Arsenic

Arsenic

Overview
Arsenic icon is a chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the symbol As, atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 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
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

 in 1250.

Arsenic is a metalloid
Metalloid
Metalloid is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, each element can usually be classified as a metal or a nonmetal. However, some elements with intermediate or mixed properties can be harder to characterize...

. It can exist in various allotropes
Allotropy
Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, known as allotropes of these elements...

, although only the grey form has important use in industry. The main use of metallic arsenic is for strengthening alloys of copper and especially lead (for example, in car batteries).
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Encyclopedia
Arsenic icon is a chemical element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...

 with the symbol As, atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...

 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
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

 in 1250.

Arsenic is a metalloid
Metalloid
Metalloid is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, each element can usually be classified as a metal or a nonmetal. However, some elements with intermediate or mixed properties can be harder to characterize...

. It can exist in various allotropes
Allotropy
Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, known as allotropes of these elements...

, although only the grey form has important use in industry. The main use of metallic arsenic is for strengthening alloys of copper and especially lead (for example, in car batteries). Arsenic is a common n-type dopant
Dopant
A dopant, also called a doping agent, is a trace impurity element that is inserted into a substance in order to alter the electrical properties or the optical properties of the substance. In the case of crystalline substances, the atoms of the dopant very commonly take the place of elements that...

 in semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 electronic devices, and the optoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon.

A few species of bacteria are able to use arsenic compounds as respiratory metabolites, and are arsenic-tolerant. Arsenic is notoriously poisonous to multicellular life because of the interaction of arsenic ions with protein thiol
Thiol
In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl group...

s. Arsenic and its compounds, especially the trioxide, are used in the production of pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

s (treated wood products), herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

s, and insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s. These applications are declining, however, as many of these compounds are being phased out. Arsenic poisoning
Arsenic poisoning
Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

 from naturally occurring arsenic compounds in drinking water remains a problem in many parts of the world.

Physical characteristics



The three most common allotropes
Allotropy
Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, known as allotropes of these elements...

 are metallic grey, yellow and black arsenic, with grey being the most common. Grey arsenic (α-As, space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...

 Rm No. 166) adopts a double-layered structure consisting of many interlocked ruffled six-membered rings. Because of weak bonding between the layers, grey arsenic is brittle and has a relatively low Mohs hardness of 3.5. Nearest and next-nearest neighbors form a distorted octahedral complex, with the three atoms in the same double-layer being slightly closer than the three atoms in the next. This relatively close packing leads to a high density of 5.73 g/cm3. Grey arsenic is a semimetal, but becomes a semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 with a bandgap of 1.2–1.4 eV if amorphized. Yellow arsenic is soft and waxy, and somewhat similar to tetraphosphorus . Both have four atoms arranged in a tetrahedral structure in which each atom is bound to each of the other three atoms by a single bond. This unstable allotrope, being molecular, is the most volatile, least dense and most toxic. Solid yellow arsenic is produced by rapid cooling of arsenic vapour, . It is rapidly transformed into the grey arsenic by light. The yellow form has a density of 1.97 g/cm3. Black arsenic is similar in structure to red phosphorus.

Isotopes



Naturally occurring arsenic is composed of one stable isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

, 75As. As of 2003, at least 33 radioisotopes have also been synthesized, ranging in atomic mass
Atomic mass
The atomic mass is the mass of a specific isotope, most often expressed in unified atomic mass units. The atomic mass is the total mass of protons, neutrons and electrons in a single atom....

 from 60 to 92. The most stable of these is 73As with a 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...

 of 80.3 days. Isotopes that are lighter than the stable 75As tend to decay by β+ decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

, and those that are heavier tend to decay by β- decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...

, with some exceptions.

At least 10 nuclear isomer
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...

s have been described, ranging in atomic mass from 66 to 84. The most stable of arsenic's isomers is 68mAs with a half-life of 111 seconds.

Chemistry


When heated in air, arsenic oxidizes to arsenic trioxide; the fumes from this reaction have an odour resembling garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...

. This odour can be detected on striking arsenide minerals such as arsenopyrite
Arsenopyrite
Arsenopyrite is an iron arsenic sulfide . It is a hard metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases elemental sulfur. When arsenopyrite is heated, it becomes magnetic and gives off toxic fumes...

 with a hammer. Arsenic (and some arsenic compounds) sublimes upon heating at atmospheric pressure, converting directly to a gaseous form without an intervening liquid state at 887 kelvins (613.9 °C). The triple point
Triple point
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium...

 is 3.63 MPa and 1090 kelvins (816.9 °C). Arsenic makes arsenic acid
Arsenic acid
Arsenic acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but only found in solution where it...

 with concentrated nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

, arsenious acid with dilute nitric acid, and arsenic trioxide
Arsenic trioxide
Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually...

 with concentrated sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

.

Compounds



Arsenic compounds resemble in some respects those of phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

, which occupies the same group (column) of the periodic table
Periodic table
The periodic table of the chemical elements is a tabular display of the 118 known chemical elements organized by selected properties of their atomic structures. Elements are presented by increasing atomic number, the number of protons in an atom's atomic nucleus...

. Arsenic is less commonly observed in the pentavalent state, however. The most common oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

s for arsenic are: −3 in the arsenide
Arsenide
Arsenide is an arsenic anion with the charge −3. The trianion is formed by the reduction of arsenic by three electrons. For example heating arsenic powder with excess sodium gives sodium arsenide . The anions have no existence in solution since they are extremely basic...

s, such as alloy-like intermetallic compounds; and +3 in the arsenite
Arsenite
In chemistry an arsenite is a chemical compound containing an arsenic oxoanion where arsenic has oxidation state +3.The different forms of the anion are the next ones:* ortho-arsenite: AsO33-* meta-arsenite: AsO2-...

s, arsenates(III), and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As ions in the mineral skutterudite
Skutterudite
Skutterudite is a cobalt arsenide mineral that has variable amounts of nickel and iron substituting for cobalt with a general formula: As3. Some references give the arsenic a variable formula subscript of 2-3. High nickel varieties are referred to as nickel-skutterudite, previously chloanthite...

. In the +3 oxidation state, arsenic is typically pyramidal, owing to the influence of the lone pair
Lone pair
In chemistry, a lone pair is a valence electron pair without bonding or sharing with other atoms. They are found in the outermost electron shell of an atom, so lone pairs are a subset of a molecule's valence electrons...

 of electrons.

Inorganic


Arsenic forms colourless, odourless, crystalline oxides As2O3
Arsenic trioxide
Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually...

