United States Transfers Depleted Uranium Rounds to Ukraine: The Legal Issues
On September 6, the United States announced it was sending 120 mm depleted uranium armor-piercing tank rounds to Ukraine for use in the 31 M1A1 Abrams tanks to be delivered this fall. In response, a Kremlin spokesman asserted that the United States’ use of depleted uranium “in the former Yugoslavia has led to ‘a galloping rise’ in cancers and other illnesses and affected the next generations living in those areas.” And following the United Kingdom’s March announcement that it would provide depleted uranium rounds, Russian Foreign Minister Sergei Lavrov charged that the United Kingdom was “ready to violate international humanitarian law as in 1999 in Yugoslavia” (see Casey-Maslen’s analysis).
The United States pushed back on the facts, with the Deputy White House Press Secretary countering that the Centers for Disease Control and Prevention (CDC) had uncovered no evidence that depleted uranium rounds cause cancer. He added that the World Health Organization (WHO) “reports that there has been no increase of leukemia or other cancers . . . following any exposure to uranium or [depleted uranium]” and that the International Atomic Energy Agency (IAEA) “has stated unequivocally that there is no proven link between [depleted uranium] exposure and increases in cancers or significant health or environmental impacts.”
The exchange continues a long-standing debate over the munitions. In this post, we assess their use under international law. Following a short explanation of deleted uranium, we examine potentially relevant weapons treaties. A discussion of the environmental provisions and general conduct of hostilities rules within international humanitarian law (IHL) follows. Based in significant part on international scientific and medical studies, we conclude that the use of depleted uranium munitions, as such, does not violate international law.
Depleted Uranium
Depleted uranium is an extremely dense material that is cheaper and easier to produce than other such materials, like tungsten. These characteristics have led to its use in the medical and industrial fields for decades.
Many military forces employ depleted uranium in armor-piercing munitions and armor plating. For example, the United States uses depleted uranium in 120 mm tank rounds, 30 mm cannon rounds fired from the A-10 Thunderbolt II aircraft, 25 mm cannon rounds used by the Army’s Bradley Fighting Vehicle, 20 mm rounds fired by the Navy’s Phalanx anti-missile system, and as a component in M1 Abrams tank armor. With respect to the munitions, the Department of Defense has explained (p. 360):
[D]epleted uranium is a material that has a characteristic that allows it to sharpen itself as it penetrates the target. The uranium shreds off the sides of the penetrator instead of squashing or mushrooming . . . . The result is the depleted uranium will penetrate more armor of a given character and type at a given range than tungsten will, no matter how we design the penetrators.
Much of the controversy surrounding depleted uranium stems from its creation as a by-product during the uranium enrichment process. Uranium is a naturally occurring metal found in soil, rock, oceans, food, and drinking water. As a result, the WHO has confirmed that it already exists in the human body due to the normal intake of water, food, and air (WHO Scientific Review p. iii).
Uranium consists of a combination of three types of radioactive isotopes: U238, U235, and U234. The latter two are the most radioactive. Naturally occurring uranium has a U235 content well below the level needed for nuclear fission. Therefore, it must be “enriched” and removed to be used for that purpose. The by-product of this process is depleted uranium. Depleted uranium has reduced U235 and U234 content compared to natural uranium, making it “considerably less radioactive” (IAEA, paras. 3-4). In addition, the U.S. Environmental Protection Agency states that it only emits alpha particles, which do not have enough energy to penetrate the skin.
Despite its wide use in the civilian sector for decades, public concern regarding the health and environmental effects of depleted uranium surfaced after the United States and the United Kingdom used depleted uranium munitions during the 1991 Gulf War against Iraq and in Operation Allied Force, the 1999 aerial bombing campaign against the Federal Republic of Yugoslavia (WHO Scientific Review p. i). Extensive use of the munitions sparked international scrutiny, including a series of United Nations Environmental Programme (UNEP) assessments in the Balkans during the early 2000s (p. 3). Reports that the United States subsequently used as many as 181,000 30 mm depleted uranium A-10 cannon rounds in Operation Iraqi Freedom reignited public debate in 2016.
During military operations, intact depleted uranium munitions, or fragments, can be deposited in soil, inside objects, on surfaces, or in water. In addition, depleted uranium particles can be aerosolized when striking hard objects, such as armor plating, or through burning due to the heat generated while penetrating objects (IAEA, para. 6). This being so, the primary pathways for human exposure are inhalation, ingestion (eating food or drinking water containing depleted uranium particles), and dermal contact (WHO Scientific Review, p. iv). Accordingly, concern has focused on potential environmental contamination issues and short and long-term impacts on human health.
