 = 14 @.@ 1 years ) , <unk> ( t1 / 2 = 
 44 @.@ 6 days ) , and <unk> ( t1 / 2 = 3 @.@ 36 hours ) . 
 The known isotopes of cadmium range in atomic mass from 94 @.@ 950 u ( <unk> ) to 131 @.@ <unk> u ( <unk> ) . For isotopes lighter than 112 u , the primary decay mode is electron capture and the dominant decay product is element 47 ( silver ) . <unk> isotopes decay mostly through beta emission producing element 49 ( indium ) . 
 One isotope of cadmium , <unk> , absorbs neutrons with high selectivity : With very high probability , neutrons with energy below the cadmium cut @-@ off will be absorbed ; those higher than the cut @-@ off will be transmitted . The cadmium cut @-@ off is about 0 @.@ 5 <unk> , and neutrons below that level are deemed slow neutrons , distinct from intermediate and fast neutrons . 
 Cadmium is created via the long s @-@ process in low @-@ medium mass stars with masses of 0 @.@ 6 to 10 solar masses , taking thousands of years . In that process , a silver atom captures a neutron and then undergoes beta decay . 
 
 = = History = = 
 
 Cadmium ( Latin <unk> , Greek <unk> meaning " calamine " , a cadmium @-@ bearing mixture of minerals that was named after the Greek mythological character <unk> , <unk> , the founder of Thebes ) was discovered simultaneously in 1817 by Friedrich Stromeyer and Karl Samuel <unk> Hermann , both in Germany , as an impurity in zinc carbonate . Stromeyer found the new element as an impurity in zinc carbonate ( calamine ) , and , for 100 years , Germany remained the only important producer of the metal . The metal was named after the Latin word for calamine , because it was found in this zinc compound . Stromeyer noted that some impure samples of calamine changed color when heated but pure calamine did not . He was persistent in studying these results and eventually isolated cadmium metal by roasting and reducing the sulfide . The potential for cadmium yellow as pigment was recognized in the 1840s , but the lack of cadmium limited this application . 
 Even though cadmium and its compounds are toxic in certain forms and concentrations , the British <unk> <unk> from 1907 states that cadmium iodide was used as a medication to treat " enlarged joints , <unk> glands , and <unk> " . 
 In 1907 , the International Astronomical Union defined the international <unk> in terms of a red cadmium spectral line ( 1 wavelength = <unk> @.@ <unk> <unk> ) . This was adopted by the 7th General Conference on <unk> and Measures in 1927 . In 1960 , the definitions of both the metre and <unk> were changed to use krypton . 
 After the industrial scale production of cadmium started in the 1930s and 1940s , the major application of cadmium was the coating of iron and steel to prevent corrosion ; in 1944 , 62 % and in 1956 , 59 % of the cadmium in the United States was used for plating . In 1956 , 24 % of the cadmium in the United States was used for a second application in red , orange and yellow pigments from sulfides and <unk> of cadmium . 
 The stabilizing effect of cadmium chemicals like the <unk> cadmium <unk> and cadmium <unk> on PVC led to an increased use of those compounds in the 1970s and 1980s . The demand for cadmium in pigments , coatings , stabilizers , and alloys declined as a result of environmental and health regulations in the 1980s and 1990s ; in 2006 , only 7 % of to total cadmium consumption was used for plating , and only 10 % was used for pigments . At the same time , these decreases in consumption were compensated by a growing demand for cadmium for nickel @-@ cadmium batteries , which accounted for 81 % of the cadmium consumption in the United States in 2006 . 
 
 = = Occurrence = = 
 
 Cadmium makes up about 0 @.@ 1 mg kg − 1 ( ppm ) of Earth 's crust . Typical background concentrations in other environmental media are : atmosphere < 5 <unk> m − 3 ; soil < 2 mg kg − 1 ; vegetation < 0 @.@ 5 mg kg − 1 ; freshwater < 1 <unk> L − 1 ; seawater < 50 <unk> L − 1 ; sediment < 2 mg kg − 1 . Compared with the more abundant 65 ppm zinc , cadmium is rare . No significant deposits of cadmium @-@ containing ores are known . <unk> ( CdS ) , the only cadmium mineral of importance , is nearly always associated with <unk> ( <unk> ) . This association is caused by <unk> similarity between zinc and cadmium , with no geological process likely to separate them . Thus , cadmium is produced mainly as a <unk> from mining , <unk> , and refining <unk> ores of zinc , and , to a lesser degree , lead and copper . Small amounts of cadmium , about 10 % of consumption , are produced from secondary sources , mainly from dust generated by recycling iron and steel scrap . Production in the United States began in 1907 , but not until after World War I did cadmium come into wide use . 
 <unk> cadmium can be found is the <unk> River basin in Siberia . 
 Rocks mined for phosphate fertilizers contain varying amounts of cadmium , resulting in a cadmium concentration of as much as 300 mg / kg in the fertilizers and a high cadmium content in agricultural soils . Coal can contain significant amounts of cadmium , which ends up mostly in <unk> dust . 
 
