Uranium in the environment
Uranium in the environment is a global health concern, and comes from both natural and man-made sources. Mining,
In the natural environment,
Uranium's radioactivity can present health and environmental issues in the case of nuclear waste produced by nuclear power plants or weapons manufacturing.
Uranium is weakly
Natural occurrence
Uranium is a naturally occurring element found in low levels within all rock, soil, and water. This is the highest-numbered element to be found naturally in significant quantities on earth. According to the United Nations Scientific Committee on the Effects of Atomic Radiation the normal concentration of uranium in soil is 300 μg/kg to 11.7 mg/kg.[6]
It is considered to be more plentiful than
Sources of uranium
Mining and milling
Mining is the largest source of uranium contamination in the environment.[1] Uranium milling creates radioactive waste in the form of tailings, which contain uranium, radium, and polonium. Consequently, uranium mining results in "the unavoidable radioactive contamination of the environment by solid, liquid and gaseous wastes".[13]
Seventy percent of global uranium resources are on or adjacent to traditional lands belonging to Indigenous people, and perceived environmental risks associated with uranium mining have resulted in environmental conflicts involving multiple actors wherein local campaigns become national or international debates.[14]
Some of these environmental conflicts have limited uranium exploration. Incidents at Ranger uranium mine in the Northern Territory of Australia and disputes over Indigenous land rights led to increased opposition to development of the nearby Jabiluka deposits and suspension of that project in the early 2000s. Similarly, environmental damage from Uranium mining on traditional Navajo lands in the southwestern United States resulted in restrictions on additional mining in Navajo lands in 2005.[14]
Occupational hazards
The radiation hazards of uranium mining and milling were not appreciated in the early years, resulting in workers exposed to high levels of radiation. Inhalation of radon gas caused sharp increases in lung cancers among underground uranium miners employed in the 1940s and 1950s.[15]
Military activity
Military activity is a source of uranium, especially at nuclear or munitions testing sites.
Combustion and impact of DU munitions can produce aerosols that disperse uranium metal into the air and water where it can be inhaled or ingested by humans.[17] A United Nations Environment Programme (UNEP) study has expressed concerns about groundwater contamination from these munitions.[18] Studies of DU aerosol exposure suggest that uranium particles would quickly settle out of the air,[19] and thus should not affect populations more than a few kilometres from target areas.[17]
Nuclear energy and waste
The nuclear power industry is also a source of uranium in the environment in the form of radioactive waste or through nuclear accidents such as Three Mile Island or the Chernobyl disaster.[14] Perceived risks of contamination associated with this industry contribute to the anti-nuclear movement.[14]
In 2020, there were over 250,000 metric tons of high-level radioactive waste being stored globally in temporary containers. This waste is produced by nuclear power plants and weapons facilities, and is a serious human health and environmental issue. There are plans to permanently dispose of high-level waste in deep geological repositories, but none of these are operational. Corrosion of aging temporary containers has caused some waste to leak into the environment.[20]
Spent
Health effects
Soluble uranium salts are toxic, though less so than those of other heavy metals such as lead or mercury. The organ which is most affected is the kidney. Soluble uranium salts are readily excreted in the urine, although some accumulation in the kidneys does occur in the case of chronic exposure. The World Health Organization has established a daily "tolerated intake" of soluble uranium salts for the general public of 0.5 μg/kg body weight (or 35 μg for a 70 kg adult): exposure at this level is not thought to lead to any significant kidney damage.[22][23]
Tiron may be used to remove uranium from the human body, in a form of chelation therapy.[24] Bicarbonate may also be used as uranium (VI) forms complexes with the carbonate ion.
Public health
Uranium mining produces
Cancer
In 1950, the US Public Health service began a comprehensive study of uranium miners, leading to the first publication of a statistical correlation between cancer and uranium mining, released in 1962.[27] The federal government eventually regulated the standard amount of radon in mines, setting the level at 0.3 WL on January 1, 1969.[28]
Out of 69 present and former uranium milling sites in 12 states, 24 have been abandoned, and are the responsibility of the
In 1990,
Depleted uranium exposure studies
The use of depleted uranium (DU) in
The toxicity of DU is a point of medical controversy. Multiple studies using cultured cells and laboratory rodents suggest the possibility of
Birth defects
Most scientific studies have found no link between uranium and birth defects, but some claim statistical correlations between soldiers exposed to DU, and those who were not, concerning reproductive abnormalities.
One study found epidemiological evidence for increased risk of birth defects in the offspring of persons exposed to DU.[37] Several sources have attributed an increased rate of birth defects in the children of Gulf War veterans and in Iraqis to inhalation of depleted uranium.[34][41] A 2001 study of 15,000 Gulf War combat veterans and 15,000 control veterans found that the Gulf War veterans were 1.8 (fathers) to 2.8 (mothers) times more likely to have children with birth defects.[42] A study of Gulf War Veterans from the UK found a 50% increased risk of malformed pregnancies reported by men over non-Gulf War veterans. The study did not find correlations between Gulf war deployment and other birth defects such as stillbirth, chromosomal malformations, or congenital syndromes. The father's service in the Gulf War was associated with increased rate of miscarriage, but the mother's service was not.[43]
In animals
Uranium causes
In soil and microbiology
Bacteria and
It has been suggested that it is possible to form a reactive barrier by adding something to the soil which will cause the uranium to become fixed. One method of doing this is to use a mineral (
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