Depleted uranium (DU; also referred to in the past as Q-metal, depletalloy, or D-38) is uranium with a lower content of the fissile isotope U-235 than natural uranium (natural uranium is about 99.27% uranium-238 (U-238), 0.72% U-235, and 0.0055% U-234). Uses of DU take advantage of its very high density of 19.1 g/cm3 (68.4% denser than lead). Civilian uses include counterweights in aircraft, radiation shielding in medical radiation therapy and industrial radiography equipment, and containers used to transport radioactive materials. Military uses include defensive armor plating and armor-piercing projectiles.
Most depleted uranium arises as a byproduct of the production of enriched uranium for use in nuclear reactors and in the manufacture of nuclear weapons. Enrichment processes generate from the uranium feed a small fraction of uranium with a higher-than-natural concentration of lower-mass uranium isotopes (in particular U-235, which is the uranium isotope supporting the fission chain reaction) with the bulk of the feed ending up as depleted uranium, in some cases with mass fractions of U-235 and U-234 less than a third of those in natural uranium.[2] U-238 has a much longer halflife than the lighter isotopes, and DU therefore emits less alpha radiation than the same mass of natural uranium: the US Defense Department states DU used in US munitions has 60% the radioactivity of natural uranium.[3]
Since the U-235 content of nuclear reactor fuel is reduced by fission, uranium recovered by nuclear reprocessing from spent nuclear reactor fuel made from natural uranium will have a lower-than-natural U-235 concentration. Such ‘reactor-depleted’ material will have different isotopics from enrichment byproduct DU, and can be distinguished from it by the presence of U-236.[4] Trace transuranics (another indicator of the use of reprocessed material) have been reported to be present in some US tank armour.[3]
The use of DU in munitions is controversial because of questions about potential long-term health effects.[5][6] Normal functioning of the kidney, brain, liver, heart, and numerous other systems can be affected by uranium exposure, because uranium is a toxic metal.[7] It is weakly radioactive and remains so because of its long physical half-life (4.468 billion years for uranium-238, 700 million years for uranium-235). The biological half-life (the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days.[8] The aerosol or spallation frangible powder produced during impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites leading to possible inhalation by human beings.[9]
The actual acute and chronic toxicity of DU is also a point of medical controversy. Multiple studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic, genetic, reproductive, and neurological effects from chronic exposure.[5] A 2005 epidemiology review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU."[10] The World Health Organization, the directing and coordinating authority for health within the United Nations which is responsible for setting health research norms and standards, providing technical support to countries and monitoring and assessing health trends, states that no risk of reproductive, developmental, or carcinogenic effects have been reported in humans due to DU exposure.[11][12] This report has been criticized by Dr. Keith Baverstock for not including possible long term effects of DU on the human body.[13]
Enriched uranium was first manufactured in the early 1940s when the United States began its nuclear weapons program. Later in the decade, Britain, France, and the Soviet Union began their nuclear weapons and nuclear power programs. It was at this time that depleted uranium was first stored as an unusable waste product (uranium hexafluoride). There was some hope that the enrichment process would be improved and fissionable isotopes of U-235 could, at some future date, be extracted from the depleted uranium. This re-enrichment recovery of the residual uranium-235 contained in the depleted uranium is no longer a matter of the future: it has been practiced for several years.[14] Also, it is possible to design civilian power reactors with unenriched fuel, but only about 10% of reactors ever built utilize that technology, and both nuclear weapons production and naval reactors require the concentrated isotope.
In the 1970s, the Pentagon reported that the Soviet military had developed armor plating for Warsaw Pact tanks that NATO ammunition could not penetrate. The Pentagon began searching for material to make denser armor-piercing projectiles. After testing various metals, ordnance researchers settled on depleted uranium.
The US and NATO militaries used DU penetrator rounds in the 1991 Gulf War, the Bosnia war,[15] bombing of Serbia, and the 2003 invasion of Iraq.[16]
While clearing a decades-old Hawaii firing range in 2005, workers found depleted uranium fins from training rounds from the formerly classified Davy Crockett recoilless gun tactical battlefield nuclear delivery system from the 1960-1970s.[17] These training rounds had been forgotten because they were used in a highly classified program and had been fired before DU had become an item of interest, more than 20 years before the Gulf War.
Natural uranium metal contains about 0.71% U-235, 99.28% U-238, and about 0.0054% U-234. In order to produce enriched uranium, the process of isotope separation removes a substantial portion of the U-235 for use in nuclear power, weapons, or other uses. The remainder, depleted uranium, contains only 0.2% to 0.4% U-235. Because natural uranium begins with such a low percentage of U-235, enrichment produces large quantities of depleted uranium. For example, producing 1 kg of 5% enriched uranium requires 11.8 kg of natural uranium, and leaves about 10.8 kg of depleted uranium with only 0.3% U-235 remaining.
