Arsenic ( ) is a
chemical element with the symbol
As,
atomic number 33 and
relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by
Albertus Magnus in 1250. Arsenic is a
metalloid. It can exist in various
allotropes, 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 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.
Arsenic is notoriously poisonous to multicellular life, although a few species of bacteria are able to use arsenic compounds as respiratory metabolites. Arsenic contamination of groundwater is a problem that affects millions of people across the world.
The three most common
allotropes are ''metallic grey'', ''yellow'' and ''black arsenic'', with grey being the most common. ''Grey arsenic'' (α-As,
space group 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/cm
3. Grey arsenic is a
semimetal, but becomes a
semiconductor 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/cm
3.'' Black arsenic'' is similar in structure to red phosphorus.
Naturally occurring arsenic is 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 80.3 days. 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.
At least 10 nuclear isomers 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.
When heated in air, arsenic
oxidizes to arsenic trioxide; the fumes from this reaction have an odour resembling
garlic. This odour 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 . The
triple point is 3.63 MPa and . Arsenic makes
arsenic acid with concentrated
nitric acid,
arsenious acid with dilute nitric acid, and
arsenic trioxide with concentrated
sulfuric acid.
Arsenic compounds 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; and +3 in the
arsenites, arsenates(III), and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As 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 is the basis of
arsenic contamination of groundwater, a problem that affects many people. Man-made arsenates include
Paris Green (copper(II) acetoarsenite),
calcium arsenate, and
lead hydrogen arsenate. The latter 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 phosphorus 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 in fact three.
The trifluoride, trichloride, tribromide, and triiodide of arsenic(III) are well known, whereas only Arsenic pentafluoride (AsF5) is the only important pentahalide. Again reflecting the lower stability of the 5+ oxidation state, the pentachloride is stable only below −50 °C.
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.
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-IV semiconductor
cadmium arsenide.
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. Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized to a less toxic form of arsenic through a process of methylation.
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.
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.
The word ''arsenic'' was borrowed from the
Syriac word ܠܐ ܙܐܦܢܝܐ ''(al) zarniqa'' and the
Persian word ''Zarnikh'', meaning "yellow
orpiment", into
Greek 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) and oxides have been known and used since ancient times.
Zosimos (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 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 in 1250 by heating soap together with arsenic trisulfide. In 1649, Johann Schröder published two ways of preparing arsenic.
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" 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 approximately 20 deaths.
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, termination 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.
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 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.
During the 18th, 19th, and 20th centuries, a number of arsenic compounds have been 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, but most commonly in the treatment of
cancer. The US
Food and Drug Administration in 2000 approved this compound for the treatment of patients with
acute promyelocytic leukemia that is resistant to
ATRA. It was also used as
Fowler's solution in
psoriasis. 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-124 is that the signal in the
PET scan 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 stimulants, and were once popular in small doses as medicine by people in the mid-18th century.
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 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 is
direct bandgap, and 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 of
lewisite (ClCH=CHAsCl
2), 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 the Vietnamese of valuable crops.
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.
Also used in bronzing and pyrotechnics.
Up to 2% of arsenic is used in lead alloys for
lead shots 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 γ-Proteobacterium ''Ectothiorhodospira shaposhnikovii''. The mechanism is unknown, but an encoded Arr enzyme may function in reverse to its known homologues.
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'') hyperaccumulates arsenic present in the soil into its leaves and has a proposed use in phytoremediation.
A
NASA-funded
astrobiology research team claimed on December 2, 2010 that the microbe strain
GFAJ-1 of the
Gammaproteobacteria (designated
Halomonadaceae) group has the ability to substitute arsenic for at least part of the
phosphorus in the molecules of its cells, including
DNA and
ATP. Bacteria from
Mono Lake, a naturally arsenic-rich site in
California, 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.
Inorganic arsenic and its compounds, upon entering the
food chain, are progressively metabolised through a process of
methylation. For example, the mold
Scopulariopsis brevicaulis produce 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.
Widespread arsenic contamination of groundwater has led to a massive epidemic of
arsenic poisoning in
Bangladesh 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 with arsenic concentrations elevated above the
World Health Organization'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 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 dissolved arsenic in the
Chao Phraya River 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, 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 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 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 (U.S.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 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 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.
Hungarian engineer László Schremmer has recently discovered that by the use of chaff-based filters it is possible to reduce the arsenic content of water to 3 microgram/litre. This is especially important in areas where the potable water is provided by filtering the water extracted from the underground aquifer.
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 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,
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.
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.
Arsenic and many of its compounds are especially potent poisons. Many water supplies close to mines are contaminated by these poisons. In the United States, the maximum allowed concentration in drinking water is 10 ppb, 5 ppb for bottled water. There is no standard for food, though in 2012 press coverage prompted calls for developing such. The People's Republic of China does have a food standard.
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 [HAsO42-; As(V)] and arsenite [H3AsO3 ; As(III)]".
Treatment of chronic arsenic poisoning is easily accomplished. British anti-lewisite (
dimercaprol) 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 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.
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; and by competing with phosphate it 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, it is presumed from
necrotic cell death, not
apoptosis. A
post mortem reveals brick-red-coloured
mucosa, owing to severe
haemorrhage. Although arsenic causes toxicity, it can also play a protective role.
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 enzymes.
Aqua Tofana
Arsenic biochemistry
Arsenic compounds
Arsenic poisoning
Arsenic toxicity
Arsenic trioxide
Fowler's solution
GFAJ-1
Grainger challenge
Hypothetical types of biochemistry
Organoarsenic chemistry
White arsenic
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
National Pollutant Inventory – Arsenic
origen.net – CCA wood and arsenic: toxicological effects of arsenic
Category:Metalloids
Category:Pnictogens
Category:Toxicology
Category:Chemical elements
Category:Endocrine disruptors
Category:IARC Group 1 carcinogens
Category:Biology and pharmacology of chemical elements
Category:Trigonal minerals
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zh:砷