 = = Production = = 
 
 The British Geological Survey reports that in 2001 , China was the top producer of cadmium with almost one @-@ sixth of the world 's production , closely followed by South Korea and Japan . 
 Cadmium is a common impurity in zinc ores , and it is most often isolated during the production of zinc . Some zinc ores concentrates from <unk> zinc ores contain up to 1 @.@ 4 % of cadmium . In the 1970s , the output of cadmium was 6 @.@ 5 pounds per ton of zinc . Zinc sulfide ores are roasted in the presence of oxygen , converting the zinc sulfide to the oxide . Zinc metal is produced either by <unk> the oxide with carbon or by electrolysis in sulfuric acid . Cadmium is isolated from the zinc metal by vacuum distillation if the zinc is <unk> , or cadmium sulfate is precipitated from the electrolysis solution . 
 
 = = Applications = = 
 
 Cadmium is a common component of electric batteries , pigments , coatings , and electroplating . 
 
 = = = Batteries = = = 
 
 In 2009 , 86 % of cadmium was used in batteries , predominantly in <unk> nickel @-@ cadmium batteries . <unk> @-@ cadmium cells have a nominal cell potential of 1 @.@ 2 V. The cell consists of a positive nickel hydroxide <unk> and a negative cadmium <unk> plate separated by an alkaline electrolyte ( potassium hydroxide ) . The European Union put a limit on cadmium in electronics in 2004 of 0 @.@ 01 % , with some exceptions , and reduced the limit on cadmium content to 0 @.@ 002 % . 
 
 = = = <unk> = = = 
 
 Cadmium electroplating , consuming 6 % of the global production , is used in the aircraft industry reduce corrosion of steel components . This coating is <unk> by <unk> salts . A limitation of cadmium plating is hydrogen embrittlement of high @-@ strength <unk> from the electroplating process . Therefore , steel parts heat @-@ treated to tensile strength above 1300 MPa ( 200 <unk> ) should be coated by an alternative method ( such as special low @-@ embrittlement cadmium electroplating processes or physical vapor deposition ) . 
 <unk> embrittlement from cadmium @-@ plated tool residues resulted in banishment of those tools ( and the implementation of routine tool testing to detect cadmium contamination ) in the A @-@ 12 / SR @-@ 71 , U @-@ 2 , and subsequent aircraft programs that use <unk> . 
 
 = = = Nuclear fission = = = 
 
 Cadmium is used in the control rods of nuclear reactors , acting as a very effective " neutron poison " to control neutron flux in nuclear fission . When cadmium rods are inserted in the core of a nuclear reactor , cadmium absorbs neutrons preventing them from creating additional fission events , thus controlling the amount of reactivity . The pressurized water reactor designed by Westinghouse Electric Company uses an alloy consisting of 80 % silver , 15 % indium , and 5 % cadmium . 
 
 = = = Compounds = = = 
 
 Cadmium oxide was used in black and white television phosphors and in the blue and green phosphors of color television <unk> ray tubes . Cadmium sulfide ( CdS ) is used as a <unk> surface coating for <unk> drums . 
 Various cadmium salts are used in paint pigments , with CdS as a yellow pigment being the most common . Cadmium selenide is a red pigment , commonly called cadmium red . To painters who work with the pigment , cadmium provides the most brilliant and durable <unk> , <unk> , and reds — so much so that during production , these colors are significantly toned down before they are ground with oils and <unk> or blended into watercolors , <unk> , <unk> , and other paint and pigment <unk> . Because these pigments are potentially toxic , users should use a barrier cream on the hands to prevent absorption through the skin even though the amount of cadmium absorbed into the body through the skin is reported to be less than 1 % . 
 In PVC , cadmium was used as heat , light , and <unk> stabilizers . Currently , cadmium stabilizers have been completely replaced with barium @-@ zinc , calcium @-@ zinc and <unk> @-@ tin stabilizers . Cadmium is used in many kinds of <unk> and bearing alloys , because a low coefficient of friction and fatigue resistance . It is also found in some of the lowest @-@ melting alloys , such as Wood 's metal . 
 