The Nuclear Regulatory Commission (NRC) defines depleted uranium as uranium with a percentage of the 235U isotope that is less than 0.711% by weight (see 10 CFR 40.4). The military specifications designate that the DU used by the U.S. Department of Defense (DoD) contain less than 0.3% 235U (AEPI, 1995). In actuality, DoD uses only DU that contains approximately 0.2% 235U (AEPI, 1995).
About 95% of the depleted uranium produced is stored as uranium hexafluoride, a crystalline solid, (D)UF6, in steel cylinders in open air storage yards close to enrichment plants. Each cylinder holds up to 12.7 tonnes (or 14 short tons) of UF6. In the U.S. 560,000 tonnes of depleted UF6 had accumulated by 1993. In 2008, 686,500 tonnes in 57,122 storage cylinders were located near Portsmouth, Ohio and Paducah, Kentucky.[18][19]
The storage of DUF6 presents environmental, health, and safety risks because of its chemical instability. When UF6 is exposed to water vapor in the air, it reacts with the moisture to produce UO2F2 (uranyl fluoride), a solid, and HF (hydrogen fluoride), a gas, both of which are highly soluble and toxic. The uranyl fluoride solid acts to plug the leak, limiting further escape of depleted UF6. Release of the hydrogen fluoride gas to the atmosphere is also slowed by the plug formation.[20] Storage cylinders must be regularly inspected for signs of corrosion and leaks and are repainted and repaired as necessary. The estimated lifetime of the steel cylinders is measured in decades.[21]
A tenfold jump in uranium prices has transformed approximately one-third of the U.S. depleted uranium inventory into an asset worth $7.6 billion, assuming DOE re-enriches the tails. This estimate is based on February 2008 market price for uranium and enrichment services, and DOE's access to sufficient uranium enrichment capacity.[22]
There have been several accidents involving uranium hexafluoride in the United States, including one in which 31 workers were exposed to a cloud of UF6 and its reaction products and a man died after inhaling some of the resulting gas. Though some of the more highly exposed workers showed evidence of short-term kidney damage (e.g., protein in the urine), none of these workers had lasting kidney toxicity from the uranium exposure.[23] The U.S. government has been converting DUF6 to solid uranium oxides for use or disposal.[24] Such disposal of the entire DUF6 inventory could cost anywhere from $15 million to $450 million.[25]
| Country | Organization | Estimated DU stocks (tonnes) |
Reported |
|---|---|---|---|
| United States | DOE | 480,000 | 2002 |
| Russia | FAEA | 460,000 | 1996 |
| France | Areva NC | 190,000 | 2001 |
| United Kingdom | BNFL | 30,000 | 2001 |
| Germany Netherlands United Kingdom |
URENCO | 16,000 | 1999 |
| Japan | JNFL | 10,000 | 2001 |
| China | CNNC | 2,000 | 2000 |
| South Korea | KAERI | 200 | 2002 |
| South Africa | NECSA | 73 | 2001 |
| Singapore | DSO National Laboratories | 60 | 2007 |
| TOTAL | 1,188,273 | 2008 |
Depleted uranium is very dense; at 19050 kg/m³, it is 1.67 times as dense as lead, only slightly less dense than tungsten and gold, and 84% as dense as osmium or iridium, which are the densest known substances under standard (i.e., Earth-surface) pressures. Thus a given mass of it has a smaller diameter than an equivalent lead projectile, with less aerodynamic drag and deeper penetration due to a higher pressure at point of impact. DU projectile ordnance is often incendiary because of its pyrophoric property.[26]
Because of its high density, depleted uranium can also be used in tank armor, sandwiched between sheets of steel armor plate. For instance, some late-production M1A1HA and M1A2 Abrams tanks built after 1998 have DU reinforcement as part of the armor plating in the front of the hull and the front of the turret, and there is a program to upgrade the rest (see Chobham armor).
Depleted uranium is used as a tamper in fission bombs.
Most military use of depleted uranium has been as 30 mm caliber ordnance, primarily the 30 mm PGU-14/B armour-piercing incendiary round from the GAU-8 Avenger cannon of the A-10 Thunderbolt II used by the United States Air Force. 25 mm DU rounds have been used in the M242 gun mounted on the U.S. Army's Bradley Fighting Vehicle and Marine Corp'sLAV-25.
The United States Marine Corps uses DU in the 25 mm PGU-20 round fired by the GAU-12 Equalizer cannon of the AV-8B Harrier, and also in the 20 mm M197 gun mounted on AH-1 Cobra helicopter gunships. The United States Navy's Phalanx CIWS's M61 Vulcan Gatling gun used 20 mm armor-piercing penetrator rounds with discarding plastic sabots which were made using depleted uranium, later changed to tungsten.
