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Depleted uranium instead of lead in munitions: the lesser evil

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Society for Radiological Protection

Journal of Radiological Protection

J. Radiol. Prot. 34 (2014) 249–252

doi:10.1088/0952-4746/34/1/249

Opinion

Depleted uranium instead of lead in munitions: the lesser evil Sergei V Jargin Peoples’ Friendship University of Russia, Clementovski per 6-82, 115184 Moscow, Russia E-mail: [email protected] Received 1 October 2013, revised 10 January 2014 Accepted for publication 15 January 2014 Published 4 March 2014 Abstract

Uranium has many similarities to lead in its exposure mechanisms, metabolism and target organs. However, lead is more toxic, which is reflected in the threshold limit values. The main potential hazard associated with depleted uranium is inhalation of the aerosols created when a projectile hits an armoured target. A person can be exposed to lead in similar ways. Accidental dangerous exposures can result from contact with both substances. Encountering uranium fragments is of minor significance because of the low penetration depth of alpha particles emitted by uranium: they are unable to penetrate even the superficial keratin layer of human skin. An additional cancer risk attributable to the uranium exposure might be significant only in case of prolonged contact of the contaminant with susceptible tissues. Lead intoxication can be observed in the wounded, in workers manufacturing munitions etc; moreover, lead has been documented to have a negative impact on the intellectual function of children at very low blood concentrations. It is concluded on the basis of the literature overview that replacement of lead by depleted uranium in munitions would be environmentally beneficial or largely insignificant because both lead and uranium are present in the environment. Keywords: depleted uranium, lead, threshold limit values

The potential risks related to depleted uranium (DU) have been described in detail in a recent publication (IAEA 2013). One aspect that should be commented on is a comparison of DU with lead: both substances are potentially harmful, while DU has been proposed and used as a substitute for lead in munitions. DU is a by-product of the enrichment of uranium for nuclear fuel; it is considerably less radioactive than natural uranium (IAEA 2013). Uranium is 1.7 times as dense as lead, and is therefore used in armour-piercing shells and bombs. Previous studies and expert reviews have failed to find any conclusive evidence linking the use of DU in 0952-4746/14/010249+04$33.00

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J. Radiol. Prot. 34 (2014) 249

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weapons with significant risks to the health of the civilian population in former combat areas or to that of former combatants (European Commission 2010). Levels of DU inhaled during the 1991 friendly fire incidents in Gulf War I have probably not caused long-term adverse pulmonary health effects (Hines et al 2013). Uranium is deposited close to the point of release (Mitsakou et al 2003). No cases have been reported where exposure to uranium is known to have caused health effects in children (IAEA 2013). Contrary to popular perception, DU is only weakly radioactive (Wessely and Hotopf 1996, McDiarmid 2001): the toxicity of DU is believed to be primarily chemical in nature with radiological activity being a lesser problem (Briner 2006). The main potential hazard associated with DU is inhalation of the aerosols created when a projectile hits an armoured target. The people most likely to receive the highest doses from DU munitions are those near a target at the time of impact or examining the target after the impact (IAEA 2013). Encountering DU fragments is of minor significance because of the low penetration depth of alpha particles emitted by uranium: they are unable to penetrate even the superficial keratin layer of human skin (Bleise et al 2003). Admittedly, exposure to DU-containing munitions can be associated with risks, for example through inadvertent ingestion of loose friable uranium oxides formed on the surface of the penetrators; more details about this are given in IAEA (2013). Note that one can be exposed to lead in similar ways, and lead is, as discussed below, more toxic than DU. As with any radioactive material, there is a risk of developing cancer from exposure to radiation emitted by DU (IAEA 2013). However, according to UNSCEAR (2006), 14 epidemiological studies conducted on more than 120 000 workers at uranium enrichment, metal fabrication and milling facilities did not find the rate of any cancer to be significantly increased. The estimated risks of lung cancer per working level month (WLM) in uranium miners are presented in table 10 of Appendix F to the UNSCEAR (1988) report. One WLM corresponds to an exposure to one working level (WL) for 170 h, which corresponds approximately to 5.1 mSv (Sanders and Scott 2006). Uranium miners are additionally exposed to the much more radioactive radon, its progeny and other radionuclides, as well as to silica dust, arsenic and diesel engine exhaust fumes (ATSDR 2013). The relative risks were minor (1.45–4.97 per 100 WLM or approximately 510 mSv) and not significantly different from the risks in non-uranium miners and those from the national surveys for miners (UNSCEAR 1988). In general, human and animal studies have not found increases in the risk of cancer from uranium exposure in tissues other than the lung (ATSDR 2013). The global average individual annual effective dose from the natural radiation background is about 2.4 mSv. Worldwide, annual exposures to natural background radiation vary widely; they are generally expected to be in the range of 1–10 mSv but can be higher, as summarized in UNSCEAR (2008). Natural background radiation is not known to be associated with any increase in health risks (UNSCEAR 2010), leaving apart the separate topic of radon and lung cancer at cumulative exposure levels of about 50 WLM (ICRP 2010). The attitude to a slight anthropogenic increase in the radiation background should therefore be realistic. Moreover, radiation hormesis, a protective or beneficial action of low radiation doses, should be taken into account; further discussion and references are in Jargin (2009, 2012). Finally, it should be mentioned here that the statement about ‘well documented evidence of . . . carcinogenic consequences of uranium internal contamination’, made in the abstract of the article by Durakovi´c (1999), is not corroborated in the text of the same article. Accordingly, little reliance can be placed on the judgement of Durakovi´c (1999) concerning the carcinogenic effects of uranium. Admittedly, uncontrolled use of DU is associated with a risk of potentially harmful exposure to alpha irradiation after inhalation and ingestion (Briner 2006). However, considering the low radioactivity of DU, the small penetration depth of alpha particles and the presence of uranium in the environment, an additional cancer risk attributable to the DU 250