Weapons Treaties
While depleted uranium is not considered a nuclear or chemical weapon, as a mildly radioactive heavy metal, it has both radiotoxic and chemical toxicity properties. This has led some to suggest that depleted uranium munitions violate various treaties. For instance, one scholar who has done excellent work on depleted uranium has pointed to preambular language in the 1963 Limited Test Ban Treaty, which confirms the parties’ “desire to put an end to the contamination of man’s environment by radioactive substances,” to suggest using depleted uranium weaponry “would appear to be in clear violation of the treaty objectives” (p. 238; Russia, United Kingdom, United States, and Ukraine are parties). But as she recognizes, the treaty does not explicitly mention depleted uranium. More to the point, we believe that stretching this preambular text to such a degree is indefensible because the “object and purpose” of the treaty is to deal with nuclear weapons.
Based on the chemical toxicity properties of depleted uranium, the 1993 Chemical Weapons Convention might also appear to apply. Such an assertion would likewise be flawed. The convention prohibits parties from developing, producing, stockpiling, using, or transferring chemical weapons (art. I), which it defines as “[m]unitions and devices, specifically designed to cause death or other harm through the toxic properties of those toxic chemicals . . . .” (art. II). It further defines a toxic chemical as “[a]ny chemical which through its chemical action on life processes can cause death, temporary incapacitation or permanent harm to humans or animals” (art. II).
Yet, the munitions employ depleted uranium to enhance their penetration capabilities; they are anti-materiel, anti-armor munitions, not anti-personnel. Moreover, the effects of depleted uranium do not qualify it as a toxic chemical by the treaty’s terms. This explains why it is not listed as a toxic chemical in the Convention’s Annex on Chemicals. This is consistent with a 2001 WHO Scientific Review, which found that even direct contact with depleted uranium for several weeks is unlikely to produce adverse health effects. Indeed, even the few medical issues caused by excessive exposure to the more radioactive naturally occurring uranium may be transitory (p. iv).
We, therefore, agree with the assessment of the committee established by the International Criminal Tribunal for the Former Yugoslavia (ICTY), which was tasked to review NATO’s 1999 bombing campaign against the Federal Republic of Yugoslavia. In its Final Report to the Prosecutor, the committee noted, “[t]here is no specific treaty ban on the use of [depleted uranium] projectiles” (para. 26).
Environmental Provisions in IHL Treaties
Although depleted uranium munitions are not explicitly banned by a treaty, it might be argued that their use is limited by the environmental provisions of the 1977 Additional Protocol I to the 1949 Geneva Conventions, to which both Russia and Ukraine are party. Although the United States recognizes that some provisions of Additional Protocol I reflect customary international law, it has long objected to any characterization of the environmental provisions as reflecting customary law (Matheson, p. 424, 436). As one of us concluded in a forthcoming co-authored piece, the United States’ position is legally sound (Biggerstaff/Schmitt).
Article 35(3) of Additional Protocol I prohibits the employment of “methods or means of warfare which are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment.” While the use of individual depleted uranium rounds would never reach the “widespread, long-term and severe damage” threshold, the cumulative effect of their usage on the environment merits consideration. For instance, the United States fired close to 10,000 depleted uranium tank rounds, expended over 67,000 25 mm depleted uranium cannon rounds from the AV-8B Harrier, and shot over 780,000 30mm depleted A-10 Thunderbolt II uranium cannon rounds during Operation Desert Storm in 1991. They totaled approximately 340 tons of depleted uranium munitions during a ground war that only lasted 100 hours.
In this regard, it is essential to understand that Article 35(3) requires significant damage to the natural environment before being triggered. Indeed, the 1987 International Committee of the Red Cross (ICRC) Commentary to the article cautions that “a method or a means of war does not become unlawful under Article 35 of the Protocol unless it cumulatively fulfils all three conditions included in the provision” (para. 1457). As one of us accordingly noted, the use of the conjunctive “and” creates a challenging, three-part test, “which is nearly impossible to meet” (p. 119).
Further complicating matters is a lack of international consensus over the standards for reaching the three-part threshold. As the ICTY’s Final Report to the Prosecutor notes, the “conditions for application are extremely stringent and their scope and contents imprecise” (para. 15). Consensus has only crystallized around “long-term,” which the drafters understood to mean “a matter of decades” (ICRC Commentary, para. 1452).
As to the terms “widespread” and “severe,” the United Nations Convention on the Prohibition of Military or any Hostile Use of Environmental Modification Techniques (ENMOD) uses similar terminology. The committee that drafted the convention understood widespread as “encompassing an area on the scale of several hundred square kilometres” and severe as “involving serious or significant disruption or harm to human life, natural and economic resources or other assets.” However, the committee explicitly stated that those definitions are not intended to apply to other international agreements, an obvious reference to Articles 35(3) and 55 of Additional Protocol I. That limitation aside, the ENMOD definitions provide some context to evaluate the Protocol’s standards.
