Wednesday, December 6, 2006

Depleted uranium

I am covering the topic of depleted uranium (DU) because you will see this brought up by those extremely against the US occupation of Iraq especially in Iraq because of the greater psychological impact it has on Iraqis who may be concerned about their exposure during the Iraqi invasion.

Major Doug Rokke will be quoted as an expert on DU, but frankly, Rokke has an agenda. His statements aren't backed up with any rigorous research. The symptoms he encountered anecdotally could have been caused by so many other factors. The WHO has a more comprehensive study at:

"Aerosols route
Depleted uranium particles or aerosols formed following impact and ignition on a hard target will be dispersed and deposited on the ground. It is reported that most of the depleted uranium dust will be deposited within a distance of 100m from the target (US Army Corps of Engineers 1997). People, most likely soldiers, close to an impact could therefore be exposed to dust by inhalation. UNEP (2000) has estimated that the inhalation and ingestion of depleted uranium contaminated dust, even under extreme conditions, and shortly after the impact of projectiles, as determined by the amount of dust that can be inhaled, would be less than about 10 millisieverts (mSv). This represents about half the annual dose limit for radiation workers. The exposure of civilians to dust and smoke at the time of an attack is less likely. Deposited uranium dust might slowly be transformed through environmental weathering processes into more mobile and soluble forms (discussed elsewhere in this section) and dispersed in the environment by air currents.

During the Gulf War, soldiers were exposed to depleted uranium by ‘friendly fire’. Fragments from penetrating depleted uranium rounds are embedded in the bodies of several soldiers and others inhaled depleted uranium aerosols generated by the impact of the depleted uranium munitions penetrating the target. Thirty-three US veterans seriously injured in friendly fire incidents have been monitored by the Baltimore Veteran Administration Medical Center since 1993. About half of them have depleted uranium fragments in their bodies. A subsequent study considered 29 veterans from the original 33. Though these veterans have higher concentrations of uranium in their urine, indicating that depleted uranium is being oxidized by body fluids, no adverse kidney effects have been observed (McDiarmid 1998 and 2000; US Department of Defense 2000).

External contact route
Picking up a penetrator and keeping it in a pocket is the only realistic way of a long period of exposure to external (beta) radiation from depleted uranium. Snihs & Ã…kerblom (2000) stated that by keeping it in the same position for several weeks, it might be possible that the dose administered to the skin would exceed the skin dose limit for the general population, though not that of radiation workers. The effect of such exposure would be localized and the delivered dose would not be sufficient to cause any deterministic effect.

Agricultural route
The possibility was mentioned to the mission that uranium dust might become incorporated in vegetables and crops. The mission was advised by the Food and Agricultural Organization of the United Nations (FAO) that in the published literature there are no known plants that preferentially accumulate uranium and the normal amounts of uranium taken up in plants would not be expected to be dangerous to humans, birds or other animals (communications between the mission team and FAO in January and February 2001).

Drinking water route
The final plausible route of exposure of the population is through drinking water contaminated by migration of soluble depleted uranium compounds in ground or surface water. In particular, possible contamination of wells or spring protection tanks close to an attack site from pieces of depleted uranium might be an isolated occurrence and its relevance should be considered further.

Absorption of depleted uranium
If or when a person comes into contact with depleted uranium from a penetrator, there is no known immediate or acute risk to life. Furthermore, the radio-medicine literature provides no evidence to assume that a person having contact (either externally or internally) with depleted uranium will develop an illness. The onset of any illness argued to be due to depleted uranium has to be related to the amount of radiation dose or amount of toxic chemical to which a person has been exposed (US Department of Defense 2000). Absorption of depleted uranium in the body following inhalation or ingestion is very limited. Mean absorption following inhalation exposure is about 0.8 to 0.9%, with less soluble compounds as uranium oxides remaining in the lungs. Absorption following ingestion also depends on the solubility of the uranium compounds, but is also limited at between 1 to 2% of the ingested amount with the remainder passed out in faeces (UNEP/UNCHS Balkans Task Force 1999).
Most of the small amount of uranium that is absorbed in the body (about 70%) will be filtered out by the kidneys and excreted in urine within 24 hours. The remaining part will be distributed to the skeleton, liver and kidneys. The time to excrete half of this remaining uranium is in the range of six months to one year.

Health effects
The radiological toxicity of depleted uranium is primarily confined to body cells that are susceptible to the effects of alpha and beta radiation. It is therefore thought that inhaled depleted uranium particles may lead to damage of lung cells and might increase the possibility of lung cancer.
Epidemiological studies provide consistent and convincing evidence of excess lung cancer, but not of leukaemia, related to alpha particle exposure among uranium miners (IARC1988; US NAS 1999). However, this effect is attributed to be related to exposure to gaseous decay products (radon). The risk of lung cancer appears to be proportional to the radiation dose received. Indeed, among nuclear workers involved in uranium processing (whose exposures to alpha particles from uranium are less than those of miners), no consistent excess of lung cancer has been found (NCRP 1978; NRC 1988; NIH 1994; Cardis & Richardson 2000; IARC 2001). Kidney dysfunction is considered the main chemically induced toxic effect of depleted uranium in humans, though this is thought to be reversible (Priest 2001). Until now, a study of 29 Gulf War veterans with embedded fragments of depleted uranium in their bodies has not shown adverse kidney effects (McDiarmid et al. 1998 & 2000). The risk of kidney effects following ingestion of depleted uranium depends on the amount of soluble uranium compounds present (effects increase with higher solubility). Information on the presence of soluble uranium compounds following the use or degradation of depleted uranium penetrators is therefore essential to evaluate the potential risk of developing kidney dysfunction."

A followup was performed 2 years later to verify if leukemia or cancer was occurring at a higher rate:

"In 2001 WHO and the (then) Department of Health and Public Welfare have looked into the incidence of leukemia in Kosovo. Records at Pristina Hospital for the past four years were examined and doctors from district hospitals have been interviewed. The initial survey indicated that the incidence of leukemia in Kosovo has not increased. WHO and the Department of Health and Social Welfare point out that, although record are not perfect, any significant increase in cancers such as leukemia would have been noticed. Doctors state that it takes a minimum of two to three years for the symptoms of leukemia to be detected."

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