Depleted Uranium

Proposal for a Research Programme on Depleted Uranium: Health, Safety and Environmental - Target

5.1 Health Effects

5.1.1. The actual health effects of U, and hence DU, have been characterised by over 50 years of epidemiological research on workers in the U and nuclear industries and further clinical and epidemiological work on military exposures since the Gulf conflict. References (2), (12) and (48) are each very substantial compilations of medical evidence quoting many hundreds of earlier references.

5.1.2. As previously stated DU poses a potential radiological and chemical toxicological health hazard. It is known to damage the kidney in high doses and its radiological properties make it a potential carcinogen. Its pyrophoric properties mean that it can produce DU oxide aerosols posing a potential inhalation hazard. Critics of DU (109) have associated its use with alleged increased rates of cancer in Iraq and the Balkans and with cancers among military personnel who have served in the Balkans.

5.1.3. DU potentially presents three basic types of health hazard: first an external radiation hazard which is well quantified for the worst case situation of DU metal in direct contact with bare skin and easily quantifiable (by the use of personal dosemeters) in other situations. A UK tank crewman would have to spend about 1,500 hours on operations, sitting in a tank fully loaded with DU ammunition, before he would reach the occupational exposure limit for an adult worker (80). This limit, which is embodied in European Legislation, is specified to be an effective dose of 50 mSv in any single year, subject to the effective dose not exceeding 20 mSv a year averaged over 5 consecutive years. Similar considerations would apply to handling spent munitions. 250 hours contact with bare skin is required to exceed the annual dose limit for the skin. The hazards are well understood and no work is proposed in this area.

5.1.4. The second hazard is from inhalation or ingestion of significant quantities of DU oxides in a battlefield or clear-up scenario. In general terms, chemical toxicity and the threat to the kidney are of most importance when soluble material is present. Tank crews, Explosive Ordnance Disposal (EOD) and Royal Electrical and Mechanical Engineers (REME) personnel would be at greatest risk. Inhalation of insoluble material presents a third and predominantly radiological risk from material lodging in the lung and increasing the lifetime risk of cancer. There may also be cause for concern arising from the transport of DU from the lung to the lymph nodes (39). Surviving troops in vehicles struck by DU are at greatest risk of inhaling high concentrations of DU, but there are no UK troops in this position.

5.1.5. Inhaled DU particles, dependent on their size, may not rapidly disperse by natural processes and may remain lodged in the lungs (39). The consequences of this in humans are uncertain. Animal studies have shown some evidence of radiation induced fibrosis of tracheo-bronchial lymph nodes after inhalation exposures to U (2). McDiarmid suggests that further studies of the potential neurocognitive effects of DU are warranted in the light of evidence that DU crosses the blood-brain barrier in rats (38).

5.1.6 The MOD has received suggestions relating to the use of animals and human volunteers to determine the solubility of DU munition residues in body fluids. The MOD considers that it would be unethical to propose such studies unless a strong case can be made for conducting them. If the literature reviews indicate that there is a requirement to enhance our understanding of pulmonary loading, absorption from the lungs into the blood and transport to and uptake by pulmonary lymph nodes, we will consider all the options available to fill such gaps before proposals to conduct research that uses animals or humans are submitted.

5.1.7. On wider health effects in other populations, no association between U exposure and cancer has been demonstrated in human beings (9,39). The US Agency for Toxic Substances and Disease Registry (ATSDR) also fails to find associations with U exposure and permanent renal disease even after large accidental exposures and other systemic effects at occupational exposures (39). The WHO examined reports of increased cancer incidence in Iraq (110). It reported an unsatisfactory cancer registration system with a "fairly gross degree of under reporting" such that little interpretation can be put on national figures (111). Anecdotal reports from the Balkans have alleged similar excesses of cancer incidence but corroborative evidence has yet to materialise. The recent EC report of experts has concluded that, with regard to radiological health consequences, "exposure to DU could not produce any detectable health effects under realistic assumptions of the doses that might be received."(1). On 12 March 2001, the WHO published its report of its Mission to Kosovo (112) and commented that there is no convincing evidence "to indicate any health impacts to the Kosovo population associated with the use of DU." It also commented adversely on the uncoordinated approach of different nations to the issue. With regard to the possible existence of synergistic effects arising from multiple exposures to toxic materials including DU, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) concluded that except for radiation and smoking, there is no evidence that low-level exposures to multiple agents yield combined effects far from additivity, or above the estimate resulting from linear extrapolation of single agent effects to lower doses (113).