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Opinion

exposure might be significant only in a case of prolonged contact of the contaminant with susceptible tissues. As for lead, the US Department of Health and Human Services (DHHS) has determined that it is reasonably anticipated to be a human carcinogen based on limited evidence from studies in humans and sufficient evidence from animal studies, while the Environmental Protection Agency (EPA) has determined that lead is a probable human carcinogen (ATSDR 2007). Uranium has many similarities to lead in its exposure mechanisms, chemistry, metabolism, target organs, etc (Briner 2006). However, lead has a longer skeletal half-life than uranium and is more toxic overall, which is reflected in the threshold limit values: for uranium and its compounds the threshold limit value in air is 0.2 mg m−3 , for inorganic lead (fumes and dust) it is 0.15 mg m−3 , for inorganic lead compounds it is 0.05 mg m−3 and for tetraethyl lead it is 0.1 mg m−3 (Plunkett 1987). Several examples from more recent guidelines can be given: the US EPA has established a maximum level for uranium in drinking water of 0.03 mg l−1 ; for lead (chloride, nitrate, sulfate, tetraethyl etc), the action level is 0.015 mg l−1 and the MCLG (maximum contaminant level goal) is zero (ATSDR 2007). The US Occupational Safety and Health Administration (OSHA) set a legal limit for worker exposure in workplace air of 0.05 mg uranium m−3 for soluble uranium and 0.25 mg uranium m−3 for insoluble uranium averaged over an 8 h working day. The time-weighted averages for permissible exposure limits for lead range from 0.05 mg m−3 ‘for toxic and hazardous substances’ to 0.1 mg m−3 for tetraethyl lead in construction and shipyard industries (ATSDR 2007, 2013). For comparison, the use of lead ammunition may result in exposure to lead dust generated during a rifle discharge at levels up to 1 mg m−3 (ATSDR 2007). Insoluble metallic DU and lead are used in munitions. More vapours will be generated during a rifle discharge after the use of lead because of the much lower temperature of evaporation, melting and boiling points of lead compared with uranium. The same must be true for the generation of dust at a discharge because of the higher hardness of uranium. Admittedly, on impact with targets, DU penetrators can ignite, breaking up into fragments and forming an aerosol of particles (IAEA 2013), but this is of minor significance for the environment. Lead intoxication can be observed in the wounded, in workers manufacturing munitions and after exposure to propellant in shooting ranges, etc (Moore 1986). Furthermore, lead has been documented to have a negative impact on the intellectual function of children at very low blood concentrations. A recent multistudy analysis concluded that current allowable blood lead concentrations need to be lowered and further preventive efforts are needed to protect children from lead toxicity (Budtz-Jørgensen et al 2013). Therefore, replacement of lead by DU in munitions would be environmentally beneficial or largely insignificant because both lead and uranium are present in the environment. Small additions would not change the large-scale balance: natural uranium is ubiquitously present in soil at a typical concentration of 3 mg kg−1 (Bleise et al 2003). In nature, uranium together with its daughters yields four to five times as many decays per second as pure non-depleted uranium (Bleise et al 2003). The author of this letter hopes for a peaceful future, but so long as munitions are manufactured, this topic will be of some significance. The physical and chemical properties of DU make it well suited for military applications. DU can be used in ammunitions suitable for piercing armour plating, e.g. on tanks, in missile nose cones and as a component of tank armour (IAEA 2013). Considering the above argument, DU could replace lead in practically all its military applications. Moreover, in view of the future development of nuclear energy, DU will continue to accumulate as a by-product; and any environmentally safe use of it, for example instead of more toxic substances such as lead, should be advocated on economic grounds. Certainly, the absence of a proven cause–effect relationship for DU and cancer does not mean that the substance is entirely safe. This issue should be further clarified by large-scale 251

