Concern that radioactive dust from the explosion of shells tipped with uranium elevated the health risks facing servicemen in Kosovo has now spread to all European military testing grounds using depleted uranium, and even to the civilian population close to such facilities.
| The British Ministry of Defence maintains that there is nothing to be alarmed about, since the risk of harm is negligible. Yet John Spellar, armed forces minister, told the House of Commons on Tuesday that soldiers who had served in the Balkans would be offered screening: despite having said, 24 hours earlier, that this was unnecessary. It is unlikely that scientific advice has changed over the previous day. The only rational explanation for this turnaround is that there has been political advice to succumb to media demands.
| But while there are doubtless military advantages of using super-hard uranium-tipped missiles, there is no significant risk from using depleted uranium.
| Between March and June 1999, thousands of 35mm calibre rounds, stuffed with depleted uranium, were fired over Kosovo, mainly by the American A-10 aircraft. The core of each round contained about 0.82 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. Natural uranium is 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. Alpha particles have little penetrative power in the air and in human tissues.
| The total mass of depleted uranium dispersed over Kosovo was at most 25 tons. Radioactivity of one round was about 10 megabecquerels (MBq). Assuming that 30,000 rounds (about 25 tons) were fired, one can easily calculate that about 300,000 MBq of uranium-238 activity were dispersed in the environment of Kosovo. Yet, in a layer of soil of just under half an inch (1cm) in Kosovo (area: 10,887 square km), radioactivity of natural uranium-238 emits about 100,000,000 MBq. Thus, 1cm-thick layer of soil in Kosovo contains about 300 times more natural uranium than was dispersed there by NATO, mainly American, weaponry.
| 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 re-suspended into the air, and also enter the food chain. But this should not lead to any observable medical consequences.
| The weak beta and gamma radiation does not pose a serious radiation protection problem. For example, radiotoxicity of inhaled uranium-238 is more than 4000 times lower than radiotoxicity of uranium-238. Because of these features of depleted uranium, its radiation protection standards are based not on its radiation but on chemical toxicity. It is similar to other heavy metals (such as lead, cadmium or mercury), and like these other metals, at high doses uranium is toxic stuff. Experimental and epidemiological studies, carried out over the past 50 years, suggest that the main adverse effect of uranium-238 is a 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 three micrograms of uranium per gram of kidney.
| In epidemiological studies of more than 32,000 workers, exposed to uranium between 1943 and 1986 in nuclear installations in the USA and UK, no health impairment that could be related to this metal was observed, other than renal problems. Among these workers the general mortality was lower than in the general population, and mortality due to all cancers and leukaemia was also lower.
| Among about 150,000 soldiers, who for various periods of time were in Kosovo between March 1999 and the end of 2000, 17 have so far died due to leukaemia. This corresponds to about 11 deaths per 100,000 soldiers. The annual leukaemia death rate in the UK is 11 per 100,000. Thus, the rate of soldiers dying due to leukaemia seems to fit the European norm.
| A few years ago, 'clusters' of leukaemia were found in several countries, in which morbidity of leukaemia was higher (up to tenfold) than in the general population. The first such cluster was discovered in the village of Seascale, near Sellafield, which is the site of the principal nuclear fuel reprocessing plant in the UK. The excess was reported in a TV programme in November 1983, and later similar clusters were found in a few other places in the UK and then in Germany, France, Canada and the USA. It was originally suspected that the cause of clusters are radioactive emissions from nuclear installations. However, it was realised quite quickly that clusters appear at other non-nuclear sites, where migration of a large number of people occurred.
| In an extensive review of the issue the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) concluded that the possible explanation for the cluster was due to spread of infection resulting from the mixing of populations from urban and rural areas. One might expect such a phenomenon to occur among large military formations. But it seems that this is not the case in Kosovo, where incidence of leukaemia rather fits the European norm. The shortest latency time for leukaemia induced by ionising radiation is two years.
| As this disease started to appear among the soldiers much earlier, and there were no reports on a dramatic increase of renal problems, the cause of leukaemia in Kosovo does not seem to be radiation of depleted uranium, but rather a natural one.
| Professor Zbigniew Jaworowski works for the Central Laboratory for Radiological Protection in Warsaw, Poland, and Dr Roger Bate lectures at Wolfson College, Cambridge University, UK
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