5.1.8. US studies (2,12,34,38) have looked at the health consequences of being in or on a vehicle struck by DU munitions or being involved in immediate rescue attempts. Those who have retained shrapnel have high levels of urinary U but exhibit none of the other adverse renal or health effects associated with exposure to U (34,38). Those without shrapnel excrete U at background levels only. Two other US reviews have failed to implicate DU in Gulf veterans’ illnesses (2,12). The recent US tests (see paragraph 3.5.2) were specifically designed to replicate exposures received by US Gulf veterans involved in DU related incidents.

5.1.9. Although background levels for U in the environment have been assessed, there has been little work carried out to determine the distribution of U in the UK population to establish normative urinary U levels and U isotope ratios in both military and civilian personnel. There is also no knowledge of the effects of the local environment on the urinary U levels of personnel currently deployed in the Balkans.

5.1.10. MOD has consulted widely on the proposed introduction of a voluntary screening programme in respect of DU. A number of areas for research have been suggested arising from the recommendations of the MOD's Expert Advisory Group (EAG) (114) and the response of external bodies (including the Royal Society (115)). They include addressing possible longer term effects and identification of the most suitable urinary U test and its application to appropriate individuals. The proposed research will complement on going studies involving Gulf War veterans, which are being overseen by the Medical Research Council (MRC).

5.1.11. It is intended that the work will be approached in a stepwise fashion to minimise nugatory effort. E.g. the baseline urinary isotopic U measures for veterans will be obtained as a preliminary to the normative urinary U study, since if isotopic ratios in veterans are not significantly different from what might be deduced from existing data on ratios in the general population, the scope of the study, and the epidemiological case control study, will need to be reassessed.

5.1.12 There is considerable debate over which measurement techniques are most appropriate for determining urinary U and its isotopic ratios, and we note that a number of laboratories that commented on MOD’s first Consultation Document on Screening have experience of measuring U in geological but not in biological samples. The Oversight Board, formed to take forward and oversee the MOD’s screening programme proposals, will advise on the most appropriate test and ensure that the measurement process is robust.

5.2.1. A great deal of environmental monitoring has been carried out around UK (95-104) and US ranges (63-77, 105) where DU munitions are test fired and much of this information is publicly available. The purpose of the monitoring has been to assess the hazard to the public from the work carried out at the ranges. Monitoring has also been carried out at sites where DU munitions were used in Kosovo (3). The monitoring has demonstrated that DU testing has had a negligible effect on the environment, other than in some localised areas in close proximity to the impact area.

5.3.1 The International Commission on Radiological Protection (ICRP) has a continuing programme of work that includes reviews of biokinetic models. Some ICRP publications present models dealing with occupational exposures that are formulated as mathematically convenient retention functions addressing only the initial uptake and net rate of decline of radionuclides in a few major repositories in the body. Others involve several organs, tissues and fluids and model feedback from systemic pools to blood plasma, loss of systemic activity by specific excretion pathways, and certain physiological processes known to influence the distribution and translocations of the given radionuclides. The advantages and limitations of the early 1990s biokinetic models have been addressed previously (116).

5.3.2 The ICRP reports its findings or updates earlier recommendations in a series of publications which address; the risks to lymph nodes from inhaled radioactive material (117), modelling of the behaviour of inhaled material within the lung (118), the development of a new systemic model for U (119), the calculation of dose coefficients based on the new lung and systemic models (120,121), a review of U biokinetics (122) and recommendations for monitoring individuals exposed to radioactive contamination (123,124). The ICRP is also developing a new model for the ingestion of radioactive materials that is due for publication in 2002 and a further publication detailing ingestion dose coefficients will follow shortly after that. ICRP Publications are reviewed by organisations such as the EC and IAEA that have adopted the recommended dose coefficients for use within the European Union (EU) given in the ICRP Publications 68 (120) and 72 (121). The MOD considers that biokinetics is an issue of wider consideration and would be more appropriately addressed by other means (e.g. within the EU radiation protection research programme).

5.3.3 The UK Government recently asked the Committee on Medical Aspects of Radiation in the Environment (COMARE) to oversee a consultative exercise to assess the risks from radioactive material taken into the body. Many of the wider issues relating to biokinetics and the risk to lymph nodes should be considered by this group and no work is proposed by the MOD at present. However, the National Radiological Protection Board (NRPB) is currently developing computer programs to implement the most recent ICRP biokinetic models on behalf of the UK nuclear industry and the MOD should review and assess the value of the work being done by the NRPB, and others, on biokinetic modelling related to uranic materials.

Last Updated: 20 Mar 02