 = = = Laboratory uses = = = 
 
 <unk> – cadmium lasers are a common source of blue @-@ ultraviolet laser light . They operate at either 325 or 422 nm in fluorescence <unk> and various laboratory experiments . Cadmium selenide quantum dots emit bright luminescence under <unk> <unk> ( He @-@ Cd laser , for example ) . The color of this luminescence can be green , yellow or red depending on the particle size . <unk> solutions of those particles are used for imaging of biological tissues and solutions with a fluorescence microscope . 
 Cadmium is a component of some compound <unk> , such as cadmium sulfide , cadmium selenide , and cadmium telluride , used for light detection and solar cells . <unk> is sensitive to infrared light and can be used as an infrared detector , motion detector , or switch in remote control devices . 
 In molecular biology , cadmium is used to block voltage @-@ dependent calcium channels from <unk> calcium ions , as well as in hypoxia research to stimulate <unk> @-@ dependent degradation of <unk> @-@ <unk> . 
 
 = = = Cadmium @-@ selective sensors = = = 
 
 Cadmium @-@ selective sensors based on the <unk> <unk> have been developed for imaging and sensing of cadmium in cells . 
 
 = = Biological role = = 
 
 Cadmium has no known function in higher organisms , but a cadmium @-@ dependent carbonic <unk> has been found in some marine diatoms . The diatoms live in environments with very low zinc concentrations and cadmium performs the function normally carried out by zinc in other <unk> . This was discovered with X @-@ ray absorption fluorescence spectroscopy ( <unk> ) . 
 The highest concentration of cadmium is absorbed in the <unk> of humans , and up to about 30 mg of cadmium is commonly inhaled throughout human childhood and adolescence . 
 Cadmium can be used to block calcium channels in chicken neurons . Analytical methods for the determination of cadmium in biological samples have been reviewed . 
 
 = = Environment = = 
 
 The <unk> of cadmium and its release to the environment has been the subject of review , as has the <unk> of cadmium in the environment . 
 Environmental concentrations can exceed adverse @-@ effect @-@ <unk> in cadmium @-@ polluted ecosystems ( e.g. in some parts of Europe ) and <unk> cadmium can accumulate in invertebrates , earthworms , <unk> , marine mammals , plants , and some algal species ; effects in animals include kidney disorders , <unk> of enzymes , disruption of calcium metabolism , and changes in cell membrane <unk> ; excess Cd uptake in plants can affect growth and metabolic processes such as <unk> and <unk> . 
 
