FACT SHEET
Depleted Uranium
1. What is Uranium?
Uranium (chemical symbol U) is a naturally occurring radioactive element. In its pure
form it is a silver-coloured heavy metal, similar to lead, cadmium and tungsten. Like
tungsten it is very dense, about 19 grams per cubic centimetre, 70% more dense
than lead. It is so dense a small 10-centimetre cube would weigh 20 kilograms.
The International Atomic Energy Agency (IAEA) defines uranium as a Low Specific
Activity material. In its natural state, it consists of three isotopes (U-234, U-235 and
U-238). Other isotopes that cannot be found in natural uranium are U-232, U-233, U236 and U-237. The table below shows the fraction by weight of the three isotopes in
any quantity of natural uranium, their half lives, and specific activity. The half life of a
radioactive isotope is the time taken for it to decay to half of its original amount of
radioactivity. The specific activity is the activity per unit mass of a particular
radionuclide and is used as a measure of how radioactive a radionuclide is. It is
expressed in the table in becquerels (Bq) per milligram (1 milligram, mg, = 0.001
grams). An activity of one becquerel (Bq) means that on average one disintegration
takes place every second.
Isotope
Relative abundance
Half life
Specific activity
by weight
(years)
(Bq mg-1)
U-238
99.28%
4510000000
12.4
U-235
0.72%
710000000
80
U-234
0.0057%
247000
231000
The activity concentration arising solely from the decay of the uranium isotopes (U234, U-235 and U-238) found in natural uranium is 25.4 Bq per mg. In nature,
1
FACT SHEET
uranium isotopes are typically found in radioactive equilibrium (i.e. the activity of
each of the radioactive progeny is equal to the activity of the uranium parent isotope)
with their radioactive decay products. Decay products of U-238 include thorium-234
(Th-234), protactinium-234 (Pa-234), U-234, Th-230, radium-226 (Ra-226), radon222 (Rn-222), polonium-218 (Po-218), lead-214 (Pb-214), bismuth-214 (Bi-214), Po214 Pb-210 and Po-210. Decay products of U-235 include Th-231, Pa-231, actinium227 (Ac-227), Th-227,Ra-223,Rn-219, Po-215, Pb-211, Bi-211 and thallium-207 (Tl207).
Isotopes of natural uranium decay by emitting mainly alpha particles. The emission
of beta particles and gamma radiations are low. The table below shows the average
energies per transformation emitted by U-238, U-235 and U-234.
Average energy emitted per transformation
Isotope
(MeV Bq-1)
Alpha
Beta
Gamma
U-238
4.26
0.01
0.001
U-235
4.47
0.048
0.154
U-234
4.84
0.0013
0.002
2. What are the existing levels of uranium in the environment?
Uranium is found in trace amounts in all rocks and soil, in water and air, and in
materials made from natural substances. It is a reactive metal, and, therefore, it is
not present as free uranium in the environment. In addition to the uranium naturally
found in minerals, the uranium metal and compounds produced by industrial
activities can also be released back to the environment.
2
FACT SHEET
Uranium can combine with other elements in the environment to form uranium
compounds. The solubility of these uranium compounds varies greatly . Uranium in
the environment is mainly found as a uranium oxide, typically as UO2, which is an
anoxic insoluble compound found in minerals and sometimes as UO 3, a moderately
soluble compound found in surface waters. Soluble uranium compounds can
combine with other chemical elements and compounds in the environment to form
other uranium compounds. The chemical form of the uranium compounds
determines how easily the compound can move through the environment, as well as
how toxic it might be. Some forms of uranium oxides are very inert and may stay in
the soil for thousands of years without moving downward into groundwater.
The average concentration of natural uranium in soil is about 2 parts per million,
which is equivalent to 2 grams of uranium in 1000 kg of soil. This means that the top
metre of soil in a typical 10 m ´ 40 m garden contains about 2 kg of uranium
(corresponding to about 50,000,000 Bq of activity just from the decay of the uranium
isotopes and ignoring the considerable activity associated with the decay of the
progeny. Concentrations of uranium in granite range from 2 parts per million to 20
parts per million. Uranium in higher concentrations (50 - 1000 mg per kg of soil) can
be found in soil associated with phosphate deposits. In air, uranium exists as dust.
