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Are depleted uranium shells causing serious
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An Overview
Depleted uranium (DU) was used in the Gulf and Balkan Wars in armor piercing shells to destroy enemy tanks. The study discussed in the following was initiated in response to horror stories regarding unintended (some would say intended) health effects among U.S. veterans and nearby civilians resulting from DU weapons use. For example, claims were made of leukemia epidemics, many birth defects, and neurological problems. After years of intense study, most of the horror stories turned out to be just that, "stories." On the other hand, some excellent scientific research has identified issues needing further research or continued monitoring.
Although the use of depleted uranium shells is not without risk to U.S. veterans and civilian populations, the health risks identified in this study were found to be very small, especially compared to other risks associated with warfare. One exception to this finding was a predicted 1.4% risk of cancer for some veterans (survivors) in vehicles hit by DU friendly fire. Also, if we postulate that some children might, over a period of years, play inside DU-destroyed vehicles for as long as 500 hours, the risk of cancer was predicted to be about 0.4%. These risks compare to a background lifetime risk of cancer fatalities (without DU exposure) of about 24%.
What are depleted uranium shells?
Depleted uranium metal is used in armor piercing military shells by the United States, Great Britain, and other nations. Depleted uranium is a byproduct of the uranium enrichment process and differs from natural uranium in that it is depleted in uranium-235; i.e., the uranium-235 content is reduced from 0.7% in natural uranium to about 0.2% in depleted uranium. U.S. and British tanks and aircraft used DU shells against enemy tanks and armored vehicles during both Gulf Wars as well as the Balkan War.
What is the concern with depleted uranium shells?
Although depleted uranium possesses ideal properties for penetrating armored vehicles, critics have asserted that exposure to depleted uranium dust during and following battle have resulted in serious health effects (such as leukemia and birth defects) among U.S. veterans and nearby civilian populations. These reports of adverse health effects have been attributed to the fact that uranium is both radioactive and chemically toxic. Reports of serious health effects attributed to depleted uranium have drawn considerable attention. If the reports are legitimate and clearly linked to depleted uranium exposure, then the attention to depleted uranium is clearly justified. If reports of depleted uranium health effects are erroneous, however, the focus on depleted uranium may discourage research into other potential causes of post-battle health effects and will divert attention from pressing issues. When assessing potential DU health effects, several questions must be asked:
1. Are all reports of adverse veteran health effects legitimate?
2. Is depleted uranium a likely cause of these health effects?
3. What other agents or environments have the potential for post-battle health effects?
4. Are Iraqi civilian claims of adverse health effects linked to DU exposure?
5. What are the likely effects of DU exposure vs. what are the possible effects?
To examine the potential for serious health effects it is necessary to determine the amount of exposure to depleted uranium and the potential health effects resulting from exposure. In addition, the health claims reported in the popular press and on the Internet must be examined to determine if the claims match health records.
DU Background
In order to understand the following analysis, some background is required. A depleted uranium armor-penetrating tank round consists of a pointed, slender depleted uranium rod approximately 27 inches long. When fired at high velocity, the very high density and self-sharpening characteristics of uranium provide a significant advantage for armor penetration. Furthermore, depleted uranium particulate ejected during impact burns explosively, typically resulting in destruction of the impacted vehicle and often killing the occupants. The impact-generated DU particulate can be inhaled or ingested by surviving vehicle occupants and DU shrapnel may become embedded in the bodies of the occupants. Depleted uranium particulate released during impact can travel downwind, exposing troops and nearby civilian populations. After hostilities have ceased, DU that has settled on the ground can be resuspended by wind or human activity. Resuspended depleted uranium particulate may then be inhaled by civilians or veterans over an extended period of time. DU-contaminated water and vegetation consumed by humans and animals can result in ingestion of DU particulate. Furthermore, veterans or civilians entering DU-destroyed vehicles may inhale DU resuspended within the vehicle or may ingest DU by hand-to-mouth contact when hands are contaminated by depleted uranium dust. External exposure to radiation emitted from DU shells may also contribute to radiation dose.
The principal health concern for depleted uranium exposure is the effect of the chemical toxicity of uranium on the kidney whenever uranium has been taken into the body. Very high intake of uranium, without medical attention, can result in kidney failure and death within a few days. Although uranium is also radioactive, both natural and depleted uranium are only slightly radioactive. For example, depleted uranium is approximately 100 billion times less radioactive than the common medical isotope molybdenum-99. Because the radioactivity of depleted uranium is very low, the risk from radiological effects are usually quite low. Exposure to radiation from DU external to the body is extremely low because the activity of depleted uranium is very low and because the principal form of radiation from DU is alpha particle radiation. Alpha particles emitted external to the body are unable to penetrate human skin. Although penetrating radiation (beta and gamma particles) are also emitted from typical DU munitions, the dose from these forms of radiation are quite low. Radiological exposure is somewhat more significant when uranium is internalized by inhalation, ingestion, or embedded fragments. Internal organs are not protected by a dead-skin layer; consequently, alpha particle radiation emitted by internalized DU can cause radiation damage to the cells of internal organs and tissue.
