From Wikipedia, the free encyclopedia
|Name, symbol||arsenic, As|
|Allotropes||grey (most common), yellow, black|
|Pronunciation||//, also // when attributive
|Arsenic in the periodic table|
|Atomic number (Z)||33|
|Group, block||group 15 (pnictogens), p-block|
|Standard atomic weight (±) (Ar)||74.921595(6)|
|Electron configuration||[Ar] 3d10 4s2 4p3|
|2, 8, 18, 5|
|Sublimation point||887 K (615 °C, 1137 °F)|
|Density near r.t.||5.727 g/cm3|
|when liquid, at m.p.||5.22 g/cm3|
|Triple point||1090 K, 3628 kPa|
|Critical point||1673 K, ? MPa|
|Heat of fusion||grey: 24.44 kJ/mol|
|Heat of vaporization||34.76 kJ/mol (?)|
|Molar heat capacity||24.64 J/(mol·K)|
|Oxidation states||5, 4, 3, 2, 1, −1, −2, −3 (a mildly acidic oxide)|
|Electronegativity||Pauling scale: 2.18|
|Ionization energies||1st: 947.0 kJ/mol
2nd: 1798 kJ/mol
3rd: 2735 kJ/mol
|Atomic radius||empirical: 119 pm|
|Covalent radius||119±4 pm|
|Van der Waals radius||185 pm|
|Thermal expansion||5.6 µm/(m·K) (at r.t.)|
|Thermal conductivity||50.2 W/(m·K)|
|Electrical resistivity||333 nΩ·m (at 20 °C)|
|Young's modulus||8 GPa|
|Bulk modulus||22 GPa|
|Brinell hardness||1440 MPa|
|Discovery||Early Bronze Age (2500 BC)|
|First isolation||Albertus Magnus (1250)|
|Most stable isotopes of arsenic|
Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid. It can exist in various allotropes, although only the gray 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 in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the most common semiconductor in use after doped silicon. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining, however.
A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably many other species, including humans. However, arsenic poisoning occurs in multicellular life if quantities are larger than needed. Arsenic contamination of groundwater is a problem that affects millions of people across the world.
- 1 Characteristics
- 2 Compounds
- 3 Occurrence and production
- 4 History
- 5 Applications
- 6 Biological role
- 7 Essential trace element in higher animals
- 8 Environmental issues
- 9 Toxicity and precautions
- 10 See also
- 11 References
- 12 Bibliography
- 13 Further reading
- 14 External links
The three most common arsenic allotropes are metallic gray, yellow, and black arsenic, with gray being the most common. Gray arsenic (α-As, space group R3m No. 166) adopts a double-layered structure consisting of many interlocked, ruffled, six-membered rings. Because of weak bonding between the layers, gray 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. Gray arsenic is a semimetal, but becomes a semiconductor with a bandgap of 1.2–1.4 eV if amorphized. Gray arsenic is also the most stable form. Yellow arsenic is soft and waxy, and somewhat similar to tetraphosphorus (P
4). 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 vapor, As
4. It is rapidly transformed into gray arsenic by light. The yellow form has a density of 1.97 g/cm3. Black arsenic is similar in structure to red phosphorus. Black arsenic can also be formed by cooling vapor at around 100–220 °C. It is glassy and brittle. It is also a poor electrical conductor.
Arsenic occurs in nature as a monoisotopic element, composed of one stable isotope, 75As. As of 2003, at least 33 radioisotopes have also been synthesized, ranging in atomic mass from 60 to 92. The most stable of these is 73As with a half-life of 80.30 days. All other isotopes have half-lives of under one day, with the exception of 71As (t1/2=65.30 hours), 72As (t1/2=26.0 hours), 74As (t1/2=17.77 days), 76As (t1/2=1.0942 days), and 77As (t1/2=38.83 hours). Isotopes that are lighter than the stable 75As tend to decay by β+ decay, and those that are heavier tend to decay by β− decay, with some exceptions.
When heated in air, arsenic oxidizes to arsenic trioxide; the fumes from this reaction have an odor resembling garlic. This odor can be detected on striking arsenide minerals such as arsenopyrite 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 K (614 °C). The triple point is 3.63 MPa and 1,090 K (820 °C). Arsenic makes arsenic acid with concentrated nitric acid, arsenious acid with dilute nitric acid, and arsenic trioxide with concentrated sulfuric acid.
Compounds of arsenic resemble in some respects those of phosphorus which occupies the same group (column) of the periodic table. Arsenic is less commonly observed in the pentavalent state, however. The most common oxidation states for arsenic are: −3 in the arsenides, such as alloy-like intermetallic compounds, +3 in the arsenites, and +5 in the arsenates and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As3−
4 ions in the mineral skutterudite. In the +3 oxidation state, arsenic is typically pyramidal owing to the influence of the lone pair of electrons.
Arsenic forms colorless, odorless, crystalline oxides As2O3 ("white arsenic") and As2O5 which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid is a weak acid. Its salts are called arsenates which are the basis of arsenic contamination of groundwater, a problem that affects many people. Synthetic arsenates include Paris Green (copper(II) acetoarsenite), calcium arsenate, and lead hydrogen arsenate. These three have been used as agricultural insecticides and poisons.
The protonation steps between the arsenate and arsenic acid are similar to those between phosphate and phosphoric acid. Unlike phosphorous acid, arsenous acid is genuinely tribasic, with the formula As(OH)3.
A broad variety of sulfur compounds of arsenic are known. Orpiment (As2S3) and realgar (As4S4) are somewhat abundant and were formerly used as painting pigments. In 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 3.
All trihalides of arsenic(III) are well known except the astatide which is unknown. Arsenic pentafluoride (AsF5) is the only important pentahalide, reflecting the lower stability of the 5+ oxidation state. (pentachloride is stable only below −50 °C.)
Arsenic is used as the group 5 element in the III-V semiconductors gallium arsenide, indium arsenide, and aluminium arsenide. The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure is completely different which results distinct bulk properties. Other arsenic alloys include the II-V semiconductor cadmium arsenide.
A large variety of organoarsenic compounds are known. Several were developed as chemical warfare agents during World War I, including vesicants such as lewisite and vomiting agents such as adamsite. Cacodylic acid, which is of historic and practical interest, arises from the methylation of arsenic trioxide, a reaction that has no analogy in phosphorus chemistry.
Occurrence and production
Minerals with the formula MAsS and MAs2 (M = Fe, Ni, Co) are the dominant commercial sources of arsenic, together with realgar (an arsenic sulfide mineral) and native arsenic. An illustrative mineral is arsenopyrite (FeAsS), which is structurally related to iron pyrite. Many minor As-containing minerals are known. Arsenic also occurs in various organic forms in the environment.
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 and the United States Geological Survey. 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 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.
|Country||2012 As2O3 Production|
|Other Countries||300 T|
|World Total||44,000 T|
The word arsenic has its origin in the Syriac word ܠܐ ܙܐܦܢܝܐ (al) zarniqa, from the Persian word زرنيخ zarnikh, meaning "yellow" (literally "gold-colored") and hence "(yellow) orpiment". It was adopted into Greek as arsenikon (ἀρσενικόν), a form that is folk etymology, being the neuter form of the Greek word arsenikos (ἀρσενικός), meaning "male", "virile". The Greek word was adopted in Latin as arsenicum, which in French became arsenic, from which the English word arsenic is taken. Arsenic sulfides (orpiment, realgar) and oxides have been known and used since ancient times. Zosimos (circa 300 AD) describes roasting sandarach (realgar) to obtain cloud of arsenic (arsenic trioxide), which he then reduces to metallic arsenic. As the symptoms of arsenic poisoning were somewhat ill-defined, it was frequently used for murder until the advent of the Marsh test, a sensitive chemical test for its presence. (Another less sensitive but more general test is the Reinsch test.) 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, arsenic was often included in bronze, which made the alloy harder (so-called "arsenical bronze"). Albertus Magnus (Albert the Great, 1193–1280) is believed to have been the first to isolate the element from a compound in 1250, by heating soap together with arsenic trisulfide. In 1649, Johann Schröder published two ways of preparing arsenic. Crystals of elemental (native) arsenic are found in nature, although rare.
