From: | Susan Gawarecki <loc@icx.net> |
Date: | 11 Jan 2001 18:39:21 -0000 |
Reply: | cpeo-military |
Subject: | [CPEO-MEF] Known properties and health impacts of DU |
There have been a number of postings to the CPEO list regarding depleted uranium ammuntion and the potential environmental and health side effects. Below are two messages regarding known properties and health impacts of DU. These were posted on January 10 to the RadSafe list, which is a forum for radiation safety professionals. References and contacts of the authors are given. --Susan Gawarecki Message 1: There are several reports in the news about the implied toxicity of depleted uranium used for projectiles and shielding material in modern warfare. It has been suggested to be a potent carcinogen and leukemia inducer. The toxicity of uranium has been under study for at least 50 years including life span studies in small animals. Depleted uranium is only very weakly radioactive, and virtually all of the observed or expected effects are from nephrotoxicity associated with deposition in the kidney tubules and glomeruli damage at high doses. The radiation doses from depleted uranium (specific activity only 15 Bq/mg)(U-238 has a 4.5 billion year half life)are very small compared to potential toxic effects from uranium ions in the body (primarily damage to kidney tubules). The main route of potentially hazardous exposure is inhalation since gastrointestinal uptake is very small (<1/10,000). Consider, for example the deposition of a respirable particle of depleted uranium dioxide in the human lung. If that particle is approximately spherical and has a diameter of 1 micrometer (aerodynamic diameter about 3 micrometer), it will emit an average of only one alpha particle every 100 days. Meanwhile the cells of the lung are being irradiated in a milieu of even more energetic alpha particles from natural radon and its decay products that are present in all the air on the surface of the earth. The total radiation dose to the lung from even relatively high exposures to airborne depleted uranium particles is not remarkable. The TLV is 0.2 mg/cubic-meter based on chemical toxicity. After inhalation, uranium will be slowly mobilized and enter the systemic circulation. The uranyl ion is the form of mobile uranium within the body. It deposits at bone surfaces and remains in the bone matrix with a half time of up to one year. It is slowly cleared to the blood and excreted via the kidneys. While in the bone, alpha radiation is emitted, but with very low intensity since depleted uranium is not very radioactive. The range of alpha radiation in the bone is about 30 micrometer and the radiation is very diffuse, so the bone marrow is not effectively irradiated by uranium in the bone. Radiation induction of leukemia requires effective high dose-rate irradiation of the bone marrow. There is no known or expected leukemia risk associated with small amounts of U-238 in the bone because the marrow is not efficiently irradiated. [The same is true for much more highly radioactive radium-226 and plutonium-239.] As to its "heavy Metal" toxicity, the closest analogy is lead. However, metallic lead has considerably higher toxicity than metallic uranium. Compounds of lead are much more hazardous than compounds of uranium since uranium tends to form relatively insoluble compounds which are not readily absorbed into the body. Also, lead within the body affects the nervous system and several biochemical processes, while the uranyl ion does not readily interfere with any major biochemical process except for depositing in the tubules of kidney where damage occurs if excess deposition occurs. Glomeruli damage has been reported at high doses as well. The kidney damage is dosage dependent and somewhat reversible. Lead bullets are probably more dangerous than uranium bullets. References: "Handbook of the Toxicology of Metals", Friberg et al.(1990), "Uranium, Plutonium, Transplutonium Elements", Hodge et al. (1973), "A five year inhalation study with natural uranium dioxide", HEALTH PHYS 25, 230-258 (1973), "Depleted Uranium In The Gulf": http://www.gulflink.osd.mil/du_ii ********************************************** Prof. Otto G. Raabe, Ph.D., CHP Institute of Toxicology & Environmental Health (Street Address: Bldg. 3792, Old Davis Road) University of California, Davis, CA 95616 E-Mail: ograabe@ucdavis.edu Phone: (530) 752-7754 FAX: (530) 758-6140 *********************************************** END Message 1 ----- Message 2: A hot question now in Europe is depleted uranium in Kosowo. I prepared a text on this subject for the Polish government. ... _____________ Zbigniew Jaworowski Central Laboratory for Radiological Protection ul. Konwaliowa 7, 03-194 Warszawa, Poland voice: (48-22)717-6250; fax: 717-5324; e-mail: jaworo@clor.waw.pl [Dr. Jaworowski is the retired Head of the Central Lab, and member and former chairman of UNSCEAR.] ------------------------------------- MEDICAL EFFECTS OF DEPLETED URANIUM IN KOSOVO Zbigniew Jaworowski Central Laboratory for Radiological Protection, Warsaw, Poland Between March and June 1999 about 3000 to 30 000 35 mm - caliber rounds, fitted with depleted-uranium, were fired over Kosovo and to a lesser extent over Serbia, mainly by American A-10 assault aircraft. The core of each round contained about 0.80 kg of almost pure uranium-238, from which its 14 radioactive daughters and uranium-235 were separated. This depleted uranium is much less radioactive than natural uranium normally present in the soil and rock, where it has since time immemorial been in equilibrium with radioactive isotopes of radium, radon, thorium, protoactine, polonium, lead and bismuth. During its decay it emits energetic alpha particles (4.26 MeV) and very weak beta (0.01 MeV) and gamma (0.001 MeV) radiation. However, its immediate short lived daughters emit a more