Analysis of depleted uranium exposure
The principal risk from low-level radiation is the possibility of induced cancers and radiation-induced birth defects. Both of these potential effects are referred to as stochastic effects; i.e., the induction of cancer and birth defects are statistically related to the dose. The greater the dose, the greater the probability of cancer or birth defect induction. Thus, to assess health effects from depleted uranium exposure it is essential to obtain a good estimate of the quantity of DU internalized by exposed veterans and civilians. Most scientific studies grouped and studied veteran exposures using the three exposure categories defined by the Department of Defense. The first category, called Level I, refers to veterans in tanks and armored vehicles accidentally hit by U.S. DU shells (friendly fire). The Level II category includes veterans working in DU-destroyed vehicles after hostilities have ceased. Level III veterans include veterans downwind of battlefields where DU weapons were used. A few studies looked at civilian populations downwind from battlefields and one study evaluated the exposure for Iraqi children playing in DU-destroyed vehicles.
At present, five detailed scientific analyses have been completed. The studies are identified as follows:
-Department of Defense Study [1]
-Fetter and von Hippel Study [2]
-Royal Society Study [3]
-Capstone Study [4]
-Sandia National Laboratories Study [5,13]
For each analysis, the first step was to determine the quantity of DU inhaled and ingested by exposed individuals and populations. In one study [5,13], the contribution to the body burden from embedded fragments was included. The second step was to predict the passage of DU through the body over the lifetime of the exposed groups. The final step was to complete the dose and health risks to each exposed group. The analysis discussed here was based on an update of the Sandia analysis. The Sandia analysis is discused in the referenced document [5,13], and obtained at the link:
Sandia Report
Predicted Cancer Risk
The risk of fatal cancer for the maximally exposed Level I veterans (only a few individuals) is about 1.4%. Thus, exposure to DU for the most highly exposed veterans resulted in an increase the risk of a cancer fatality, compared to the U.S. average of about 24% (without DU exposure), to about 25.4%. Almost all of the DU-induced cancer risk is associated with the risk incurred for lung cancer. Even for the maximum case with fragments included, the risks for all other cancer types are very small. The typical Level II veteran risk is about 0.01% and the cancer risks predicted for Level III veterans is about 0.000001%. Hence, the cancer risk for the typical Level III veteran is increased from about 24% to about 24.000001%. However, most Gulf War veterans had no significant exposure to depleted uranium. These findings are consistent with medical records for U.S. troops in the 1991 Gulf War [6] and Italian ground troops in the Balkan War [7].
The caner risk for downwind civilians is about 0.000003%, far too low to result in observable cancers. A maximally exposed child playing for hundreds of hours in DU-destroyed vehicles would incur a risk of about 0.4%. The predicted risk of leukemia for this maximally exposed child is about 0.003%. The cancer risk for the nominally exposed child is much smaller than for the maximally exposed child. If another mechanism associated with depleted uranium exposure can induce cancers (such as synergistic chemical-radiation effects), it is possible that the cancer risks are greater than the predicted risks. Further research into possible synergistic chemical-radiation effects is needed.
Predicted Birth Defects
The risks of radiation-induced genetic birth defects are predicted to be extremely small. For the most highly exposed veteran, the predicted risk is about 0.004% compared to the U.S. average of about 8% per live birth. For the typical exposed veteran or downwind civilian, the predicted risk of birth defects from depleted uranium exposure is about 0.00000001%. It may be possible, however, that chemically induced birth defects could result from in utero exposure to depleted uranium. Domingo et al. have shown that very high incidences of birth defects result when pregnant rats and mice are given large doses of uranium acetate [8]. However, the depleted uranium doses given to the test rats were about one million times greater than the depleted uranium internalized by downwind veterans and civilians. Some perspective can be gained by noting that the inhaled uranium concentrations by downwind veterans and civilians are within the range of typical internalization of natural uranium in the environment by inhalation and ingestion. A number of birth defect studies were performed for children of other Gulf War veterans. In one study of 75,000 births, 7.45% of the Gulf War veteran children were born with birth defects, compared to 7.59% for children of veterans not deployed in the Gulf [9]. In another study, statistically significant excesses were found for a few specific types of birth defects out of 46 birth-defect categories (i.e., tricuspid valve insufficiency, aortic valve stenosis, and renal agenesis). The authors concluded, “We did not have the ability to determine if the excess was caused by inherited or environmental factors, or was due to chance because of myriad reasons, including multiple comparisons” [10].
