Beryllium
23.53
Beryllium is the chemical element with the symbol Be and atomic number 4.
A bivalent element, beryllium is found naturally only combined with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. The free element is a steel-gray, strong, lightweight brittle alkaline earth metal. It is primarily used as a hardening agent in alloys, notably beryllium copper. Structurally, beryllium's very low density (1.85 times that of water), high melting point (1278 °C), high temperature stability, and low coefficient of thermal expansion, make it in many ways an ideal aerospace material, and it has been used in rocket nozzles and is a significant component of planned space telescopes. Because of its relatively high transparency to X-rays and other ionizing radiation types, beryllium also has a number of uses as filters and windows for radiation and particle physics experiments.
Commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium produces a direct corrosive effect to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in susceptible persons.
Beryllium is a relatively rare element in both the Earth and the universe. The element is not known to be necessary or useful for either plant or animal life.
History
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Beryllium was discovered by Louis-Nicolas Vauquelin in 1798 as a component of beryl and in emeralds. Friedrich Wöhler[5] and Antoine Bussy independently isolated the metal in 1828 by reacting potassium and beryllium chloride. Beryllium's chemical similarity to aluminum was probably why beryllium was missed in previous searches.[6]
[edit] Etymology
The name beryllium comes (via Latin: Beryllus and French: Béryl) from the Greek βήρυλλος, bērullos, beryl, from Prakrit veruliya (वॆरुलिय), from Pāli veḷuriya (वेलुरिय); veḷiru (भेलिरु) or, viḷar (भिलर्), "to become pale," in reference to the pale semiprecious gemstone beryl.[7] The original source of the word "Beryllium" is the Sanskrit word: वैडूर्य vaidurya-, which is of Dravidian origin and could be derived from the name of the modern city of Belur.[8] For about 160 years, beryllium was also known as glucinum or glucinium (with the accompanying chemical symbol "Gl"[9]), the name coming from the Greek word for sweet: γλυκυς, due to the sweet taste of its salts.
Characteristics
Physical
Beryllium has one of the highest melting points of the light metals. It has exceptional elastic rigidity (Young's modulus 287 GPa). The modulus of elasticity of beryllium is approximately 50% greater than that of steel. The combination of this modulus plus beryllium's relatively low density gives it an unusually fast sound conduction speed at standard conditions (about 12.9 km/s). Other significant properties are the high values for specific heat (1925 J·kg−1·K−1) and thermal conductivity (216 W·m−1·K−1), which make beryllium the metal with the best heat dissipation characteristics per unit weight. In combination with the relatively low coefficient of linear thermal expansion (11.4 × 10−6 K−1), these characteristics ensure that beryllium demonstrates a unique degree of dimensional stability under conditions of thermal loading.[10]
At standard temperature and pressures beryllium resists oxidation when exposed to air (its ability to scratch glass is due to the formation of a thin layer of the hard oxide BeO). It resists corrosion by concentrated nitric acid.[11]
Nuclear
Beryllium has a large scattering cross section for high-energy neutrons, thus effectively slowing the neutrons to the thermal energy range where the cross section is low (0.008 barn). The predominant beryllium isotope 9Be also undergoes a (n,2n) neutron reaction to 8Be, that is beryllium is a neutron multiplier, releasing more neutrons than it absorbs. Beryllium is highly permeable to X-rays, and neutrons are liberated when it is hit by alpha particles.[10]
Isotopes
Of beryllium's isotopes, only 9Be is stable and the others are relatively unstable or rare. It is thus a mononuclidic element.
Cosmogenic 10Be is produced in the atmosphere by cosmic ray spallation of oxygen and nitrogen. Cosmogenic 10Be accumulates at the soil surface, where its relatively long half-life (1.36 million years) permits a long residence time before decaying to 10B. Thus, 10Be and its daughter products have been used to examine soil erosion, soil formation from regolith, the development of lateritic soils, as well as variations in solar activity and the age of ice cores. Solar activity is inversely correlated with 10Be production, because solar wind decreases flux of galactic cosmic rays which reach Earth.