 ("white arsenic") and As2O5
Arsenic pentoxide
Arsenic pentoxide is the inorganic compound with the formula As2O5. This glassy, white solid is relatively unstable, consistent with the rarity of the As oxidation state. More common, and far more important commercially, is arsenic oxide ....

, which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid
Arsenic acid
Arsenic acid is the chemical compound with the formula H3AsO4. More descriptively written as AsO3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but only found in solution where it...

 is a weak acid. Its salts are called arsenate
Arsenate
The arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....

s, e.g., Paris Green
Paris Green
Paris Green is an inorganic compound more precisely known as copper acetoarsenite. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks...

 (copper(II) acetoarsenite), calcium arsenate
Calcium arsenate
Calcium arsenate is an extremely poisonous chemical compound that most commonly exists as a colorless to white amorphous solid. It was originally used as a pesticide and as a germicide...

, and lead hydrogen arsenate
Lead hydrogen arsenate
Lead hydrogen arsenate, also called lead arsenate, acid lead arsenate or LA, chemical formula PbHAsO4, is an inorganic insecticide used primarily against the potato beetle.-Chemistry:It is usually produced using the following reaction:...

. The latter three have been used as agricultural
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 insecticide
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

s and poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

s. The protonation steps between the arsenate and arsenic acid are similar to those between 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...

 and phosphoric acid
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...

. However, arsenite and arsenous acid
Arsenous acid
Arsenous acid, also known as arsenious acid, is the inorganic compound with the formula H3AsO3. It is known to occur in aqueous solutions, but it has not been isolated as a pure material, although this fact does not detract from the significance of As3.-Properties:As3 is a pyramidal molecule...

 contain arsenic bonded to three oxygen and not hydrogen atoms, in contrast to phosphite
Phosphite
A phosphite is a salt of phosphorous acid. The phosphite ion is a polyatomic ion with a phosphorus central atom where phosphorus has an oxidation state of +3...

 and phosphonic acid, which contains a non-acidic P-H bond. Arsenous acid is genuinely tribasic, whereas phosphonic acid is not.

A broad variety of sulfur compounds of arsenic are known. Orpiment (As2S3
Arsenic trisulfide
Arsenic trisulfide is the inorganic compound with the formula As2S3. This bright yellow solid is a well known mineral orpiment , has been used as a pigment, and has played a role in the analysis of arsenic compounds. This chalcogenide material is a group V/VI, intrinsic p-type semiconductor and...

) and realgar (As4S4) are somewhat abundant and were formerly used as painting pigments. Other sulfides include As4S3 and As4S10. Arsenic has a formal oxidation state of +2 in As4S4, which features As-As bonds so that the total covalency of As is still in fact three.

The trifluoride, trichloride, tribromide, and triiodide of arsenic(III) are well known, whereas only AsF5 is the main pentahalide. Arsenic pentafluoride
Arsenic pentafluoride
Arsenic pentafluoride is a chemical compound of arsenic and fluorine. The oxidation state of arsenic is +5.-Synthesis:Arsenic pentafluoride can be prepared by direct combination of arsenic and fluorine:...

 is stable at room temperature, whereas the pentachloride
Arsenic pentachloride
Arsenic pentachloride is a chemical compound of arsenic and chlorine. This compound was first prepared in 1976 through the UV irradiation of arsenic trichloride, AsCl3, in liquid chlorine at −105°C. AsCl5 decomposes at around −50°C. The structure of the solid was finally determined in 2001...

 is stable only below −50 °C.

Organoarsenic compounds




A large variety of organoarsenic compounds are known. Several were developed as chemical warfare agents during World War I, including vesicants
Blister agent
A blister agent, or vesicant, is a chemical compound that causes severe skin, eye and mucosal pain and irritation. They are named for their ability to cause severe chemical burns, resulting in painful water blisters on the bodies of those affected...

 such as lewisite
Lewisite
Lewisite is an organoarsenic compound, specifically an arsine. It was once manufactured in the U.S. and Japan as a chemical weapon, acting as a vesicant and lung irritant...

 and vomiting agents such as adamsite
Adamsite
Adamsite or DM is an organic compound; technically, an arsenical diphenylaminechlorarsine, that can be used as a riot control agent. DM belongs to the group of chemical warfare agents known as vomiting agents or sneeze gases...

. Cacodylic acid
Cacodylic acid
Cacodylic acid is the chemical compound with the formula 2AsO2H. Derivatives of cacodylic acid, cacodylates, were frequently used as herbicides. For example, "Agent Blue," one of the chemicals used during the Vietnam War, is a mixture of cacodylic acid and sodium cacodylate...

, which is of historic and practical interest, arises from the methylation
Methylation
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

 of arsenic trioxide, a reaction that has no analogy in phosphorus chemistry.

Alloys


Arsenic is used as the group 5 element in the III-V semiconductors gallium arsenide, indium arsenide, and aluminium arsenide
Aluminium arsenide
Aluminium arsenide or aluminum arsenide is a semiconductor material with almost the same lattice constant as gallium arsenide and aluminium gallium arsenide and wider band gap than gallium arsenide.-Properties:...

. The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure
Electronic band structure
In solid-state physics, the electronic band structure of a solid describes those ranges of energy an electron is "forbidden" or "allowed" to have. Band structure derives from the diffraction of the quantum mechanical electron waves in a periodic crystal lattice with a specific crystal system and...

 is completely different, which results distinct bulk properties. Other arsenic alloys include the II-IV semiconductor cadmium arsenide
Cadmium arsenide
Cadmium arsenide is a crystalline semiconductor with a tetragonal structure in the II-V family. It is a narrow gap semiconductor with an energy gap of 0.14 eV. The electron mobility is very large at ambient temperature...

.

Occurrence and production



Mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

s with the formula MAsS and MAs2 (M = Fe, Ni, Co) are the dominant commercial sources of arsenic, together with realgar
Realgar
Realgar, α-As4S4, is an arsenic sulfide mineral, also known as "ruby sulphur" or "ruby of arsenic". It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts...

 (an arsenic sulfide mineral) and native arsenic. An illustrative mineral is arsenopyrite
Arsenopyrite
Arsenopyrite is an iron arsenic sulfide . It is a hard metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases elemental sulfur. When arsenopyrite is heated, it becomes magnetic and gives off toxic fumes...

 (Fe
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

AsS
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

), which is structurally related to iron pyrite. Many minor As-containing minerals are known. Arsenic also occurs in various organic forms in the environment. Inorganic arsenic and its compounds, upon entering the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

, are progressively metabolized to a less toxic form of arsenic through a process of methylation
Methylation
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

.