Based on the high degree of damage to the natural environment required to violate Article 35’s widespread, long-term, and severe threshold, even extensive use of depleted uranium munitions is unlikely to reach that threshold. Regarding the widespread requirement, the WHO and IAEA (p. 14) have only noted detectable localized contamination from depleted uranium munition usage. The widest-spread contamination was from the small, aerosolized particles caused by depleted uranium munitions impacting metal, which are also the quickest to be washed away by wind and precipitation. Munitions embedded in the soil only affect the area of impact, pock-marking an area but not covering large swaths of terrain.
Damage caused by the depleted uranium munitions would also need to last decades to violate the provision. Beyond the fact that wind and rain can dissipate aerosolized particles of depleted uranium, the WHO has concluded that contamination fades into the natural environment over days and years (not decades) (p. 147). Although depleted uranium remains radioactive for a long time, the low amounts of radioactivity it emits (compared to the naturally occurring uranium already present in the soil) means that most contamination will dissipate into the normal background radiation levels. As such, it is unlikely that even widespread depleted uranium contamination would result in detectable increases in radioactivity or chemical toxicity over decades.
Finally, the environmental damage caused by the depleted uranium munitions must be severe before triggering Article 35(3). The UNEP Report mentioned above, which was conducted in close cooperation with the IAEA and WHO, observed that “even in areas with widespread depleted uranium contamination, the overall levels of radioactivity were low and within acceptable international standards, with no immediate dangers from either particle-based or waterborne toxicity” (p. 3). Since December 2007, the UN General Assembly has adopted eight resolutions, each requesting member States to provide information on the effects caused by depleted uranium munitions (see Resolutions 62/30, 63/54, 65/55, 67/36, 69/57, 71/70, 73/38, 75/42, and 77/49). As of December 2022, States had still not provided information to contradict the findings in the 2010 report. Based on UNEP’s findings and the lack of countervailing evidence, it is unlikely that even extensive depleted uranium munition use damages the environment to a degree that violates Article 35(3) for parties to that instrument.
Article 55 of Additional Protocol I provides additional environmental protection. Like Article 35(3), it provides that “[c]are shall be taken in warfare to protect the natural environment against widespread, long-term and severe damage.” However, Article 55 goes further by prohibiting “the use of methods or means of warfare which are intended or may be expected to cause such damage to the natural environment and thereby to prejudice the health or survival of the population.” In other words, whereas Article 35(3) addresses damage to the environment itself, Article 55 focuses on the impact of environmental damage on the human population.
The ICRC’s Commentary on the article observes that the term health “is concerned not only with acts which jeopardize the survival of the population, but also with those which could seriously prejudice health, such as congenital defects, degenerations or deformities. Temporary or short-term effects are not taken into account” (para. 2135).
No scientific studies have suggested that depleted uranium exposure causes the qualifying health effects. For instance, a 2016 United Nations Scientific Committee on the Effects of Atomic Radiation Report to the General Assembly found that Gulf War veterans exposed to depleted uranium had “no clinically significant pathologies” compared to their cohorts (p. 438). It also noted that long-term studies of Gulf War veterans with embedded depleted uranium fragments “have found no clinically meaningful adverse effects” (p. 438).
The WHO similarly concluded that there is “no convincing evidence of an association between exposure to [depleted uranium] and clinical outcomes, including any type of cancer and congenital malformations.” And the UN General Assembly has repeatedly stated “that studies conducted so far by relevant international organizations have not provided a detailed enough account of the magnitude of the potential long-term effects on human beings and the environment of the use of armaments and ammunitions containing depleted uranium” (see Resolutions 65/55, 67/36, 69/57, 71/70, 73/38, 75/42, and 77/49). Therefore, based on current scientific and medical information, it is improbable that the use of depleted uranium munitions would prejudice the health or survival of the population in a conflict zone to the extent that it triggers Article 55.
General Conduct of Hostilities Rules
Commentators sometimes point to a number of general conduct of hostilities rules found in IHL when discussing depleted uranium. None renders the battlefield use of depleted uranium in munitions or otherwise unlawful per se.
Customary IHL prohibits using weapons that are calculated to cause superfluous injury or are of a nature to cause unnecessary suffering. This rule is codified in Article 35(2) of Additional Protocol I. It is also reflected in the U.S. Department of Defense’s Law of War Manual (§ 6.6), which discusses its long lineage in IHL. In 1996 and 1997, the UN Human Rights Commission’s Sub-Commission on Prevention of Discrimination and Protection of Minorities passed motions that cited weapons containing depleted uranium as of concern with respect to the prohibition (see here; see also here).