 = = Safety = = 
 
 The <unk> aspects of cadmium toxicity have been reviewed . 
 The most dangerous form of occupational exposure to cadmium is inhalation of fine dust and fumes , or ingestion of highly soluble cadmium compounds . Inhalation of cadmium fumes can result initially in metal <unk> fever but may progress to chemical <unk> , pulmonary <unk> , and death . 
 Cadmium is also an environmental hazard . Human exposure is primarily from fossil fuel combustion , phosphate fertilizers , natural sources , iron and steel production , cement production and related activities , <unk> metals production , and municipal solid waste <unk> . Bread , root crops , and vegetables also contribute to the cadmium in modern populations . 
 There have been a few instances of general population poisoning as the result of long @-@ term exposure to cadmium in contaminated food and water , and research into an estrogen mimicry that may induce breast cancer is ongoing . In the decades leading up to World War II , mining operations contaminated the <unk> River in Japan with cadmium and traces of other toxic metals . As a consequence , cadmium accumulated in the rice crops along the riverbanks downstream of the mines . Some members of the local agricultural communities consumed the contaminated rice and developed itai @-@ itai disease and renal abnormalities , including <unk> and <unk> . 
 The victims of this poisoning were almost exclusively post @-@ <unk> women with low iron and other mineral body stores . Similar general population cadmium exposures in other parts of the world have not resulted in the same health problems because the populations maintained sufficient iron and other mineral levels . Thus , although cadmium is a major factor in the itai @-@ itai disease in Japan , most researchers have concluded that it was one of several factors . Cadmium is one of six substances banned by the European Union 's <unk> on <unk> <unk> ( <unk> ) directive , which <unk> hazardous substances in electrical and electronic equipment but allows for certain exemptions and <unk> from the scope of the law . The International Agency for Research on Cancer has classified cadmium and cadmium compounds as carcinogenic to humans . Although occupational exposure to cadmium is linked to lung and prostate cancer , there is still a substantial controversy about the <unk> of cadmium in low environmental exposure . Recent data from <unk> studies suggest that intake of cadmium through diet associates to higher risk of <unk> , breast and prostate cancer as well as to <unk> in humans . A recent study has demonstrated that <unk> tissue is characterized by higher levels of cadmium in current and former smoking females . 
 Cadmium exposure is a risk factor associated with a large number of illnesses including kidney disease , early <unk> , <unk> , and <unk> diseases . Although studies show a significant correlation between cadmium exposure and occurrence of disease in human populations , a necessary molecular mechanism has not been identified . One hypothesis holds that cadmium is an <unk> <unk> and some experimental studies have shown that it can interact with different <unk> signaling pathways . For example , cadmium can bind to the estrogen receptor alpha , and affect signal transduction along the estrogen and <unk> signaling pathways at low doses . 
 Tobacco smoking is the most important single source of cadmium exposure in the general population . An estimated 10 % of the cadmium content of a cigarette is inhaled through smoking . Absorption of cadmium through the lungs is more effective than through the gut , and as much as 50 % of the cadmium inhaled in cigarette smoke may be absorbed . On average , cadmium concentrations in the blood of smokers is 4 times 5 times greater and in the kidney , 2 – 3 times greater than non @-@ smokers . Despite the high cadmium content in cigarette smoke , there seems to be little exposure to cadmium from passive smoking . 
 In a non @-@ smoking population , food is the greatest source of exposure . High quantities of cadmium can be found in crustaceans , <unk> , <unk> , and algae products . However , grains , vegetables , and <unk> roots and <unk> are consumed in much greater quantity in the US , and are the source of the greatest dietary exposure . Most plants bio @-@ accumulate metal toxins like Cd , and when <unk> to form organic fertilizers yield a product which can often contain high amounts ( e.g. , over 0 @.@ 5 mg ) of metal toxins for every <unk> of <unk> . <unk> made from animal dung ( e.g. , cow dung ) or urban waste can contain similar amounts of Cd . The Cd added to the soil from fertilizers ( rock <unk> or organic fertilizers ) become bio @-@ available and toxic only if the soil <unk> is low ( i.e. , acidic soils ) . Zinc is chemically similar to cadmium and some evidence indicates the presence of <unk> ions reduces cadmium toxicity . 
 Zinc , <unk> , <unk> , and Fe ions , and <unk> with <unk> C are used to treat Cd intoxication , though it is not easily reversed . 
 
 = = = Regulations = = = 
 
 Because of the adverse effects of cadmium on the environment and human health , the supply and use of cadmium is restricted in Europe under the <unk> Regulation . 
 The <unk> Panel on <unk> in the Food Chain specifies that 2 @.@ 5 <unk> / kg body weight is a <unk> weekly intake for humans . The Joint <unk> / WHO Expert Committee on Food <unk> has declared 7 <unk> / kg <unk> to be the provisional <unk> weekly intake level . 
 The US Occupational Safety and Health Administration ( <unk> ) has set the permissible exposure limit ( <unk> ) for cadmium at a time @-@ weighted average ( TWA ) of 0 @.@ <unk> ppm . The National Institute for Occupational Safety and Health ( <unk> ) has not set a recommended exposure limit ( <unk> ) and has designated cadmium as a known human <unk> . The <unk> ( immediately dangerous to life and health ) level for cadmium is 9 mg / m3 . 
 
 = = = Product recalls = = = 
 
 In May 2006 , a sale of the seats from Arsenal F.C. ' s old stadium , Highbury in London , England was cancelled when the seats were discovered to contain trace amounts of cadmium . Reports of high levels of cadmium use in children 's jewelry in 2010 led to a US Consumer Product Safety Commission investigation . The U.S. <unk> issued specific recall notices for cadmium content in jewelry sold by Claire 's and Wal @-@ Mart stores . 
 In June 2010 , McDonald 's voluntarily recalled more than 12 million promotional " <unk> Forever After 3D " <unk> <unk> <unk> because of the cadmium levels in paint pigments on the <unk> . The glasses were manufactured by <unk> International , of <unk> , <unk> , USA . 
 
 