Cadet's fuming liquid (impure cacodyl), often claimed as the first synthetic organometallic compound, was synthesized in 1760 by Louis Claude Cadet de Gassicourt by the reaction of potassium acetate with arsenic trioxide.
In the Victorian era, "arsenic" ("white arsenic" or arsenic trioxide) was mixed with vinegar and chalk and eaten by women to improve the complexion 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 around 20 deaths.
Two pigments based on arsenic have been widely used since their discovery – Paris Green and Scheele's Green. After arsenic's toxicity became widely known, they were less often used as pigments, so these compounds were more often used as insecticides. In the 1860s, an arsenic byproduct of dye production, London Purple – a solid consisting of a mixture of arsenic trioxide, aniline, lime, and ferrous oxide, which is insoluble in water and very toxic by inhalation and ingestion – was widely used, but Paris Green, another arsenic-based dye, was later substituted for it. With better understanding of the toxicology mechanism, two other compounds were used starting in the 1890s. Arsenite of lime and arsenate of lead were used widely as insecticides until the discovery of DDT in 1942.
The toxicity of arsenic to insects, bacteria, and fungi led to its use as a wood preservative. In the 1950s, a process of treating wood with chromated copper arsenate (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 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 and poisons. For example, lead hydrogen arsenate was a common insecticide on fruit trees, but contact with the compound sometimes resulted in brain damage among those working the sprayers. In the second half of the 20th century, monosodium methyl arsenate (MSMA) and disodium methyl arsenate (DSMA) – less- toxic organic forms of arsenic – have replaced lead arsenate in agriculture. With the exception of cotton farming, the use of the organic arsenicals was phased out until 2013.
Arsenic is used as a feed additive in poultry and swine production, in particular in the U.S. to increase weight gain, improve feed efficiency, and to prevent disease. An example is roxarsone, which had been used as a broiler starter by about 70% of U.S. broiler growers. The Poison-Free Poultry Act of 2009 proposed to ban the use of roxarsone in industrial swine and poultry production. Alpharma, a subsidiary of Pfizer Inc., which produces roxarsone, voluntarily suspended sales of the drug in response to studies showing elevated levels of inorganic arsenic, a carcinogen, in treated chickens. A successor to Alpharma, Zoetis, continues to sell nitarsone, primarily for use in turkeys.
Arsenic is intentionally added to the feed of chickens raised for human consumption. Organic arsenic compounds are less toxic than pure arsenic, and promote the growth of chickens. Under some conditions, the arsenic in chicken feed can end up getting converted back to its toxic inorganic form.
During the 18th, 19th, and 20th centuries, a number of arsenic compounds were used as medicines, including arsphenamine (by Paul Ehrlich) and arsenic trioxide (by Thomas Fowler). Arsphenamine, as well as neosalvarsan, was indicated for syphilis and trypanosomiasis, but has been superseded by modern antibiotics.
Arsenic trioxide has been used in a variety of ways over the past 500 years, most commonly in the treatment of cancer, but in medications as diverse as Fowler's solution in psoriasis. The US Food and Drug Administration in the year 2000 approved this compound for the treatment of patients with acute promyelocytic leukemia that is resistant to all-trans retinoic acid.
Recently, new research has been done in locating tumors using arsenic-74 (a positron emitter). The advantages of using this isotope instead of the previously used iodine-124 is that the signal in the PET scan is clearer as the body tends to transport iodine to the thyroid gland producing signal noise.
The main use of metallic arsenic is in alloying with lead. Lead components in car batteries are strengthened by the presence of a very small percentage of arsenic. Dezincification can be strongly reduced by adding arsenic to brass, a copper-zinc alloy. "Phosphorus Deoxidized Arsenical Copper" with an arsenic content of 0.3% has an increased corrosion stability in certain environments. Gallium arsenide is an important semiconductor material, used in integrated circuits. Circuits made from GaAs are much faster (but also much more expensive) than those made in silicon. Unlike silicon, it has a direct bandgap, so can be used in laser diodes and LEDs to directly convert electricity into light.
After World War I, the United States built up a stockpile of 20,000 tonnes of lewisite (ClCH=CHAsCl2), a chemical weapon that is a vesicant (blister agent) and lung irritant. The stockpile was neutralized with bleach and dumped into the Gulf of Mexico after the 1950s. During the Vietnam War, the United States used Agent Blue, a mixture of sodium cacodylate and its acid form, as one of the rainbow herbicides to deprive North Vietnamese soldiers of foliage cover and rice.
- Copper acetoarsenite was used as a green pigment known under many names, including Paris Green and Emerald Green. It caused numerous arsenic poisonings. Scheele's Green, a copper arsenate, was used in the 19th century as a coloring agent in sweets.
- In bronzing and pyrotechnics
- Up to 2% of arsenic is used in lead alloys for lead shot and bullets.
- 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.
Some species of bacteria obtain their energy by oxidizing various fuels while reducing arsenate to arsenite. Under oxidative environmental conditions some bacteria use arsenite, which is oxidized to arsenate as fuel for their metabolism. The enzymes involved are known as arsenate reductases (Arr).
In 2008, bacteria were discovered that employ a version of photosynthesis in the absence of oxygen with arsenites as electron donors, 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 PHS-1 has been isolated and is related to the gammaproteobacterium Ectothiorhodospira shaposhnikovii. The mechanism is unknown, but an encoded Arr enzyme may function in reverse to its known homologues.
Essential trace element in higher animals
There is evidence for the essentiality of arsenic as a trace mineral in birds (chickens), and in mammals (rats, hamsters, and goats). However, the biological mechanism for its essential function is not known.
Arsenic has been linked to epigenetic changes, heritable changes in gene expression that occur without changes in DNA sequence. These include DNA methylation, histone modification, and RNA interference. Toxic levels of arsenic cause significant DNA hypermethylation of tumor suppressor genes p16 and p53, thus increasing risk of carcinogenesis. These epigenetic events have been studied in vitro using human kidney cells and in vivo using rat liver cells and peripheral blood leukocytes in humans. Inductively 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.
Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized through a process of methylation. For example, the mold Scopulariopsis brevicaulis produces significant amounts of trimethylarsine if inorganic arsenic is present. The organic compound arsenobetaine 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.
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. Arsenic is absorbed by all plants, but is more concentrated in leafy vegetables, rice, apple and grape juice, and seafood. An additional route of exposure is through inhalation.
Occurrence in drinking water
Extensive arsenic contamination of groundwater has led to widespread arsenic poisoning in Bangladesh and neighboring countries. It is estimated that approximately 57 million people in the Bengal basin are drinking groundwater with arsenic concentrations elevated above the World Health Organization's standard of 10 parts per billion (ppb). However, a study of cancer rates in Taiwan suggested that significant increases in cancer mortality appear only at levels above 150 ppb. 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 and the Bangladeshi government undertook a massive shallow tube well 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, such as Vietnam and Cambodia have geological environments conducive to generation of high-arsenic groundwaters. Arsenicosis was reported in Nakhon Si Thammarat, Thailand in 1987, and the Chao Phraya River is suspected of containing high levels of naturally occurring dissolved 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, Michigan, Wisconsin, Minnesota 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, 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 of 100 parts per billion (i.e., above the 10 parts per billion drinking water standard) 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.