Chemical Effects
The estimated peak depleted uranium concentration for the maximally exposed Level I veteran is very high. The chronic uranium concentrations in the kidney for Level II and III veterans and all civilians are less than 0.1 micro gram DU/g kidney. This concentration is below the minimal value reported for adverse kidney effects from chronic and acute kidney exposures. Although adverse kidney health effects have not been reported for Level I veterans, maximally exposed veterans may have experienced undiagnosed transient kidney effects associated with high concentrations of DU in the kidney.
Because uranium is a heavy metal, depleted uranium internalization may be associated with neurotoxic effects. Pellmar et al. [11] found that for rats implanted with DU pellets, uranium concentrated in the hippocampus area of the brain. Also, excitability of neurons in the hippocampus was reduced for rats with significant internalized DU, although no behavioral differences were observed from a battery of behavioral tests. Among veterans, McDiarmid et al. observed a statistically lower score in one type of neurocognitive test for veterans with high uranium concentrations in their urine; however, normal functioning was not affected and the measured effect appears to be declining [12].
Conclusions
The Sandia analysis predicted a very low risk of cancers for most veterans and all downwind civilians. A few maximally exposed U.S. veterans were predicted to incur a cancer risk of about 1.4% compared to the U.S. average of about 24%. A maximally exposed child playing for hundreds of hours in DU-destroyed vehicles would incur a risk of about 0.4%. The risk of birth defects for all veterans and civilians was predicted to be extremely small. These predictions are consistent with medical statistics for U.S. veterans. These findings are also generally consistent with the findings from previous scientific studies on depleted uranium health effects. Continued testing and monitoring is needed to explore the possibility of unanticipated mechanisms that could affect the health of individuals exposed to depleted uranium. Many other potential agents must be considered as potential contributors to adverse health effects. These other potential agents include pyridostigmine bromide (PB), pesticides, indigenous infectious diseases, exposure to oil well fires, exposure to chemical warfare agents, vaccines, sand, and stress. For civilians, malnutrition and disease may also contribute to severe health effects.
References
[1] USACHPPM, Depleted Uranium- Human Exposure Assessment and Health Risk Characterization In Support of the Environmental Exposure Report "Depleted Uranium in the Gulf," 2000. Depleted Uranium in the Gulf.
[2] Fetter S, and von Hippel FN. The hazard posed by depleted uranium munitions. Science and Global Security 1999.
[3] Royal Society, The Health Hazards of Depleted Uranium Munitions Part I, London, UK: The Royal Society; 2001. Parts 1 and 2
[4] Parkhurst MA, Szrom F, Guilmette RA, Holmes TD, Cheng YS, and Kenoyer JL, et al. Capstone Depleted Uranium Aerosols: Generation And Characterization, Volumes 1 and 2. Pacific Northwest National Laboratory report PNNL-14168, October 2004.
[5] Marshall, AC. An analysis of Uranium Dispersal and Health Effects Using a Gulf War Case Study, Sandia National Laboratory Report SAND2005-4331 July, 2005.
[6] PAC, Presidential Advisory Committee Presidential Advisory Committee on Gulf War Illnesses, Final Report, Chapter 3, 2005.
[7] Italian Ministry of Defense. Preliminary report - Investigative Commission of the Italian Ministry of Defense on the incidence of malignant neoplasia among military personnel involved in operations in Bosnia and Kosovo. March 2001.
[8] Domingo JL. Reproductive and developmental toxicity of natural and depleted uranium: a review. Reprod Toxicol 2001; 15.
[9] Cowan DN, DeFraites RF, Gray GC, Goldenbaum MB, and Wishik SM. The risk of birth defects among children of Persian Gulf War veterans. N Engl J Med 1997; 336
[10] Araneta MRG, Scglangen KM, Edmonds LD, Destiche DA, Merz RD, and Hobbs CA, et al. Prevalence of birth defects among infants of gulf war veterans in Arkansas, Arizona, California, Georgia, Hawaii, and Iowa. Birth Defects Res A Clin Mol Teratol 2003; 67.
[11] Pellmer TC, Hogan JB, Benson KA, and Landauer MR. Toxicological Evaluation Of Depleted Uranium In Rats: Six Month Evaluation Point, Bethesda, MD: Armed Forces Radiobiology Research Institute; 1998.
[12] McDiarmid, MA, Squibb K, Engelhardt S, Oliver M, Gucer P, Wilson PD, et al. Surveillance of depleted uranium exposed gulf war veterans: health effects observed in an enlarged friendly fire cohort. J Occup Environ Med 2001; 43.
[13] Marshall, AC, Gulf war depleted uranium risks, J Expo Sci Environ Epidemiol advance online publication, February 14, 2007; doi:10.1038/sj.jes.7500551
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http://zfacts.com/p/261.html | 01/18/12 07:21 GMT
Modified: Fri, 15 Jun 2007 14:48:21 GMT
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