Uranium in the environment
Encyclopedia
Uranium in the environment refers to the science of the sources, environmental behaviour, and effects of uranium
on humans and other animals. Uranium is weakly radioactive and remains so because of its long physical half-life
(4.468 billion years for uranium-238
). The biological half-life
(the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days. Normal functioning of the kidney
, brain
, liver
, heart
, and numerous other systems can be affected by uranium exposure, because uranium is a toxic metal
. The use of depleted uranium (DU) in munitions is controversial because of questions about potential long-term health effects.
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.
It is considered to be more plentiful than antimony
, beryllium
, cadmium
, gold
, mercury
, silver
, or tungsten
and is about as abundant as tin
, arsenic
or molybdenum
. It is found in many minerals including uraninite
(most common uranium ore), autunite
, uranophane
, torbernite
, and coffinite
. Significant concentrations of uranium occur in some substances such as phosphate
rock deposits, and minerals such as lignite
, and monazite
sands in uranium-rich ore
s (it is recovered commercially from these sources).
Seawater
contains about 3.3 parts per billion of uranium by weight (3.3 µg/kg) as uranium(VI) forms soluble carbonate
complexes. The extraction of uranium from seawater has been considered as a means of obtaining the element.
Uranium is weakly radioactive and remains so because of its long physical half-life
(4.468 billion years for uranium-238
). The biological half-life
(the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days.
and other decay products of uranium are normally more important than the uranium in tailings ponds at the mines and ore processing centers.
Depleted uranium (DU) is useful because of its very high density
of 19.1 g
/cm3 (68.4% denser than lead). Civilian uses include counterweights in aircraft, radiation shielding in medical radiation therapy
and industrial radiography
equipment, and containers used to transport radioactive materials. Military uses include defensive armor plating and armor-piercing
projectiles.
Uranium metal can disperse into the air and water, United Nations Environment Programme (UNEP)
study says in part:
The U.S. has admitted that there have been over 100 "friendly fire" incidents in which members of the U.S. military have been struck by DU munitions, and that an unknown number have been exposed to DU via inhalation of combustion products from burning DU munitions.
and uranium trioxide.
In pure water, schoepite
{(UO2)8O2(OH)12.12(H2O)} is formed in the first week and then after four months studtite
{(UO2)O2·4(H2O)} was formed.
Uranium metal
reacts with water
to form hydrogen
gas, this reaction forms uranium dioxide
and 2% to 9% uranium hydride
. It is important to note that the rate of corrosion due to water is far greater than that caused by oxygen at temperatures around 100 °C (212 °F). At pH values below 2 the corrosion rate at 100 °C goes down greatly, while as pH values go from 7 upwards the corrosion rate declines. Gamma irradiation has little effect on the corrosion rate.
Oxygen gas inhibits the corrosion of uranium by water.
fuel is very insoluble in water, it is likely to release uranium (and fission products) even more slowly than borosilicate glass when in contact with water.
Note that while the vast majority of the uranium is removed by PUREX
nuclear reprocessing
, a small amount of uranium is left in the raffinate
from the first cycle of the PUREX process. In addition because of the decay of the transplutonium minor actinides
and the residual plutonium
in the waste the concentration of uranium will increase on the waste. This will occur on a time scale of hundreds and thousands of years.
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.
The antidote
for uranium in humans is bicarbonate
, this is used because uranium (VI) forms complexes with carbonate
. An alternative is to use tiron (sodium 4,5-dihydroxybenzene-1,3-disulfonate).
, brain
, liver
, heart
, and numerous other systems can be affected by uranium exposure, because uranium is a toxic metal
. The aerosol produced during impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites leading to possible inhalation by human beings. During a three week period of conflict in 2003 in Iraq
, 1,000 to 2,000 tonnes of DU munitions were used.
The actual acute and chronic toxicity of DU is also a point of medical controversy. Multiple studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic
, gene
tic, reproductive, and neurological effects from chronic exposure.
A 2005 epidemiology
review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU." The World Health Organization
, the directing and coordinating authority for health within the United Nations which is responsible for setting health research norms and standards, providing technical support to countries and monitoring and assessing health trends, states that no risk of reproductive, developmental, or carcinogenic effects have been reported in humans due to DU exposure. This report has been criticized by Dr. Keith Baverstock for not including possible long term effects of DU on human body.
One study concluded that epidemiological evidence is consistent with an increased risk of birth defects in the offspring of persons exposed to DU. Environmental groups and others have expressed concern about the health effects of depleted uranium, and there is some debate over the matter. Some people have raised concerns about the use of this material, particularly in munitions, because of its mutagenicity, teratogenicity in mice, and neurotoxicity, and its suspected carcinogenic potential. Additional concerns address unexploded DU munitions leeching into groundwater over time.
