Cobalt

refined cobalt (99.9% purity) cut from a large plate Cobalt is a ferromagnetic metal with a specific gravity of 8.9. The Curie temperature is and the magnetic moment is 1.6–1.7 Bohr magnetons per atom. Cobalt has a relative permeability two-thirds that of iron. Metallic cobalt occurs as two crystallographic structures: hcp and fcc. The ideal transition temperature between the hcp and fcc structures is , but in practice the energy difference between them is so small that random intergrowth of the two is common. Cobalt is a weakly reducing metal that is protected from oxidation by a passivating oxide film. It is attacked by halogens and sulfur. Heating in oxygen produces Co3O4 which loses oxygen at to give the monoxide CoO. At ordinary temperatures, it reacts slowly with mineral acids, and very slowly with moist, but not dry, air. ==Compounds==

Common oxidation states of cobalt include +2 and +3, although compounds with oxidation states ranging from −3 to +5 are also known. A common oxidation state for simple compounds is +2 (cobalt(II)). These salts form the pink-colored metal aquo complex in water. Addition of chloride gives the intensely blue . Oxygen and chalcogen compounds Several oxides of cobalt are known. Green cobalt(II) oxide (CoO) has rocksalt structure. It is readily oxidized with water and oxygen to brown cobalt(III) hydroxide (Co(OH)3). At temperatures of 600–700 °C, CoO oxidizes to the blue cobalt(II,III) oxide (Co3O4), which has a spinel structure. Black cobalt(III) oxide (Co2O3) is also known. Cobalt oxides are antiferromagnetic at low temperature: CoO (Néel temperature 291 K) and Co3O4 (Néel temperature: 40 K), which is analogous to magnetite (Fe3O4), with a mixture of +2 and +3 oxidation states. The principal chalcogenides of cobalt are the black cobalt(II) sulfides, CoS2 (pyrite structure), (spinel structure), and CoS (nickel arsenide structure). The reduction potential for the reaction + e− → is +1.92 V, beyond that for chlorine to chloride, +1.36 V. Consequently, cobalt(III) chloride would spontaneously reduce to cobalt(II) chloride and chlorine. Because the reduction potential for fluorine to fluoride is so high, +2.87 V, cobalt(III) fluoride is one of the few simple stable cobalt(III) compounds. Cobalt(III) fluoride, which is used in some fluorination reactions, reacts vigorously with water. Cobalt(III) forms a wide variety of coordination complexes with ammonia and amines, which are called ammine complexes. Examples include , (chloropentamminecobalt(III)), and cis- and trans-. The corresponding ethylenediamine complexes are also well known. Analogues are known where the halides are replaced by nitrite, hydroxide, carbonate, etc. Alfred Werner worked extensively on these complexes in his Nobel-prize winning work. The robustness of these complexes is demonstrated by the optical resolution of tris(ethylenediamine)cobalt(III) (). Cobalt(II) forms a wide variety of complexes, but mainly with weakly basic ligands. The pink-colored cation hexaaquocobalt(II) is found in several routine cobalt salts such as the nitrate and sulfate. Upon addition of excess chloride, solutions of the hexaaquo complex converts to the deep blue , which is tetrahedral. Softer ligands like triphenylphosphine form complexes with Co(II) and Co(I), examples being bis- and tris(triphenylphosphine)cobalt(I) chloride, and . These Co(I) and Co(II) complexes represent a link to the organometallic complexes described below. Organometallic compounds Cobaltocene is a structural analog to ferrocene, with cobalt in place of iron. Cobaltocene is much more sensitive to oxidation than ferrocene. Cobalt carbonyl (Co2(CO)8) is a catalyst in carbonylation and hydrosilylation reactions. Vitamin B12 (see below) is an organometallic compound found in nature and is the only vitamin that contains a metal atom. An example of an alkylcobalt complex in the otherwise uncommon +4 oxidation state of cobalt is the homoleptic complex tetrakis(1-norbornyl)cobalt(IV) (Co(1-norb)4), a transition metal-alkyl complex that is notable for its resistance to β-hydrogen elimination, in accord with Bredt's rule. The cobalt(III) and cobalt(V) complexes and are also known. ==Isotopes==