Other naturally occurring pathways of exposure include volcanic ash, weathering of arsenic-containing minerals and ores, and dissolved in groundwater. It is also found in food, water, soil, and air. The most common pathway of exposure for humans is ingestion, and the predominant source of arsenic in our diet is through seafood. An additional route of exposure is through inhalation.


In 2005, China was the top producer of white arsenic with almost 50% world share, followed by Chile, Peru, and Morocco, according to the British Geological Survey
British Geological Survey
The British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...

 and the United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

. Most operations in the US and Europe have closed for environmental reasons. The arsenic is recovered mainly as a side product from the purification of copper. Arsenic is part of the smelter dust from copper, gold, and lead smelters.

On roasting
Roasting (metallurgy)
Roasting is a step in the processing of certain ores. More specifically, roasting is a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component. Often before roasting, the ore has already been partially purified, e.g. by froth...

 in air of arsenopyrite, arsenic sublimes as arsenic(III) oxide leaving iron oxides, while roasting without air results in the production of metallic arsenic. Further purification from sulfur and other chalcogens is achieved by sublimation in vacuum or in a hydrogen atmosphere or by distillation from molten lead-arsenic mixture.

History




The word arsenic was borrowed from the Syriac
Syriac language
Syriac is a dialect of Middle Aramaic that was once spoken across much of the Fertile Crescent. Having first appeared as a script in the 1st century AD after being spoken as an unwritten language for five centuries, Classical Syriac became a major literary language throughout the Middle East from...

 word ܠܐ ܙܐܦܢܝܐ (al) zarniqa and the Persian
Persian language
Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...

 word Zarnikh, meaning "yellow orpiment
Orpiment
Orpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...

", into Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 as arsenikon (Αρσενικόν). It is also related to the similar Greek word arsenikos (Αρσενικός), meaning "masculine" or "potent". The word was adopted in Latin arsenicum and Old French arsenic, from which the English word arsenic is derived. Arsenic sulfides (orpiment, realgar
Realgar
Realgar, α-As4S4, is an arsenic sulfide mineral, also known as "ruby sulphur" or "ruby of arsenic". It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts...

) and oxides have been known and used since ancient times. Zosimos
Zosimos of Panopolis
Zosimos of Panopolis was an Egyptian or Greek alchemist and Gnostic mystic from the end of the 3rd and beginning of the 4th century AD. He was born in Panopolis, present day Akhmim in the south of Egypt, ca. 300. He wrote the oldest known books on alchemy, of which quotations in the Greek language...

 (circa 300 AD) describes roasting sandarach (realgar) to obtain cloud of arsenic (arsenious oxide), which he then reduces to metallic arsenic. As the symptoms of arsenic poisoning
Arsenic poisoning
Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

 were somewhat ill-defined, it was frequently used for murder
Murder
Murder is the unlawful killing, with malice aforethought, of another human being, and generally this state of mind distinguishes murder from other forms of unlawful homicide...

 until the advent of the Marsh test
Marsh test
The Marsh test is a highly sensitive method in the detection of arsenic, especially useful in the field of forensic toxicology when arsenic was used as a poison...

, a sensitive chemical test for its presence. (Another less sensitive but more general test is the Reinsch test
Reinsch test
The Reinsch test is an initial indicator to detect the presence of one or more of the following heavy metals in a biological sample, and is often used by toxicologists where poisoning by such metals is suspected.* Antimony* Arsenic* Bismuth* Selenium...

.) Owing to its use by the ruling class to murder one another and its potency and discreetness, arsenic has been called the Poison of Kings and the King of Poisons.

During the Bronze Age
Bronze Age
The Bronze Age is a period characterized by the use of copper and its alloy bronze as the chief hard materials in the manufacture of some implements and weapons. Chronologically, it stands between the Stone Age and Iron Age...

, arsenic was often included in bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...

, which made the alloy harder (so-called "arsenical bronze
Arsenical bronze
Arsenical bronze is an alloy in which arsenic is added to copper as opposed to, or in addition to other constituent metals. The use of arsenic with copper, either as the secondary constituent or with another component such as tin, results in a stronger final product and better casting...

").
Albertus Magnus
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

 (Albert the Great, 1193–1280) is believed to have been the first to isolate the element in 1250 by heating soap together with arsenic trisulfide
Arsenic trisulfide
Arsenic trisulfide is the inorganic compound with the formula As2S3. This bright yellow solid is a well known mineral orpiment , has been used as a pigment, and has played a role in the analysis of arsenic compounds. This chalcogenide material is a group V/VI, intrinsic p-type semiconductor and...

. In 1649, Johann Schröder
Johann Schröder
Johann Schröder was a German physician and pharmacologist who was the first person to recognise that arsenic was an element. In 1649, he produced the elemental form of arsenic by heating its oxide, and published two methods for its preparation.-References:...

 published two ways of preparing arsenic.

Cadet's fuming liquid
Cadet's fuming liquid
Cadet's fuming liquid was the first organometallic compound to be synthesized. In 1760, the French chemist Louis Claude Cadet de Gassicourt synthesized a red liquid by the reaction of potassium acetate with arsenic trioxide....

 (impure cacodyl
Cacodyl
Cacodyl, dicacodyl, tetramethyldiarsine, alkarsine or minor part of the "Cadet's fuming liquid" 2As—As2 is a poisonous oily liquid with a garlicky odor...

), often claimed as the first synthetic organometallic compound
Organometallic chemistry
Organometallic chemistry is the study of chemical compounds containing bonds between carbon and a metal. Since many compounds without such bonds are chemically similar, an alternative may be compounds containing metal-element bonds of a largely covalent character...

, was synthesized in 1760 by Louis Claude Cadet de Gassicourt
Louis Claude Cadet de Gassicourt
Louis Claude Cadet de Gassicourt was a French chemist who synthesised the first organometalic compound.He obtained a red liquid by the reaction of potassium acetate with arsenic trioxide...

 by the reaction of potassium acetate
Potassium acetate
Potassium acetate is the potassium salt of acetic acid.-Preparation:It can be prepared by reacting a potassium-containing base such as potassium hydroxide or potassium carbonate with acetic acid:...

 with arsenic trioxide
Arsenic trioxide
Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually...

.