Very small, dust-like particles of uranium in the air are deposited onto surface water,
plant surfaces, and soil. These particles of uranium eventually end up back in the soil
or in the bottom of lakes, rivers, and ponds, where they mix with the natural uranium
that is already there. Typical activity concentrations of uranium in air are around 2
µBq per cubic metre. (UNSCEAR 2000).
Most of the uranium in water comes from dissolved uranium from rocks and soil; only
a very small part is from the settling of uranium dust out of the air. Activity
concentrations of U-238 and U-234 in drinking water are between a few tenths of a
mBq per litre to a few hundred mBqs per litre, although activity concentrations as
3
FACT SHEET
high as 150 Bq per litre have been measured in Finland (UNSCEAR 2000). Activity
concentrations of U-235 are generally more than twenty times lower.
Uranium in plants is the result of its absorption from the soil into roots and other plant
parts. Typical activity concentrations of uranium isotopes in vegetables are slightly
higher than those found in drinking water. The range of activity concentrations of U238 measured in grain and leafy vegetables is between 1 mBq per kg and 400 mBq
per kg and between 6 mBq per kg and 2200 mBq per kg respectively, while activity
concentrations of U-235 are 20 times lower. Activity concentrations in root
vegetables are generally lower (UNSCEAR 2000).
The uranium transferred to livestock through ingestion of grass and soil is eliminated
quickly through urine and feces. Activity concentrations of U-238 measured in milk
and meat products around the world are in the range of 0.1 mBq per kg to 17 mBq
per kg and 1 mBq per kg to 20 mBq per kg respectively, with activity concentrations
of U-235 more than 20 times lower (UNSCEAR 2000).
3. What is Depleted Uranium (DU)?
In order to produce fuel for certain types of nuclear reactors and nuclear weapons,
uranium has to be "enriched" in the U-235 isotope, which is responsible for nuclear
fission. During the enrichment process the fraction of U-235 is increased from its
natural level (0.72% by mass) to between 2% and 94% by mass. The by-product
uranium mixture (after the enriched uranium is removed) has reduced concentrations
of U-235 and U-234. This by-product of the enrichment process is known as
depleted uranium (DU). The official definition of depleted uranium given by the US
Nuclear Regulatory Commission (NRC) is uranium in which the percentage fraction
by weight of U-235 is less than 0.711%. Typically, the percentage concentration by
weight of the uranium isotopes in DU used for military purposes is: U-238: 99.8%; U235: 0.2%; and U-234: 0.001%.
4
FACT SHEET
The table below compares percentages of uranium isotopes by weight and activity in
natural and depleted uranium.
Relative isotopic abundance
Isotope
Natural
Uranium
Depleted
Uranium
By weight
By activity
By weight
By activity
U-238
99.28%
48.8%
99.8%
83.7%
U-235
0.72%
2.4%
0.2%
1.1%
U-234
0.0057%
48.8%
0.001%
15.2%
4. Is DU more or less radioactive than natural uranium?
DU is considerably less radioactive than natural uranium because not only does it
have less U-234 and U-235 per unit mass than does natural uranium, but in addition,
essentially all traces of decay products beyond U-234 and Th-231 have been
removed during extraction and chemical processing of the uranium prior to
enrichment. The specific activity of uranium alone in DU is 14.8 Bq per mg compared
with 25.4 Bq per mg for natural uranium. It takes a long time for the uranium decay
products to reach (radioactive) equilibrium with the uranium isotopes. For example it
takes almost 1 million years for Th-230 to reach equilibrium with U-234.
5. Are people naturally exposed to uranium?
Small amounts of natural uranium are ingested and inhaled by everyone every day.
It has been estimated (UNSCEAR 2000) that the average person ingests 1.3 µg (1
µg = 1 microgram = 0.000001g) (0.033 Bq) of uranium per day, corresponding to an
annual intake of 11.6 Bq. . It has also been estimated that the average person
inhales 0.6 µg (15 mBq) every year. Typically, the average person will receive a
5
FACT SHEET
dose of less than 1 µSv per year from ingestion and inhalation of uranium. In
addition, an average individual will receive a dose of about 120 µSv per year from
ingestion and inhalation of decay products of uranium, such as Ra-226 and its
progeny in water, Rn-222 in homes and Po-210 in cigarette smoke.