59Co is the only stable cobalt isotope and the only isotope that exists naturally on Earth. Twenty-two radioisotopes have been characterized: the most stable, 60Co, has a half-life of 5.2714 years; 57Co has a half-life of 271.81 days; 56Co has a half-life of 77.24 days; and 58Co has a half-life of 70.84 days. All the other radioactive isotopes of cobalt have half-lives shorter than 18 hours, and in most cases shorter than 1 second. This element also has 4 meta states, all of which have half-lives shorter than 15 minutes. The isotopes of cobalt range from 50Co to 78Co. The primary decay mode for isotopes with atomic masses less than that of the only stable isotope, 59Co, is electron capture and the primary mode of decay in isotopes with atomic mass greater than that is beta decay. The primary decay products below 59Co are element 26 (iron) isotopes; above that the decay products are element 28 (nickel) isotopes. and has a magnetic quadrupole moment. Among all NMR active nuclei, 59Co has the largest chemical shift range and the chemical shift can be correlated with the spectrochemical series. Resonances are observed over a range of 20000 ppm, the width of the signals being up to 20 kHz. A widely used standard is potassium hexacyanocobaltate (0.1M in ), which, due to its high symmetry, has a rather small line width. Systems of low symmetry can yield broadened signals to an extent that renders the signals unobservable in fluid phase NMR, but still observable in solid state NMR. ==Etymology==

Many different stories about the origin of the word "cobalt" have been proposed. In one version the element cobalt was named after "", the name which 16th century German silver miners had given to a nuisance type of ore which occurred that was corrosive and issued poisonous gas. Agricola did not make a connection between the similarly named ore and spirit. However, a causal connection (ore blamed on "kobel") was made by a contemporary, and a word origin connection (word "formed" from cobalus) made by a late 18th century writer. Later, Grimms' dictionary (1868) noted the kobalt/kobelt ore was blamed on the mountain spirit () which was also held responsible for "stealing the silver and putting out an ore that caused poor mining atmosphere (Wetter Another theory given by the Etymologisches Wörterbuch derives the term from ) which occurs as noxious fumes. An etymology from Slavonic '''' was suggested by Emanuel Merck (1902). W. W. Skeat and J. Berendes construed as "parasite", i.e. as an ore parasitic to nickel, but this explanation is faulted for its anachronism since nickel was not discovered until 1751. ==History==

Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes, and ceramics. Cobalt has been detected in Egyptian sculpture, Persian jewelry from the third millennium BC, in the ruins of Pompeii, destroyed in 79 AD, and in China, dating from the Tang dynasty (618–907 AD) and the Ming dynasty (1368–1644 AD). Cobalt has been used to color glass since the Bronze Age. The excavation of the Uluburun shipwreck yielded an ingot of blue glass, cast during the 14th century BC. One possible origin of the word cobalt is the 16th century German "", a type of ore. The first attempts to smelt those ores for copper or silver failed, yielding simply powder (cobalt(II) oxide) instead. Because the primary ores of cobalt always contain arsenic, smelting the ore oxidized the arsenic into the highly toxic and volatile arsenic oxide, adding to the notoriety of the ore. Paracelsus, Georgius Agricola, and Basil Valentine all referred to such silicates as "cobalt". Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt , showing it to be a previously unknown element, distinct from bismuth and other traditional metals. Brandt called it a new "semi-metal", He showed that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period. All previously known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers. During the 19th century, a significant part of the world's production of cobalt blue (a pigment made with cobalt compounds and alumina) and smalt (cobalt glass powdered for use for pigment purposes in ceramics and painting) was carried out at the Norwegian Blaafarveværket. The first mines for the production of smalt in the 16th century were located in Norway, Sweden, Saxony and Hungary. With the discovery of cobalt ore in New Caledonia in 1864, the mining of cobalt in Europe declined. With the discovery of ore deposits in Ontario, Canada, in 1904 and the discovery of even larger deposits in the Katanga Province in the Congo in 1914, mining operations shifted again. The impact on the world cobalt economy from this conflict was smaller than expected: cobalt is a rare metal, the pigment is highly toxic, and the industry had already established effective ways for recycling cobalt materials. In some cases, industry was able to change to cobalt-free alternatives. This isotope was famously used at Columbia University in the 1950s to establish parity violation in radioactive beta decay. After World War II, the US wanted to guarantee the supply of cobalt ore for military uses (as the Germans had been doing) and prospected for cobalt within the US. High purity cobalt was highly sought after for its use in jet engines and gas turbines. An adequate supply of the ore was found in Idaho near Blackbird canyon. Calera Mining Company started production at the site. Cobalt demand has further accelerated in the 21st century as an essential constituent of materials used in rechargeable batteries, superalloys, and catalysts. ==Occurrence==