In the Victorian era
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

, "arsenic" ("white arsenic" trioxide) was mixed with vinegar
Vinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...

 and chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

 and eaten by women to improve the complexion
Complexion
Complexion refers to the natural color, texture, and appearance of the skin, especially that of the face.-History:The word "complexion" is derived from the Late Latin complexi, which initially referred in general terms to a combination of things, and later in physiological terms, to the balance of...

 of their faces, making their skin paler to show they did not work in the fields. Arsenic was also rubbed into the faces and arms of women to "improve their complexion". The accidental use of arsenic in the adulteration of foodstuffs led to the Bradford sweet poisoning in 1858, which resulted in approximately 20 deaths.

Agricultural



The toxicity of arsenic to insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, bacteria
Bacteria
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...

 and fungi led to its use as a wood preservative. In the 1950s a process of treating wood with chromated copper arsenate
Chromated copper arsenate
Chromated copper arsenate is a wood preservative used for timber treatment since the mid-1930s. It is a mix of chromium, copper and arsenic formulated as oxides or salts. It preserves the wood from decay fungi, wood attacking insects, including termites, and marine borers...

 (also known as CCA or Tanalith) was invented, and for decades this treatment was the most extensive industrial use of arsenic. An increased appreciation of the toxicity of arsenic resulted in a ban for the use of CCA in consumer products; the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 and United States initiated this process in 2004. CCA remains in heavy use in other countries however, e.g. Malaysian rubber plantations.

Arsenic was also used in various agricultural insecticides, termination and poisons. For example, lead hydrogen arsenate
Lead hydrogen arsenate
Lead hydrogen arsenate, also called lead arsenate, acid lead arsenate or LA, chemical formula PbHAsO4, is an inorganic insecticide used primarily against the potato beetle.-Chemistry:It is usually produced using the following reaction:...

 was a common insecticide on fruit tree
Fruit tree
A fruit tree is a tree which bears fruit that is consumed or used by people — all trees that are flowering plants produce fruit, which are the ripened ovaries of flowers containing one or more seeds. In horticultural usage, the term 'fruit tree' is limited to those that provide fruit for...

s, but contact with the compound sometimes resulted in brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...

 among those working the sprayers. In the second half of the 20th century, monosodium methyl arsenate
Monosodium methyl arsenate
Monosodium methyl arsenate is an arsenic-based herbicide and fungicide. It is an organic arsenate; but it is a less toxic organic form of arsenic, which has replaced the role of lead hydrogen arsenate in agriculture. It is one of the most common herbicides used on golf courses. It is typically...

 (MSMA) and disodium methyl arsenate
Disodium methyl arsenate
Disodium methyl arsonate is an arsenic-based herbicide.Trade names include Metharsinat, Arrhenal, Disomear, Metharsan, Stenosine, Tonarsan, Tonarsin, Arsinyl, Arsynal, and Diarsen.-See also:* Cacodylic acid* Monosodium methyl arsenate...

 (DSMA) – less toxic organic forms of arsenic – have replaced lead arsenate in agriculture.

Arsenic is still added to animal food, in particular in the U.S. as a method of disease prevention and growth stimulation. One example is roxarsone, which is used as a broiler
Broiler
A broiler is a type of chicken raised specifically for meat production. Modern commercial broilers, typically known as Cornish crosses or Cornish-Rocks are specially bred for large scale, efficient meat production and grow much faster than egg or traditional dual purpose breeds...

 starter by about 70% of the broiler growers since 1995. The Poison-Free Poultry Act of 2009 proposes to ban the use of roxarsone in industrial swine and poultry production.

Medical use


During the 18th, 19th, and 20th centuries, a number of arsenic compounds have been used as medicines, including arsphenamine
Arsphenamine
Arsphenamine, also known as Salvarsan and 606, is a drug that was used beginning in the 1910s to treat syphilis and trypanosomiasis...

 (by Paul Ehrlich
Paul Ehrlich
Paul Ehrlich was a German scientist in the fields of hematology, immunology, and chemotherapy, and Nobel laureate. He is noted for curing syphilis and for his research in autoimmunity, calling it "horror autotoxicus"...

) and arsenic trioxide
Arsenic trioxide
Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually...

 (by Thomas Fowler). Arsphenamine as well as neosalvarsan
Neosalvarsan
Neosalvarsan is a synthetic chemotherapeutic that is an organoarsenic compound. It became available in 1912 and superseded the more toxic and less water-soluble salvarsan as an effective treatment for syphilis...

 was indicated for syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

 and trypanosomiasis
Trypanosomiasis
Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. Approximately 500,000 men, women and children in 36 countries of sub-Saharan Africa suffer from human African trypanosomiasis which is caused by...

, but has been superseded by modern antibiotics. Arsenic trioxide has been used in a variety of ways over the past 500 years, but most commonly in the treatment of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. The US Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

 in 2000 approved this compound for the treatment of patients with acute promyelocytic leukemia
Acute promyelocytic leukemia
Acute promyelocytic leukemia is a subtype of acute myelogenous leukemia , a cancer of the blood and bone marrow. It is also known as acute progranulocytic leukemia; APL; AML with t, PML-RARA and variants; FAB subtype M3 and M3 variant.In APL, there is an abnormal accumulation of immature...

 that is resistant to ATRA. It was also used as Fowler's solution
Fowler's solution
Fowler's solution is a solution containing potassium arsenite that once was prescribed as a remedy or a tonic. A Dr. Fowler of Stafford, England proposed its use in 1786 as a substitute for a patent medicine, "tasteless ague drop." It was prescribed in the United States until the late 1950s for a...

 in psoriasis
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...

. Recently new research has been done in locating tumours using arsenic-74 (a positron emitter). The advantages of using this isotope instead of the previously used iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

-124 is that the signal in the PET scan
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 is clearer as the body tends to transport iodine to the thyroid gland producing a lot of noise.

In subtoxic doses, soluble arsenic compounds act as stimulant
Stimulant
Stimulants are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...

s, and were once popular in small doses as medicine by people in the mid-18th century.

Alloys


The main use of metallic arsenic is for alloying with copper and especially lead. Lead components in car batteries are strengthened by the presence of a few percent of arsenic. Gallium arsenide is an important semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 material, used in integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s. Circuits made from GaAs are much faster (but also much more expensive) than those made in silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

. Unlike silicon it is direct bandgap, and so can be used in laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

s and LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

s to directly convert electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 into light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

.

Military


After World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, the United States built up a stockpile of of lewisite
Lewisite
Lewisite is an organoarsenic compound, specifically an arsine. It was once manufactured in the U.S. and Japan as a chemical weapon, acting as a vesicant and lung irritant...