Because of the differences in diet, there is a wide variation in consumption levels of
uranium around the world, but, primarily, intake depends on the amount of uranium
in the water people drink. In some parts of the world, the concentration of uranium in
water is very high, and this results in much higher intakes of uranium from drinking
water than from food. For example, consumption of uranium in parts of Finland can
be tens of micrograms per day.
For information on levels of natural uranium in the human body, see:

ICRP Publication 23: International Commission on Radiological Protection,
Reference Man: Anatomical Physiological and Metabolic Characteristics.
ICRP Publication 23, Pergamon Press, Oxford (1975)

RAND Report: Author(s): Harley N. H, Foulkes E. C., Hilborne L. H, Hudson
A., Anthony C., R., A Review of the Scientific Literature as It Pertains to Gulf
War Illnesses. Vol. 7, Depleted Uranium. RAND Report MR-1018/7-OSD
(1999)
For information on average human doses, see:

UNSCEAR Reports: UNITED NATIONS, Sources and effects of Ionizing
Radiation, Report to the General Assembly with Scientific Annexes, United
Nations Scientific Committee On The Effects Of Atomic Radiation,
(UNSCEAR), UN, New York (1988, 1993, 1996, 2000).
Internet Links:
6
FACT SHEET

ICRP: http://www.icrp.org or or
http://www.elsevier.nl/inca/publications/store/1/3/3/9/5/ for ICRP Publication
23.

RAND: http://www.rand.org or http://www.rand.org/publications (no particular
link to report on DU).
UNSCEAR: http://www.unscear.org/.
6. What are the military uses of depleted uranium?
Uranium's physical and chemical properties make it very suitable for military uses.
DU is used in the manufacturing of ammunitions used to pierce armour plating, such
as those found on tanks, in missile nose cones and as a component of tank armour.
Armour made of depleted uranium is much more resistant to penetration by
conventional anti-armour ammunitions than conventional hard rolled steel armour
plate.
Armour piercing ammunitions are generally referred to as "kinetic energy
penetrators". DU is preferred to other metals, because of its high density, its
pyrophoric nature (DU self-ignites when exposed to temperatures of 600° to 700°
and high pressures), and its property of becoming sharper, through adiabatic
shearing, as it penetrates armour plating . On impact with targets, DU penetrators
ignite, breaking up in fragments, and forming an aerosol of particles ("DU dust")
whose size depends on the angle of the impact, the velocity of the penetrator, and
the temperature. These fine dust particles, can catch fire spontaneously in air. Small
pieces may ignite in a fire and burn, but tests have shown that large pieces, like the
penetrators used in anti-tank weapons, or in aircraft balance weights, will not
normally ignite in a fire.
For more information on the military uses of depleted uranium see:
http://www.gulflink.osd.mil or http://www.nato.int.
7
FACT SHEET
7. There are reports of impurities in DU. What are they?
The vast majority of depleted uranium used by the US Department of Defense
comes from the enrichment of natural uranium and is provided by the US
Department of Energy. However, between the 1950s and 1970s, the US Department
of Energy enriched some reprocessed uranium extracted from spent reactor fuel in
order to reclaim the U-235 that did not fission. Unlike natural uranium, the
reprocessed uranium contained anthropogenic (man-made) radionuclides including
the uranium isotope U-236, small amounts of transuranics (elements heavier than
uranium, such as neptunium, plutonium and americium) and fission products such as
technetium-99. As a result, the depleted uranium by-product from the enrichment of
reprocessed uranium also contained these anthropogenic radionuclides, albeit at
very low levels. During the enrichment of reprocessed uranium, the inside surfaces
of the equipment also became coated with these anthropogenic radionuclides and as
this same equipment was used for the enrichment of natural uranium, these
radionuclides later contaminated the DU produced from the enrichment of natural
uranium as well. The exact amount is not known. Radiochemical analysis of depleted
uranium samples indicate that these trace impurities are in the parts per billion level
and result in less than a one percent increase in the radiation dose from the depleted
uranium. The US Nuclear Regulatory Commission was aware of the existence of
these trace contaminants in DU and determined them to be safe. The presence of U236 and Pu-239/240 in depleted uranium has been confirmed by analyses of
penetrators collected during the UNEP-led mission to Kosovo in November 2000.
