Although it received little attention at the time, journalist Samuel Oakford broke the story last month that the Pentagon has confirmed using weapons containing depleted uranium (DU) in Syria against ISIS targets—an about face from a previously articulated position.  (A-10 gunships are also flying in Iraq, although there has been no reporting so far on DU use there). How significant is this from a law-of-war perspective?  Given the lack of a treaty or customary law rule dedicated to regulating DU weapons, their use is evaluated under the general international humanitarian law (IHL) principles that apply to indiscriminate attacks, weapons that are by nature indiscriminate or that cause superfluous injury and unnecessary suffering, and means or methods of warfare that are intended, or may be expected, to cause severe harm to the natural environment.  These concepts are difficult to apply, however, with respect to DU because the science behind its long-term impact on human health and the environment remains indeterminate.

DU is a byproduct of enriching uranium ore for use as fuel in nuclear reactors or (less so today) in nuclear weapons; it is essentially what is left over (the U-238 isotope) from the process of purifying the fissile isotope of uranium (U-235). Given its high density (1.7 times that of lead), DU has both offensive and defensive utilities.  It is used in munitions aimed at piercing armor (including jacketed “penetrators” and landmines), within certain equipment (such as in defensive tank panels or in aircraft counterweights requiring maximum mass in minimum space), and for radiation shielding.  The U.S. Department of Energy manages huge DU stockpiles (generally produced as byproducts of the uranium enrichment process), so additional civilian and military uses are constantly being sought. 

Contrary to popular belief, DU is only slightly radioactive; indeed, it is 40 to 60 percent less radioactive than naturally occurring uranium, which itself is only mildly radioactive.  DU is, however, toxic, particularly when inside the body (in the form of fragments or dust, when aerosolized upon impact, or if wounds are contaminated).  In addition to combat exposure, contact can come from friendly fire incidents or during the disposal of damaged equipment.  

The Department of Defense claims that no significant health problems have been associated with exposure to DU, including in service members who served in the First Gulf War (where DU was widely used) or in animal studies. (The Veterans Administration site devoted to DU exposure is here). Likewise, in a 2001 post-conflict assessment, the United Nations Environmental Programme found no signs of contamination or reports of health effects in NATO peacekeepers who served in Kosovo, where DU projectiles were also used.  These conclusions are not shared by all observers, and complaints about “Gulf War Syndrome” (which encompasses DU poisoning) and horrific birth defects in places like Fallujah, where there was extensive use of DU, continue to surface. DU may also cause environmental damage, particularly if it gets in the food chain.  All told, at this point in time, the science and the medical data seem inconclusive.

The legality of using DU in armed conflict situations is in question, in part because the science is too. There is no treaty dedicated to regulating the production, use, destruction, or stockpiling of DU weapons as there is with respect to other problematic weapons and weapon systems, such as biological or chemical weapons, cluster munitions, anti-personnel landmines, and blinding laser weapons. A civil society organization, the International Coalition to Ban Uranium Weapons, has drafted a notional treaty on DU, based on the same structure as the Cluster Munitions Convention (a draft is here), but it has yet to be subjected to sustained multilateral negotiations.  

Absent a targeted treaty, any use of DU weaponry will be evaluated under ordinary IHL principles.  The International Committee of the Red Cross (ICRC) has produced a monumental study of the customary international law of armed conflict.  There are a number of rules of relevance to DU:

  • Besides the rules against directly targeting civilians, there is also a rule prohibiting indiscriminate attacks—attacks that cannot distinguish between civilians and civilian objects (on the one hand) and combatants or military objectives (on the other). (Rule 11 of the ICRC CIL Study).
  • In addition there are general bans under IHL on weapons that cause superfluous injury or unnecessary suffering (Rule 70 of the ICRC CIL Study) or weapons that are inherently indiscriminate (Rule 71 of the Study).  
  • Finally, of relevance is the ban on weapons that “are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment” (Rule 45 of the ICRC CIL Study). This latter Rule sets a high (some would say too high), and cumulative, threshold, which many assume would exclude “ordinary battlefield damage.”

