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SCHER (2010)

Resumen & Detalles:
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Uranio empobrecido

9. Conclusion

9.1 Question 1

The SCHER is asked for an opinion building on an evaluation of available reports, including but not restricted to those referenced above, as to the environmental and health risks posed by DU.
Since DU has a much lower radioactivity as compared to natural U and U-containing ores, it is generally agreed that the chemical toxicity of U is the major hazard descriptor regarding assessment of health risk due to potential exposures to DU (UNEP, 2001, 2002, 2003, 2007; UNEP/UNCHS, 1999; WHO, 2001, 2003b). SCHER agrees with this concept. Therefore, the toxicity data on natural U can be applied to assess DU since the chemistry and the chemical toxicology of isotopes are identical. Human health risk due to chemical toxicity and radiation from U and DU only occur when the uranium is ingested or inhaled.

The human toxicity of U is comparatively well studied; the major target organ for soluble U salts is the kidney. Both in rodents and in rabbits, repeated administration of U with drinking water gave NOAELs or LOAELs of 60μg/kg bw/day based on subtle histopathological changes in the kidney. These NOAELs/LOAELs have been transformed in tolerable daily intake for natural U with an uncertainty factor of 100 to give a TDI of 0.6 μg/kg bw per day. Since DU shows an identical toxicity to that of natural U, this TDI is also applicable to DU.
As alpha particles emitted from DU have a very limited range in tissue, DU is not a significant external radiation hazard. Therefore, health effects expected from external radiation caused by DU are limited to unrealistic direct skin contact scenarios. Intake of DU from the environment after use of DU ammunition could not be demonstrated and environmental concentrations of DU, except very close to deposited penetrators and tanks hit, are very low. SCHER therefore agrees with the conclusion of UNEP, IAEA and others that environmental and human health risks due to a potential widespread distribution of DU are not expected due to the very limited exposure to DU as compared to background exposures to natural U (EU-EURATOM, 2001; UNEP, 2001, 2002, 2003, 2007; UNEP/UNCHS, 1999; WHO, 2001, 2003b). Higher exposures to DU dust will only occur when entering vehicles hit by DU ammunition shortly after the hit, and in combat situations when in close proximity to a tank hit by DU ammunition. Therefore, vehicles hit by DU should be made inaccessible to the general public and be properly disposed. Used DU ammunition should also be collected and properly disposed.

9.2 Question 2

In particular, SCHER is asked to assess those risks that may arise from exposure to DU in contaminated areas following military activities with weapons containing DU.
Internal exposure to DU can occur through inhalation, ingestion, and embedded fragments or contaminated wounds (mainly for soldiers). Inhalation of dust is considered as one of the major pathways of DU exposure in combat situations and may also occur from re-suspended particles. Detailed assessments of such exposures have been performed. UNEP, IAEA, several State Governments and research organisations quantified environmental exposures to DU in the Balkans, Kuwait and in Iraq. Presence of DU and natural U can be assessed with high sensitivity by quantifying U isotopes by ICP- MS or by specific radiological techniques.

The many available measurements show that DU, after military use in combat, will mainly be located inside of military vehicles hit by DU ammunition and in their close vicinity. DU ammunition in soil will slowly corrode and hotspots with high local concentrations of DU may remain locally close to the impact site. Based on the available data, only a very small part of the DU released after the impact on a hard target will be more widely distributed in the environment.

DU intake with food and drinking water in areas with use of DU ammunition is well below tolerable exposure levels regarding chemical and radiological toxicity of U and DU. In summary, these studies have shown that general contamination with DU, even in areas of heavy fighting with documented or presumed intensive use of DU ammunition, is very low; in many cases, presence of DU could not be detected despite the use of highly sensitive methods like ICP-MS and alpha-spectrometry.

In the opinion of SCHER, the environmental monitoring, which included soil, drinking water and biota, was adequate to conclude that, except in areas very close to destroyed vehicles and penetrators, DU contamination in the war zones is not widespread and is generally low. Due to the low exposures, possible risks for terrestrial and aquatic ecosystems are considered very low.

Besides environmental measurements, biomonitoring for the presence of DU has been performed in military personnel and long-term Kosovo residents. Most of these studies have failed to find increased concentrations of DU in the sampled population. Therefore, SCHER agrees with the conclusions of UNEP and other reports that exposures of the general population to DU from environmental sources after military uses are very low. Due to the very low exposures, which do not significantly increase the body burden of U isotopes , additional health risks are not expected.

Further support for an absence of health effects of lower DU exposures can be derived from the medical monitoring of Gulf War veterans with embedded DU shrapnels and health monitoring of other veterans. Individuals with embedded DU shrapnel have much higher concentrations of total U in blood and urine as compared to the general population and to soldiers without direct DU exposure (Gwiazda et al. 2004). Sub-clinical effects have been observed in high-level DU concentrations (McDiarmid et al., 2009), but overt health effects due to the release of DU from the embedded shrapnel were not observed (McDiarmid et al., 2009) by health monitoring for more than 16 years.

9.3 Question 3

SCHER is asked to take into account both the chemical and radiological toxicities of DU and, if appropriate, their possible synergistic relations

Since all U isotopes are radioactive and have an identical chemical toxicity, the available information on health effects of U always represents a combination of radiological effects and chemical toxicity. It is therefore impossible to study chemical and radiological effects of U separately. Health effects based on this combination serve as a basis for deriving tolerable exposures. A potential combination of radioactivity and chemical toxicity is therefore covered. Any synergy between chemical toxicity and radioactivity is less pronounced with DU as compared to natural U due to the lower radioactivity of DU.

generated during each cardiac cycle. This is defined as systolic blood pressure. The diastolic blood pressure is the level of pressure at which sounds disappear completely when the artery is not compressed and blood flow is restored. In 1905 Korotkov described the auscultatory method; this is the observation of the repetitive sounds generated by the blood flow (Korotkov 1905). As the cuff pressure reduces gradually during the deflation the Korotkov sound changes in intensity and quality, and five different stages can be distinguished (Korotkov 1905).

The indirect blood pressure measurement with mercury sphygmomanometers has been shown to be valuable in several clinical circumstances. Their extensive use has allowed the collection of the necessary evidence to identify arterial hypertension as a major risk factor for cardiovascular diseases. Most epidemiological and clinical data on hypertension as a cardio-vascular risk factor have been obtained by this blood pressure measuring device. Based on this relation to clinical disease and long-lasting experience, blood pressure measurement using the mercury sphygmomanometer currently is regarded as the gold standard method for indirect measurement of blood pressure.

Cogeneris SPRL posee los derechos de autor de la Estructura de Tres Niveles utilizada para la divulgación de esta opinión del SCHER