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animal experiments, reliably shielded from all vested interests and biases, evaluating possible long-term complications of the inhalation and ingestion of DU- and lead-containing dust. Measurements of the DU and lead content in dust in the affected areas should be performed to evaluate potential risks. In conclusion, replacement of lead by DU in munitions would be environmentally beneficial or largely insignificant, whereas accidental dangerous exposures can result from contact with both substances. References ATSDR (Agency for Toxic Substances and Disease Registry) 2007 Toxicological Profile for Lead (Atlanta, GA: United States Department of Health and Human Services, Public Health Service) ww w.atsdr.cdc.gov/toxprofiles/TP.asp?id=96&tid=22 (accessed 8 January 2014) ATSDR 2013 Toxicological Profile for Uranium (Atlanta, GA: United States Department of Health and Human Services, Public Health Service) www.atsdr.cdc.gov/ToxProfiles/ TP.asp?id=440&tid=77 (accessed 8 January 2014) Bleise A, Danesi P R and Burkart W 2003 Properties, use and health effects of depleted uranium (DU): a general overview J. Environ. Radioact. 64 93–112 Briner W E 2006 The evolution of depleted uranium as an environmental risk factor: lessons from other metals Int. J. Environ. Res. Public Health 3 129–35 Budtz-Jørgensen E, Bellinger D, Lanphear B, Grandjean P and International Pooled Lead Study Investigators 2013 An international pooled analysis for obtaining a benchmark dose for environmental lead exposure in children Risk Anal. 33 450–61 Durakovi´c A 1999 Medical effects of internal contamination with uranium Croat. Med. J. 40 49–66 European Commission 2010 Scientific Committee of Health and Environmental Risks (SCHER). Preliminary Opinion on the Environmental and Health Risks Posed by Depleted Uranium http://ec.eu ropa.eu/health/scientific committees/environmental risks/docs/scher o 119.pdf (accessed 8 January 2014) Hines S E, Gucer P, Kligerman S, Breyer R, Centeno J, Gaitens J, Oliver M, Engelhardt S, Squibb K and McDiarmid M 2013 Pulmonary health effects in Gulf War I service members exposed to depleted uranium J. Occup. Environ. Med. 55 937–44 IAEA (International Atomic Energy Agency) 2013 Features: Depleted Uranium International Atomic Energy Agency News Centre www.iaea.org/newscenter/features/du/du qaa.shtml#q3 (accessed 8 January 2014) ICRP (International Commission on Radiological Protection) 2010 Lung cancer risk from radon and progeny and statement on radon ICRP Publication 115; Ann. ICRP 40 (1) Jargin S V 2009 Overestimation of Chernobyl consequences: biophysical aspects Radiat. Environ. Biophys. 48 341–4 Jargin S V 2012 Hormesis and radiation safety norms Hum. Exp. Toxicol. 31 671–5 McDiarmid M A 2001 Depleted uranium and public health BMJ 322 123–4 Mitsakou C, Eleftheriadis K, Housiadas C and Lazaridis M 2003 Modeling of the dispersion of depleted uranium aerosol Health Phys. 84 538–44 Moore M R 1986 Sources of lead exposure The Lead Debate: The Environment, Toxicology and Child Health ed R Landsdown and W Yule (London: Croom Helm) pp 131–92 Plunkett E R 1987 Handbook of Industrial Toxicology (London: Edward Arnold) Sanders C L and Scott B R 2006 Smoking and hormesis as confounding factors in radiation pulmonary carcinogenesis Dose-Response 6 53–79 UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) 1988 Report. Sources, Effects and Risks of Ionizing Radiation (1988 Report to the General Assembly, with Annexes) (New York: UNSCEAR) pp 407–543 (annex F) UNSCEAR 2006 Report. Effects of Ionizing Radiation (2006 Report to the General Assembly, with Annexes vol I) (New York: UNSCEAR) pp 17–322 (annex A) UNSCEAR 2008 Sources and Effects of Ionizing Radiation (2008 Report to the General Assembly, with Annexes vol I) (New York: UNSCEAR) pp 223–463 (annex B) UNSCEAR 2010 Summary of Low-Dose Radiation Effects on Health (2010 Report on the Effects of the Atomic Radiation) (New York: UNSCEAR) pp 4–14 Wessely S and Hotopf M 1996 Gulf War syndrome Chemical Warfare Agents. Toxicology and Treatment ed T C Marrs et al (Chichester: Wiley) pp 355–74 252

Depleted uranium instead of lead in munitions: the lesser evil.

Uranium has many similarities to lead in its exposure mechanisms, metabolism and target organs. However, lead is more toxic, which is reflected in the...
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