The activity concentration of U-236 in the penetrators was of the order of 60000 Bq
per kg, while the activity concentration of plutonium varied from 0.8 to 12.87 Bq per
kg.
Further information on this can be found at:
8
FACT SHEET

http://www.gulflink.osd.mil/du_ii/du_ii_s03.htm#2 and
http://www.gulflink.osd.mil/du_ii/du_ii_s03.htm#TAB C - Properties and
Characteristics of DU.

http://www.nato.int.

http://www.iaea.org/NewsCenter/Focus/DU/finalreport.pdf.
8. What studies have been done on people exposed to Uranium or
DU?
Since the advent of the nuclear age, there has been widespread use of uranium
involving the mining of uranium ore, enrichment, and nuclear fuel fabrication. These
industries have employed large numbers of people, and studies of the health of
working populations have been carried out. The main risk to miners, and not just
those involved in uranium mining, comes from exposures to radon (mainly Rn-222)
gas and its decay products. A study of miners who worked in poorly ventilated mines
at a time when the hazards of radon were not known and thushad been exposed to
high levels of radon, demonstrated that this group had an excess of lung cancers
and that the risk of cancer increased with increasing exposure to radon gas. Studies
of workers exposed to uranium in the nuclear fuel cycle have also been carried out.
There are some reported excesses of cancers but, unlike the miners, no correlation
with exposure can be seen. The main finding of these studies has been that the
health of workers is better than the average population. This "healthy worker effect"
is thought to be due to the selection process inherent in employment and to the
overall benefits of employment.
Regarding exposures to DU, there have been studies of the health of military
personnel who saw action in the Gulf War (1990-1991) and during the Balkan
conflicts (1994-99). A small number of Gulf war veterans have inoperable fragments
of DU embedded in their bodies. They have been the subject of intense study and
the results have been published. These veterans show elevated excretion levels of
9
FACT SHEET
DU in urine but, so far, there have been no observable health effects due to DU in
this group. There have also been epidemiological studies of the health of military
personnel who saw action in conflicts where DU was used, comparing them with the
health of personnel who were not in the war zones. The results of these studies have
been published and the main conclusion is that the war veterans do show a small
(i.e., not statistically significant) increase in mortality rates, but this excess is due to
accidents rather than disease. This cannot be linked to any exposures to DU.
For information on doses and risks to miners, see:

Lubin J., Boice J.D., Edling C. et al., Radon and lung cancer risk: A joint
analyses of 11 underground miners studies, US Department of Health and
Human Services, NIH Publication 94-3644, Washington D.C. (1994).
For information on the health of people working with uranium, see:

McGeoghegan D. and Binks K., J Radiol Prot 20 11-137 (2000).
For information on studies of military personnel exposed or potentially exposed to
DU see:

M A McDiarmid et alia, Environ. Res. A 82 168-180 (2000), G J Macfarlane et
alia, The Lancet 356 17-21 (2000).
9. What is the behaviour of uranium in the body?
Uranium is introduced into the body mainly through ingestion of food and water and
inhalation of air.
When inhaled, uranium is attached to particles of different sizes. The size of the
uranium aerosols and the solubility of the uranium compounds in the lungs and gut
influence the transport of uranium inside the body. Coarse particles are caught in the
10
FACT SHEET
upper part of the respiratory system (nose, sinuses, and upper part of the lungs)
from where they are exhaled or transferred to the throat and then swallowed. Fine
particles reach the lower part of the lungs (alveolar region). If the uranium
compounds are not easily soluble, the uranium aerosols will tend to remain in the
lungs for a longer period of time (up to 16 years), and deliver most of the radiation
dose to the lungs. They will gradually dissolve and be transported into the blood
stream. For more soluble compounds, uranium is absorbed more quickly from the
lungs into the blood stream. About 10% of it will initially concentrate in the kidneys.
Most of the uranium ingested is excreted in feces within a few days and never
reaches the blood stream. The remaining fraction will be transferred into the blood
stream. Most of the uranium in the blood stream is excreted through urine in a few
days, but a small fraction remains in the kidneys and bones and other soft tissue.
10. How could uranium and DU be harmful to people? Has DU or
uranium been definitely linked to human cancer?