Another use of depleted uranium is in kinetic energy penetrators anti-armor rounds, such as the 120 mm sabot rounds fired from the M1A1 and M1A2 Abrams.[27] Kinetic energy penetrator rounds consist of a long, relatively thin penetrator surrounded by discarding sabot. Staballoys are metal alloys of depleted uranium with a very small proportion of other metals, usually titanium or molybdenum. One formulation has a composition of 99.25% by mass of depleted uranium and 0.75% by mass of titanium. Staballoys are approximately 1.67 times as dense as lead and are designed for use in kinetic energy penetrator armor-piercing ammunition. The US Army uses DU in an alloy with around 3.5% titanium.
According to recent research,[28] at least some of the most promising tungsten alloys that have been considered as replacement for depleted uranium in penetrator ammunitions, such as tungsten-cobalt or tungsten-nickel-cobalt alloys, also possess extreme carcinogenic properties, which by far exceed those (confirmed or suspected) of depleted uranium itself: 100% of rats implanted with a pellet of such alloys developed lethal rhabdomyosarcoma within a few weeks.
Depleted uranium is favored for the penetrator because it is self-sharpening and pyrophoric.[26] On impact with a hard target, such as an armored vehicle, the nose of the rod fractures in such a way that it remains sharp. The impact and subsequent release of heat energy causes it to disintegrate to dust and burn when it reaches air because of its pyrophoric properties.[26] When a DU penetrator reaches the interior of an armored vehicle, it catches fire, often igniting ammunition and fuel, killing the crew, and possibly causing the vehicle to explode. DU is used by the U.S. Army in 120 mm or 105 mm cannons employed on the M1 Abrams tank. The Russian military has used DU ammunition in tank main gun ammunition since the late 1970s, mostly for the 115 mm guns in the T-62 tank and the 125 mm guns in the T-64, T-72, T-80, and T-90 tanks.
The DU content in various ammunition is 180 g in 20 mm projectiles, 200 g in 25 mm ones, 280 g in 30 mm, 3.5 kg in 105 mm, and 4.5 kg in 120 mm penetrators. DU was used during the mid-1990s in the U.S. to make grenades, cluster bombs, and mines, but those applications have been discontinued, according to Alliant Techsystems. The US Navy used DU in its 20 mm Phalanx CIWS guns, but switched in the late 1990s to armor-piercing tungsten.
Depleted uranium is also suspected, by Doug Rokke,[29] to be used in a variety of U.S. manufactured bombs and missiles, in particular bunker buster or high penetrating ordinance such as versions of the GBU-28 fitted with the BLU-113 advanced unitary penetrator, and the BLU-116 where increased warhead density allows for increased penetration.[30][31][32] If this is the case, very large quantities of depleted uranium may be contained within each bomb or missile, which would be largely vaporized on impact- the widespread use of these weapons would thus constitute a major source of depleted uranium contamination.[33] Depleted uranium has also been utilized in High explosive anti-tank warheads (HEAT), one example is the Russian 3BK-21B 125mm HEAT tank round.[30][34]
It is thought that between 17 and 20 countries have weapons incorporating depleted uranium in their arsenals. They include the U.S., the UK, France, Russia, China, India, Turkey, Saudi Arabia, Israel, Bahrain, Egypt, Kuwait, Pakistan, Thailand, Iraq and Taiwan. DU ammunition is manufactured in 18 countries. Only the US and the UK have acknowledged using DU weapons.[35]
In a three week period of conflict in Iraq during 2003 it was estimated over 1000 tons of depleted uranium munitions were used.[36]
In 1996 the International Court of Justice (ICJ) gave an advisory opinion on the "legality of the threat or use of nuclear weapons".[37] This made it clear, in paragraphs 54, 55 and 56, that international law on poisonous weapons—the Second Hague Declaration of 29 July 1899, Hague Convention IV of 18 October 1907 and the Geneva Protocol of 17 June 1925—did not cover nuclear weapons, because their prime or exclusive use was not to poison or asphyxiate. This ICJ opinion was about nuclear weapons, but the sentence "The terms have been understood, in the practice of States, in their ordinary sense as covering weapons whose prime, or even exclusive, effect is to poison or asphyxiate," also removes depleted uranium weaponry from coverage by the same treaties as their primary use is not to poison or asphyxiate, but to destroy materiel and kill soldiers through kinetic energy.
The Sub-Commission on Prevention of Discrimination and Protection of Minorities of the United Nations Human Rights Commission,[38] passed two motions[39] — the first in 1996[40] and the second in 1997.[41] They listed weapons of mass destruction, or weapons with indiscriminate effect, or of a nature to cause superfluous injury or unnecessary suffering and urged all states to curb the production and the spread of such weapons. Included in the list was weaponry containing depleted uranium. The committee authorized a working paper, in the context of human rights and humanitarian norms, of the weapons.