However, the purpose of using depleted uranium in armor-piercing projectiles is to enhance the munition’s effectiveness at defeating armored vehicles compared to other munitions; its use in the projectiles is not “calculated” to exacerbate injury (DoD Law of War Manual §6.5.7). Moreover, long-term studies have shown that depleted uranium does not cause clinically significant medical issues, even when fragments are embedded in a combatant’s body. Thus, there is no meaningful additional harm to humans to qualify as unnecessary suffering. And even if there were, it would not be “unnecessary” given depleted uranium’s contribution to the effectiveness of the munitions.
Customary IHL also prohibits indiscriminate weapons, a ban found in Article 51 of Additional Protocol I for parties to that instrument. The DoD Law of War Manual explains that “[t]he test for whether a weapon is inherently indiscriminate is whether its use necessarily violates the principles of distinction and proportionality” (§6.7.2). With respect to distinction, depleted uranium tank and cannon rounds are highly accurate, direct fire weapons. But weapons also can be indiscriminate because their effects . . . are of a nature to strike military objectives and civilians or civilian objects without distinction” (Additional Protocol I, art. 51(4)(c)).
As discussed above, depleted uranium can be aerosolized, making it susceptible to spreading uncontrollably. However, the very mechanisms by which it might spread also dissipate its harmful effects. In any event, scientific studies demonstrate that those effects are highly unlikely to be harmful (a de minimis level).
Although the ICTY’s Final Report to the Prosecutor observed that “the underlying principles of the law of armed conflict such as proportionality are applicable” to the use of depleted uranium munitions, it is difficult to imagine a situation in which depleted uranium would be indiscriminate on the basis of violating the customary rule of proportionality. That rule appears in Articles 51(5)(b) and 57(2)(a)(iii) of Additional Protocol I and is reflected in the DoD Law of War Manual (§ 5.10). In text echoing the former, the latter provides, “Combatants must refrain from attacks in which the expected loss of civilian life, injury to civilians, and damage to civilian objects incidental to the attack would be excessive in relation to the concrete and direct military advantage expected to be gained” (§ 5.10).
The proportionality question is, therefore, whether the potential environmental and health impacts of using depleted uranium in a particular attack are excessive relative to the military benefits the attack is likely to yield. This evaluation is always situational. It will differ, for instance, based on the target (e.g., an enemy’s main battle tank versus a truck) and the amount and type of munitions used to achieve the attack’s objective (e.g., one 30 mm round versus 340 tons). Based on the prevailing scientific and medical data, it is unlikely that the residual harm caused by using depleted uranium munitions would ever be excessive during attacks in which it is used for its intended purpose.
Finally, customary IHL requires the taking of feasible precautions during an attack to limit harm to civilians and civilian objects. Codified in Article 57(1) of Additional Protocol I for parties to the instrument, the rule also appears in the DoD Law of War Manual (§ 5.11). As the Manual notes, “Depending on the circumstances, the process of ‘weaponeering’ in a strike against a target can be used to reduce the risk of harm to civilians and civilian objects by selecting munitions of appropriate size and type, as well as appropriate aim points, while offering the same or superior military advantage in neutralizing or destroying a military objective” (§ 5.11.6).
The purpose of using depleted uranium in munitions is to enhance attack effectiveness compared to other munitions. In other words, the rationale for using them is that other means of attack would be less suitable for achieving the military objective. Using a different type of metal alloy for armor-piercing munitions would likely risk greater collateral damage, for more of the less effective munitions would need to be employed to disable enemy armor and other intended targets. As should be apparent, the requirement to take feasible precautions in attack would seldom mandate a different means of attack.
Conclusion
Neither weapons law nor IHL currently prohibits the use of depleted uranium munitions as such, although they, like all weapons, are subject to the general conduct of hostilities rules governing attacks. Nevertheless, States employing or transferring them would be well-advised to remain sensitive to the fact that they remain controversial. And in areas where depleted uranium munitions are used extensively, the WHO’s recommendations concerning environmental and population monitoring and post-conflict clean-up should be considered when feasible.
***
Michael N. Schmitt is the G. Norman Lieber Distinguished Scholar at the United States Military Academy at West Point. He is also Professor of Public International Law at the University of Reading and Professor Emeritus and Charles H. Stockton Distinguished Scholar-in-Residence at the United States Naval War College.
Major Kevin S. Coble is an active-duty Army judge advocate and a military professor in the Stockton Center for International Law in Newport, Rhode Island.
Photo credit: Lance Cpl. Garry J. Welch, U.S. Marine Corps
