Depleted Uranium - FAQ
Sheet
Prepared by the Depleted
Uranium Follow-up Program
VA Maryland Healthcare
System, Baltimore Division
January 2000 (rev. January
2002)
1. What is depleted uranium
(DU) and how does it differ
from natural uranium?
Uranium is an element found
naturally in soil, water,
and mineral deposits. It is
a weakly radioactive
substance. It is composed
of 3 naturally occurring
isotopes (isotopes are atoms
that differ only in their
number of neutrons; they
have similar physical
properties), 238U, 235U, and
234U.
Depleted uranium is a
man-made by-product. It is
what remains after the more
radioactive isotopes, 234U
and 235U, are removed from
natural uranium in order to
make enriched uranium.
Enriched uranium, which
contains more radioactive
isotopes, is primarily used
as fuel in nuclear reactors.
The isotopes in uranium
occur in uranium and
depleted uranium in the
following concentrations:
Natural Uranium Depleted
Uranium
Isotope
Concentration of isotopes
Concentration of isotopes
234U 0.006% 0.001%
235U 0.72% 0.20%
238U 99.28% 99.80%
Relative
Radioactivity
1.0 0.6
As you can see, all uranium,
not just DU, is made up of
almost all 238U.
Natural and depleted uranium
differ only in their
radioactivity. Depleted
uranium is about half as
radioactive as natural
uranium. Their chemical
properties, however, are the
same. It is the chemical
properties that are
responsible for many of the
health effects of concern,
such as possible kidney
effects.
2. Why does the 24-hour
urine test measure total
uranium and not DU?
The 24-hour urine test
measures total uranium. A
total uranium count includes
DU plus any natural uranium
from the food you eat and
the water you drink. The
chemical properties of
uranium that may affect
health are related to
systemic body burden level,
or total uranium. Total
uranium is measured by the
total urinary uranium
concentration in a 24-hour
period.
3. Why do you use a
standardized measure instead
of the total measure?
In the past, some people
have tried to measure urine
uranium levels by just
looking at the total measure
of uranium present. This
method is misleading because
it does not take into
account how diluted or
concentrated the urine might
be. (For example, if
someone drank a large amount
of water during the testing
period, the urine would be
diluted.) To correct for
this problem, standardized
measures are used.
The word “standardized” on
the laboratory report means
that the reported values for
urine uranium are presented
in micrograms of uranium per
gram of urine creatinine, a
waste product always found
in urine. (A microgram is a
millionth of a gram. There
are about 30 grams in an
ounce). This method of
calculating the amount of
uranium corrects for how
diluted or concentrated the
urine is at the time of the
test. It allows one urine
sample to be more accurately
compared to another. The
recognized standard of
practice for biologic
monitoring is to use
standardized values.
4. Why isn’t the presence of
any uranium in the urine
considered abnormal?
Uranium is present in the
food we eat and the water we
drink. We are all exposed
to naturally occurring
uranium. The amount of
uranium in our urine is a
reflection of this natural
exposure. Therefore, all of
us will have some uranium in
our urine. The amount of
uranium taken in through
food and water is due to the
amount of uranium in the
specific areas where we
live. Some geographic areas
have higher concentrations
of uranium in the soil and
water than do others.
5. Is there a way to tell
how much of the uranium in
the urine is DU?
It is only possible to
determine how much of the
uranium present in the urine
is DU if there is enough
total uranium to be
detected. For samples with
total uranium levels below a
certain minimum level, it is
very difficult, if not
impossible, to accurately
measure the different
amounts of natural vs.
depleted uranium.
If a sample has a total
uranium content that is
greater than what we expect
to see as a result of
natural environmental
exposure, it is sent for
isotopic analysis to
determine how much of the
total uranium is DU.
6. What is isotopic
analysis and why is it
important?