Several sources have attributed the increase in the rate of birth defects in the children of Gulf War
veterans and in Iraqis to depleted uranium inhalation exposure, A 2001 study of 15,000 February 1991 U.S. 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.
In a study of UK troops, "Overall, the risk of any malformation among pregnancies reported by men was 50% higher in Gulf War Veterans (GWV) compared with Non-GWVs". The conclusion of the study stated "We found no evidence for a link between paternal deployment to the Gulf war and increased risk of stillbirth, chromosomal malformations, or congenital syndromes. Associations were found between fathers' service in the Gulf war and increased risk of miscarriage and less well-defined malformations, but these findings need to be interpreted with caution as such outcomes are susceptible to recall bias. The finding of a possible relationship with renal anomalies requires further investigation. There was no evidence of an association between risk of miscarriage and mothers' service in the gulf."
s and other animals. Uranium was shown to have cytotoxic, genotoxic and carcinogenic effects in animal studies. It has been shown in rodent
s and frog
s that water soluble forms of uranium are teratogenic.
can reduce and fix uranium in soil
s. These bacterium change soluble U(VI) into the highly insoluble complex forming U(IV) ion, hence stopping chemical leaching.
) while a second method is to add a food substance such as acetate
to the soil. This will enable bacteria to reduce the uranium (VI) to uranium (IV) which is much less soluble. In peat
-like soils the uranium will tend to bind to the humic acids, this tends to fix the uranium in the soil.
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
on humans and other animals. Uranium is weakly radioactive and remains so because of its long physical half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
(4.468 billion years for uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
). The biological half-life
Biological half-life
The biological half-life or elimination half-life of a substance is the time it takes for a substance to lose half of its pharmacologic, physiologic, or radiologic activity, as per the MeSH definition...
(the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days. Normal functioning of the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, and numerous other systems can be affected by uranium exposure, because uranium is a toxic metal
Toxic metal
Toxic metals are metals that form poisonous soluble compounds and have no biological role, i.e. are not essential minerals, or are in the wrong form. Often heavy metals are thought as synonymous, but lighter metals also have toxicity, such as beryllium, and not all heavy metals are particularly...
. The use of depleted uranium (DU) in munitions is controversial because of questions about potential long-term health effects.
Natural occurrence
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
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
United Nations Scientific Committee on the Effects of Atomic Radiation
The United Nations Scientific Committee on the Effects of Atomic Radiation was set up by resolution of the United Nations General Assembly in 1955. 21 countries are designated to provide scientists to serve as members of the committee which holds formal meetings annually and submits a report to...
the normal concentration of uranium in soil is 300 μg/kg to 11.7 mg/kg.
It is considered to be more plentiful than antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
, beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
, cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
, gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
, mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
, or tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
and is about as abundant as tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
, arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
or molybdenum
Molybdenum
Molybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The name is from Neo-Latin Molybdaenum, from Ancient Greek , meaning lead, itself proposed as a loanword from Anatolian Luvian and Lydian languages, since its ores were confused with lead ores...
. It is found in many minerals including uraninite
Uraninite
Uraninite is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2, but also contains UO3 and oxides of lead, thorium, and rare earth elements...
(most common uranium ore), autunite
Autunite
Autunite with formula: Ca22·10-12H2O is a yellow - greenish fluorescent mineral with a hardness of 2 - 2½. Autunite crystallizes in the tetragonal system and often occurs as tabular square crystals. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore...
, uranophane
Uranophane
Uranophane Ca22·5H2O is a rare calcium uranium silicate hydrate mineral that forms from the oxidation of uranium bearing minerals. Uranophane is also known as uranotile. It has a yellow color and is radioactive....
, torbernite
Torbernite
The chemical formula of torbenite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates...
, and coffinite
Coffinite
Coffinite is a uranium-bearing silicate mineral with formula: U1-x4x.It occurs as black incrustations, dark to pale-brown in thin section. It has a grayish black streak. It has a brittle to conchoidal fracture. The hardness of coffinite is between 5 and 6.It was first described in 1954 for an...
. Significant concentrations of uranium occur in some substances such as phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
rock deposits, and minerals such as lignite
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
, and monazite
Monazite
Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. There are actually at least four different kinds of monazite, depending on relative elemental composition of the mineral:...
sands in uranium-rich ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
s (it is recovered commercially from these sources).
Seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
contains about 3.3 parts per billion of uranium by weight (3.3 µg/kg) as uranium(VI) forms soluble carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
complexes. The extraction of uranium from seawater has been considered as a means of obtaining the element.
Uranium is weakly radioactive and remains so because of its long physical half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
(4.468 billion years for uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
). The biological half-life
Biological half-life
The biological half-life or elimination half-life of a substance is the time it takes for a substance to lose half of its pharmacologic, physiologic, or radiologic activity, as per the MeSH definition...
(the average time it takes for the human body to eliminate half the amount in the body) for uranium is about 15 days.
Mining
During the extraction of uranium ore and its processing, some releases of uranium occur. The releases of radiumRadium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
and other decay products of uranium are normally more important than the uranium in tailings ponds at the mines and ore processing centers.
Metal
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of 19.1 g
Gram
The gram is a metric system unit of mass....
/cm3 (68.4% denser than lead). Civilian uses include counterweights in aircraft, radiation shielding in medical radiation therapy
Radiation therapy
Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...
and industrial radiography
Radiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
equipment, and containers used to transport radioactive materials. Military uses include defensive armor plating and armor-piercing
Armor-piercing shot and shell
An armor-piercing shell is a type of ammunition designed to penetrate armor. From the 1860s to 1950s, a major application of armor-piercing projectiles was to defeat the thick armor carried on many warships. From the 1920s onwards, armor-piercing weapons were required for anti-tank missions...
projectiles.
Uranium metal can disperse into the air and water, United Nations Environment Programme (UNEP)
United Nations Environment Programme
The United Nations Environment Programme coordinates United Nations environmental activities, assisting developing countries in implementing environmentally sound policies and practices. It was founded as a result of the United Nations Conference on the Human Environment in June 1972 and has its...
study says in part:
- "The most important concern is the potential for future groundwater contaminationRadioactive contaminationRadioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...
by corroding penetrators (ammunition tips made out of DU). The munition tips recovered by the UNEP team had already decreased in mass by 10-15% in this way. This rapid corrosionCorrosionCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
speed underlines the importance of monitoring the water quality at the DU sites on an annual basis."
Combustion
Studies of depleted uranium aerosol exposure suggest that uranium combustion product particles would quickly settle out of the air, and thus could not affect populations more than a few kilometres from target areas.The U.S. has admitted that there have been over 100 "friendly fire" incidents in which members of the U.S. military have been struck by DU munitions, and that an unknown number have been exposed to DU via inhalation of combustion products from burning DU munitions.
Corrosion
It has been reported that the corrosion of uranium in a silica rich aqueous solution forms both uranium dioxideUranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
and uranium trioxide.
In pure water, schoepite
Schoepite
Schoepite, empirical formula 8O12•12 is a rare alteration product of uraninite in hydrothermal uranium deposits. It may also form directly from ianthinite. The mineral presents as a transparent to translucent yellow, lemon yellow, brownish yellow, or amber orthorhombic tabular crystals...
{(UO2)8O2(OH)12.12(H2O)} is formed in the first week and then after four months studtite
Studtite
Studtite, chemical formula [O22]·2 or UO4·4, is a secondary uranium mineral containing peroxide formed by the alpha-radiolysis of water during formation...
{(UO2)O2·4(H2O)} was formed.
Uranium metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
reacts with water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
to form hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas, this reaction forms uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
and 2% to 9% uranium hydride
Uranium hydride
Uranium hydride, also called uranium trihydride is an inorganic compound, a hydride of uranium.-Properties:Uranium hydride is a highly toxic, brownish gray to brownish black pyrophoric powder or brittle solid. Its specific gravity at 20 °C is 10.95, much lower than that of uranium...
. It is important to note that the rate of corrosion due to water is far greater than that caused by oxygen at temperatures around 100 °C (212 °F). At pH values below 2 the corrosion rate at 100 °C goes down greatly, while as pH values go from 7 upwards the corrosion rate declines. Gamma irradiation has little effect on the corrosion rate.
Oxygen gas inhibits the corrosion of uranium by water.
Nuclear waste
Spent uranium dioxideUranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
fuel is very insoluble in water, it is likely to release uranium (and fission products) even more slowly than borosilicate glass when in contact with water.
Note that while the vast majority of the uranium is removed by PUREX
PUREX
PUREX is an acronym standing for Plutonium - URanium EXtraction — de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel. It is based on liquid-liquid extraction ion-exchange.The PUREX process was invented by Herbert H. Anderson and...
nuclear reprocessing
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...
