physicians
already know that depleted uranium is not the cause of these illnesses
and thus any investigations into the cause of these illnesses should
focus on other possible causes.




If we are to offer any measure of relief or solace to these suffering
people, and to gain some important additional knowledge of the cause of
their illness, we should not waste our valuable and limited energies,
resources, and time attempting to point the finger at depleted uranium
as the culprit, when it is already known that uranium is almost
certainly not the cause of the problem.
With respect to reactions with the soil, in time depleted uranium will
likely leach into the soil and become mixed with it. It will for all
practical purposes be chemically indistinguishable from the natural
uranium that is already present in the soil all over the earth. One
could create all kinds of scenarios, but probably the best way to think
about DU in the soil is to compare it with lead. Because lead and
uranium are so similar from a toxicological standpoint, the concerns
are about the same.



Ronald L. Kathren, CHP

Professor Emeritus
Washington State University