 (ClCH=CHAsCl2), a chemical weapon
Chemical warfare
Chemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...

 that is a vesicant (blister agent) and lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 irritant. The stockpile was neutralized with bleach and dumped into the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...

 after the 1950s. During the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

 the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 used Agent Blue
Agent Blue
Agent Blue is one of the "rainbow herbicides" that is known for its use by the United States during the Vietnam War. It was sprayed on rice paddies and other crops in an attempt to deprive the Viet Cong of valuable crops. Agent Blue is a mixture of two arsenic-containing compounds, sodium...

, a mixture of sodium cacodylate and its acid form, as one of the rainbow herbicides
Rainbow Herbicides
The Rainbow Herbicides are a group of chemicals used by the United States military in Southeast Asia during the Vietnam War. Success with Project AGILE field tests with herbicides in South Vietnam in 1961 led to the formal herbicidal program Trail Dust...

 to deprive the Vietnamese of valuable crops.

Other uses

  • Copper acetoarsenite was used as a green pigment
    Pigment
    A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

     known under many names, including 'Paris Green
    Paris Green
    Paris Green is an inorganic compound more precisely known as copper acetoarsenite. It is a highly toxic emerald-green crystalline powder that has been used as a rodenticide and insecticide, and also as a pigment, despite its toxicity. It is also used as a blue colorant for fireworks...

    ' and 'Emerald Green'. It caused numerous arsenic poisoning
    Arsenic poisoning
    Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

    s. Scheele's Green
    Scheele's Green
    Scheele's Green, also called Schloss Green, is chemically a cupric hydrogen arsenite , CuHAsO3. It is a compound similar to Paris Green...

    , a copper arsenate, was used in the 19th century as a coloring agent in sweets
    SweetS
    was a Japanese idol group. Put together through auditions, the group debuted in 2003 on the avex trax label. Although the group met minor success, they disbanded after three years with the release of a final single in June 2006....

    .
  • Also used in bronzing
    Bronzing
    Bronzing is a process by which a bronze-like surface is applied to other materials . Some bronzing processes are merely simulated finishes applied to existing metal surfaces, or coatings of powdered metal that give the appearance of a solid metal surface...

     and pyrotechnics
    Pyrotechnics
    Pyrotechnics is the science of using materials capable of undergoing self-contained and self-sustained exothermic chemical reactions for the production of heat, light, gas, smoke and/or sound...

    .
  • Up to 2% of arsenic is used in lead alloys for lead shot
    Lead shot
    Lead shot is a collective term for small balls of lead. These were the original projectiles for muskets and early rifles, but today lead shot is fired primarily from shotguns. It is also used for a variety of other purposes...

    s and bullet
    Bullet
    A bullet is a projectile propelled by a firearm, sling, or air gun. Bullets do not normally contain explosives, but damage the intended target by impact and penetration...

    s.
  • Arsenic is added in small quantities to alpha-brass to make it dezincification resistant. This grade of brass is used to make plumbing fittings or other items that are in constant contact with water.
  • Arsenic is also used for taxonomic sample preservation.
  • Until recently arsenic was used in optical glass. Modern glass manufacturers, under pressure from environmentalists, have removed it, along with lead
    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...

    .

Bacteria



Some species of bacteria
Bacteria
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...

 obtain their energy by oxidizing
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 various fuels while reducing
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 arsenate to arsenite. Under oxidative environmental conditions some bacteria use arsenite, which is oxidized to arsenate as fuel for their metabolism. The enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s involved are known as arsenate reductases
Arsenate reductase (glutaredoxin)
In enzymology, an arsenate reductase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are arsenate and glutaredoxin, whereas its 3 products are arsenite, glutaredoxin disulfide, and H2O....

 (Arr).

In 2008, bacteria were discovered that employ a version of photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 in the absence of oxygen with arsenites as electron donor
Electron donor
An electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process....

s, producing arsenates (just as ordinary photosynthesis uses water as electron donor, producing molecular oxygen). Researchers conjecture that, over the course of history, these photosynthesizing organisms produced the arsenates that allowed the arsenate-reducing bacteria to thrive. One strain
Strain (biology)
In biology, a strain is a low-level taxonomic rank used in three related ways.-Microbiology and virology:A strain is a genetic variant or subtype of a micro-organism . For example, a "flu strain" is a certain biological form of the influenza or "flu" virus...

 PHS-1 has been isolated and is related to the γ-Proteobacterium Ectothiorhodospira shaposhnikovii. The mechanism is unknown, but an encoded Arr enzyme may function in reverse to its known homologues
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

.

Heredity


Arsenic has been linked to epigenetic changes that are heritable changes in gene expression that occur without changes in DNA sequence and include DNA methylation, histone modification, and RNA interference. Toxic levels of arsenic cause significant DNA hypermethylation of tumour suppressor genes p16 and p53, thus increasing risk of carcinogenesis. These epigenetic events have been observed in in vitro studies with human kidney cells and in vivo tests with rat liver cells and peripheral blood leukocytes in humans. Inductive coupled plasma mass spectrometry (ICP-MS) is used to detect precise levels of intracellular arsenic and its other bases involved in epigenetic modification of DNA. Studies investigating arsenic as an epigenetic factor will help in developing precise biomarkers of exposure and susceptibility.

The Chinese brake fern (Pteris vittata
Pteris vittata
Pteris vittata, commonly known variously as the Chinese brake, Chinese ladder brake, or simply ladder brake, is a species of fern in the genus Pteris. It is indigenous to Asia, tropical Africa and Australia. The type specimen was collected in China by Pehr Osbeck.-Habitat and distribution:Pteris...

) hyperaccumulates arsenic present in the soil into its leaves and has a proposed use in phytoremediation
Phytoremediation
Phytoremediation Phytoremediation Phytoremediation (from the Ancient Greek , and Latin (restoring balance or remediation) describes the treatment of environmental problems (bioremediation) through the use of plants that mitigate the environmental problem without the need to excavate the...

.

Arsenic reported substituting for phosphorus as a building block of life


A NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

-funded astrobiology
Astrobiology
Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and habitable planets outside our Solar System, the search for evidence of prebiotic chemistry,...

 research team claimed on December 2, 2010 that the microbe strain GFAJ-1
GFAJ-1
GFAJ-1 is a strain of rod-shaped bacterium in the family Halomonadaceae. The extremophile was isolated from the hypersaline and alkaline Mono Lake in eastern California by a research team led by NASA astrobiologist Felisa Wolfe-Simon...

 of the Gammaproteobacteria
Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae , Vibrionaceae and Pseudomonadaceae. An exceeding number of important pathogens belongs to this class, e.g...

