Depleted Uranium: Slow, silent killer
ulhasj at SPAMbom4.vsnl.net.in
Tue Feb 13 18:26:26 MST 2001
Volume 18 - Issue 03, Feb. 03 - 16, 2001
Slow, silent killer
While the proven risk from radiation exposure is an increased likelihood of
developing cancer, some studies have noted other health effects too.
ON January 4 this year, European Commission President Romano Prodi became
the latest European leader to demand an investigation into claims that
depleted uranium (D.U.) used in the North Atlantic Treaty Organisation's
(NATO) munitions had caused deaths or illnesses among Balkan peacekeepers.
Public concern over the health hazards caused by D.U. munitions dates back
to the Gulf war, when D.U. was first used in combat. Exposure to D.U. has
been suggested as one of the causes for the massive crisis in public health
in Iraq following the war. This is somewhat unlikely to be the case. The
larger danger is to soldiers who were in vehicles hit by D.U. munitions,
their rescuers and individuals who spent extended periods of time in these
vehicles as part of clean-up. Indeed, in the years following that war,
several U.S. war veterans have complained of a variety of medical problems,
which have collectively been given the name 'Gulf war syndrome'. While the
Pentagon has by and large maintained that there is no evidence to suggest
that D.U. is linked to the syndrome, it is likely that at least some subset
of the symptoms is related to exposure to D.U.
Uranium as found in nature has two significant isotopes (isotopes have the
same number of protons in their nuclei but differ in the number of
neutrons). The primary isotope is uranium-238 (U-238) which constitutes
approximately 99.3 per cent of the total available uranium. The remaining
0.7 per cent is uranium-235 (U-235). To use uranium in nuclear weapons or in
nuclear reactors, it has to be enhanced in the U-235 fraction. Depleted
uranium refers to the "waste" material (and therefore available for free)
left behind when natural uranium is enriched in its U-235 content. A typical
D.U. composition has 99.8 per cent U-238 and 0.2 per cent U-235. The
principal component, U-238, has a radioactive half-life of 4.5 billion
The choice of D.U. for use in munitions is made mainly because of its high
density, about twice that of lead. During the Gulf war, D.U. was used to
make tank-fired shells (with 4-5 kilogram D.U. penetrator rods) and
30-millimetre rounds (with a 0.3 kg D.U. penetrator) fired by "tank
killing" aircraft. When these strike a hard target, such as a tank, a large
fraction of their energy is converted into heat in a very short period of
time, converting much of the D.U. into small, hot fragments and particles.
The smaller fragments can burn, generating D.U.-oxide aerosol. D.U. is also
used as an armour component in some tanks.
Exposure to uranium could be of two kinds - external, that is, when the
uranium is outside the body, and internal, when uranium has entered the body
through air, food, wounds, embedded shrapnel and so on. The health hazard
due to exposure to uranium would result from its radioactivity and chemical
toxicity. When the uranium is outside the body, only its radioactive
properties are pertinent; chemical toxicity comes into play only in the case
of internal exposures.
Radiation from the decay of uranium and various resultant radioactive
isotopes can be of three kinds - Alpha, Beta and Gamma. Alpha particles
cannot penetrate the inert outer layer of the human skin. They do not
contribute to any external radiation threat. They are hazardous only if
there is internal consumption. Beta particles are usually hazardous only if
bare uranium comes in direct contact with the skin. Gamma rays are far more
penetrating and could deliver external radiation doses.
Because the primary decay mode of uranium is through Alpha particles,
radiation doses from external exposure are relatively insignificant. It has
been estimated that people living in the vicinity of damaged vehicles would
receive external doses of at the most 10 per cent of the background
radiation dose that all of us receive. However, D.U., when it is in contact
with bare skin for long periods of time, could result in a significant Beta
radiation dose. For example, children in Iraq play in abandoned tanks or
with shell fragments, thus putting themselves at greater risk.
Radiation doses could be much larger in the case of internal exposure.
Ingestion of D.U. is a less significant risk since almost all of the uranium
is excreted within a few days. More serious is the inhalation of very small
D.U. particles, which can stay imbedded deep in the lungs, typically for
months or even years. Since 10-35 per cent of the oxide produced when D.U.
munitions strike a target and burn is in the form of particles that are
respirable, people who are inside tanks that are hit or those who enter
such tanks later on are likely to inhale these particles.
The kind of damage caused by such inhalation depends on the particles'
solubility in body fluids, which determines the rate at which inhaled or
ingested D.U. is absorbed into the bloodstream. Fine, insoluble aerosols
result in higher radiation doses, while soluble aerosols pose greater risks
of chemical toxicity because they are absorbed into the bloodstream quickly.
Once in the blood, uranium concentrates in the kidneys and bones.
In the kidney, the chemical toxicity effects of D.U. can cause renal damage.
The threshold concentration level that results in damage to the kidney is a
matter of controversy. The literature on D.U. frequently cites 3
micrograms/gram of kidney tissue (that is, 3 ppm) as a threshold even
though renal change in animals following exposure to uranium has frequently
been observed at levels well below the threshold. In the case of other toxic
elements like lead, as the sensitivity of measurements increase, studies
have recognised very small effects at lower levels of exposure. It may,
therefore, be premature to assume the existence of a firm threshold, below
which adverse effects will not occur.