Nuclear explosions also form 10Be by a reaction of fast neutrons with 13C in the carbon dioxide in air. This is one of the historical indicators of past activity at nuclear test sites.[12]
The fact that 7Be and 8Be have very short half-lives has profound cosmological consequences. Elements heavier than beryllium could not be produced by nuclear fusion in the Big Bang. This is due to the lack of sufficient time during the Big Bang nucleosynthesis phase to produce carbon by fusion of 4He nuclei and the very low concentrations of available 8Be. Astronomer Fred Hoyle first showed that the energy levels of 8Be and 12C allow carbon production by the triple-alpha process in helium-fueled stars where more synthetic time is available, thus making life possible from the supernova "ash" from these stars. (See also Big Bang nucleosynthesis).[13]
7Be decays by electron capture, therefore its decay rate is dependent upon its electron configuration – a rare occurrence in nuclear decay.[14]
The shortest-lived known isotope of beryllium is 13Be which decays through neutron emission. It has a half-life of 2.7 × 10−21 second. 6Be is also very short-lived with a half-life of 5.0 × 10−21 second.[11]
The exotic isotopes 11Be and 14Be are known to exhibit a nuclear halo.[15]
Chemical
Beryllium has the electronic configuration [He] 2s2. In its chemistry beryllium exhibits the +2 oxidation state and the only evidence of lower valence of beryllium is in the solubility of the metal in BeCl2.[16] The small atomic radius ensures that the Be2+ ion would be highly polarizing leading to significant covalent character in beryllium's bonding.[17] Beryllium is 4 coordinate in complexes e.g. [Be(H2O)4]2+ and tetrahaloberyllates, BeX2−4. This characteristic is used in analytical techniques using EDTA as a ligand which preferentially forms octahedral complexes – thus absorbing other cations such as Al3+ which might interfere, for example in the solvent extraction of a complex formed between Be2+ and acetylacetone.[18]
Beryllium metal sits above aluminium in the electrochemical series and would be expected to be a reactive metal, however it is passivated by an oxide layer and does not react with air or water even at red heat.[17] Once ignited however beryllium burns brilliantly forming a mixture of beryllium oxide and beryllium nitride.[17] Beryllium dissolves readily in non-oxidizing acids, such as HCl and H2SO4, but not in nitric as this forms the oxide and this behavior is similar to that of aluminium metal. Beryllium, again similarly to aluminium, dissolves in warm alkali to form the beryllate anion, Be(OH)2−4, and hydrogen gas. The solutions of salts, e.g. beryllium sulfate and beryllium nitrate are acidic because of hydrolysis of the [Be(H2O)4]2+ ion; for example
- [Be(H2O)4]2+ + H2O
[Be(H2O)3(OH)]+ + H3O+
Compounds
Beryllium forms binary compounds with many non-metals. Beryllium hydride is an amorphous white solid believed to be built from corner-sharing {BeH4} tetrahedra.[19]
All four anhydrous halides are known. BeF2 has a silica-like structure with corner-shared BeF4 tetrahedra. BeCl2 and BeBr2 have chain structures with edge-shared tetrahedra. They all have linear monomeric gas phase forms.[17]
Beryllium oxide, BeO, is a white, high-melting-point solid, which has the wurtzite structure with a thermal conductivity as high as some metals. BeO is amphoteric. Beryllium hydroxide, Be(OH)2 has low solubility in water and is amphoteric. Salts of beryllium can be produced by reacting Be(OH)2 with acid.[17]
Beryllium sulfide, selenide and telluride all have the zincblende structure.[16]
Beryllium nitride, Be3N2 is a high-melting-point compound which is readily hydrolyzed. Beryllium azide, BeN6 is known and beryllium phosphide, Be3P2 has a similar structure to Be3N2.[16]
A number of beryllium borides are known, Be5B, Be4B, Be2B, BeB2, BeB6, BeB12.[16]
Beryllium carbide, Be2C, is a high melting, brick red compound that reacts with water to give methane.[16] No beryllium silicide has been identified.[17]
Basic beryllium nitrate and basic beryllium acetate have similar tetrahedral structures with four beryllium atoms coordinated to a central oxide ion.[16]
Occurrence
The beryllium concentration of the Earth's surface rocks is ca. 4–6 ppm. Beryllium is a constituent of about 100 out of about 4000 known minerals, the most important of which are bertrandite (Be4Si2O7(OH)2), beryl (Al2Be3Si6O18), chrysoberyl (Al2BeO4), and phenakite (Be2SiO4). Precious forms of beryl are aquamarine, bixbite and emerald.[10]
Production
Because of its high affinity for oxygen at elevated temperatures and its ability to reduce water when its oxide film is removed, the extraction of beryllium from its compounds is very difficult. Although electrolysis of a fused mixture of beryllium and sodium fluorides was used to isolate the element in the nineteenth century, the metal's high melting point makes this process more energy intensive than the corresponding production of alkali metals. Early in the twentieth century, the production of beryllium by the thermal decomposition of beryllium iodide was investigated following the success of a similar process for the production of zirconium, but this proved to be uneconomic for volume production.[20]
Beryllium metal did not become readily available until 1957. Currently, most is produced by reducing beryllium fluoride with magnesium metal. The price on the US market for vacuum-cast beryllium ingots was 338 US$ per pound ($745/kg) in 2001.[21]
- BeF2 + Mg → MgF2 + Be
Applications
Radiation windows