energetic beta (2.29 MeV) and gamma (1.00 MeV) radiation. Alpha particles penetrate to a rather short distance in the air and in human tissues. The total mass of depleted uranium dispersed over Kosovo ranged between 2.5 and 25 tons. The radioactivity of one round was about 10 megabecquerels (MBq). Assuming that 30 000 rounds were fired, one can easily calculate that a total activity of about 300 000 MBq of uranium-238 activity was dispersed over the environment of Kosovo. In a 1 cm thick layer of soil in Kosovo (area: 10 887 km2) the radioactivity of natural uranium-238 in equilibrium with its daughters amounts to about 100 000 000 MBq. Thus, a 1-cm thick layer of soil in Kosovo contains about 300 times more natural uranium than that dispersed there by American forces. However, at the target sites, the local concentrations of depleted uranium may be higher than the average concentration of natural uranium in the soil. From these patches of activity depleted uranium may be resuspended into the air, and also enter the food chain. This, however, should not lead to any observable medical consequences. The weak beta and gamma radiation does not pose any serious radiation protection problems. For example, radiotoxicity of inhaled uranium-238 (in terms of Sv per Bq) is over 1000 times lower than radiotoxicity of cesium-137. Because of these features of depleted uranium, its radiation protection standards are based not on its radioactivity but on its chemical toxicity. Like other heavy metals (lead, cadmium, or mercury) uranium is a toxic agent. Experimental and epidemiological studies, carried out over half a century, suggest that the main adverse effect of uranium-238 is chemical impairment of the renal function. Secondary protection standards for uranium-238 (for example concentration limits in air and food) are based on a limit of 3 micrograms of uranium per gram of kidney. In epidemiological studies of over 32 000 workers, exposed to uranium between 1943 and 1986 in nuclear installations in the USA and UK, except for renal problems, no other health impairment was observed, which could be related to this metal. Among this worker cohort mortality due to all diseases was lower than in the general population, and mortality due to all cancers and leukemia was also lower. Among about 150 000 soldiers, who for various periods of time were stationed in Kosowo between March 1999 and the end of 2000, up to now 17 died due to leukemia. This corresponds to about 11 deaths per 100 000 soldiers. The annual leukemia death rate in the United Kingdom is 11 per 100 000. Thus, the rate of soldiers dying due to leukemia appears to agree with European norms. Some years ago "clusters" of leukemia were found in several countries, in which the morbidity of leukemia was higher (up to ten times) than that in the general population. The first of such clusters was discovered in the village of Seascale, near Sellafield, which is the site of the main nuclear fuel reprocessing plant in the United Kingdom. The excess was reported in a television program in November 1983, and later similar clusters were found in other places in the UK and later in Germany, France, Canada and the USA. At first it was suspected that the cause of clusters are radioactive emissions from nuclear installations. However, it was soon realized that they also appear at other non-nuclear sites where migration of large number of people occurred. In an extensive review of these findings in its 1994 report UNSCEAR concluded that a possible explanation is that these excesses are due to a spread of infection resulting from the mixing of populations from urban and rural areas. One might expect that this phenomenon could also occur among large military formations. But this may not be the case in Kosovo, where the incidence of leukemia fits the European norm rather well. The shortest latency time for leukemia induced by ionizing radiation is two years. As this disease began to appear among the soldiers much earlier, and since no reports on a dramatic increase of renal problems were filed, the cause of leukemia in Kosovo, does not seem to be radiation from depleted uranium, but rather a natural one. This is supported also by the fact that no increase in diseases of kidneys, which are a critical organ for uranium, occurred among the soldiers in Kosovo. Professor T. Domanski from Poland before few years served as a head of a study group of the Ministry of Health of Kuwait responsible for estimation of health effects depleted-uranium munition in this desert country. He recently reported that according to estimate of this group about 100 000 rounds with depleted uranium were fired over Kuwait during the Gulf War, what corresponds to about 300 tons of uranium dispersed in the environment. Unexploded munition, splinters and military equipment destroyed with uranium munition are stored at depots in the desert. Uranium contamination of the ground, up to a level 10 to 20 times higher than average natural level, was found only to a distance of up to 100 meters from the depots, and no contamination of local vegetation was observed. Professor Domanski reported that until 1998 no increase of leukemia and other cancers was observed in Kuwait, that might be related to depleted uranium. So, is this just much ado about nothing, or is it merely an expression of a negative feeling towards a new type of ammunition or towards Americans? END Message 2 -- ..................................................... Susan L. Gawarecki, Ph.D., Executive Director Oak Ridge Reservation Local Oversight Committee ----- A schedule of meetings on DOE issues is posted on our Web site http://www.local-oversight.org/meetings.html - E-mail loc@icx.net ..................................................... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
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