 (designated Halomonadaceae
Halomonadaceae
The Halomonadaceae are a family of halophilic Proteobacteria.-History:The family was originally created in 1988 to contain the genera Halomonas and Deleya....

) group has the ability to substitute arsenic for at least part of the phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 in the molecules of its cells, including DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 and ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

. Bacteria from Mono Lake
Mono Lake
Mono Lake is a large, shallow saline lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in a basin that has no outlet to the ocean...

, a naturally arsenic-rich site in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, were cultured in an environment high in arsenic but low in phosphorus. This finding has faced strong criticism from the scientific community, many scientists have argued that there is no evidence that arsenic is actually incorporated into biomolecules. Independent confirmation of this finding has not yet been possible.

Biomethylation of arsenic


Inorganic arsenic and its compounds, upon entering the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

, are progressively metabolised through a process of methylation
Methylation
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

. For example, the mold Scopulariopsis brevicaulis produce significant amounts of trimethylarsine
Trimethylarsine
Trimethylarsine is the chemical compound with the formula 3As, commonly abbreviated AsMe3 or TMAs. This organic derivative of arsine has been used as a source of arsenic in microelectronics industry, a building block to other organoarsenic compounds, and serves as a ligand in coordination...

 if inorganic arsenic is present. The organic compound arsenobetaine
Arsenobetaine
Arsenobetaine is an organoarsenic compound that is the main source of arsenic found in fish. It is the arsenic analog of trimethylglycine, commonly known as betaine...

 is found in some marine foods such as fish and algae, and also in mushrooms in larger concentrations. The average person's intake is about 10–50 µg/day. Values about 1000 µg are not unusual following consumption of fish or mushrooms. But there is little danger in eating fish because this arsenic compound is nearly non-toxic.

Arsenic in drinking water



Widespread arsenic contamination of groundwater has led to a massive epidemic of arsenic poisoning
Arsenic poisoning
Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

 in Bangladesh
Water supply and sanitation in Bangladesh
Water supply and sanitation in Bangladesh is characterized by a number of achievements and challenges. The share of the population with access to an improved water source was estimated at 98% in 2004, a very high level for a low-income country. This has been achieved to a large extent through the...

 and neighbouring countries. As of this writing, 42 major incidents around the world have been reported on groundwater arsenic contamination. It is estimated that approximately 57 million people are drinking groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 with arsenic concentrations elevated above 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...

's standard of 10 parts per billion. However, a study of cancer rates in Taiwan suggested that significant increases in cancer mortality appear only at levels above 150 parts per billion. The arsenic in the groundwater is of natural origin, and is released from the sediment into the groundwater, owing to the anoxic conditions of the subsurface. This groundwater began to be used after local and western NGOs
Non-governmental organization
A non-governmental organization is a legally constituted organization created by natural or legal persons that operates independently from any government. The term originated from the United Nations , and is normally used to refer to organizations that do not form part of the government and are...

 and the Bangladeshi government undertook a massive shallow tube well
Water well
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...

 drinking-water program in the late twentieth century. This program was designed to prevent drinking of bacteria-contaminated surface waters, but failed to test for arsenic in the groundwater. Many other countries and districts in Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, such as Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 and Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...

 have geological environments conducive to generation of high-arsenic groundwaters. Arsenicosis was reported in Nakhon Si Thammarat
Nakhon Si Thammarat
Nakhon Si Thammarat is a town in southern Thailand, capital of the Nakhon Si Thammarat Province and the Nakhon Si Thammarat district. It is about south of Bangkok, on the east coast of the Malay Peninsula. The city was the administrative center of southern Thailand during most of its history. ...

, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

 in 1987, and the dissolved arsenic in the Chao Phraya River
Chao Phraya River
The Chao Phraya is a major river in Thailand, with its low alluvial plain forming the centre of the country. It runs through Bangkok, the capital city, and then empties into the Gulf of Thailand.-Etymology:...

 is suspected of containing high levels of naturally occurring arsenic, but has not been a public health problem owing to the use of bottled water.

In the United States, arsenic is most commonly found in the ground waters of the southwest. Parts of New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

, Michigan
Michigan
Michigan is a U.S. state located in the Great Lakes Region of the United States of America. The name Michigan is the French form of the Ojibwa word mishigamaa, meaning "large water" or "large lake"....

, Wisconsin
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

, Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

 and the Dakotas are also known to have significant concentrations of arsenic in ground water. Increased levels of skin cancer have been associated with arsenic exposure in Wisconsin, even at levels below the 10 part per billion drinking water standard. According to a recent film funded by the US Superfund
Superfund
Superfund is the common name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 , a United States federal law designed to clean up sites contaminated with hazardous substances...

, millions of private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may contain levels that exceed established limits.

Low-level exposure to arsenic at concentrations found commonly in US drinking water compromises the initial immune response to H1N1 or swine flu infection according to NIEHS-supported scientists. The study, conducted in laboratory mice, suggests that people exposed to arsenic in their drinking water may be at increased risk for more serious illness or death in response to infection from the virus.

Epidemiological evidence from Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 shows a dose-dependent connection between chronic arsenic exposure and various forms of cancer, in particular when other risk factors, such as cigarette smoking, are present. These effects have been demonstrated to persist below 50 parts per billion.

Analyzing multiple epidemiological studies on inorganic arsenic exposure suggests a small but measurable risk increase for bladder cancer at 10 parts per billion. According to Peter Ravenscroft of the Department of Geography at the University of Cambridge, roughly 80 million people worldwide consume between 10 and 50 parts per billion arsenic in their drinking water. If they all consumed exactly 10 parts per billion arsenic in their drinking water, the previously cited multiple epidemiological study analysis would predict an additional 2,000 cases of bladder cancer alone. This represents a clear underestimate of the overall impact, since it does not include lung or skin cancer, and explicitly underestimates the exposure. Those exposed to levels of arsenic above the current WHO standard should weigh the costs and benefits of arsenic remediation.

Early (1973) evaluations of the removal of dissolved arsenic by drinking water treatment processes demonstrated that arsenic is very effectively removed by co-precipitation with either iron or aluminum oxides. The use of iron as a coagulant, in particular, was found to remove arsenic with efficiencies exceeding 90%. Several adsorptive media systems have been approved for point-of-service use in a study funded by the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 (U.S.EPA) and the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...

