Depleted uranium (DU) is a waste product from the nuclear weapons and civil nuclear power programmes. Natural uranium contains too little of the readily fissionable isotope, 235-U for either use in weapons of the current generation of nuclear reactors. Natural uranium is thus enriched by various processes to increase the 235-U content leaving mainly 238-U, depleted uranium, as the waste product.
DU has found a number of applications, including counter-weights in aircraft, armour plating in tanks, shielding from radiation, in keels for yachts and as munitions. None of these applications are associated with the properties of uranium deployed in the nuclear applications.
Uranium is obtained from ores and so has to be extensively purified after extraction. The soluble compounds of U produced in these processes are regarded as extremely toxic and thus handled in ways that preclude inhalation. However, as U occurs naturally and is thus in the environment but in forms in which it can be inhaled it is invariably insoluble. Ingested U, soluble and insoluble is excreted before entering the blood stream and becoming “systemic”. Thus, normally the only risk from U from the environment is to the lung from inhaled insoluble U particles.
Where U is used in munitions (bullets and bombs) to penetrate hardened targets (using its high density) the munition may shatter and since U is pyrophoric, catch fire and burn, producing oxide particles which are partially soluble and, thus, potentially a source of systemic U if inhaled. In the environs of a munitions factory that burned scrap DU on a regular basis environmental contamination with DU has been demonstrated and residents and employees shown to have a systemic burden of DU.
U binds avidly to bio-molecules including DNA. Laboratory experiments have show that U is genotoxic, that is, it damages DNA in several ways. Most importantly it can modify the transcription of the DNA in cells in which it is located, implying that it can modify the phenotype of the cell. All disease has as its root the modification of the normal cellular phenotype.
It is claimed that the absence of epidemiological evidence associating DU with disease is evidence of its safety. However, there is no evidence because the appropriate studies have not been undertaken on a known exposed population.The absence of evidence does not in this case prove the absence of effect.
An excellent video animation prepared by the International Coalition to Ban Depleted Uranium Weapons describes the action of DU and can be found here.
Evidence on the genotoxicity of DU as presented to the Belgian Parliament in 2006 can be found here.
The toxicity of Depleted uranium