The requested UN working paper was delivered in 2002[42] by Y.K.J. Yeung Sik Yuen in accordance with Sub-Commission on the Promotion and Protection of Human Rights resolution 2001/36. He argues that the use of DU in weapons, along with the other weapons listed by the Sub‑Commission, may breach one or more of the following treaties: the Universal Declaration of Human Rights, the Charter of the United Nations, the Genocide Convention, the United Nations Convention Against Torture, the Geneva Conventions including Protocol I, the Convention on Conventional Weapons of 1980, and the Chemical Weapons Convention. Yeung Sik Yuen writes in Paragraph 133 under the title "Legal compliance of weapons containing DU as a new weapon":
Annex II to the Convention on the Physical Protection of Nuclear Material 1980 (which became operative on 8 February 1997) classifies DU as a category II nuclear material. Storage and transport rules are set down for that category which indicates that DU is considered sufficiently "hot" and dangerous to warrant these protections. But since weapons containing DU are relatively new weapons no treaty exists yet to regulate, limit or prohibit its use. The legality or illegality of DU weapons must therefore be tested by recourse to the general rules governing the use of weapons under humanitarian and human rights law which have already been analysed in Part I of this paper, and more particularly at paragraph 35 which states that parties to Protocol I to the Geneva Conventions of 1949 have an obligation to ascertain that new weapons do not violate the laws and customs of war or any other international law. As mentioned, the International Court of Justice considers this rule binding customary humanitarian law.
In 2001, Carla Del Ponte, then the chief prosecutor for the International Criminal Tribunal for the Former Yugoslavia, said that NATO's use of depleted uranium in former Yugoslavia could be investigated as a possible war crime.[43] Louise Arbour, Del Ponte's predecessor as chief prosecutor, had created a small, internal committee, made up of staff lawyers, to assess the allegation. Their findings, that were accepted and endorsed by Del Ponte,[44] concluded that:
There is no specific treaty ban on the use of DU projectiles. There is a developing scientific debate and concern expressed regarding the impact of the use of such projectiles and it is possible that, in future, there will be a consensus view in international legal circles that use of such projectiles violate general principles of the law applicable to use of weapons in armed conflict. No such consensus exists at present.[45]
Some states and the International Coalition to Ban Uranium Weapons, a coalition of more than 155 non-governmental organizations, have asked for a ban on the production and military use of depleted uranium weapons.[46]
The European Parliament has repeatedly passed resolutions requesting an immediate moratorium on the further use of depleted uranium ammunition,[47][48] but France and Britain – the only EU states that are permanent members of the United Nations Security Council – have consistently rejected calls for a ban,[49] maintaining that its use continues to be legal, and that the health risks are entirely unsubstantiated.[50]
In 2007 France, Britain, the Netherlands, and the Czech Republic voted against a United Nations General Assembly resolution to hold a debate in 2009 about the effects of the use of armaments and ammunitions containing depleted uranium. All other European Union nations voted in favour or abstained.[51] The ambassador from the Netherlands explained his negative vote as being due to the reference in the preamble to the resolution "to potential harmful effects of the use of depleted uranium munitions on human health and the environment [which] cannot, in our view, be supported by conclusive scientific studies conducted by relevant international organizations."[52] None of the other permanent members of the United Nations Security Council supported the resolution as China was absent for the vote, Russia abstained and the United States voted against the resolution.[51]
In September 2008, and in response to the 2007 General Assembly resolution, the UN Secretary General published the views of 15 states alongside those of the International Atomic Energy Agency (IAEA) and World Health Organization (WHO). The IAEA and WHO evidence differed little from previous statements on the issue.[53] The report was largely split between states concerned about depleted uranium's use such as Finland, Cuba, Japan, Serbia, Argentina and predominantly NATO members who do not consider the use of depleted uranium munitions problematic.[53]
In December 2008, 141 states supported a resolution requesting that three UN agencies: United Nations Environment Programme (UNEP), WHO and IAEA update their research on the impact of uranium munitions by late 2010 – to coincide with the General Assembly's 65th Session, four voted against, 34 abstained and 13 were absent[54] As before Britain and France voted against the resolution. All other European Union nations voted in favour or abstained: the Netherlands, which voted against a resolution in 2007, voted in favour, as did Finland and Norway, both of which had abstained in 2007, while the Czech Republic, which voted against the resolution in 2007, abstained. The two other states that voted against the resolution were Israel and the United States (both of which voted against in 2007), while as before China was absent for the vote, and Russia abstained.[54]
On June 21, 2009, Belgium became the first country in the world to ban: "inert ammunition and armour that contains depleted uranium or any other industrially manufactured uranium."[55] The move followed a unanimous parliamentary vote on the issue on 22 March 2007. The text of the 2007 law allowed for two years to pass until it came into force.[56] In April 2009, the Belgian Senate voted unanimously to restrict investments by Belgian banks into the manufacturers of depleted uranium weapons.[57]
In September 2009, the Latin American Parliament passed a resolution calling for a regional moratorium on the use, production and procurement of uranium weapons. It also called on the Parlatino's members to work towards an international uranium weapons treaty.[58]
In December 2010 the UN General Assembly passed a resolution calling on users of depleted uranium to hand over quantitative and geographical data on their use, to the relevant authorities of affected states when requested to do so. The resolution passed by 148 votes to four, with 30 abstentions. Five states that have abstained on previous resolutions in 2007 and 2008 voted in favour – Belgium, Bosnia & Herzegovina, Greece, Luxembourg and Slovenia, and no former supporters changed position. The UK, US, Israel and France voted against.[59]
In April 2011, the Congress of Costa Rica passed a law prohibiting uranium weapons in its territories, becoming the second country in the world to do so.[60] In November 2010, the Irish Senate also passed a bill seeking to outlaw depleted uranium weapons; it is now expected to be considered by the Dáil before passage into law.[61]
Depleted uranium has a very high density and is primarily used as shielding material for other radioactive material, and as ballast. Examples include sailboat keels, as counterweights and as shielding in industrial radiography cameras.
