Malignant Effects: depleted uranium as a carcinogen and genotoxin
A PDF version of Malignant Effects is available to download at the end of this article.
What is depleted uranium?
Depleted uranium (DU) is a by-product of the uranium enrichment process. It is used by a number of states in armour-piercing tank shells and bullets.
The use of DU weapons is controversial because DU is radioactive and chemically toxic. Its use can generate particles that can be inhaled or ingested. DU creates large quantities of contaminated wreckage and hotspots of persistent contamination that present a hazard to civilians long after conflict ends.
What is DNA?
DNA is the chemical molecule which contains the inherited genetic information used by all known cell-based life-forms.
DNA is present in almost every cell in the body. DNA could be described as the instruction manual for the organism in which it is present. DNA has the ability to make copies of itself, this is done when cells divide and replicate.
What is genotoxicity?
Genotoxic substances can cause damage to DNA or change the way DNA functions within an organism.
In some cases, a damaged cell can become cancerous, or a mutation in the DNA can be passed on to daughter cells or even to the offspring of the organism.
How can DU damage DNA?
DU is known to damage DNA in several ways. DU emits ionizing radiation, which consists of subatomic particles travelling at high speed. If these particles hit DNA, the collision can cause damage to the DNA.
Experiments have also shown that DU can damage DNA, by joining to it in a chemical bond, forming what are called uranium-DNA adducts. Exposure to DU has also been shown to cause damage to DNA through a chemical process known as oxidation.
How do we know it can do this?
Scientists have shown that DU is genotoxic in a number of different ways.
As well as adducts, which have been observed in hamster cells, a number of experiments have shown that exposure to DU can cause breaks in the strands of DNA. Several studies have shown that DU exposure can cause mutations in rats and in cells in the laboratory. Exposure to DU has been shown to cause oxidative damage to DNA in rats and several kinds of small fish.
Experiments in human bone cells and in mice have shown that exposure to DU can cause genomic instability in immature human bone cells and in mice. Genomic instability means that cells are more likely to undergo changes. The offspring of the mice exposed to DU were more likely to have mutations in their DNA, meaning that genomic instability was passed from parent to child.
A number of studies show that DU exposure can cause different changes to chromosomes in human cells. Chromosomes are the structures formed by the coiled DNA within cells. The changes DU exposure causes in the chromosomes are often used by scientists to identify whether cells have been exposed to a genotoxic substance or effect. Biological indicators like this which are known to be associated with a given effect are called ‘biomarkers’.
What we don’t know and why?
Many of the experiments scientists use to assess whether a genotoxic effect has taken place look for the after-effects or biomarkers of the damage. These are often easier to locate and identify than the damage itself.
Because of this, it is not always possible to identify exactly how the DU has damaged DNA (this is called the mechanism), even though the biomarkers show that a genotoxic effect has occurred. Some studies suggest that radioactivity is the most significant mechanism in the genotoxicity of DU, others that a chemical reaction may play more of a role; it has not been possible however to reach a definite conclusion from the studies which have been carried out to date.
Most of what we know about whether DU is genotoxic comes from tests on cells and animals but it is important to work out whether DU is also genotoxic in humans. One of the major reasons for this is the lack of subjects for this kind of study. Very few studies have ever been carried out to identify civilians who have been exposed to DU. Identifying civilians at risk is difficult as militaries often do not say where they have fired DU weapons. Some studies have looked at soldiers from NATO countries but these have only found a few who had measurable levels of DU in their bodies. It is important for studies to look at as many people as possible.
The US Department of Veterans Affairs has funded some studies on a small group of veterans from the 1991 Gulf War, studies which have been running since 1994. The studies have some limitations in their design but some have investigated genotoxic effects. Most of these studies did not find any link between DU exposure and genotoxic effects but because of the small number of subjects it is difficult to draw meaningful conclusions. However, one experiment did show a significant increase of a type of mutation in the highest DU-exposed veterans.
Can DU cause cancer?
Cancer is usually the result of a number of independent DNA changes, which together promote cancerous cell growth and the development of a tumour.
Many studies have shown that exposure to DU can cause cells to transform to a malignant type, meaning that they have the characteristics of cancer cells. These changes have been shown in human lung and bone cells, as well as in rats and mice.
The World Health Organisation’s (WHO) International Agency for Research on Cancer (IARC) has developed a framework to assess whether substances can cause cancer. Under the IARC framework DU inside the body is classified as carcinogenic in humans because of the type of radiation it emits. This is confirmed by the many studies on DU’s genotoxic effects.
Because not enough studies have been done on civilians who have to live, work or play in or around sites contaminated by DU we cannot be certain about whether DU contamination in the environment is also a carcinogenic risk. As DU can get into people after it is used it seems clear that DU in the environment should be considered a probable, or at least a possible, carcinogen under IARC’s framework.
Are civilians at risk from DU from weapons?
Without more information on how much DU might get into the bodies of civilians after DU weapons are used, it is very difficult to accurately quantify their risk of cancer or other health effects.