 (NSF). A team of European and Indian scientists and engineers have set up six arsenic treatment plants in West Bengal
West Bengal
West Bengal is a state in the eastern region of India and is the nation's fourth-most populous. It is also the seventh-most populous sub-national entity in the world, with over 91 million inhabitants. A major agricultural producer, West Bengal is the sixth-largest contributor to India's GDP...

 based on in-situ remediation method (SAR Technology). This technology does not use any chemicals and arsenic is left as an insoluble form (+5 state) in the subterranean zone by recharging aerated water into the aquifer and thus developing an oxidation zone to support arsenic oxidizing micro-organisms. This process does not produce any waste stream or sludge and is relatively cheap.

Another effective and inexpensive method to remove arsenic from contaminated well water is to sink wells 500 feet or deeper to reach purer waters. A recent 2011 study funded by the U.S. National Institute of
Environmental Health Sciences' Superfund Research Program shows that deep sediments can remove arsenic and take it out of circulation. Through this process called adsorption in which arsenic sticks to the surfaces of deep sediment articles, arsenic can be naturally removed from well water.

Magnetic separations of arsenic at very low magnetic field gradient
Gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....

s have been demonstrated in point-of-use water purification with high-surface-area and monodisperse
Monodisperse
A collection of objects are called monodisperse, or monosized, if they have the same size and shape when discussing particles, and the same mass when discussing polymers...

 magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...

 (Fe3O4) nanocrystal
Nanocrystal
B. D. Fahlman has described a nanocrystal as any nanomaterial with at least one dimension ≤ 100nm and that is singlecrystalline.-Summary:More properly, any material with a dimension of less than 1 micrometre, i.e., 1000 nanometers, should be referred to as a nanoparticle, not a nanocrystal...

s. Using the high specific surface area of Fe3O4 nanocrystals the mass of waste associated with arsenic removal from water has been dramatically reduced.

Epidemiological studies have suggested a correlation between chronic consumption of drinking water contaminated with arsenic and the incidence of all leading causes of mortality. The literature provides reason to believe arsenic exposure is causative in the pathogenesis of diabetes.

Wood preservation in the US


As of 2002, US-based industries consumed 19,600 metric tons of arsenic. Ninety percent of this was used for treatment of wood with chromated copper arsenate
Chromated copper arsenate
Chromated copper arsenate is a wood preservative used for timber treatment since the mid-1930s. It is a mix of chromium, copper and arsenic formulated as oxides or salts. It preserves the wood from decay fungi, wood attacking insects, including termites, and marine borers...

 (CCA). In 2007, 50% of the 5,280 metric tons of consumption was still used for this purpose. In the United States, the use of arsenic in consumer products was discontinued for residential, and general consumer construction on December 31, 2003 and alternative chemicals are now used, such as Alkaline Copper Quaternary
Alkaline copper quaternary
Alkaline Copper Quaternary is a water based wood preservative method. The treatment is made up of copper, a fungicide, and a quaternary ammonium compound , an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Europe, Japan and...

, borate
Borate
Borates are chemical compounds which contain oxoanions of boron in oxidation state +3. The simplest borate ion, BO33−, has a trigonal planar structure. Other borates are made up of trigonal BO3 or tetrahedral BO4 structural units, sharing oxygen atoms...

s, copper azole, cyproconazole, and propiconazole
Propiconazole
Propiconazole is a triazole fungicide, also known as a DMI, or demethylation inhibiting fungicide due to its binding with and inhibiting the 14-alpha demethylase enzyme from demethylating a precursor to ergosterol. Without this demethylation step, the ergosterols are not incorporated into the...

.

Although discontinued, this application is also one of the most concern to the general public. The vast majority of older pressure-treated wood was treated with CCA. CCA lumber is still in widespread use in many countries, and was heavily used during the latter half of the 20th century as a structural and outdoor building material
Building material
Building material is any material which is used for a construction purpose. Many naturally occurring substances, such as clay, sand, wood and rocks, even twigs and leaves have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more...

. Although the use of CCA lumber was banned in many areas after studies showed that arsenic could leach out of the wood into the surrounding 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...

 (from playground equipment, for instance), a risk is also presented by the burning of older CCA timber. The direct or indirect ingestion of wood ash from burnt CCA lumber has caused fatalities in animals and serious poisonings in humans; the lethal human dose is approximately 20 grams of ash. Scrap CCA lumber from construction and demolition sites may be inadvertently used in commercial and domestic fires. Protocols for safe disposal of CCA lumber do not exist evenly throughout the world; there is also concern in some quarters about the widespread landfill
Landfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...

 disposal of such timber.

Mapping of industrial releases in the US


One tool that maps releases of arsenic to particular locations in the United States and also provides additional information about such releases is TOXMAP
TOXMAP
TOXMAP is a geographic information system from the United States National Library of Medicine that uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's Toxics Release Inventory and Superfund programs...

. TOXMAP is a Geographic Information System (GIS) from the Division of Specialized Information Services of the United States National Library of Medicine
United States National Library of Medicine
The United States National Library of Medicine , operated by the United States federal government, is the world's largest medical library. Located in Bethesda, Maryland, the NLM is a division of the National Institutes of Health...

 (NLM) that uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

's (EPA) Toxics Release Inventory
Toxics Release Inventory
The Toxics Release Inventory is a publicly available database containing information on toxic chemical releases and other waste management activities in the United States.-Summary of requirements:...

 and Superfund Basic Research Program
Superfund Basic Research Program
The Superfund Research Program was created within the National Institute of Environmental Health Sciences in 1986 under the Superfund Amendments and Reauthorization Act...

s. TOXMAP is a resource funded by the US Federal Government. TOXMAP's chemical and environmental health information is taken from NLM's Toxicology Data Network (TOXNET) and PubMed
PubMed
PubMed is a free database accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez information retrieval system...

, and from other authoritative sources.

Toxicity and precautions




Arsenic and many of its compounds are especially potent poisons. Many water supplies close to mines are contaminated by these poisons. Arsenic disrupts ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

 production through several mechanisms. At the level of the citric acid cycle
Citric acid cycle
The citric acid cycle — also known as the tricarboxylic acid cycle , the Krebs cycle, or the Szent-Györgyi-Krebs cycle — is a series of chemical reactions which is used by all aerobic living organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and...

, arsenic inhibits lipoic acid
Lipoic acid
Lipoic acid , also known as α-lipoic acid and Alpha Lipoic Acid is an organosulfur compound derived from octanoic acid. LA contains two vicinal sulfur atoms attached via a disulfide bond and is thus considered to be oxidized...