Industrial radiography cameras include a very high activity gamma radiation source (typically Ir-192 with an activity above 10 TBq). Depleted uranium is often used in the cameras as a shield to protect individuals from the gamma source. Typically the uranium shield is supported and enclosed in polyurethane foam for thermal, mechanical and oxidation protection.[62]
Consumer product uses have included incorporation into dental porcelain, used for false teeth to simulate the fluorescence of natural teeth, and uranium-bearing reagents used in chemistry laboratories (e.g. uranyl acetate, used in analytical chemistry and as a stain in electron microscopy). Uranium (both depleted uranium and natural uranium) was widely used as a coloring matter for porcelain and glass in the 19th and early-to-mid-20th century. The practice was largely discontinued in the late 20th century. In 1999 concentrations of 10% depleted uranium were being used in "jaune no.17" a yellow enamel powder that was being produced in France by Cristallerie de Saint-Paul, a manufacturer of enamel pigments. The depleted uranium used in the powder was sold by Cogéma's Pierrelatte facility. In February 2000, Cogema discontinued the sale of depleted uranium to producers of enamel and glass.[63]
Aircraft that contain depleted uranium trim weights (Boeing 747–100 for example) may contain between 400 to 1,500 kg of DU. This application is controversial because the DU may enter the environment if the aircraft were to crash. The metal can also oxidize to a fine powder in a fire. Its use has been phased out in many newer aircraft. Boeing and McDonnell-Douglas discontinued using DU counterweights in the 1980s. Depleted uranium was released during the crash of El Al Flight 1862, in which 152 kg was lost, but an extensive study concluded that there was no evidence to link depleted uranium from the plane to any health problems.[64] Counterweights manufactured with cadmium plating are considered non-hazardous while the plating is intact.[65]
U.S. Nuclear Regulatory Commission regulations at 10 CFR 40.25 establish a general license for the use of depleted uranium contained in industrial products or devices for mass-volume applications. This general license allows anyone to possess or use depleted uranium for authorized purposes. Generally, a registration form is required, along with a commitment to not abandon the material. Agreement states may have similar, or more stringent, regulations.
Pen Duick VI, a boat designed by André Mauric and used for racing, was equipped with a keel in depleted uranium. It was later replaced by a standard lead keel.
Depleted uranium has been used in a number of sampling calorimeters (such as in the D0[66] and ZEUS[67] detectors) in due to its high density and natural radioactivity.
Normal functioning of the kidney, brain, liver, heart, and numerous other systems can be affected by uranium exposure, because in addition to being weakly radioactive, uranium is a toxic metal.[7] DU is less toxic than other heavy metals such as arsenic and mercury.[68] It is weakly radioactive but remains radioactive because of its long half-life. The Agency for Toxic Substances and Disease Registry states that: "to be exposed to radiation from uranium, you have to eat, drink, or breathe it, or get it on your skin."[69]
However, the Institute of Nuclear Technology-Radiation Protection of Attiki, Greece, has noted that "the aerosol produced during impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites or can be inhaled by civilians and military personnel."[9] The U.S. Department of Defense claims that no human cancer of any type has been seen as a result of exposure to either natural or depleted uranium.[70]
As early as 1997, British Army doctors warned the British MoD (Ministry of Defence) that exposure to depleted uranium increased the risk of developing lung, lymph and brain cancer, and recommended a series of safety precautions.[71] According to a report issued summarizing the advice of the doctors, 'Inhalation of insoluble uranium dioxide dust will lead to accumulation in the lungs with very slow clearance - if any . . . Although chemical toxicity is low, there may be localised radiation damage of the lung leading to cancer." The report warns that 'All personnel... should be aware that uranium dust inhalation carries a long-term risk... [the dust] has been shown to increase the risks of developing lung, lymph and brain cancers."[71]
Studies using cultured cells and laboratory rodents continue to suggest the possibility of leukemogenic, genetic, reproductive, and neurological effects from chronic exposure.[5] In addition, the UK Pensions Appeal Tribunal Service in early 2004 attributed birth defect claims from a February 1991 Gulf War combat veteran to depleted uranium poisoning.[72][73] Also, a 2005 epidemiology review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU."[10]
Its use in incendiary ammunition is controversial because of potential adverse health effects and its release into the environment.[74][75][76][77][78][79] Besides its residual radioactivity, U-238 is a heavy metal whose compounds are known from laboratory studies to be toxic to mammals.