Most civilians in a country contaminated by DU weapons will not come into contact with contamination, and will face only minimal risks. However, those living or working near contaminated sites are more at risk of exposure, particularly if they are not aware of the contamination. DU weapons have been used in populated areas and against many different kinds of targets. This has made it more likely that people will come into contact with DU.
It is possible to use modelling to make an estimate of risk but until we have reliable data to assess how much DU can get into the bodies of civilians who have been exposed to DU, or what harm it would cause, there will be considerable uncertainties.
What does all this mean?
Peer-reviewed studies on the genotoxicity of DU show that DU has the potential to damage DNA or change how it works.
While the studies reviewed in this report mostly rely on data from laboratory and animal experiments, the range of studies, and the fact that these results have been observed in several different animal species amount to a strong body of evidence on the potential effects of DU on human health.
There have been several large-scale desk studies on the possible effects of DU weapons which assessed the risks to be relatively small. However, many were produced before most of the studies detailed in this report had been published, and others did not properly take this evidence into account.
There is an immediate and pressing need for more data on the exposure risk to civilians from DU in the environment; studies to quantify this risk should be carried out urgently. All sites where DU has been used must be identified and assessed.
Even without this work being done, it is clear that DU has the potential to cause cancer and other health problems through its genotoxic effects. DU is a dangerous substance, and should never be released into the environment in an uncontrolled fashion. Its use in weapons causes long-lived contamination and is wholly unacceptable. Enough is now known about the risks from their use to justify an immediate moratorium on the use of DU weapons, followed by a global ban.
While the evidence from laboratory studies supports this, many of these studies emerged a decade or more after the first battlefield use of DU weapons. The potential for harm to civilians during that time delay shows that in the future we cannot wait until after all the scientific evidence is assembled before acting.
A new review system is required in order to prevent toxic and environmentally damaging substances being used in weapons in the future. It must be rooted in precaution, open to external scrutiny and it must better balance military needs with the need to protect civilians.
1. Full disclosure of targeting data
Efforts to better understand the behaviour of DU in the environment, the risks residues may pose to civilians on a site-by-site basis and risk awareness and clearance work have all been hampered by the ongoing reluctance of users to release targeting data.
The issue of transparency has been raised by many, most notably the United Nations General Assembly, where a call for the transfer of quantitative and geographic data on DU use has featured in its biennial DU resolution since 2010. The UK Royal Society called for long-term environmental monitoring in 2003, while the WHO and UNEP have repeatedly stated that remedial work is necessary around target sites. Without detailed firing coordinates, this work cannot proceed in a meaningful way.
2. Determine the extent of civilian exposure
The models and projections intended to predict the extent of civilian exposure to DU particulate are imprecise and little real-world data is available to accurately determine the risks DU poses in the wide variety of settings that characterise its use in conflict.
The primary focus of research efforts to date has been on military personnel – and not communities or individuals living with DU contamination. Such data is skewed towards exposure scenarios specific to military settings and is unlikely to reflect the risks from DU exposure faced by vulnerable individuals, such as children or pregnant women. There is therefore a pressing need for the international community to assist with the commission and funding of civilian exposure studies. A desirable long-term outcome would be for all potentially exposed civilians to be offered tests analysing both DU excretion and biomarkers specific to DU-induced damage. The data from these studies would help inform efforts to reduce civilian harm by targeting remediation and management work and improving risk awareness projects.
3. Precaution must guide munitions development
The history of DU’s development and use, which far outpaced the understanding of its risks, underscores the need for more stringent precautionary safeguards during the development of new weapons.
The rush to deploy DU weapons resulted in the dispersal of large quantities of contamination with little understanding of its potential health or environmental impact. Notably, most of the studies in this report post-date DU’s first use by decades. Even today, significant knowledge gaps remain. The choice of toxic materials in munitions must carry with it a responsibility to understand their potential impact prior to deployment. No future weapons development should be undertaken without a risk assessment on their constituents, with a presumption against including those that behave in a similar way to known toxic, genotoxic or carcinogenic materials. Similar assessments on weapons currently in use would be desirable and problematic substances should be phased out.
4. Ban uranium weapons
This report has found that a growing body of research shows that DU is a carcinogen. Set against studies analysing its mode of use in conflict and in light of the lack of obligations to mitigate the risks it poses after conflict, it becomes clear that its use must stop.
The users of DU have shown themselves unwilling to be bound by the consequences of their actions. The failure to disclose targeting data or follow their own targeting guidelines has placed civilians at unacceptable risk. The recommendations of international and expert agencies have been adopted selectively or ignored. At times, users have actively opposed or blocked efforts to evaluate the risks associated with contamination. History suggests it is unlikely that DU use will be stopped voluntarily: an international agreement banning the use of uranium in conventional weapons is therefore required.
- 1524 Kb - Format pdfICBUWThe purpose of this report is to introduce the reader to the growing weight of evidence relating to how DU can damage DNA, interfere with cellular processes and contribute to the development of cancer. The report uses peer-reviewed studies, many of which have been published during the last decade and, wherever possible, has sought to simplify the scientific language to make it accessible to the lay reader.