In sufficient amounts, uranium that is ingested or inhaled can be harmful because of
its chemical toxicity. Like mercury, cadmium, and other heavy-metal ions, excess
uranyl ions depress renal function (i.e., affect the kidneys). High concentrations in
the kidney can cause damage and, in extreme cases, renal failure. The general
medical and scientific consensus is that in cases of high intake, uranium is likely to
become a chemical toxicology problem before it is a radiological problem. Since
uranium is mildly radioactive, once inside the body it also irradiates the organs, but
the primary health effect is associated with its chemical action on body functions.
In many countries, current occupational exposure limits for soluble uranium
compounds are related to a maximum concentration of 3 µg uranium per gram of
kidney tissue. Any effects caused by exposure of the kidneys at these levels are
considered to be minor and transient. Current practices, based on these limits,
11
FACT SHEET
appear to protect workers in the uranium industry adequately. In order to ensure that
this kidney concentration is not exceeded, legislation restricts long term (8 hour)
workplace air concentrations of soluble uranium to 0.2 mg per cubic metre and short
term (15 minute) to 0.6 mg per cubic metre.
Like any radioactive material, there is a risk of developing cancer from exposure to
radiation emitted by natural and depleted uranium. This risk is assumed to be
proportional to the dose received. Limits for radiation exposure are recommended by
the International Commission on Radiological Protection (ICRP) and have been
adopted in the IAEA's Basic Safety Standards. The annual dose limit for a member
of the public is 1 mSv, while the corresponding limit for a radiation worker is 20 mSv.
The additional risk of fatal cancer associated with a dose of 1 mSv is assumed to be
about 1 in 20,000. This small increase in lifetime risk should be considered in light of
the risk of 1 in 5 that everyone has of developing a fatal cancer . It must also be
noted that cancer may not become apparent until many years after exposure to a
radioactive material.
It is possible to estimate how much DU an individual could be exposed to before the
above chemical and radiological limits are exceeded. The table below shows how
much depleted uranium would have to be inhaled or ingested to lead to a kidney
concentration of 3µg per gram of kidney (chemical toxicity limit) or to a dose of 1
mSv (radiation dose limit). These values have been calculated with the biokinetic
models currently recommended by the International Commission on Radiological
Protection (ICRP). The values have been calculated for two types of uranium
compounds: 'moderately soluble' compounds, such as UO3 and U3O8 and 'insoluble'
compounds, such as UO2.
Route of intake
12
Intake leading to a
Intake leading to a dose
kidney concentration of
of 1 mSv
FACT SHEET
3 µg per gram
Inhalation of reference
Mass
Activity
Mass
Activity
(mg)
(Bq)
(mg)
(Bq)
230
3400
32
480
7400
110000
11
160
400
5900
1500
22000
4000
59000
8800
130000
'moderately soluble' DU
aerosol
Inhalation of a reference
'insoluble' DU aerosol
Ingestion of a reference
'moderately soluble' DU
compound
Ingestion of a reference
'insoluble' DU compound
It should be borne in mind that the amounts required to give a kidney concentration
of 3 µm per gram would be larger if the intake was given over a longer period of time,
since it would give the kidneys more time to excrete the DU. The table shows that,
for ingestion of DU, the chemical toxicity limit of 3 µg per gram of kidney tissue
needs a smaller intake than the radiological limit (for a member of the public) of 1
mSv. For inhalation of a DU aerosol, the reverse is the case.
In addition to the radiological hazard from uranium isotopes, there is also a potential
risk associated with other radionuclides that are formed from the radioactive decay of
uranium isotopes and that can be found in the food ingested or in the air inhaled.
The values in the table above were calculated taking into account the build up of
these radionuclides inside the body, but do not include the contribution of these
radionuclides in the food ingested or in the air inhaled.
13
FACT SHEET
Another potential harmful effect is due to external exposure to the radiation emitted
by uranium isotopes. The main radiation emitted by isotopes of uranium is alpha
particles (helium nuclei). The range of these alpha particles in air is of the order of
one centimetre, while in the case of tissue, they can barely penetrate the external
dead layer of the skin. For comparison, beta-particles (electrons) are capable of
penetrating about a centimetre of tissue, while gamma-radiation (high energy
photons) can pass through the body. Therefore, the potential risk from external
exposure to uranium isotopes is exceedingly low, unless the uranium is introduced
directly into the body (e.g. through a wound). Moreover, as alpha particles cannot
travel very far from the source, an individual can only be exposed by coming in direct
contact with uranium isotopes. This is not the case however with natural uranium,
where people are also exposed to the more penetrating beta and gamma radiation
emitted by the decay products of uranium that are normally found in equilibrium with
the uranium isotopes. In the case of DU, the only beta emitting decay products
present are Th-234, Pa-234m andTh-231, all of which emit low intensity gammaradiation, and, thus the risk from external exposure to DU is considerably lower than
for exposure to natural uranium.