Isotopic analysis is the
measurement of the different
components (isotopes) of
uranium. The three isotopes
making up uranium, 234U,
235U, and 238U, occur in
different proportions in
natural uranium compared to
DU (see question #1 of this
FAQ Sheet). Since all
uranium (both natural and DU)
is mostly 238U, it is the
ratio of the amount of 238U
to the amount of the other
isotopes (234U and 235U)
that tells us whether there
is any DU in the sample.
7. What health effects can
be expected from exposure to
DU?
Health effects are related
not only to the presence of
the uranium, but also to the
amount of time or duration a
person is exposed. It is
unlikely that there will be
long-term health effects in
humans after a single
exposure to uranium. It is
important to note that any
health effects are due to
the presence of the total
amount of uranium present,
not just the DU.
The primary health concern
is uranium’s chemical
toxicity, particularly its
effects on the kidney. To
date, there have been no
reports of differences in
kidney (renal) function
between the group exposed to
DU and the control group not
exposed to DU.
8. What is the cancer risk
from exposure to depleted
uranium?
Uranium miners and millers
are the two worker groups
who have been studied to see
the effects of long-term
exposure to natural
uranium. Although these
groups exhibit a higher than
normal incidence of lung
cancer, we know that they
have also been exposed to
radon, a decay product of
uranium. Radon is a known
carcinogen. The higher
rates of lung cancer are due
to the radon present in the
uranium mines.
9. But doesn’t uranium break
down into radon?
Any radioactive element is
subject to a decay of its
radiologic intensity over
time. It takes thousands of
years for uranium to break
down enough for radon to be
formed. Much of the radon
that miners were exposed to
was in the mines
themselves. In addition,
when DU is manufactured, the
radiologic decay “time
clock” is reset and starts
over. Since the DU used
during the Gulf War was made
in the past 50 years, radon
has not had enough time to
build up.
10. Who are the people
being followed at the
Baltimore VA Medical Center?
The Depleted Uranium
Follow-up Program at the
Baltimore VA Medical Center
is a clinical surveillance
program started in 1993.
The purpose of a clinical
surveillance program is to
follow a group of people
over time to see how their
health changes. In this
program, soldiers who were
in or on a vehicle when it
was hit by DU during a
friendly fire incident are
being followed.
In 1998, the Depleted
Uranium Follow-up Program
added another job to its
mission. The Program
coordinates the urine
uranium testing portion of
the Gulf War Registry
Examination for veterans and
the Comprehensive Clinical
Evaluation Program for
active duty personnel.
Program staff members report
the results of tests to
individuals and their
primary care providers
within VA and military
health care institutions.
It is the responsibility of
the individual’s primary
care provider to discuss
these results with them.
11. What health effects are
present in the Baltimore
group?
So far, few health effects
have been found. Soldiers
who still have DU shrapnel
fragments have a higher than
expected urine uranium
level. In 1997, there were
some subtle changes in
neuropsychological test
results. These changes are
evident only at the group
level. That is, we only see
these differences when we
compare the group with a
higher than normal urine
uranium value to the group
with a lower urine uranium
value. When looked at again
in 1999, these differences
between groups were no
longer there.
Soldiers with injuries and
those who still have
shrapnel have symptoms
associated with their
injuries. Otherwise, the
health measures of the
Baltimore participants is no
different from the health
measures of soldiers who
were in the Gulf War but not
exposed to DU. This
comparison group of soldiers
who were not exposed to DU
was examined in 1997.
One other blood measure of a
neuroendocrine hormone (prolactin)
was also elevated at the
group level in 1997 in the
high uranium group. This
did not appear to be of
clinical significance or to
have caused a change in
sexual function. In the
1999 evaluation, this
finding was no longer
present.
12. Can you estimate what
the urine uranium level was
8 years ago from the sample
taken today that is in the
normal range?
Any measure of uranium taken
at any given point in time
is a combination of what is
left from previous exposure
to uranium (from any source)
and from recent exposure
through food and water.
Most likely, the current
result represents what the
true value is. We can’t
assume that this value is an
amount left over from a
previous higher value.