Because of its low atomic number and very low absorption for X-rays, the oldest and still one of the most important applications of beryllium is in radiation windows for X-ray tubes. Extreme demands are placed on purity and cleanliness of Be to avoid artifacts in the X-ray images. Thin beryllium foils are used as radiation windows for X-ray detectors, and the extremely low absorption minimizes the heating effects caused by high intensity, low energy X-rays typical of synchrotron radiation. Vacuum-tight windows and beam-tubes for radiation experiments on synchrotrons are manufactured exclusively from beryllium. In scientific setups for various X-ray emission studies (e.g., energy-dispersive X-ray spectroscopy) the sample holder is usually made of beryllium because its emitted X-rays have much lower energies (~100 eV) than X-rays from most studied materials.[10]
Because of its low atomic number beryllium is almost transparent to energetic particles. Therefore it is used to build the beam pipe around the collision region in collider particle physics experiments. Notably all four main detector experiments at the Large Hadron Collider accelerator (ALICE, ATLAS, CMS, LHCb) use a beryllium beam-pipe.
Also many high-energy particle physics collision experiments such as the Large Hadron Collider, the Tevatron, the SLAC and others contain beam pipes made of beryllium. Beryllium's low density allows collision products to reach the surrounding detectors without significant interaction, its stiffness allows a powerful vacuum to be produced within the pipe to minimize interaction with gases, its thermal stability allows it to function correctly at temperatures of only a few degrees above absolute zero, and its diamagnetic nature keeps it from interfering with the complex multipole magnet systems used to steer and focus the particle beams.[22]
Mechanical
Because of its stiffness, light weight, and dimensional stability over a wide temperature range, beryllium metal is used for lightweight structural components in the defense and aerospace industries in high-speed aircraft, missiles, space vehicles and communication satellites. Several liquid-fuel rockets use nozzles of pure beryllium.[23][24]
Beryllium is used as an alloying agent in the production of beryllium copper, which contains up to 2.5% beryllium. Beryllium-copper alloys are used in many applications because of their combination of high electrical and thermal conductivity, high strength and hardness, nonmagnetic properties, along with good corrosion and fatigue resistance. These applications include the making of spot welding electrodes, springs, non-sparking tools and electrical contacts.
Beryllium was also used in Jason pistols which were used to strip paint from the hulls of ships. In this case, beryllium was alloyed to copper and used as a hardening agent.[25]
The excellent elastic rigidity of beryllium has led to its extensive use in precision instrumentation, e.g. in gyroscope inertial guidance systems, and in support structures for optical systems.[10]
Beryllium mirrors are a field of particular interest. Large-area mirrors, frequently with a honeycomb support structure, are used, for example, in meteorological satellites where low weight and long-term dimensional stability are critical. Smaller beryllium mirrors are used in optical guidance systems and in fire-control systems, e.g. in the German Leopard 1 and Leopard 2 main battle tanks. In these systems, very rapid movement of the mirror is required which again dictates low mass and high rigidity. Usually the beryllium mirror is coated with hard electroless nickel plating which can be more easily polished to a finer optical finish than beryllium. In some applications, though, the beryllium blank is polished without any coating. This is particularly applicable to cryogenic operation where thermal expansion mismatch can cause the coating to buckle.[10]
The James Webb Space Telescope[26] will have 18 hexagonal beryllium sections for its mirrors. Because JWST will face a temperature of 33 degrees K, the mirror is made of beryllium, capable of handling extreme cold better than glass. Beryllium contracts and deforms less than glass—and remains more uniform—in such temperatures.[27] For the same reason, the optics of the Spitzer Space Telescope are entirely built of beryllium metal.[28]
An earlier major application of beryllium was in brakes for military aircraft because of its hardness, high melting point and exceptional heat dissipation. Environmental considerations have led to substitution by other materials.[10]
Cross-rolled beryllium sheet is an excellent structural support for printed circuit boards in surface-mount technology. In critical electronic applications, beryllium is both a structural support and heat sink. The application also requires a coefficient of thermal expansion that is well matched to the alumina and polyimide-glass substrates. The beryllium-beryllium oxide composite "E-Materials" have been specially designed for these electronic applications and have the additional advantage that the thermal expansion coefficient can be tailored to match diverse substrate materials.[10]
Magnetic
Beryllium is non-magnetic. Therefore, beryllium-based tools are used by military naval EOD-personnel when working on or around naval mines, as these often have fuzes that detonate on direct magnetic contact or when influenced by a magnetic field.[29] They are also found in maintenance and construction materials near MRI scanners. Magnetic tools would be pulled by the scanner's strong magnetic field. Apart from being difficult to remove once magnetic items are stuck in the scanner, the missile-effect can have dangerous consequences.[30] In the telecommunications industry, tools made of beryllium are used to tune the highly magnetic klystrons used for high power microwave applications.