Some Canadians are drinking water that contains inorganic arsenic. Private-dug–well waters are most at risk for containing inorganic arsenic. Preliminary well water analysis typically does not test for arsenic. Researchers at the Geological Survey of Canada have modelled relative variation in natural arsenic hazard potential for the province of New Brunswick. This study has important implications for potable water and health concerns relating to inorganic arsenic.
Epidemiological evidence from Chile 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 ppb.
Analyzing multiple epidemiological studies on inorganic arsenic exposure suggests a small but measurable risk increase for bladder cancer at 10 ppb. According to Peter Ravenscroft of the Department of Geography at the University of Cambridge, roughly 80 million people worldwide consume between 10 and 50 ppb arsenic in their drinking water. If they all consumed exactly 10 ppb 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 (US EPA) and the National Science Foundation (NSF). A team of European and Indian scientists and engineers have set up six arsenic treatment plants in West Bengal 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 US 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 particles, arsenic can be naturally removed from well water.
Magnetic separations of arsenic at very low magnetic field gradients have been demonstrated in point-of-use water purification with high-surface-area and monodisperse magnetite (Fe3O4) nanocrystals. 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.
It has recently been discovered that by the use of chaff-based filters reduces the arsenic content of water to 3 µg/L. This may find applications in areas where the potable water is provided by filtering the water extracted from the underground aquifer.
San Pedro de Atacama
For several centuries, the people of San Pedro de Atacama in Chile have been drinking water that is contaminated with arsenic, and it is believed that they may have developed some immunity to the ill effects of consuming it.
Redox transformation of arsenic in natural waters
Arsenic is unique among the trace metalloids and oxyanion-forming trace metals (e.g. As, Se, Sb, Mo, V, Cr, U, Re). It is sensitive to mobilization at pH values typical of natural waters (pH 6.5–8.5) under both oxidizing and reducing conditions. Arsenic can occur in the environment in several oxidation states (-3, 0, +3 and +5), but in natural waters it is mostly found in inorganic forms as oxyanions of trivalent arsenite [As(III)] or pentavalent arsenate [As(V)]. Organic forms of arsenic are produced by biological activity, mostly in surface waters, but are rarely quantitatively important. Organic arsenic compounds may, however, occur where waters are signiﬁcantly impacted by industrial pollution.
Arsenic may be solubilized by various processes. When pH is high, arsenic may be released from surface binding sites that lose their positive charge. When water levels drops and sulfide minerals are exposed to air, arsenic trapped in sulfide minerals can be released into water. When organic carbon is present in water, bacteria are fed by directly reducing As(V) to As(III) or by reducing the element at the binding site attached there and releases arsenic.
The aquatic transformations of arsenic are affected by pH, reduction-oxidation potential, organic matter concentration and the concentrations and forms of other elements especially iron and manganese. The main factors are pH and the redox potential. Generally, the main forms of arsenic under oxic conditions are H3AsO4, H2AsO4−, HAsO42−, and AsO43− at pH 2, 2-7, 7-11 and 11, respectively. Under reducing conditions, H3AsO4 is predominant at pH 2-9.
The oxidation and reduction of arsenic affect its ability to migrate in subsurface environments. Arsenite is the most stable soluble form of arsenic in reducing environments and arsenate, which is less mobile than arsenite, is dominant in oxidizing environments at neutral pH. Therefore, arsenic may be more mobile under reducing conditions. The reducing environment is also rich in organic matter which may enhance the solubility of arsenic compounds. As a result, the adsorption of arsenic is reduced and dissolved arsenic accumulates in groundwater. That is why the arsenic content is higher in reducing environments than in oxidizing environments.
The presence of sulfur is another factor that affects the transformation of arsenic in natural water. Arsenic can precipitate when metal sulfides form. In this way, arsenic is removed from the water and its mobility decreases. When oxygen is present, bacteria oxidize reduced sulfur to generate energy, potentially releasing bound arsenic.
Redox reactions involving Fe also appear to be essential factors in the fate of arsenic in aquatic systems. The reduction of iron oxyhydroxides plays a key role in the release of arsenic to water. So arsenic can be enriched in water with elevated Fe concentrations. Under oxidizing conditions, arsenic can be mobilized from pyrite or iron oxides especially at elevated pH. Under reducing conditions, arsenic can be mobilized by reductive desorption or dissolution when associated with iron oxides. The reductive desorption occurs under two circumstances. One is when arsenate is reduced to arsenite which adsorbs to iron oxides less strongly. The other results from a change in the charge on the mineral surface which leads to the desorption of bound arsenic.
Some species of bacteria catalyze redox transformations of arsenic. Dissimilatory arsenate-respiring prokaryotes (DARP) speed up the reduction of As(V) to As(III). DARP use As(V) as the electron acceptor of anaerobic respiration and obtain energy to survive. Other organic and inorganic substances can be oxidized in this process. Chemoautotrophic arsenite oxidizers (CAO) and heterotrophic arsenite oxidizers (HAO) convert As(III) into As(V). CAO combine the oxidation of As(III) with the reduction of oxygen or nitrate. They use obtained energy to fix produce organic carbon from CO2. HAO cannot obtain energy from As(III) oxidation. This process may be an arsenic detoxification mechanism for the bacteria.
Equilibrium thermodynamic calculations predict that As(V) concentrations should be greater than As(III) concentrations in all but strongly reducing conditions, i.e. where SO42− reduction is occurring. However, abiotic redox reactions of arsenic are slow. Oxidation of As(III) by dissolved O2 is a particularly slow reaction. For example, Johnson and Pilson (1975) gave half-lives for the oxygenation of As(III) in seawater ranging from several months to a year. In other studies, As(V)/As(III) ratios were stable over periods of days or weeks during water sampling when no particular care was taken to prevent oxidation, again suggesting relatively slow oxidation rates. Cherry found from experimental studies that the As(V)/As(III) ratios were stable in anoxic solutions for up to 3 weeks but that gradual changes occurred over longer timescales. Sterile water samples have been observed to be less susceptible to speciation changes than non-sterile samples. Oremland found that the reduction of As(V) to As(III) in Mono Lake was rapidly catalyzed by bacteria with rate constants ranging from 0.02 to 0.3 day−1.
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 (CCA). In 2007, 50% of the 5,280 metric tons of consumption was still used for this purpose. In the United States, the voluntary phasing-out of arsenic in production of consumer products and residential and general consumer construction products began on 31 December 2003, and alternative chemicals are now used, such as Alkaline Copper Quaternary, borates, copper azole, cyproconazole, and propiconazole.
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. 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 (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 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 is a Geographic Information System (GIS) from the Division of Specialized Information Services of the United States National Library of Medicine (NLM) that uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs. 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, and from other authoritative sources.
Physical, chemical, and biological methods have been used to decrease the concentration of arsenic in contaminated water. Among these methods, bioremediation has been suggested to be cost effective and environmentally friendly Bioremediation of ground water contaminated with arsenic aims to convert arsenite, the toxic form of arsenic to humans, to arsenate. Arsenate (+5 oxidation state) is the dominant form of arsenic in surface water, while arsenite (+3 oxidation state) is the dominant form in hypoxic to anoxic environments. Arsenite is more soluble and mobile than arsenate. Many species of bacteria can transform arsenite to arsenate in anoxic conditions by using arsenite as an electron donor. This is a useful method in ground water remediation. Another bioremediation strategy is to use plants that accumulate arsenic in their tissues via phytoremediation but the disposal of contaminated plant material needs to be considered. In order to choose a suitable bioremediation approach for a site, its environmental conditions needs to be evaluated. Some sites may require the addition of an electron acceptor while others require added microbes (bioaugmentation). Regardless of the method used, constant monitoring is required to prevent future contamination.
Toxicity and precautions
Arsenic and many of its compounds are especially potent poisons.