There have been a number of studies of workers exposed to uranium (see question
8) and, despite some workers being exposed to large amounts of uranium, there is
no evidence that either natural uranium or DU is carcinogenic. This lack of evidence
is seen even for lung cancer following inhalation of uranium. As a precaution for risk
assessment and to set dose limits, DU is assumed to be potentially carcinogenic, but
the lack of evidence for a definite cancer risk in studies over many decades is
significant and should put the results of assessments in perspective.
11. How can uranium affect children?
Like adults, children are exposed to small amounts of uranium in air, food, and
drinking water. However, no cases have been reported where exposure to uranium
14
FACT SHEET
is known to have caused health effects in children. It is not known whether children
differ from adults in their susceptibility to health effects from uranium exposure. In
experiments, very young animals have been found to absorb more uranium into their
blood than adult animals when they are fed uranium.
lt is not known if exposure to uranium has effects on the development of the human
fetus. There have been reports of birth defects and an increase in fetal deaths in
animals fed with very high doses of uranium in drinking water. In an experiment with
pregnant animals, only a very small amount (0.03%) of the injected uranium reached
the fetus. Even less uranium is likely to reach the fetus in mothers exposed to
uranium through inhalation and ingestion. There are no available data of
measurements of uranium in breast milk. Because of its chemical properties, it is
unlikely that uranium would concentrate in breast milk.
The effect of exposure to uranium on the reproductive system is not known. Very
high doses of uranium have caused a reduction in sperm counts in some
experiments with laboratory animals, but the majority of studies have shown no
effects.
12. What are the potential routes of exposure from depleted uranium
ammunitions?
The main potential hazard associated with depleted uranium ammunitions is the
inhalation of the aerosols created when DU ammunitions hit an armoured target. The
size, distribution, and chemical composition of the particles released on impact will
be highly variable, but the fraction of the aerosols that can enter the lung can be as
high as 96%. A typical composition of these aerosols is about 60% U 3O8, 20% UO2,
and about 20% other amorphous oxides (Schripsick et al., 1984). Both U3O8 and
UO2 are insoluble compounds. The individuals most likely to receive the highest
15
FACT SHEET
doses from DU ammunitions are, therefore, those near a target at the time of impact
or those who examine a target (or enter a tank) in the aftermath of the impact.
A potential exposure pathway for those visiting or living in DU affected areas after
the aerosols have settled is the inhalation of DU particles in the soil that have been
re-suspended through the action of wind or human activities. The risk will be lower
because the re-suspended uranium particles combine with other material and
increase in size and, therefore, a smaller fraction of the uranium inhaled will reach
the deep part of the lungs. Another possible route of exposure is the inadvertent or
deliberate ingestion of soil. For example, farmers working in a field where DU
ammunitions were fired could inadvertently ingest small quantities of soil, while
children sometimes deliberately eat soil.
In the long term, the exposure pathways that become more important are ingestion
of DU incorporated in drinking water and the food chain through migration from the
soil or direct deposition on vegetation. The risk from ingestion of food and water is
generally low, because uranium is not effectively transported in the food chain.
It has also been estimated that a large fraction of DU ammunitions fired from an
aircraft probably miss their intended target. The majority of these projectiles will be
buried at various depths under the surface of the ground and even in buildings.
Some of them could be lying around on the ground surface in the vicinity of the
target. The physical state of these ammunitions will be very variable, depending on
the characteristics of the ground, ranging from small fragments to whole intact
penetrators.
Individuals, who might find and handle these ammunitions could be exposed to
external radiation emitted by DU. For example, a farmer ploughing a field may dig up
an intact projectile some time afterwards. Because of the type of radiation emitted by
DU, the dose received would be significant only if the person exposed was in contact
with DU projectiles. In addition, people could, through handling the penetrators,
16
FACT SHEET
inadvertently ingest some of the loose friable uranium oxides formed through
weathering of the surface of the penetrators.