, which is a cofactor
Cofactor (biochemistry)
A cofactor is a non-protein chemical compound that is bound to a protein and is required for the protein's biological activity. These proteins are commonly enzymes, and cofactors can be considered "helper molecules" that assist in biochemical transformations....

 for pyruvate dehydrogenase
Pyruvate dehydrogenase
Pyruvate dehydrogenase complex is a complex of three enzymes that transform pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the...

; and by competing with phosphate it uncouples oxidative phosphorylation
Oxidative phosphorylation
Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate . Although the many forms of life on earth use a range of different nutrients, almost all aerobic organisms carry out oxidative phosphorylation to produce ATP,...

, thus inhibiting energy-linked reduction of NAD+
Nicotinamide adenine dinucleotide
Nicotinamide adenine dinucleotide, abbreviated NAD, is a coenzyme found in all living cells. The compound is a dinucleotide, since it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamide.In metabolism, NAD is involved...

, mitochondrial respiration and ATP synthesis. Hydrogen peroxide production is also increased, which, it is speculated, has potential to form reactive oxygen species and oxidative stress. These metabolic interferences lead to death from multi-system organ failure
Organ failure
Organ dysfunction is a condition where an organ does not perform its expected function. Organ failure is organ dysfunction to such a degree that normal homeostasis cannot be maintained without external clinical intervention.It is not a diagnosis...

, it is presumed from necrotic cell death, not apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

. A post mortem reveals brick-red-coloured mucosa, owing to severe haemorrhage. Although arsenic causes toxicity, it can also play a protective role.

Elemental arsenic and arsenic compounds are classified as "toxic
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

" and "dangerous for the environment" in the European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 under directive 67/548/EEC
Directive 67/548/EEC
The Dangerous Substances Directive is one of the main European Union laws concerning chemical safety. It was made under Article 100 of the Treaty of Rome...

.

The International Agency for Research on Cancer
International Agency for Research on Cancer
The International Agency for Research on Cancer is an intergovernmental agency forming part of the World Health Organisation of the United Nations....

 (IARC) recognizes arsenic and arsenic compounds as group 1 carcinogens, and the EU lists arsenic trioxide, arsenic pentoxide
Arsenic pentoxide
Arsenic pentoxide is the inorganic compound with the formula As2O5. This glassy, white solid is relatively unstable, consistent with the rarity of the As oxidation state. More common, and far more important commercially, is arsenic oxide ....

 and arsenate
Arsenate
The arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....

 salts as category 1 carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

s.

Arsenic is known to cause arsenicosis owing to its manifestation in drinking water, “the most common species being arsenate [HAsO42-; As(V)] and arsenite [H3AsO3 ; As(III)]”. The ability of arsenic to undergo redox conversion between As(III) and As(V) makes its availability in the environment more abundant. According to Croal, Gralnick, Malasarn and Newman, “[the] understanding [of] what stimulates As(III) oxidation and/or limits As(V) reduction is relevant for bioremediation of contaminated sites (Croal). The study of chemolithoautotrophic As(III) oxidizers and the heterotrophic As(V) reducers can help the understanding of the oxidation and/or reduction of arsenic.

Treatment of chronic arsenic poisoning is easily accomplished. British anti-lewisite (dimercaprol
Dimercaprol
Dimercaprol or British anti-Lewisite , is a compound developed by British biochemists at Oxford University during World War II. It was developed secretly as an antidote for lewisite, the now-obsolete arsenic-based chemical warfare agent. Today, it is used medically in treatment of arsenic,...

) is prescribed in dosages of 5 mg/kg up to 300 mg each 4 hours for the first day. Then administer the same dosage each 6 hours for the second day. Then prescribe this dosage each 8 hours for eight additional days. However the Agency for Toxic Substances and Disease Registry (ATSDR) states that the long-term effects of arsenic exposure cannot be predicted. Blood, urine, hair, and nails may be tested for arsenic; however, these tests cannot foresee possible health outcomes from the exposure. Excretion occurs in the urine and long-term exposure to arsenic has been linked to bladder and kidney cancer in addition to cancer of the liver, prostate, skin, lungs and nasal cavity.

Occupational exposure and arsenic poisoning
Arsenic poisoning
Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

 may occur in persons working in industries involving the use of inorganic arsenic and its compounds, such as wood preservation, glass production, nonferrous metal alloys, and electronic semiconductor manufacturing. Inorganic arsenic is also found in coke oven emissions associated with the smelter industry.

Biochemical basis of arsenic toxicity


The high affinity of arsenic(III) oxides for thiols is usually assigned as the cause of the high toxicity. Thiols, in the form of cysteine residues, are situated at the active sites of many important enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s.

See also



  • Aqua Tofana
    Aqua Tofana
    Aqua Tofana was a strong poison that was reputedly widely used in Naples and Rome, Italy...

  • Arsenic biochemistry
    Arsenic biochemistry
    Arsenic biochemistry refers to biochemical processes that can use arsenic or its compounds, such as arsenate. Arsenic is a moderately abundant element on the earth's crust, and although many arsenic compounds are often considered highly toxic, a wide variety of organoarsenic compounds are produced...


Arsenic compounds
  • Arsenic poisoning
    Arsenic poisoning
    Arsenic poisoning is a medical condition caused by increased levels of the element arsenic in the body. Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme...

  • Arsenic toxicity
    Arsenic toxicity
    Arsenic and many of its compounds are especially potent poisons. Arsenic disrupts ATP production through several mechanisms. At the level of the citric acid cycle, arsenic inhibits pyruvate dehydrogenase and by competing with phosphate it uncouples oxidative phosphorylation, thus inhibiting...

  • Arsenic trioxide
    Arsenic trioxide
    Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually...

  • Fowler's solution
    Fowler's solution
    Fowler's solution is a solution containing potassium arsenite that once was prescribed as a remedy or a tonic. A Dr. Fowler of Stafford, England proposed its use in 1786 as a substitute for a patent medicine, "tasteless ague drop." It was prescribed in the United States until the late 1950s for a...

  • GFAJ-1
    GFAJ-1
    GFAJ-1 is a strain of rod-shaped bacterium in the family Halomonadaceae. The extremophile was isolated from the hypersaline and alkaline Mono Lake in eastern California by a research team led by NASA astrobiologist Felisa Wolfe-Simon...

  • Grainger challenge
    Grainger challenge
    The Grainger challenge is a scientific competition to find an economical way to remove arsenic from arsenic-contaminated groundwater. This competition is being funded by the United States National Academy of Engineering and the Grainger Foundation and is meant to help provide safe drinking water to...

  • Hypothetical types of biochemistry
  • Organoarsenic chemistry
  • White arsenic


External links