Metallic uranium is prone to slow corrosion and small pieces are pyrophoric at room temperature in air.[26] When depleted uranium munitions penetrate armor or burn, they create depleted uranium oxides in the form of dust that can be inhaled or contaminate wounds. Additionally, fragments of munitions or armor can become embedded in the body.
The chemical toxicity of depleted uranium is about a million times greater in vitro than its radiological hazard.[80] Health effects of DU are determined by factors such as the extent of exposure and whether it was internal or external. Three main pathways exist by which internalization of uranium may occur: inhalation, ingestion, and embedded fragments or shrapnel contamination. Properties such as phase (e.g. particulate or gaseous), oxidation state (e.g. metallic or ceramic), and the solubility of uranium and its compounds influence their absorption, distribution, translocation, elimination and the resulting toxicity. For example, metallic uranium is less toxic compared to hexavalent uranium(VI) uranyl compounds such as uranium trioxide.[81][82]
| Compilation of 2004 Review[7] Information Regarding Uranium Toxicity | |||
|---|---|---|---|
| Body system | Human studies | Animal studies | In vitro |
| Renal | Elevated levels of protein excretion, urinary catalase and diuresis | Damage to Proximal convoluted tubules, necrotic cells cast from tubular epithelium, glomerular changes | No studies |
| Brain/CNS | Decreased performance on neurocognitive tests | Acute cholinergic toxicity; Dose-dependent accumulation in cortex, midbrain, and vermis; Electrophysiological changes in hippocampus | No studies |
| DNA | Increased reports of cancers | Increased urine mutagenicity and induction of tumors | Binucleated cells with micronuclei, Inhibition of cell cycle kinetics and proliferation; Sister chromatid induction, tumorigenic phenotype |
| Bone/muscle | No studies | Inhibition of periodontal bone formation; and alveolar wound healing | No studies |
| Reproductive | Uranium miners have more first born female children | Moderate to severe focal tubular atrophy; vacuolization of Leydig cells | No studies |
| Lungs/respiratory | No adverse health effects reported | Severe nasal congestion and hemorrage, lung lesions and fibrosis, edema and swelling, lung cancer | No studies |
| Gastrointestinal | Vomiting, diarrhea, albuminuria | n/a | n/a |
| Liver | No effects seen at exposure dose | Fatty livers, focal necrosis | No studies |
| Skin | No exposure assessment data available | Swollen vacuolated epidermal cells, damage to hair follicles and sebaceous glands | No studies |
| Tissues surrounding embedded DU fragments | Elevated uranium urine concentrations | Elevated uranium urine concentrations, perturbations in biochemical and neuropsychological testing | No studies |
| Immune system | Chronic fatigue, rash, ear and eye infections, hair and weight loss, cough. May be due to combined chemical exposure rather than DU alone | No studies | No studies |
| Eyes | No studies | Conjunctivitis, irritation inflammation, edema, ulceration of conjunctival sacs | No studies |
| Blood | No studies | Decrease in RBC count and hemoglobin concentration | No studies |
| Cardiovascular | Myocarditis resulting from the uranium ingestion, which ended 6 months after ingestion | No effects | No studies |
Uranium is pyrophoric when finely divided.[26] It will corrode under the influence of air and water producing insoluble uranium(IV) and soluble uranium (VI) salts. Soluble uranium salts are toxic. Uranium slowly accumulates in several organs, such as the liver, spleen, and kidneys. The World Health Organization has established a daily "tolerated intake" of soluble uranium salts for the general public of 0.5 µg/kg body weight, or 35 µg for a 70 kg adult.