Nuclear
Beryllium is used in nuclear weapon designs as the outer layer of the pit of the primary stage, surrounding the fissile material. It is a good pusher for implosion, and a very good neutron reflector, as in beryllium moderated reactors.[31]
Beryllium is sometimes used in neutron sources, in which the beryllium is mixed with an alpha emitter such as 210Po, 226Ra, 239Pu or 241Am. The "Urchin" neutron initiator in early nuclear weapons used beryllium-polonium combination.[31]
Beryllium is used in the Joint European Torus fusion research facility and will be used in ITER, to condition the plasma facing components.[32] Beryllium has also been proposed as a cladding material for nuclear fuel, due to its combination of mechanical, chemical, and nuclear properties.[10]
Acoustics
Beryllium's characteristics (low weight and high rigidity) make it useful as a material for high-frequency speaker drivers. Until recently, most beryllium tweeters used an alloy of beryllium and other metals due to beryllium's high cost and difficulty to form. These challenges, coupled with the high performance of beryllium, caused some manufacturers to falsely claim using pure beryllium.[33] Some high-end audio companies manufacture pure beryllium tweeters or speakers using these tweeters. Because beryllium is many times more expensive than titanium, hard to shape due to its brittleness, and toxic if mishandled, these tweeters are limited to high-end and public address applications.[34][35][36]
Electronic
Beryllium is a p-type dopant in III-V compound semiconductors. It is widely used in materials such as GaAs, AlGaAs, InGaAs, and InAlAs grown by molecular beam epitaxy (MBE).[37]
Beryllium oxide is useful for many applications that require the combined properties of an electrical insulator and an excellent heat conductor, with high strength and hardness, and a very high melting point. Beryllium oxide is frequently used as an insulator base plate in high-power transistors in RF transmitters for telecommunications. Beryllium oxide is also being studied for use in increasing the thermal conductivity of uranium dioxide nuclear fuel pellets.[38]
Beryllium compounds were used in fluorescent lighting tubes, but this use was discontinued because of berylliosis in the workers manufacturing the tubes.[39]
Toxicity
The toxicity of beryllium depends upon the duration, intensity and frequency of exposure (features of dose), as well as the form of beryllium and the route of exposure (i.e. inhalation, dermal, ingestion). According to the International Agency for Research on Cancer (IARC), beryllium and beryllium compounds are Category 1 carcinogens; they are carcinogenic to both animals and humans.[40] Chronic berylliosis is a pulmonary and systemic granulomatous disease caused by exposure to beryllium. Acute beryllium disease in the form of chemical pneumonitis was first reported in Europe in 1933 and in the United States in 1943. Cases of chronic berylliosis were first described in 1946 among workers in plants manufacturing fluorescent lamps in Massachusetts. Chronic berylliosis resembles sarcoidosis in many respects, and the differential diagnosis is often difficult. It occasionally killed early workers in nuclear weapons design, such as Herbert Anderson.[41]
Although the use of beryllium compounds in fluorescent lighting tubes was discontinued in 1949, potential for exposure to beryllium exists in the nuclear and aerospace industries and in the refining of beryllium metal and melting of beryllium-containing alloys, the manufacturing of electronic devices, and the handling of other beryllium-containing material.