The stable isotope of cobalt is produced in supernovae through the r-process. It comprises 0.0029% of the Earth's crust where it is frequently associated with nickel. Both are characteristic components of meteoric iron, though cobalt is much less abundant in iron meteorites than nickel. As with nickel, cobalt in meteoric iron alloys may have been well enough protected from oxygen and moisture to remain as the free (but alloyed) metal. In the ocean cobalt typically reacts with chlorine. Cobalt in compound form occurs in copper and nickel minerals. It is the major metallic component that combines with sulfur and arsenic in the sulfidic cobaltite (CoAsS), safflorite (CoAs2), glaucodot (), and skutterudite (CoAs3) minerals. Small amounts of cobalt compounds are found in most rocks, soils, plants, and animals. Free cobalt (the native metal) was reported from samples in the Kola Superdeep Borehole and in Moon rocks from the Luna 24 mission, possibly as a result of impacts. Cobalt is also a constituent of tobacco smoke. The tobacco plant readily absorbs and accumulates heavy metals like cobalt from the surrounding soil in its leaves. These are subsequently inhaled during tobacco smoking. ==Production==

The main ores of cobalt are cobaltite, erythrite, glaucodot and skutterudite (see above), but most cobalt is obtained by reducing the cobalt by-products of nickel and copper mining and smelting. Since cobalt is generally produced as a by-product, the supply of cobalt depends to a great extent on the economic feasibility of copper and nickel mining in a given market. Demand for cobalt was projected to grow 6% in 2017. Primary cobalt deposits are rare, such as those occurring in hydrothermal deposits, associated with ultramafic rocks, typified by the Bou-Azzer district of Morocco. At such locations, cobalt ores are mined exclusively, albeit at a lower concentration, and thus require more downstream processing for cobalt extraction. Several methods exist to separate cobalt from copper and nickel, depending on the concentration of cobalt and the exact composition of the used ore. One method is froth flotation, in which surfactants bind to ore components, leading to an enrichment of cobalt ores. Subsequent roasting converts the ores to cobalt sulfate, and the copper and the iron are oxidized to the oxide. Leaching with water extracts the sulfate together with the arsenates. The residues are further leached with sulfuric acid, yielding a solution of copper sulfate. Cobalt can also be leached from the slag of copper smelting. The products of the above-mentioned processes are transformed into the cobalt oxide (Co3O4). This oxide is reduced to metal by the aluminothermic reaction or reduction with carbon in a blast furnace. ==Extraction==