With time, chemical weathering will cause the metallic DU of penetrators in the
ground to corrode and disperse in the soil. The DU in the soil will be in an oxidized,
soluble chemical form and migrate to surface and groundwater from where it will
eventually be incorporated into the food chain, which then can be consumed. It is
difficult to predict how long it would take for individuals to be exposed to DU through
this pathway, but it is reasonable to assume that it would take several years before
enhanced levels of DU could be measured in water and food.
For information on properties of airborne uranium, see:

Scripsick, R.C., Crist, K.C, Tillery, M.I., Soderholm, S.C., Differences in in
vitro dissolution properties of settled and airborne uranium material, Report
presented at Conference on occupational radiation safety in mining, Toronto,
Ontario (Canada) 15-18 Oct 1984, Los Alamos National Lab, NM (USA)
(1984).
13. What are the possible radiation hazards from handling DU
projectiles?
The contact dose rate from a DU penetrator is about 2 mSv per hour, primarily from
beta particle decay from DU progeny. At this dose rate it is unlikely that prolonged
contact with a DU penetrator would lead to skin burns (erythema) or any other acute
radiation effect. Nevertheless, the dose that could be delivered from handling of DU
ammunitions is such that the exposure and handling time should be kept to a
minimum and protective apparel (gloves should be worn A public information
campaign may, therefore, be required to ensure that people avoid handling the
projectiles. This should form part of any risk assessment and such precautions
should depend on the scope and number of ammunitions used in an area.
17
FACT SHEET
14. What is the likely impact of DU on the environment?
The environmental impact of depleted uranium depends on the specific situation
where DU ammunitions are used and the physical, chemical, and geological
characteristics of the environment affected.
However, some general conclusions can still be made. Studies carried out at test
ranges show that most of the DU aerosols created by the impact of penetrators
against an armoured target settle within a short time (minutes) of the impact and in
close proximity to the target site, although smaller particles may be carried to a
distance of several hundred metres by the wind.
Once the DU aerosols settle on the ground, the depleted uranium particles combine
with other material and increase in size, becoming less of an inhalation hazard. The
potential risk from inhalation will be associated with material that is re-suspended
from the ground by the action of the wind or by human activities, such as ploughing.
With time, the concentrations of depleted uranium on the ground surface will
decrease due to wind and precipitation that will transport the depleted uranium away
or wash it into the soil. Any risk associated with inhalation of re-suspended material
will thus decrease with time.
Depleted uranium present in the soil can migrate to surface and groundwater and
flow into water streams. Plants will also uptake DU present in soil and in water. A
very small fraction of DU in vegetation and water is the result of direct deposition
onto water surfaces. The chemical and physical composition of the soil will
determine the solubility and transportability of the DU particles. The DU in water and
vegetation will be transferred to livestock through ingestion of grass, soil, and water.
Studies have shown that bio-accumulation of uranium in plants and animals is not
very high and, therefore, uranium is not effectively transported in the food chain.
18
FACT SHEET
Depleted uranium in the soil will be in an oxidized, soluble chemical form and
migrate to surface and groundwater and be incorporated into the food chain. It is
difficult to predict how long it would take for this to occur. As a result of chemical
weathering, DU projectiles lying on the ground or buried under the surface will
corrode with time, slowly converting the metallic uranium of the DU penetrators into
uranium oxides. The specific soil characteristics will determine the rate and chemical
form of the oxidation and the rate of migration and solubility of the depleted uranium.
This environmental pathway may result in the long term (in the order of several
years) in enhanced levels of depleted uranium being dissolved in ground water and
drinking water.
Consumption of water and food is a potential long term route of intake of DU. Given
this, monitoring of water sources may be a useful means to assess the potential for
intake via ingestion. If the levels were considered unacceptable, some form of
filtration/ion exchange system could be implemented to reduce levels of DU.
Source: www.iaea.org
For more information contact;
National Nuclear Regulator
Communications & Stakeholder Relations Office
Tel: (+27) 12 674 7100/09
Fax: 0865884450
Email: enquiry@nnr.co.za
Website: www.nnr.co.za
19