Early researchers tasted beryllium and its various compounds for sweetness in order to verify its presence. Modern diagnostic equipment no longer necessitates this highly risky procedure and no attempt should be made to ingest this highly toxic substance. Beryllium and its compounds should be handled with great care and special precautions must be taken when carrying out any activity which could result in the release of beryllium dust (lung cancer is a possible result of prolonged exposure to beryllium laden dust).
This substance can be handled safely if certain procedures are followed. No attempt should be made to work with beryllium before familiarization with correct handling procedures.
A successful test for beryllium in air and on surfaces has been recently developed and published as an international voluntary consensus standard (ASTM D7202; www.astm.org). The procedure uses dilute ammonium bifluoride for dissolution and fluorescence detection with beryllium bound to sulfonated hydroxybenzoquinoline, allowing detection up to 100 times lower than the recommended limit for beryllium concentration in the workplace. Fluorescence increases with increasing beryllium concentration. The new procedure has been successfully tested on a variety of surfaces and is effective for the dissolution and ultratrace detection of refractory beryllium oxide and siliceous beryllium (ASTM D7458).[42]
Inhalation
Beryllium is harmful if inhaled and the effects depend on the duration, intensity, and frequency of exposure. If beryllium concentrations in air are high enough (greater than 100 µg/m3), an acute condition can result, called acute beryllium disease, which resembles pneumonia. Occupational and community air standards are effective in preventing most acute lung damage. Long-term beryllium exposure can increase the risk of developing lung cancer. The more common serious health problem from beryllium today is chronic beryllium disease (CBD), discussed below. It continues to occur in industries as diverse as metal recycling, dental laboratories, alloy manufacturing, nuclear weapons production and metal machine shops that work with alloys containing small amounts of beryllium. A 2008 report from the United States National Research Council said that worker exposure to beryllium should be kept "at the lowest feasible level," as the agency's research could not establish any safe level of exposure.[43]
Acute beryllium disease
Overexposure to beryllium can cause inflammation of the upper and/or lower respiratory tracts. The symptoms of acute beryllium disease are non-specific, resembling other inhalational injuries, viral infections, or pneumonia[44]. Upper respiratory findings include nasopharyngitis and tracheobronchitis. Symptoms may include irritation of the nares and pharynx, epistaxis, cough, and a metallic taste. Nasopharyngitis can progress to formation of nasal fissures, ulcerations, or perforation. Therapy is supportive and includes removal from further beryllium exposure. Acute beryllium pneumonitis produces severe cough (occasionally with blood-streaked sputum), chest pain or burning, and shortness of breath[44]. The patient is usually ill-appearing, and present with hypoxemia, cyanosis, tachycardia, and shallow rapid breathing. Systemic symptoms include fever (usually low-grade), malaise, and anorexia. The chest X-ray can reveal diffuse, bilateral alveolar infiltrates. There is no specific diagnostic test for acute beryllium disease. Biopsy of the lungs reveals a nonspecific granulomatous inflammation. Treatment is supportive, including oxygen supplementation as needed, and removal from further beryllium exposure. Corticosteroids are sometimes tried, but there are no good controlled studies reported. The signs and symptoms of acute beryllium pneumonitis usually resolve over several weeks to months, but it may be fatal, and about 15-20% of cases may progress to CBD[45].