, a small amount of uranium is left in the raffinate
Raffinate
Raffinating something is a technique used in metallurgy to remove impurities from liquid material. There are many different kinds of raffination, for example you can use vacuum to extract hydrogen from metals....
from the first cycle of the PUREX process. In addition because of the decay of the transplutonium minor actinides
Minor actinides
The minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium...
and the residual plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
in the waste the concentration of uranium will increase on the waste. This will occur on a time scale of hundreds and thousands of years.
Health effects
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
or mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
. The organ which is most affected is the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
. Soluble uranium salts are readily excreted in the urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
, although some accumulation in the kidneys does occur in the case of chronic exposure. The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
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.
The antidote
Antidote
An antidote is a substance which can counteract a form of poisoning. The term ultimately derives from the Greek αντιδιδοναι antididonai, "given against"....
for uranium in humans is bicarbonate
Bicarbonate
In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...
, this is used because uranium (VI) forms complexes with carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
. An alternative is to use tiron (sodium 4,5-dihydroxybenzene-1,3-disulfonate).
Depleted uranium exposure
The use of depleted uranium (DU) in munitions is controversial because of questions about potential long-term health effects. Normal functioning of the kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
, and numerous other systems can be affected by uranium exposure, because uranium is a toxic metal
Toxic metal
Toxic metals are metals that form poisonous soluble compounds and have no biological role, i.e. are not essential minerals, or are in the wrong form. Often heavy metals are thought as synonymous, but lighter metals also have toxicity, such as beryllium, and not all heavy metals are particularly...
. The aerosol produced during impact and combustion of depleted uranium munitions can potentially contaminate wide areas around the impact sites leading to possible inhalation by human beings. During a three week period of conflict in 2003 in Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....
, 1,000 to 2,000 tonnes of DU munitions were used.
The actual acute and chronic toxicity of DU is also a point of medical controversy. Multiple studies using cultured cells and laboratory rodents suggest the possibility of leukemogenic
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
, gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
tic, reproductive, and neurological effects from chronic exposure.
A 2005 epidemiology
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU." The World Health Organization
World Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
, the directing and coordinating authority for health within the United Nations which is responsible for setting health research norms and standards, providing technical support to countries and monitoring and assessing health trends, states that no risk of reproductive, developmental, or carcinogenic effects have been reported in humans due to DU exposure. This report has been criticized by Dr. Keith Baverstock for not including possible long term effects of DU on human body.
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 concluded that epidemiological evidence is consistent with an increased risk of birth defects in the offspring of persons exposed to DU. Environmental groups and others have expressed concern about the health effects of depleted uranium, and there is some debate over the matter. Some people have raised concerns about the use of this material, particularly in munitions, because of its mutagenicity, teratogenicity in mice, and neurotoxicity, and its suspected carcinogenic potential. Additional concerns address unexploded DU munitions leeching into groundwater over time.
Several sources have attributed the increase in the rate of birth defects in the children of Gulf War
Gulf War
The Persian Gulf War , commonly referred to as simply the Gulf War, was a war waged by a U.N.-authorized coalition force from 34 nations led by the United States, against Iraq in response to Iraq's invasion and annexation of Kuwait.The war is also known under other names, such as the First Gulf...
veterans and in Iraqis to depleted uranium inhalation exposure, A 2001 study of 15,000 February 1991 U.S. 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.
In a study of UK troops, "Overall, the risk of any malformation among pregnancies reported by men was 50% higher in Gulf War Veterans (GWV) compared with Non-GWVs". The conclusion of the study stated "We found no evidence for a link between paternal deployment to the Gulf war and increased risk of stillbirth, chromosomal malformations, or congenital syndromes. Associations were found between fathers' service in the Gulf war and increased risk of miscarriage and less well-defined malformations, but these findings need to be interpreted with caution as such outcomes are susceptible to recall bias. The finding of a possible relationship with renal anomalies requires further investigation. There was no evidence of an association between risk of miscarriage and mothers' service in the gulf."
Animals
It has been reported that uranium has caused reproductive defects, and other health problems in rodents, frogFrog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s and other animals. Uranium was shown to have cytotoxic, genotoxic and carcinogenic effects in animal studies. It has been shown in rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s and frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s that water soluble forms of uranium are teratogenic.
Bacterial biochemistry
It has been shown that bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
can reduce and fix uranium in soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s. These bacterium change soluble U(VI) into the highly insoluble complex forming U(IV) ion, hence stopping chemical leaching.
Behaviour in soil
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 (apatiteApatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
) while a second method is to add a food substance such as acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...
to the soil. This will enable bacteria to reduce the uranium (VI) to uranium (IV) which is much less soluble. In peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
-like soils the uranium will tend to bind to the humic acids, this tends to fix the uranium in the soil.