Elemental arsenic and arsenic compounds are classified as "toxic" and "dangerous for the environment" in the European Union under directive 67/548/EEC. The International Agency for Research on Cancer (IARC) recognizes arsenic and arsenic compounds as group 1 carcinogens, and the EU lists arsenic trioxide, arsenic pentoxide and arsenate salts as category 1 carcinogens.
Arsenic is known to cause arsenicosis owing to its manifestation in drinking water, "the most common species being arsenate [HAsO2−
4; As(V)] and arsenite [H3AsO3; As(III)]".
Legal limits, food, and drink
In the United States, since 2006, the maximum concentration in drinking water allowed by the Environmental Protection Agency (EPA) is 10 ppb and the FDA set the same standard in 2005 for bottled water.[unreliable source?] The Department of Environmental Protection for New Jersey set a drinking water limit of 5 ppb in 2006. The IDLH (immediately dangerous to life and health) value for arsenic metal and inorganic arsenic compounds is 5 mg/m3. The Occupational Safety and Health Administration has set the permissible exposure limit (PEL) to a time-weighted average (TWA) of 0.01 mg/m3, and the National Institute for Occupational Safety and Health (NIOSH) has set the recommended exposure limit (REL) to a 15-minute constant exposure of 0.002 mg/m3. The PEL for organic arsenic compounds is a TWA of 0.5 mg/m3.
In 2008, based on its ongoing testing of a wide variety of American foods for toxic chemicals, the U.S. Food and Drug Administration set 23 ppb as the "level of concern" for inorganic arsenic apple and pear juices based on non-carcinogenic effects, and began refusing imports and demanding recalls for domestic products exceeding this level. In 2011, the national Dr. Oz television show broadcast a program highlighting tests performed by an independent lab hired by the producers. Though the methodology was disputed (it did not distinguish between organic and inorganic arsenic) the tests showed levels of arsenic up to 36 ppb. In response, FDA testing of the worst brand from the Oz show showed much lower levels, and its ongoing testing found 95% of apple juice samples were below the level of concern. Later testing by Consumer Reports showed inorganic arsenic at levels slightly above 10 ppb, with the organization urging parents to reduce consumption. In July 2013, after taking into account consumption by children, chronic exposure, and carcinogenic effect, the FDA established an "action level" of 10 ppb for apple juice, the same as the drinking water standard.
Concern about arsenic in rice in Bangladesh was raised in 2002, but at the time only Australia had a legal limit for the level found in food (one milligram per kilogram). The People's Republic of China has a food standard of 150 ppb for arsenic, as of 2011. Further concern was raised about people who were eating U.S. rice exceeding WHO standards for personal arsenic intake in 2005.
In the United States in 2012, testing by separate groups of researchers at the Children's Environmental Health and Disease Prevention Research Center at Dartmouth College (early in the year, focusing on urinary levels in children) and Consumer Reports (in November) found levels of arsenic in rice which resulted in calls for the FDA to set limits. The FDA released some testing results in September 2012, and as of July 2013 is still collecting data in support of a new potential regulation. It has not recommended any changes in consumer behavior. Consumer Reports recommended that the EPA and FDA eliminate arsenic-containing fertilizer, drugs, and pesticides in food production; that the FDA establish a legal limit for food; that industry change production practices to lower arsenic levels, especially in food for children; and that consumers test home water supplies, eat a varied diet, and cook rice with excess water which is drained off (reducing inorganic arsenic by about one third along with a slight reduction in vitamin content). Evidence-based public health advocates also recommend that, given the lack of regulation or labeling for arsenic in the U.S., children should eat no more than 1.5 servings per week of rice and should not drink rice milk as part of their daily diet before age 5. They also offer recommendations for adults and infants on how to limit arsenic exposure from rice, drinking water, and fruit juice.
Occupational exposure limits
|Argentina||Confirmed human carcinogen|
|Australia||TWA 0.05 mg/m3Carcinogen|
|Belgium||TWA 0.1 mg/m3Carcinogen|
|Bulgaria||Confirmed human carcinogen|
|Colombia||Confirmed human carcinogen|
|Denmark||TWA 0.01 mg/m3|
|Egypt||TWA 0.2 mg/m3|
|Hungary||Ceiling concentration 0.01 mg/m3 Skin, carcinogen|
|India||TWA 0.2 mg/m3|
|Japan||Group 1 carcinogen|
|Jordan||Confirmed human carcinogen|
|Mexico||TWA 0.2 mg/m3|
|New Zealand||TWA 0.05 mg/m3Carcinogen|
|Norway||TWA 0.02 mg/m3|
|Philippines||TWA 0.5 mg/m3|
|Poland||TWA 0.01 mg/m3|
|Singapore||Confirmed human carcinogen|
|South Korea||TWA 0.01 mg/m3|
|Sweden||TWA 0.01 mg/m3|
|Thailand||TWA 0.5 mg/m3|
|Turkey||TWA 0.5 mg/m3|
|United Kingdom||TWA 0.1 mg/m3|
|United States||TWA 0.01 mg/m3|
|Vietnam||Confirmed human carcinogen|
Toxicity in animals
|Calcium arsenate||Rat||20 mg/kg||oral|
|Calcium arsenate||Mouse||794 mg/kg||oral|
|Calcium arsenate||Rabbit||50 mg/kg||oral|
|Calcium arsenate||Dog||38 mg/kg||oral|
|Lead arsenate||Rabbit||75 mg/kg||oral|
LD50 values reported in Toxicology Letters 133:1-16 (review by Hughes et al., 2002)
|im = injected intramuscularly
ip = administered intraperitoneally
The high affinity of arsenic(III) oxides for thiols is usually assigned as the cause of the high toxicity. Thiols, usually in the form of cysteine residues, but also in cofactors such as lipoic acid and coenzyme A, are situated at the active sites of many important enzymes.
Arsenic disrupts ATP production through several mechanisms. At the level of the citric acid cycle, arsenic inhibits lipoic acid, which is a cofactor for pyruvate dehydrogenase. In addition, by competing with phosphate, arsenate uncouples oxidative phosphorylation, thus inhibiting energy-linked reduction of NAD+, 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. The organ failure is presumed to be from necrotic cell death, not apoptosis, since energy reserves have been too depleted for apoptosis to occur.
Although arsenic causes toxicity it can also play a protective role.
Exposure risks and remediation
Occupational exposure and arsenic poisoning 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.
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. It has been proposed that As(III) which is more toxic than Arsenic (V) can be removed from the ground water using baker's yeast Saccharomyces cerevisiae.
Treatment of chronic arsenic poisoning is possible. British anti-lewisite (dimercaprol) is prescribed in doses of 5 mg/kg up to 300 mg every 4 hours for the first day, then every 6 hours for the second day, and finally every 8 hours for 8 additional days. However the USA's 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.
- Standard Atomic Weights 2013. Commission on Isotopic Abundances and Atomic Weights
- Gokcen, N. A (1989). "The As (arsenic) system". Bull. Alloy Phase Diagrams 10: 11–22. doi:10.1007/BF02882166.
- Ellis, Bobby D.; MacDonald, Charles L. B. (2004). "Stabilized Arsenic(I) Iodide: A Ready Source of Arsenic Iodide Fragments and a Useful Reagent for the Generation of Clusters". Inorganic Chemistry 43 (19): 5981–6. doi:10.1021/ic049281s. PMID 15360247.
- Cverna, Fran (2002). ASM Ready Reference: Thermal properties of metals. ASM International. pp. 8–. ISBN 978-0-87170-768-0. pdf.
- Lide, David R., ed. (2000). "Magnetic susceptibility of the elements and inorganic compounds". Handbook of Chemistry and Physics (PDF) (81 ed.). CRC press. ISBN 0849304814.
- Sabina C. Grund; Kunibert Hanusch; Hans Uwe Wolf (2005), "Arsenic and Arsenic Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a03_113.pub2
- Norman, Nicholas C (1998). Chemistry of Arsenic, Antimony and Bismuth. Springer. p. 50. ISBN 978-0-7514-0389-3.
- Biberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic Chemistry. Academic Press. ISBN 978-0-12-352651-9.
- Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Arsen". Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 675–681. ISBN 3-11-007511-3.
- Madelung, Otfried (2004). Semiconductors: data handbook. Birkhäuser. pp. 410–. ISBN 978-3-540-40488-0. Retrieved 2011-10-24.
- Arsenic Element Facts. chemicool.com
- Georges, Audi; Bersillon, O.; Blachot, J.; Wapstra, A.H. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
- Chisholm, Hugh, ed. (1911). "Arsenic". Encyclopædia Britannica 2 (11th ed.). Cambridge University Press. pp. 651–654.
- Uher, Ctirad (2001). "Recent Trends in Thermoelectric Materials Research I: Skutterudites: Prospective novel thermoelectrics". Semiconductors and Semimetals 69: 139–253. doi:10.1016/S0080-8784(01)80151-4. ISBN 978-0-12-752178-7.
- "Arsenic: arsenic(II) sulfide compound data". WebElements.com. Archived from the original on 11 December 2007. Retrieved 2007-12-10.
- Tanaka, A (2004). "Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide". Toxicology and Applied Pharmacology 198 (3): 405–11. doi:10.1016/j.taap.2003.10.019. PMID 15276420.
- Ossicini, Stefano; Pavesi, Lorenzo; Priolo, Francesco (1 January 2003). Light Emitting Silicon for Microphotonics. ISBN 978-3-540-40233-6. Retrieved 2013-09-27.
- Din, M.B.; Gould, R.D. (1998). "High field conduction mechanism of the evaporated cadmium arsenide thin films". ICSE'98. 1998 IEEE International Conference on Semiconductor Electronics. Proceedings (Cat. No.98EX187): 168. doi:10.1109/SMELEC.1998.781173. ISBN 0-7803-4971-7.
- Ellison, Hank D. (2007). Handbook of chemical and biological warfare agents. CRC Press. ISBN 978-0-8493-1434-6.
- Girard, James (2010). Principles of Environmental Chemistry. Jones & Bartlett Learning. ISBN 978-0-7637-5939-1.
- Somani, Satu M (2001). Chemical warfare agents: toxicity at low levels. CRC Press. ISBN 978-0-8493-0872-7.
- Emsley 2011, p. 52
- Matschullat, Jörg (2000). "Arsenic in the geosphere — a review". The Science of the Total Environment 249 (1–3): 297–312. doi:10.1016/S0048-9697(99)00524-0. PMID 10813460.
- Brooks, William E. "Mineral Commodity Summaries 2007: Arsenic" (PDF). United States Geological Survey. Archived (PDF) from the original on 17 December 2008. Retrieved 2008-11-25.
- Brooks, William E. "Minerals Yearbook 2007: Arsenic" (PDF). United States Geological Survey. Archived (PDF) from the original on 17 December 2008. Retrieved 2008-11-08.
- Whelan, J. M.; Struthers, J. D.; Ditzenberger, J. A. (1960). "Separation of Sulfur, Selenium, and Tellurium from Arsenic". Journal of the Electrochemical Society 107 (12): 982–985. doi:10.1149/1.2427585.
- Edelstein, Daniel L. "Mineral Commodity Summaries 2013: Arsenic" (PDF). United States Geological Survey. Retrieved 2013-09-10.
- "arsenic". Online Etymology Dictionary. Retrieved 2010-05-15.
- Bentley, Ronald; Chasteen, Thomas G. (2002). "Arsenic Curiosa and Humanity" (PDF). The Chemical Educator 7 (2): 51–60. doi:10.1007/s00897020539a. Archived from the original (PDF) on 7 February 2009.
- Holmyard John Eric (2007). Makers of Chemistry. Read Books. ISBN 1-4067-3275-3.
- Vahidnia, A.; Van Der Voet, G. B.; De Wolff, F. A. (2007). "Arsenic neurotoxicity – a review". Human & Experimental Toxicology 26 (10): 823–32. doi:10.1177/0960327107084539. PMID 18025055.
- Lechtman, H. (1996). "Arsenic Bronze: Dirty Copper or Chosen Alloy? A View from the Americas". Journal of Field Archaeology 23 (4): 477–514. doi:10.2307/530550. JSTOR 530550.
- Charles, J. A. (1967). "Early Arsenical Bronzes-A Metallurgical View". American Journal of Archaeology 71 (1): 21–26. doi:10.2307/501586. JSTOR 501586.
- Emsley, John (2001). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press. pp. 43, 513, 529. ISBN 0-19-850341-5.
- (Comte), Antoine-François de Fourcroy (1804). A general system of chemical knowledge, and its application to the phenomena of nature and art. pp. 84–.
- Seyferth, Dietmar (2001). "Cadet's Fuming Arsenical Liquid and the Cacodyl Compounds of Bunsen". Organometallics 20 (8): 1488–1498. doi:10.1021/om0101947.
- Turner, Alan (1999). "Viewpoint: the story so far: An overview of developments in UK food regulation and associated advisory committees". British Food Journal 101 (4): 274–283. doi:10.1108/00070709910272141.
- "London purple. (8012-74-6)", Chemical Book
- Lanman, Susan W. (2000). "Colour in the Garden: 'Malignant Magenta'". Garden History 28 (2): 209–221. doi:10.2307/1587270. JSTOR 1587270.
- Holton, E. C. (1926). "Insecticides and Fungicides". Industrial & Engineering Chemistry 18 (9): 931–933. doi:10.1021/ie50201a018.
- Murphy, E.A.; Aucott, M (1998). "An assessment of the amounts of arsenical pesticides used historically in a geographical area". Science of the Total Environment 218 (2–3): 89–101. doi:10.1016/S0048-9697(98)00180-6.
- Marlatt, C. L (1897). Important Insecticides: Directions for Their Preparation and Use. p. 5.
- Kassinger, Ruth (20 April 2010). Paradise Under Glass: An Amateur Creates a Conservatory Garden. ISBN 978-0-06-199130-1.
- Rahman, FA; Allan, DL; Rosen, CJ; Sadowsky, MJ (2004). "Arsenic availability from chromated copper arsenate (CCA)-treated wood". Journal of environmental quality 33 (1): 173–80. doi:10.2134/jeq2004.0173. PMID 14964372.
- Lichtfouse, Eric (2004). "Electrodialytical Removal of Cu, Cr and As from Threaded Wood". In Lichtfouse, Eric; Schwarzbauer, Jan; Robert, Didier. Environmental Chemistry: Green Chemistry and Pollutants in Ecosystems. Berlin: Springer. ISBN 978-3-540-22860-8.
- Mandal, Badal Kumar; Suzuki, K. T. (2002). "Arsenic round the world: a review". Talanta 58 (1): 201–235. doi:10.1016/S0039-9140(02)00268-0. PMID 18968746.
- Peryea, F. J. (20–26 August 1998). Historical use of lead arsenate insecticides, resulting in soil contamination and implications for soil remediation. 16th World Congress of Soil Science. Montpellier, France.
- "organic arsenicals". EPA.
- Nachman, Keeve E; Graham, Jay P.; Price, Lance B.; Silbergeld, Ellen K. (2005). "Arsenic: A Roadblock to Potential Animal Waste Management Solutions". Environmental Health Perspectives 113 (9): 1123–1124. doi:10.1289/ehp.7834.
- "Arsenic" (PDF). Agency for Toxic Substances and Disease Registry. Section 5.3, p. 310.
- Jones, F. T. (2007). "A Broad View of Arsenic". Poultry Science 86 (1): 2–14. doi:10.1093/ps/86.1.2. PMID 17179408.