Epidemiological studies and toxicological tests on laboratory animals point to it as being immunotoxic,[83] teratogenic,[84][85] neurotoxic,[86] with carcinogenic and leukemogenic potential.[87] A 2005 report by epidemiologists concluded: "the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU."[10]
Early studies of depleted uranium aerosol exposure assumed that uranium combustion product particles would quickly settle out of the air[88] and thus could not affect populations more than a few kilometers from target areas,[89] and that such particles, if inhaled, would remain undissolved in the lung for a great length of time and thus could be detected in urine.[90] Burning uranium droplets violently produce a gaseous vapor comprising about half of the uranium in their original mass.[91] Uranyl ion contamination in uranium oxides has been detected in the residue of DU munitions fires.[92][93]
External exposure to radiation from pure depleted uranium is less of a concern, because the alpha particle emitted by its isotopes travel only a few centimetres in air or can be stopped by a sheet of paper. Also, the low concentration of uranium-235 that remains in depleted uranium emits only a small amount of low-energy gamma radiation. However, internal alpha radiation exposure from a particle lodged in tissues is a more serious matter, because adjacent tissues will be irradiated.
According to the World Health Organization, a radiation dose from it would be about 60% of that from purified natural uranium with the same mass; the radiological dangers are lower due to its longer half-life and the removal of the more radioactive isotopes. However, in a matter of a month or so, depleted uranium generates amounts of thorium-234 and protactinium-234 which emit beta particles at almost the same rate as that of the alpha particles from the uranium-238.
Approximately 90 micrograms of natural uranium, on average, exist in the human body as a result of normal intake of water, food and air. Most is in the skeleton. The biochemistry of depleted uranium is, for all practical purposes, the same as natural uranium.
Increased rates of immune system disorders and other wide-ranging symptoms, including chronic pain, fatigue and memory loss, have been reported in over one quarter of combat veterans of the 1991 Gulf War.[95] Combustion products from depleted uranium munitions are being considered as one of the potential causes by the Research Advisory Committee on Gulf War Veterans' Illnesses, as DU was used in 30 mm and smaller caliber machine-gun bullets on a large scale for the first time in the Gulf War. Veterans of the conflicts in the Persian Gulf, Bosnia and Kosovo have been found to have up to 14 times the usual level of chromosome abnormalities in their genes.[96][97] Serum-soluble genotoxic teratogens produce congenital disorders, and in white blood cells causes immune system damage.[98]
Human epidemiological evidence is consistent with increased risk of birth defects in the offspring of persons exposed to DU.[10] A 2001 study of 15,000 February 1991 U.S. Gulf War combat veterans and 15,000 control veterans found that the Gulf War veterans were 1.8 (fathers) to 2.8 (mothers) times more likely to have children with birth defects.[99] After examination of children's medical records two years later, the birth defect rate increased by more than 20%:
In early 2004, the UK Pensions Appeal Tribunal Service attributed birth defect claims from a February 1991 Gulf War combat veteran to depleted uranium poisoning.[101][102] Children of British soldiers who fought in wars in which depleted uranium ammunition was used are at greater risk of suffering genetic diseases such as congenital malformations, commonly called "birth defects," passed on by their fathers. In a study of U.K. troops, "Overall, the risk of any malformation among pregnancies reported by men was 50% higher in Gulf War Veterans (GWV) compared with Non-GWVs."[103]
The U.S. Army has commissioned ongoing research into potential risks of depleted uranium and other projectile weapon materials like tungsten, which the U.S. Navy has used in place of DU since 1993. Studies by the U.S. Armed Forces Radiobiology Research Institute conclude that moderate exposures to either depleted uranium or uranium present a significant toxicological threat.[104]
One particular subgroup of veterans which may be at higher risk comprises those who have internally retained fragments of DU from shrapnel wounds. A laboratory study on rats produced by the Armed Forces Radiobiology Research Institute showed that, after a study period of 6 months, rats treated with depleted uranium coming from implanted pellets, comparable to the average levels in the urine of Desert Storm veterans with retained DU fragments, had developed a significant tendency to lose weight with respect to the control group.[105]
Substantial amounts of uranium were accumulating in their brains and central nervous systems, and showed a significant reduction of neuronal activity in the hippocampus in response to external stimuli. The conclusions of the study show that brain damage from chronic uranium intoxication is possible at lower doses than previously thought. Results from computer-based neurocognitive tests performed in 1997 showed an association between uranium in the urine and "problematic performance on automated tests assessing performance efficiency and accuracy."[106]
In 2003 Professor Brian Spratt FRS, chairman of the Royal Society's working group on depleted uranium, said: "The question of who carries out the initial monitoring and clean-up is a political rather than scientific question," and "the coalition needs to acknowledge that depleted uranium is a potential hazard and make in-roads into tackling it by being open about where and how much depleted uranium has been deployed."[36]
Since 2001, medical personnel at the Basra hospital in southern Iraq have reported a sharp increase in the incidence of child leukemia and genetic malformation among babies born in the decade following the Gulf War. Iraqi doctors attributed these malformations to possible long-term effects of DU, an opinion which was echoed by several newspapers.[78][107][108][109] In 2004, Iraq had the highest mortality rate due to leukemia of any country.[110] The International Coalition to Ban Uranium Weapons (ICBUW) has made a call to support an epidemiological study in the Basra region, as asked for by Iraqi doctors,[111] but no peer-reviewed study has yet been undertaken in Basra.