Assuming no significant damage below 1 ppm, physicists Steve Fetter and
Frank von Hippel use a combination of rough estimates and test data to
estimate the amount of uranium that individuals might inhale under various
circumstances (Science and Global Security Volume 8:2 (1999), pp.125-161).
For individuals who are outside vehicles struck by D.U., they conclude: "It
is virtually impossible that any U.S. soldier outside of a struck vehicle
could have inhaled a dangerous amount of D.U.-aerosol from penetrator
impacts. It seems unlikely that even Iraqi soldiers on the "highway of
death" between Kuwait City and Basra, other than those in vehicles struck by
D.U. munitions, could have received doses in excess of U.S. occupational
radiation or toxicity standards." However, in the case of those inside a
vehicle that has been hit, Fetter and von Hippel estimate that they could
potentially inhale large enough amounts leading to kidney damage or other
Another group of individuals who are potentially affected are those who have
shrapnel of D.U. embedded in their bodies. Removing such shrapnel is often
quite difficult and so there is a constant radiation dose. Over time, the
embedded shrapnel gradually dissolve and lead to uranium accumulation in the
kidney. Of these, the radiation dose is likely to be significant in them. A
final category of individuals who could breathe in considerable amounts of
D.U. are those who enter vehicles after they have been struck, either to
rescue fellow-soldiers, remove munitions or equipment, or to clean or repair
There are many uncertainties that have to be factored into these estimates
and damage assessments. First, there is uncertainty about the exact number
of soldiers who were exposed to D.U. through one or more of these routes.
Hence it is not possible to make precise estimates about how many may be
affected. In typical fashion, the Pentagon did not take any urine samples
from soldiers for nearly two years, thereby making it impossible to estimate
how much D.U. different individuals had been exposed to.
Second, there are uncertainties about the behaviour of uranium in the body.
Multiple models have been proposed with significant variations. A comparison
of uranium distribution in the body of a dead employee of a uranium workshop
and the International Commission on Radiological Protection (ICRP) model
found in autopsy that the presence of uranium in the lungs and lymph nodes
was less than 1 per cent of the predicted values [Health Risks of Radon and
Other Internally Deposited Alpha-Emitters (BEIR IV) (Washington DC: National
Academy Press, 1988), p. 282].
There are also significant differences between different species in the
matter of sensitivity; this becomes important because the question of which
animal (dog or rat) is a better model for uranium effects in humans is yet
to be settled. Gender sensitivity has also been noted in the case of rats,
with the male requiring on an average about 2.5 times more uranium for
lethality than the female.
Third, while the well-proven risk from radiation exposure is an increased
likelihood of developing cancer, some studies have noted other health
effects too. For example, chromosome aberrations, that is, genetic effects,
have been reported in uranium miners and there is some evidence that
uranium may affect the immune system. Uranium exposure has been found to
result in developmental defects in mice, and a decrease in weight and length
in dogs as well as an increase in the number of still births.
Finally, there are potential synergistic effects that could be caused by
exposure to both D.U. and chemicals from the widespread bombing of
petrochemical factories and fertilizer plants, and the many oil wells that
were set on fire. Interestingly, U.S. troops involved in the Gulf war were
administered pyridostigmine bromide, a relatively new vaccine, to protect
them against biological and chemical weapons; a survey underwritten by the
Pentagon has linked the Gulf war syndrome to this vaccine. There is some
evidence from experiments in mice and dogs that the combination of Alpha
radiation from uranium and chemical toxicity produces a greater toxic effect
on the kidney than either does separately (Health Risks of Radon and Other
Internally Deposited Alpha-Emitters, p. 286). Given the almost complete
lack of data, it is impossible to confirm or rule out such synergistic
effects, let alone quantify the risks.
In the light of these uncertainties, the claim by the U.S. Department of
Defence that the few veterans being monitored are "not sick from the heavy
metal or radiological toxicity of D.U." is definitely overstated. As the
U.S. National Academy of Sciences ' Biological Effects of Ionising Radiation
Committee noted, the available epidemiological studies involving uranium
exposure had only limited power to detect increased rates of either serious
renal disease or increased rates of malignant tumours. The committee also
recommended that "at present, it is premature to attempt a risk estimate for
the probability of developing renal damage, and there is an evident need for
well-controlled epidemiological studies." It is worth recalling that over
the course of the previous century the level of occupational radiation dose
considered "safe" has decreased by approximately a factor of 30 as better
studies of health effects were conducted.
In the final analysis, though it is unlikely to be the primary cause for
widespread sickness in Iraq or among Gulf war veterans, one can say that
D.U. is unsafe and clearly poses health risks to people exposed to it. When
the much more evident suffering due to sanctions have failed to evoke any
change in policies or even sympathy - best epitomised by former U.S.
Secretary of State Madeline Albright's 1995 statement that the half a
million (or more) Iraqi children killed by the sanctions were "worth it" -
it is no surprise that the much smaller health impacts as those from the
exposure to D.U. have been disregarded by U.S. authorities, and now by NATO.
The development and use of D.U. munitions is yet another instance of how the
U.S. nuclear industry works together with the military industrial complex
to support U.S. imperialism around the world, regardless of the
consequences. For this political reason, in addition to its health impacts,
the use of D.U. must be opposed.
M. V. Ramana works at the Centre for Energy and Environmental Studies,
Princeton University, United States.
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