- Bottemiller, Helena (26 September 2009). "Bill Introduced to Ban Arsenic Antibiotics in Feed". Food Safety News. Retrieved 2011-01-10.
- Staff (8 June 2011). "Questions and Answers Regarding 3-Nitro (Roxarsone)". U.S. Food and Drug Administration. Retrieved 2012-09-21.
- Gray, Theodore (Apr 3, 2012). "Arsenic". In Gray, Theodore; Mann, Nick. Elements: A Visual Exploration of Every Known Atom in the Universe. Hachette Books. ISBN 1579128955.
- Gibaud, Stéphane; Jaouen, Gérard (2010). "Arsenic – based drugs: from Fowler's solution to modern anticancer chemotherapy". Topics in Organometallic Chemistry. Topics in Organometallic Chemistry 32: 1–20. doi:10.1007/978-3-642-13185-1_1. ISBN 978-3-642-13184-4.
- Huet, P. M.; Guillaume, E.; Cote, J.; Légaré, A.; Lavoie, P.; Viallet, A. (1975). "Noncirrhotic presinusoidal portal hypertension associated with chronic arsenical intoxication". Gastroenterology 68 (5 Pt 1): 1270–1277. PMID 1126603.
- Antman, Karen H. (2001). "The History of Arsenic Trioxide in Cancer Therapy". The oncologist 6 (Suppl 2): 1–2. doi:10.1634/theoncologist.6-suppl_2-1. PMID 11331433.
- Jennewein, Marc; Lewis, M. A.; Zhao, D.; Tsyganov, E.; Slavine, N.; He, J.; Watkins, L.; Kodibagkar, V. D.; O'Kelly, S.; Kulkarni, P.; Antich, P.; Hermanne, A.; Rösch, F.; Mason, R.; Thorpe, Ph. (2008). "Vascular Imaging of Solid Tumors in Rats with a Radioactive Arsenic-Labeled Antibody that Binds Exposed Phosphatidylserine". Journal of Clinical Cancer 14 (5): 1377–1385. doi:10.1158/1078-0432.CCR-07-1516. PMC 3436070. PMID 18316558.
- Bagshaw, N.E. (1995). "Lead alloys: Past, present and future". Journal of Power Sources 53: 25–30. Bibcode:1995JPS....53...25B. doi:10.1016/0378-7753(94)01973-Y.
- Joseph, Günter; Kundig, Konrad J. A; Association, International Copper (1999). "Dealloying". Copper: Its Trade, Manufacture, Use, and Environmental Status. pp. 123–124. ISBN 978-0-87170-656-0.
- Nayar (1997). The Metals Databook. p. 6. ISBN 978-0-07-462300-8.
- "Blister Agents". Code Red – Weapons of Mass Destruction. Retrieved 2010-05-15.
- Westing, Arthur H. (1972). "Herbicides in war: Current status and future doubt". Biological Conservation 4 (5): 322–327. doi:10.1016/0006-3207(72)90043-2.
- Westing, Arthur H. (1971). "Forestry and the War in South Vietnam". Journal of Forestry 69: 777–783.
- Timbrell, John (2005). "Butter Yellow and Scheele's Green". The Poison Paradox: Chemicals as Friends and Foes. Oxford University Press. ISBN 978-0-19-280495-2.
- Cross, J. D.; Dale, I. M.; Leslie, A. C. D.; Smith, H. (1979). "Industrial exposure to arsenic". Journal of Radioanalytical Chemistry 48: 197–208. doi:10.1007/BF02519786.
- Guruswamy, Sivaraman (1999). "XIV. Ammunition". Engineering Properties and Applications of Lead Alloys. CRC Press. pp. 569–570. ISBN 978-0-8247-8247-4.
- Davis, Joseph R; Handbook Committee, ASM International (1 August 2001). "Dealloying". Copper and copper alloys. p. 390. ISBN 978-0-87170-726-0.
- "Arsenic Supply Demand and the Environment". Pollution technology review 214: Mercury and arsenic wastes: removal, recovery, treatment, and disposal. William Andrew. 1993. p. 68. ISBN 978-0-8155-1326-1.
- Stolz, John F.; Basu, Partha; Santini, Joanne M.; Oremland, Ronald S. (2006). "Arsenic and Selenium in Microbial Metabolism". Annual Review of Microbiology 60: 107–30. doi:10.1146/annurev.micro.60.080805.142053. PMID 16704340.
- Mukhopadhyay, Rita; Rosen, Barry P; Phung, Le T; Silver, Simon (2002). "Microbial arsenic: From geocycles to genes and enzymes". FEMS Microbiology Reviews 26 (3): 311–25. doi:10.1111/j.1574-6976.2002.tb00617.x. PMID 12165430.
- Kulp, T. R; Hoeft, S. E.; Asao, M.; Madigan, M. T.; Hollibaugh, J. T.; Fisher, J. C.; Stolz, J. F.; Culbertson, C. W.; Miller, L. G.; Oremland, R. S. (2008). "Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California". Science 321 (5891): 967–970. Bibcode:2008Sci...321..967K. doi:10.1126/science.1160799. PMID 18703741. Lay summary – Chemistry World, 15 August 2008.
- Erb, T. J.; Kiefer, P.; Hattendorf, B.; Günther, D.; Vorholt, J. A. (2012). "GFAJ-1 is an Arsenate-Resistant, Phosphate-Dependent Organism". Science 337 (6093): 467–70. Bibcode:2012Sci...337..467E. doi:10.1126/science.1218455. PMID 22773139.
- Reaves, M. L.; Sinha, S.; Rabinowitz, J. D.; Kruglyak, L.; Redfield, R. J. (2012). "Absence of Detectable Arsenate in DNA from Arsenate-Grown GFAJ-1 Cells". Science 337 (6093): 470–3. arXiv:1201.6643. Bibcode:2012Sci...337..470R. doi:10.1126/science.1219861. PMC 3845625. PMID 22773140.
- Anke M. Arsenic. In: Mertz W. ed., Trace elements in human and Animal Nutrition, 5th ed. Orlando, FL: Academic Press, 1986, 347-372; Uthus E.O., Evidency for arsenical essentiality, Environ. Geochem. Health, 1992, 14:54-56; Uthus E.O., Arsenic essentiality and factors affecting its importance. In: Chappell W.R, Abernathy C.O, Cothern C.R. eds., Arsenic Exposure and Health. Northwood, UK: Science and Technology Letters, 1994, 199-208.
- Baccarelli, A.; Bollati, V. (2009). "Epigenetics and environmental chemicals". Current Opinion in Pediatrics 21 (2): 243–251. doi:10.1097/MOP.0b013e32832925cc. PMC 3035853. PMID 19663042.
- Nicholis, I.; Curis, E.; Deschamps, P.; Bénazeth, S. (2009). "Arsenite medicinal use, metabolism, pharmacokinetics and monitoring in human hair". Biochimie 91 (10): 1260–7. doi:10.1016/j.biochi.2009.06.003. PMID 19527769.
- Lombi, E.; Zhao, F. -J.; Fuhrmann, M.; Ma, L. Q.; McGrath, S. P. (2002). "Arsenic Distribution and Speciation in the Fronds of the Hyperaccumulator Pteris vittata". New Phytologist 156 (2): 195–203. doi:10.1046/j.1469-8137.2002.00512.x. JSTOR 1514012.
- Sakurai, Teruaki Sakurai (2003). "Biomethylation of Arsenic is Essentially Detoxicating Event". Journal of Health Science 49 (3): 171–178. doi:10.1248/jhs.49.171.
- Reimer, K.J.; Koch, I.; Cullen, W.R. (2010). "Organoarsenicals. Distribution and transformation in the environment". Metal ions in life sciences 7: 165–229. doi:10.1039/9781849730822-00165. ISBN 978-1-84755-177-1. PMID 20877808.