The United States Geological Survey estimates world reserves of cobalt at 11,000,000 metric tons. The Democratic Republic of the Congo (DRC) currently produces 63% of the world's cobalt. This market share may reach 73% by 2025 if planned expansions by mining producers like Glencore Plc take place as expected. Bloomberg New Energy Finance has estimated that by 2030, global demand for cobalt could be 47 times more than it was in 2017. Democratic Republic of the Congo Changes that Congo made to mining laws in 2002 attracted new investments in Congolese copper and cobalt projects. In 2016, Chinese ownership of cobalt production in the Congo was estimated at over 10% of global cobalt supply, forming a key input to the Chinese cobalt refining industry and granting China substantial influence over the global cobalt supply chain. Chinese control of Congolese cobalt has raised concern in Western nations which have sought to reduce supply chain reliance upon China and have expressed concern regarding labor and human rights violations in cobalt mines in the DRC. Glencore's Mutanda Mine shipped 24,500 tons of cobalt in 2016, 40% of Congo DRC's output and nearly a quarter of global production. After oversupply, Glencore closed Mutanda for two years in late 2019. Glencore's Katanga Mining project is resuming as well and should produce 300,000 tons of copper and 20,000 tons of cobalt by 2019, according to Glencore. On 9 March 2018, President Joseph Kabila updated the 2002 mining code, increasing royalty charges and declaring cobalt and coltan "strategic metals". The 2002 mining code was effectively updated on 4 December 2018. In February 2025, the DRC implemented a four-month suspension of cobalt exports, citing an oversupply of the metal amid a price decline to its lowest level in 21 years. Cobalt, a key byproduct of copper mining, is an essential material in battery technology. The DRC accounts for approximately 75 percent of the global supply. Within the country, the China Molybdenum Company (CMOC) dominates the industry, contributing roughly 40 percent of the world's cobalt production. Over the past year, CMOC has significantly increased its output, doubling production from two of its mines in the DRC from 56,000 tonnes to 114,000 tonnes. Labor conditions Artisanal mining supplied 17% to 40% of the DRC production as of 2016. Mining pollutes the vicinity and exposes local wildlife and indigenous communities to toxic metals thought to cause birth defects and breathing difficulties, according to health officials. Child labor is used in mining cobalt from African artisanal mines. Human rights activists have highlighted this and investigative journalism reporting has confirmed it. This revelation prompted cell phone maker Apple Inc., on 3 March 2017, to stop buying ore from suppliers such as Zhejiang Huayou Cobalt who source from artisanal mines in the DRC, and begin using only suppliers that are verified to meet its workplace standards. In 2023, Apple announced it would convert to using recycled cobalt by 2025. There is a push globally by the EU and major car manufacturers (OEM) for global production of cobalt to be sourced and –produced sustainably, responsibly and traceability of the supply chain. Mining companies are adopting and practising ESG initiatives in line with OECD Guidance and putting in place evidence of zero to low carbon footprint activities in the supply chain production of lithium-ion batteries. These initiatives are already taking place with major mining companies, artisanal and small-scale mining companies (ASM). Car manufacturers and battery manufacturer supply chains: Tesla, VW, BMW, BASF and Glencore are participating in several initiatives, such as the Responsible Cobalt Initiative and Cobalt for Development study. In 2018 BMW Group in partnership with BASF, Samsung SDI and Samsung Electronics have launched a pilot project in the DRC over one pilot mine, to improve conditions and address challenges for artisanal miners and the surrounding communities. The political and ethnic dynamics of the region have in the past caused outbreaks of violence and years of armed conflict and displaced populations. This instability affected the price of cobalt and also created perverse incentives for the combatants in the First and Second Congo Wars to prolong the fighting, since access to diamond mines and other valuable resources helped to finance their military goals—which frequently amounted to genocide—and also enriched the fighters themselves. While DR Congo has in the 2010s not recently been invaded by neighboring military forces, some of the richest mineral deposits adjoin areas where Tutsis and Hutus still frequently clash, unrest continues although on a smaller scale and refugees still flee outbreaks of violence. Cobalt extracted from small Congolese artisanal mining endeavors in 2007 supplied a single Chinese company, Congo DongFang International Mining. A subsidiary of Zhejiang Huayou Cobalt, one of the world's largest cobalt producers, Congo DongFang supplied cobalt to some of the world's largest battery manufacturers, who produced batteries for ubiquitous products like the Apple iPhones. Because of accused labour violations and environmental concerns, LG Chem subsequently audited Congo DongFang in accordance with OECD guidelines. LG Chem, which also produces battery materials for car companies, imposed a code of conduct on all suppliers that it inspects. In December 2019, International Rights Advocates, a human rights NGO, filed a landmark lawsuit against Apple, Tesla, Dell, Microsoft and Google company Alphabet for "knowingly benefiting from and aiding and abetting the cruel and brutal use of young children" in mining cobalt. The companies in question denied their involvement in child labour. In 2024 the court ruled that the suppliers facilitate force labor but the US tech companies are not liable because they don't operate as a shared enterprise with the suppliers and that the "alleged injuries are not fairly traceable" to any of the defendants' conduct. The book Cobalt Red alleges that workers including children suffer injuries, amputations, and death as the result of the hazardous working conditions and mine tunnel collapses during artisanal mining of cobalt in the DRC. Since child and slave labor have been repeatedly reported in cobalt mining, primarily in the artisanal mines of DR Congo, technology companies seeking an ethical supply chain have faced shortages of this raw material and the price of cobalt metal reached a nine-year high in October 2017, more than US$30 a pound, versus US$10 in late 2015. After oversupply, the price dropped to a more normal $15 in 2019. As a reaction to the issues with artisanal cobalt mining in DR Congo a number of cobalt suppliers and their customers have formed the Fair Cobalt Alliance (FCA) which aims to end the use of child labor and to improve the working conditions of cobalt mining and processing in the DR Congo. Members of FCA include Zhejiang Huayou Cobalt, Sono Motors, the Responsible Cobalt Initiative, Fairphone, Glencore and Tesla, Inc. Canada In 2017, some exploration companies were planning to survey old silver and cobalt mines in the area of Cobalt, Ontario, where significant deposits are believed to lie. Cobalt mined in Canada is a by-product of nickel mining. Even so, in 2023 the country produced more than 5,000 tons of cobalt (43% is mined in Newfoundland and Labrador, the rest in Ontario, Manitoba and Quebec). Exports of cobalt and cobalt products totaled $568 million in 2023. Cuba Canada's Sherritt International processes cobalt ores in nickel deposits from the Moa mines in Cuba, and the island has several others mines in Mayarí, Camagüey, and Pinar del Río. Continued investments by Sherritt International in Cuban nickel and cobalt production while acquiring mining rights for 17–20 years made the communist country third for cobalt reserves in 2019, before Canada itself. Indonesia Starting from smaller amounts in 2021, Indonesia began producing cobalt as a byproduct of nickel production. By 2022, the country had become the world's second-largest cobalt producer, with Benchmark Mineral Intelligence forecasting Indonesian output to make up 20 percent of global production by 2030. Cobalt production increased from 1,300 tons to 20,500 tons between 2015 and 2024 due to the Indonesian government's strategic initiative to develop a robust domestic supply chain for electric vehicles. An export ban in 2020 has ensured an influx of foreign investment in nickel and cobalt processing in the country. ==Applications==