A medical survey, "Cancer, Infant Mortality and Birth Sex Ratio in Fallujah, Iraq 2005–2009" published in July 2010, states that the “Increase in cancer and birth defects…are alarmingly high” and that infant mortality 2009/2010 has reached 13.6%. The group compares the dramatic increase, five years after the actual war 2004, or exposure, with the lymphoma Italian peacekeepers [112] developed after the Balkan wars, and the increased cancer risk in certain parts of Sweden due to the Chernobyl fallout. The origin and time of introduction of the carcinogenic agent causing the genetic stress, the group will address in a separate report.[113]
In 2001, doctors at the Serb-run hospital in Kosovska Mitrovica say the number of patients suffering from malignant diseases has increased by 200% since 1998.[114] In the same year, the World Health Organization reported that data from Kosovo was inconclusive and called for further studies.[115]
A 2003 study by the United Nations Environment Programme (UNEP) in Bosnia and Herzegovina stated that low levels of contaminate were found in drinking water and air particulate at DU penetrator impact points. The levels were stated as not a cause for alarm. Yet, Pekka Haavisto, chairman of the UNEP DU projects stated, "The findings of this study stress again the importance of appropriate clean-up and civil protection measures in a post-conflict situation."[116]
The Canadian Uranium Medical Research Centre obtained urine samples from bombed civilian areas in Jalalabad that showed concentrations of 80-400 ng/L of undepleted uranium, far higher than the typical concentration in the British population of ~5 ng/L.[117]
Studies in 2005 and earlier have concluded that DU ammunition has no measurable detrimental health effects.
A 1999 literature review conducted by the Rand Corporation stated: "No evidence is documented in the literature of cancer or any other negative health effect related to the radiation received from exposure to depleted or natural uranium, whether inhaled or ingested, even at very high doses,"[118] and a RAND report authored by the U.S. Defense department undersecretary charged with evaluating DU hazards considered the debate to be more political than scientific.[119]
A 2001 oncology study concluded that "the present scientific consensus is that DU exposure to humans, in locations where DU ammunition was deployed, is very unlikely to give rise to cancer induction".[120] Former NATO Secretary General Lord Robertson stated in 2001 that "the existing medical consensus is clear. The hazard from depleted uranium is both very limited, and limited to very specific circumstances".[121]
A 2002 study from the Australian defense ministry concluded that “there has been no established increase in mortality or morbidity in workers exposed to uranium in uranium processing industries... studies of Gulf War veterans show that, in those who have retained fragments of depleted uranium following combat related injury, it has been possible to detect elevated urinary uranium levels, but no kidney toxicity or other adverse health effects related to depleted uranium after a decade of follow-up.”[122] Pier Roberto Danesi, then-director of the International Atomic Energy Agency (IAEA) Seibersdorf +Laboratory, stated in 2002 that "There is a consensus now that DU does not represent a health threat".[123]
The IAEA reported in 2003 that, "based on credible scientific evidence, there is no proven link between DU exposure and increases in human cancers or other significant health or environmental impacts," although "Like other heavy metals, DU is potentially poisonous. In sufficient amounts, if DU is ingested or inhaled it can be harmful because of its chemical toxicity. High concentration could cause kidney damage." The IAEA concluded that while depleted uranium is a potential carcinogen, there is no evidence that it has been carcinogenic in humans.[124]
A 2005 study by Sandia National Laboratories’ Al Marshall used mathematical models to analyze potential health effects associated with accidental exposure to depleted uranium during the 1991 Gulf War. Marshall’s study concluded that the reports of cancer risks from DU exposure are not supported by his analysis nor by veteran medical statistics. Marshall also examined possible genetic effects due to radiation from depleted uranium.[125] Chemical effects, including potential reproductive issues, associated with depleted uranium exposure were discussed in some detail in a subsequent journal paper. [126]
Elevated radiation levels consistent with very low level atmospheric depleted uranium contamination have been found in air samples taken by the UK Atomic Weapons Establishment at several monitoring sites in Britain. These elevated readings appear to coincide with Operation Anaconda in Afghanistan, and the Shock and Awe bombing campaign at the start of the Second Gulf War.[30][127]
On October 4, 1992, an El Al Boeing 747-F cargo aircraft Flight 1862, crashed into an apartment building in Amsterdam. Local residents and rescue workers complained of various unexplained health issues which were being attributed to the release of hazardous materials during the crash and subsequent fires. Authorities conducted an epidemiological study in 2000 of those believed to be affected by the accident. The study concluded that there was no evidence to link depleted uranium (used as counter balance weights on the elevators of the plane) to any of the reported health complaints.[64]
Scientific bodies
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