- Bentley, Ronald; Chasteen, TG (2002). "Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth". Microbiology and Molecular Biology Reviews 66 (2): 250–271. doi:10.1128/MMBR.66.2.250-271.2002. PMC 120786. PMID 12040126.
- Cullen, William R; Reimer, Kenneth J. (1989). "Arsenic speciation in the environment". Chemical Reviews 89 (4): 713–764. doi:10.1021/cr00094a002.
- "Case Studies in Environmental Medicine (CSEM) Arsenic Toxicity Exposure Pathways" (PDF). Agency for Toxic Substances & Disease Registry. Retrieved 2010-05-15.
- "Arsenic in Food: FAQ". 5 December 2011. Retrieved 2010-04-11.
- Arsenic. The Agency for Toxic Substances and Disease Registry (2009).
- Meharg, Andrew (2005). Venomous Earth – How Arsenic Caused The World's Worst Mass Poisoning. Macmillan Science. ISBN 978-1-4039-4499-3.
- Henke, Kevin R (28 April 2009). Arsenic: Environmental Chemistry, Health Threats and Waste Treatment. p. 317. ISBN 978-0-470-02758-5.
- Lamm, S. H.; Engel, A.; Penn, C. A.; Chen, R.; Feinleib, M. (2006). "Arsenic cancer risk confounder in southwest Taiwan data set". Environ. Health Perspect. 114 (7): 1077–82. doi:10.1289/ehp.8704. PMC 1513326. PMID 16835062.
- Kohnhorst, Andrew (2005). "Arsenic in Groundwater in Selected Countries in South and Southeast Asia: A Review". J Trop Med Parasitol 28: 73.
- "Arsenic in Drinking Water: 3. Occurrence in U.S. Waters" (PDF). Retrieved 2010-05-15.
- Welch, Alan H.; Westjohn, D.B.; Helsel, Dennis R.; Wanty, Richard B. (2000). "Arsenic in Ground Water of the United States: Occurrence and Geochemistry". Ground Water 38 (4): 589–604. doi:10.1111/j.1745-6584.2000.tb00251.x.
- Knobeloch, L. M.; Zierold, K. M.; Anderson, H. A. (2006). "Association of arsenic-contaminated drinking-water with prevalence of skin cancer in Wisconsin's Fox River Valley". J. Health Popul Nutr 24 (2): 206–13. PMID 17195561.
- "In Small Doses:Arsenic". The Dartmouth Toxic Metals Superfund Research Program. Dartmouth College.
- Courtney, D; Ely, Kenneth H.; Enelow, Richard I.; Hamilton, Joshua W. (2009). "Low Dose Arsenic Compromises the Immune Response to Influenza A Infection in vivo". Environmental Health Perspectives 117 (9): 1441–7. doi:10.1289/ehp.0900911. PMC 2737023. PMID 19750111.
- Klassen, R.A.; Douma, S.L.; Ford, A.; Rencz, A.; Grunsky, E. (2009). "Geoscience modeling of relative variation in natural arsenic hazard in potential in New Brunswick" (PDF). Geological Survey of Canada. Archived from the original (PDF) on 2 May 2013. Retrieved 2012-10-14.
- Ferreccio, C.; Sancha, A. M. (2006). "Arsenic exposure and its impact on health in Chile". J Health Popul Nutr 24 (2): 164–75. PMID 17195557.
- Chu, H. A.; Crawford-Brown, D. J. (2006). "Inorganic arsenic in drinking water and bladder cancer: a meta-analysis for dose-response assessment". Int. J. Environ. Res. Public Health 3 (4): 316–22. doi:10.3390/ijerph2006030039. PMID 17159272.
- "Arsenic in drinking water seen as threat – USATODAY.com". USA Today. 30 August 2007. Retrieved 2008-01-01.
- Gulledge, John H.; O'Connor, John T. (1973). "Removal of Arsenic (V) from Water by Adsorption on Aluminum and Ferric Hydroxides". J. American Water Works Assn. 65 (8): 548–552.
- O'Connor, J. T.; O'Connor, T. L. "Arsenic in Drinking Water: 4. Removal Methods" (PDF).
- "In situ arsenic treatment". insituarsenic.org. Retrieved 2010-05-13.
- Radloff, K. A.; Zheng, Y.; Michael, H. A.; Stute, M.; Bostick, B. C.; Mihajlov, I.; Bounds, M.; Huq, M. R.; Choudhury, I.; Rahman, M.; Schlosser, P.; Ahmed, K.; Van Geen, A. (2011). "Arsenic migration to deep groundwater in Bangladesh influenced by adsorption and water demand". Nature Geoscience 4 (11): 793–798. Bibcode:2011NatGe...4..793R. doi:10.1038/ngeo1283. PMC 3269239. PMID 22308168.
- Yavuz, Cafer T; Mayo, J. T.; Yu, W. W.; Prakash, A.; Falkner, J. C.; Yean, S.; Cong, L.; Shipley, H. J.; Kan, A.; Tomson, M.; Natelson, D.; Colvin, V. L. (2005). "Low-Field Magnetic Separation of Monodisperse Fe3O4 Nanocrystals". Science 314 (5801): 964–967. doi:10.1126/science.1131475. PMID 17095696.
- Meliker, JR; Wahl, RL; Cameron, LL; Nriagu, JO (2007). "Arsenic in drinking water and cerebrovascular disease, diabetes mellitus, and kidney disease in Michigan: A standardized mortality ratio analysis". Environmental Health 6: 4. doi:10.1186/1476-069X-6-4. PMC 1797014. PMID 17274811.
- Tseng, Chin-Hsiao; Tai, Tong-Yuan; Chong, Choon-Khim; Tseng, Ching-Ping; Lai, Mei-Shu; Lin, Boniface J.; Chiou, Hung-Yi; Hsueh, Yu-Mei; Hsu, Kuang-Hung; Chen, CJ (2000). "Long-Term Arsenic Exposure and Incidence of Non-Insulin-Dependent Diabetes Mellitus: A Cohort Study in Arseniasis-Hyperendemic Villages in Taiwan". Environmental Health Perspectives 108 (9): 847–51. doi:10.1289/ehp.00108847. PMC 2556925. PMID 11017889.[dead link]
- Newspaper article (in Hungarian) published by Magyar Nemzet on 15 April 2012.
- Goering, P.; Aposhian, HV; Mass, MJ; Cebrián, M; Beck, BD; Waalkes, MP (1999). "The enigma of arsenic carcinogenesis: Role of metabolism". Toxicological Sciences 49 (1): 5–14. doi:10.1093/toxsci/49.1.5. PMID 10367337.
- Hopenhayn-Rich, C; Biggs, ML; Smith, AH; Kalman, DA; Moore, LE (1996). "Methylation study of a population environmentally exposed to arsenic in drinking water". Environmental Health Perspectives 104 (6): 620–628. doi:10.1289/ehp.96104620. PMC 1469390. PMID 8793350.
- Smith, AH; Arroyo, AP; Mazumder, DN; Kosnett, MJ; Hernandez, AL; Beeris, M; Smith, MM; Moore, LE (2000). "Arsenic-induced skin lesions among Atacame?o people in Northern Chile despite good nutrition and centuries of exposure" (PDF). Environmental Health Perspectives 108 (7): 617–620. doi:10.1289/ehp.00108617. PMC 1638201. PMID 10903614.
- Smedley, P. L., and D. G. Kinniburgh. "A review of the source, behaviour and distribution of arsenic in natural waters." Applied geochemistry 17.5 (2002): 517-568.
- How Does Arsenic Get into the Groundwater
- Wang Junfeng. "A preliminary study of trivalent arsenic removal in groundwater". Tianjin: Nankai University, 2003
- Zeng Zhaohua, Zhang Zhiliang (2002). "The formation of As element in groundwater and the controlling factor". Shanghai Geology 87 (3): 11–15.