Many of these rules derived from Additional Protocol I to the 1949 Geneva Conventions, which the United States has signed but not ratified.  The ICRC indicates that all of these rules, with the potential exception of Rule 45 governing harm to the natural environment, are equally applicable in non-international armed conflicts, or NIACs.  The ICRC commentary associated with these weapons rules lists a number of presumptively prohibited weapons but does not specifically mention DU.  

Assuming that DU weapons are not utilized in the vicinity of civilians or civilian territory, Rule 70 would govern because it is addressed to harm to combatants and other armed actors.  The ICRC identifies the United States as a persistent objector to Rule 70 (along with France and the United Kingdom when it comes to nuclear weapons).  The commentary around Rule 70 speaks of the “inevitability of serious permanent disability” and the infliction of “a harm greater than that unavoidable to achieve legitimate military objectives” (quoting the International Court of Justice’s Advisory Opinion on the Use or Threat of Use of Nuclear Weapons at ¶78). The ICC Statute includes a version of this prohibition as a war crime when committed in international armed conflicts (IACs) when it penalizes:

intentionally launching an attack in the knowledge that such attack will cause … widespread, long-term and severe damage to the natural environment which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated.  

The ICC’s Elements of Crimes emphasizes that the crime is premised on a knowledge mens rea and that this involves a consideration of the information available to the defendant at the time (the so-called Rendulic rule).

Absent better data on the immediate and long-term effects of DU on human health and the natural environment, however, it is difficult to apply these norms with any specificity.

DU use has not been subjected to rigorous judicial consideration yet.  NATO forces used depleted uranium projectiles in Operation Allied Force in 1998.  The Prosecutor of the International Criminal Tribunal for the former Yugoslavia created a committee to consider whether to bring any charges against individuals hailing from NATO member states in connection with the intervention.  In its report, the Committee found that there was evidence that DU projectiles were dropped by NATO aircraft, but concluded that there was no international consensus on whether the use of such projectiles violated general principles of international humanitarian law (IHL), or the law of armed conflict (¶ 26).

Iraq, which has one of the highest DU contaminations on the planet stemming from the First Gulf War, has called for such a ban and for assistance for victims and environmental remediation The U.N. General Assembly has considered DU armaments multiple times (with only the US, UK, France and Israel consistently voting against such resolutions, although a number of European states abstain), and passed its sixth resolution earlier this month with 146 states voting in favor of it. In 2012, for example, the General Assembly issued a resolution calling for the application of the precautionary principle to DU armaments and post-conflict management and decontamination.  According to that principle—which remains controversial as an international law concept—possible scientific uncertainty should not preclude the implementation of measures to prevent environmental harm or protect human life (see Principle 15 of the Rio Declaration on Environment and Development).

Oakford’s research is part of a larger project to document the use of DU in Iraq during the First Gulf War under the auspices of George Washington University, which obtained particularized records of DU use (in terms of the number of sorties and the nature of the targets) in the First Gulf War through the Freedom of Information Act. More accurate data about the use of these weapons will help better understand the immediate and long-term epidemiological and environmental effects of this weapon as well as aid ongoing cleanup efforts in Iraq. (There are few hard obligations in the law for post-conflict management of DU contamination.) Until we know more about DU’s effects, there is little that existing law can do to regulate and/or prevent its use. The current use adds to these data and our ability to evaluate this weapon.  Regardless of whether long-term harm can be proven, according to one commentator,

Depleted uranium tends to arouse a fair degree of anxiety whenever it is used, based largely on a misunderstanding of its nature.  The enormous adverse publicity which it attracts would seem to outweigh its relatively limited benefits.

Image: Staff Sgt. Jonathan Steffen — U.S. Air Force