In 2016, of cobalt was used. Special cobalt-chromium-molybdenum alloys like Vitallium are used for prosthetic parts (hip and knee replacements). Cobalt alloys are also used for dental prosthetics as a useful substitute for nickel, which may be allergenic. Some high-speed steels also contain cobalt for increased heat and wear resistance. The special alloys of aluminium, nickel, cobalt and iron, known as Alnico, and of samarium and cobalt (samarium–cobalt magnet) are used in permanent magnets. It is also alloyed with 95% platinum for jewelry, yielding an alloy suitable for fine casting, which is also slightly magnetic. In addition to structural and magnetic roles, cobalt alloys are critical in aerospace-grade electrical components. They are used in connectors, thermal switches, and microsensors that must endure extreme temperatures, vibration, and radiation—conditions typical in satellites, fighter aircraft, and hypersonic systems. These alloys maintain conductivity and mechanical integrity even under fluctuating mission-critical loads. Batteries Lithium cobalt oxide (LiCoO2, aka "LCO"), first sold commercially in 1991 by Sony, was widely used in lithium-ion battery cathodes until the 2010s. The material is composed of cobalt oxide layers with the lithium intercalated. These LCO batteries continue to dominate the market for consumer electronics. Batteries for electric cars however have shifted to lower cobalt technologies. In 2018 most cobalt in batteries was used in a mobile device, a more recent application for cobalt is rechargeable batteries for electric cars. This industry increased five-fold in its demand for cobalt from 2016 to 2020, which made it urgent to find new raw materials in more stable areas of the world. Demand is expected to continue or increase as the prevalence of electric vehicles increases. Exploration in 2016–2017 included the area around Cobalt, Ontario, an area where many silver mines ceased operation decades ago. As of August 2020 battery makers have gradually reduced the cathode cobalt content from 1/3 (NMC 111) to 1/5 (NMC 442) to currently 1/10 (NMC 811) and have also introduced the cobalt free lithium iron phosphate cathode into the battery packs of electric cars such as the Tesla Model 3. Research was also conducted by the European Union into the possibility of eliminating cobalt requirements in lithium-ion battery production. In September 2020, Tesla outlined their plans to make their own, cobalt-free battery cells. Nickel–cadmium Catalysts Several cobalt compounds are oxidation catalysts. Cobalt acetate is used to convert xylene to terephthalic acid, the precursor of the bulk polymer polyethylene terephthalate. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as "drying agents" through the oxidation of drying oils. The same carboxylates are used to improve the adhesion between steel and rubber in steel-belted radial tires. In addition they are used as accelerators in polyester resin systems. Cobalt-based catalysts are used in reactions involving carbon monoxide. Cobalt is also a catalyst in the Fischer–Tropsch process for the hydrogenation of carbon monoxide into liquid fuels. Cobalt-60 has a radioactive half-life of 5.27 years. Loss of potency requires periodic replacement of the source in radiotherapy and is one reason why cobalt machines have been largely replaced by linear accelerators in modern radiation therapy. Cobalt-57 (Co-57 or 57Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for vitamin B uptake, and for the Schilling test. Cobalt-57 is used as a source in Mössbauer spectroscopy and is one of several possible sources in X-ray fluorescence devices. It is used in creating permanent magnets like Alnico magnets, known for their strong magnetic properties used in electric motors, sensors, and MRI machines. It is also used in production of magnetic alloys like cobalt steel, widely used in magnetic recording media such as hard disks and tapes. Cobalt's ability to maintain magnetic properties at high temperatures makes it valuable in magnetic recording applications, ensuring reliable data storage devices. Cobalt also contributes to specialized magnets such as samarium-cobalt magnets, which are vital in electronics for components like sensors and actuators. Other uses • Cobalt is used in electroplating for its attractive appearance, hardness, and resistance to oxidation. • It is also used as a base primer coat for porcelain enamels. ==Biological role==