- Y. Zheng, M. Stute, A.van Geen (2004). "Redox control of arsenic mobilization in Bangladesh groundwater". Applied Geochemistry 19: 201–214
- Mary Ann Thomas (2007). "The Association of Arsenic With Redox Conditions, Depth, and Ground-Water Age in the Glacial Aquifer System of the Northern United States".U.S. Geological Survey,Virginia:1-18.
- Hong Bin (2006). "Influence of microbes on biogeochemistry of arsenic mechanism of arsenic mobilization in groundwater". Advances in earth science 21 (1): 77–82.
- Johnson, D. L., and M. E. Q. Pilson. "The oxidation of arsenite in seawater." Environmental letters 8.2 (1975): 157-171.
- Cherry, J. A., et al. "Arsenic species as an indicator of redox conditions in groundwater." Developments in Water Science 12 (1979): 373-392.
- Cullen, William R., and Kenneth J. Reimer. "Arsenic speciation in the environment." Chemical Reviews 89.4 (1989): 713-764.
- Oremland, Ronald S., et al. "Bacterial dissimilatory reduction of arsenate and sulfate in meromictic Mono Lake, California." Geochimica et Cosmochimica Acta 64.18 (2000): 3073-3084.
- Reese, Jr., Robert G. "Commodity Summaries 2002: Arsenic" (PDF). United States Geological Survey. Archived (PDF) from the original on 17 December 2008. Retrieved 2008-11-08.
- "Chromated Copper Arsenate (CCA)". US Environmental Protection Agency.
- "TRI Releases Map". Toxmap.nlm.nih.gov. Archived from the original on 20 March 2010. Retrieved 2010-03-23.
- TOXNET – Databases on toxicology, hazardous chemicals, environmental health, and toxic releases. Toxnet.nlm.nih.gov. Retrieved 2011-10-24.
- Jain, CK; Singh, RD (2012). "Technological options for the removal of arsenic with special reference to South East Asia". Journal of Environmental Management 107: 1–8. doi:10.1016/j.jenvman.2012.04.016. PMID 22579769.
- Goering, P. (2013). "Bioremediation of arsenic-contaminated water: recent advances and future prospects". Water, Air, & Soil Pollution 224. doi:10.1007/s11270-013-1722-y.
- Goering, P. (2015). "Anaerobic arsenite oxidation with an electrode serving as the sole electron acceptor: A novel approach to the bioremediation of arsenic-polluted groundwater.". Journal of Hazardous Materials 283 (2015) 617–622 283: 617–622. doi:10.1016/j.jhazmat.2014.10.014.
- Arsenic Rule. U.S. Environmental Protection Agency. Adopted 22 January 2001; effective 23 January 2006.
- "Supporting Document for Action Level for Arsenic in Apple Juice". Fda.gov. Retrieved 2013-08-21.
- Lawmakers Urge FDA to Act on Arsenic Standards. Foodsafetynews.com (2012-02-24). Retrieved 2012-05-23.
- "A Homeowner's Guide to Arsenic in Drinking Water". New Jersey Department of Environmental Protection. Retrieved 2013-08-21.
- "NIOSH Pocket Guide to Chemical Hazards #0038". National Institute for Occupational Safety and Health (NIOSH).
- "NIOSH Pocket Guide to Chemical Hazards #0039". National Institute for Occupational Safety and Health (NIOSH).
- Total Diet Study and Toxic Elements Program
- Kotz, Deborah (14 September 2011). "Does apple juice have unsafe levels of arsenic? – The Boston Globe". Boston.com. Retrieved 2013-08-21.
- Morran, Chris. "Consumer Reports Study Finds High Levels Of Arsenic & Lead In Some Fruit Juice". consumerist.com.
- "Arsenic contamination of Bangladeshi paddy field soils: implications for rice contribution to arsenic consumption : Nature News". Nature.com. 22 November 2002. Retrieved 2013-08-21.
- "Tainted wells pour arsenic onto food crops". New Scientist. 6 December 2002. Retrieved 2013-08-21.
- "Rice as a source of arsenic exposure".
- Peplow, Mark (2 August 2005). "US rice may carry an arsenic burden". Nature News. doi:10.1038/news050801-5.
- "EHP – Rice Consumption and Urinary Arsenic Concentrations in U.S. Children". Ehp.niehs.nih.gov. Retrieved 2013-08-21.
- "High Levels Of Arsenic Found In Rice". NPR. 2 March 2012. Retrieved 2013-08-21.
- "Arsenic in Your Food | Consumer Reports Investigation". Consumerreports.org. 1 November 2012. Retrieved 2013-08-21.
- "FDA Looks for Answers on Arsenic in Rice". Fda.gov. 19 September 2012. Retrieved 2013-08-21.
- "Arsenic in Rice". Fda.gov. Retrieved 2013-08-21.
- "Questions & Answers: FDA's Analysis of Arsenic in Rice and Rice Products". Fda.gov. 21 March 2013. Retrieved 2013-08-21.
- "Arsenic in Rice: What You Need to Know". UC Berkeley Wellness. Retrieved 3 September 2014.
- "Arsenic". RTECS. National Institute for Occupational Safety and Health (NIOSH).
- Korea Occupational Safety & Health Agency
- KOSHA GUIDE H-120-2013
- Hughes, Michael F (2002). "Arsenic toxicity and potential mechanisms of action". Toxicology Letters 133 (1): 1–16. doi:10.1016/S0378-4274(02)00084-X. PMID 12076506.
- Klaassen, Curtis; Watkins, John (2003). Casarett and Doull's Essentials of Toxicology. McGraw-Hill. p. 512. ISBN 978-0-07-138914-3.
- "OSHA Arsenic". United States Occupational Safety and Health Administration. Archived from the original on 12 October 2007. Retrieved 2007-10-08.
- Croal, Laura R.; Gralnick, Jeffrey A.; Malasarn, Davin; Newman, Dianne K. (2004). "The Genetics of Geochemisty". Annual Review of Genetics 38: 175–206. doi:10.1146/annurev.genet.38.072902.091138. PMID 15568975.
- Roy, Debarshi; Gaur, Priya; Verma, Neeraj; Pathireddy, Monika; Singh, Krishna.P. (2013). "Bioremediation of Arsenic (III) from Water Using Baker Yeast Sacchromyces cerevisiae". International Journal of Environmental Bioremediation & Biodegradation 1: 14–19. doi:10.12691/ijebb-1-1-3.
- The Psychiatric, Psychogenic and Somatopsychic Disorders Handbook. New Hyde Park, NY: Medical Examination Publishing Co. 1978. pp. 81–82. ISBN 0-87488-596-5.
- The Tox Guide for Arsenic (2007). The US Agency for Toxic Substances and Disease Registry.
- Emsley, John (2011). "Arsenic". Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 47–55. ISBN 0-19-960563-7.
- James G. Whorton (2011). The Arsenic Century. Oxford University Press. ISBN 978-0-19-960599-6.
|Wikimedia Commons has media related to Arsenic.|
|Look up arsenic in Wiktionary, the free dictionary.|
- CTD's Arsenic page and CTD's Arsenicals page from the Comparative Toxicogenomics Database
- A Small Dose of Toxicology
- Arsenic in groundwater Book on arsenic in groundwater by IAH's Netherlands Chapter and the Netherlands Hydrological Society
- Contaminant Focus: Arsenic by the EPA.
- Environmental Health Criteria for Arsenic and Arsenic Compounds, 2001 by the WHO.
- Evaluation of the carcinogenicity of arsenic and arsenic compounds by the IARC.
- National Institute for Occupational Safety and Health – Arsenic Page
- Arsenic at The Periodic Table of Videos (University of Nottingham)
|Periodic table (Large cells)|