Cobalt is essential to the metabolism of all animals. It is a key constituent of cobalamin, also known as vitamin B, the primary biological reservoir of cobalt as an ultratrace element. Proteins based on cobalamin use corrin to hold the cobalt. Coenzyme B12 features a reactive C-Co bond that participates in the reactions. In humans, B12 has two types of alkyl ligand: methyl and adenosyl. MeB12 promotes methyl (−CH3) group transfers. The adenosyl version of B12 catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to Su-CoA, an important step in the extraction of energy from proteins and fats. Although far less common than other metalloproteins (e.g. those of zinc and iron), other cobaltoproteins are known besides B12. These proteins include methionine aminopeptidase 2, an enzyme that occurs in humans and other mammals that does not use the corrin ring of B12, but binds cobalt directly. Another non-corrin cobalt enzyme is nitrile hydratase, an enzyme in bacteria that metabolizes nitriles. Cobalt deficiency In humans, consumption of cobalt-containing vitamin B12 meets all needs for cobalt. For cattle and sheep, which meet vitamin B12 needs via synthesis by resident bacteria in the rumen, there is a function for inorganic cobalt. In the early 20th century, during the development of farming on the North Island Volcanic Plateau of New Zealand, cattle suffered from what was termed "bush sickness". It was discovered that the volcanic soils lacked the cobalt salts essential for the cattle food chain. The "coast disease" of sheep in the Ninety Mile Desert of the Southeast of South Australia in the 1930s was found to originate in nutritional deficiencies of trace elements cobalt and copper. The cobalt deficiency was overcome by the development of "cobalt bullets", dense pellets of cobalt oxide mixed with clay given orally for lodging in the animal's rumen. File:Cobalamin.svg |alt=chemical diagram of cobalamin molecule|Cobalamin File:CSIRO ScienceImage 10487 Cobalt deficient sheep.jpg |alt=two cobalt-deficient sheep facing away from camera|Cobalt-deficient sheep ==Health issues==

}} The LD50 value for soluble cobalt salts has been estimated to be between 150 and 500 mg/kg. In the US, the Occupational Safety and Health Administration (OSHA) has designated a permissible exposure limit (PEL) in the workplace as a time-weighted average (TWA) of 0.1 mg/m3. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.05 mg/m3, time-weighted average. The IDLH (immediately dangerous to life and health) value is 20 mg/m3. Chronic cobalt ingestion has caused serious health problems at doses far less than the lethal dose. In 1966, the addition of cobalt compounds to stabilize beer foam in Canada led to a peculiar form of toxin-induced cardiomyopathy, which came to be known as ''beer drinker's cardiomyopathy''. Cobalt metal is suspected of causing cancer (i.e., possibly carcinogenic, IARC Group 2B) as per the International Agency for Research on Cancer (IARC) Monographs. It causes respiratory problems when inhaled. It also causes skin problems when touched; after nickel and chromium, cobalt is a major cause of contact dermatitis. ==Notes==