Chronic beryllium disease (CBD)
The average rate of sensitization to beryllium ranges from 1-5%, depending upon exposure details[46][47]. Sensitization is not an illness, but some of these individuals, if inhaling sufficient quantities of beryllium dust in the micrometer-size range, may have an inflammatory reaction that principally targets the respiratory system and skin. This condition is called chronic beryllium disease (CBD), and can occur within a few months or many years (average 10 years in some series[48]) after exposure to higher-than-normal levels of beryllium (greater than 0.2 µg/m3). This disease causes fatigue, weakness, night sweats and can cause difficulty in breathing and a persistent dry cough. It can result in anorexia, weight loss, and may also lead to right-side heart enlargement and heart disease in advanced cases. Typically, CBD has an insidious onset and runs an indolent course. Some people who are sensitized to beryllium may not have symptoms, and just being sensitized is not a recognized health effect. CBD occurs when the body's immune system recognizes beryllium particles as foreign material and mounts an immune system attack against the particles. Because these particles are typically inhaled into the lungs, the lungs become the major site where the immune system responds. The lung sacs become inflamed and fill with large numbers of white blood cells that accumulate wherever beryllium particles are found. These cells form balls around the beryllium particles called "granulomas." When enough of these develop, they interfere with the normal function of the organ. Over time, the lungs become stiff and lose their ability to help transfer oxygen from the air into the bloodstream. Early on in the disease, there may be a mild obstructive ventilatory defect. In advanced cases, there is a restrictive defect and reduced diffusion capacity. Patients with CBD develop difficulty inhaling and exhaling sufficient amounts of air, and the amount of oxygen in their bloodstreams falls. Most of the clinical features of CBD are indistinguishable from thoracic involvement with sarcoidosis. The chest radiograph usually reveals bilateral, mid- and upper-lobe predominant reticulonodular infiltrates, as well as hilar and mediastinal adenopathy. For suspected cases of CBD, fiber-optic bronchoscopy with bronchoalveolar lavage (BAL) is indicated. The BAL fluid should undergo beryllium lymphocyte proliferation testing (BAL BeLPT), the "gold standard" for the diagnosis. The measurement of beryllium in urine or tissue does not establish the diagnosis, and there are technical and interpretive problems with these tests. Blood BeLPT detects approximately 70-90% of CBD cases. CBD is treatable, but not curable with traditional drugs and medicine. Removal from further beryllium exposure is advisable. Treatment includes supplemental oxygen and corticosteroids (such as prednisone) to lower the body's overreaction to beryllium. If therapy with corticosteroid is successful, treatment is usually continued lifelong because of disease relapse after steroid cessation[44]. In general, CBD worsens without treatment. Prognosis is best for those diagnosed at an earlier stage. Overall mortality rates are 5-38%[49]. The general population is unlikely to develop acute or chronic beryllium disease because ambient air levels of beryllium are normally very low (<0.03>3).[50]
Ingestion
Swallowing beryllium has not been reported to cause effects in humans because very little beryllium is absorbed from the stomach and intestines. Harmful effects have sometimes been seen in animals ingesting beryllium.[51]
Dermatological effects
Beryllium can cause local irritation and contact dermatitis. Beryllium contact with skin that has been scraped or cut may cause rashes, ulcers, or bumps under the skin called granulomas.[52] Beryllium dust or powder can irritate the eyes, producing itching, burning, or conjunctivitis.
Effects on children
There are no studies on the health effects of children exposed to beryllium, although individual cases of CBD have been reported in children of beryllium workers from the 1940s. It is unknown whether children differ from adults in their susceptibility to beryllium. It is unclear whether beryllium is teratogenic.[53]
Detection in the body
Beryllium can be measured in the urine and blood. The amount of beryllium in blood or urine may not indicate time or quantity of exposure. Beryllium levels can also be measured in lung and skin samples. While such measurements may help establish that exposure has occurred, other tests are used to determine if that exposure has resulted in health effects. A blood test, the blood beryllium lymphocyte proliferation test (BeLPT), identifies beryllium sensitization and has predictive value for CBD. The BeLPT has become the standard test for detecting beryllium sensitization and CBD in individuals who are suspected of having CBD and to help distinguish it from similar conditions such as sarcoidosis. It is also the main test used in industry health programs to monitor whether disease is occurring among current and former workers who have been exposed to beryllium on the job. The test can detect disease that is at an early stage, or can detect disease at more advanced stages of illness as well. The BeLPT can also be performed using cells obtained from a person's lung by a procedure called "bronchoscopy".[54]
Industrial release and occupational exposure limits
Typical levels of beryllium that industries may release into the air are of the order of 0.01 µg/m3, averaged over a 30-day period, or 2 µg/m3 of workroom air for an 8-hour work shift. Compliance with the current U.S. Occupational Safety and Health Administration (OSHA) permissible exposure limit for beryllium of 2 µg/m3 has been determined to be inadequate to protect workers from developing beryllium sensitization and CBD. The American Conference of Governmental Industrial Hygienists (ACGIH), which is an independent organization of experts in the field of occupational health, has proposed a threshold limit value (TLV) of 0.05 µg/m3 in a 2006 Notice of Intended Change (NIC). This TLV is 40 times lower than the current OSHA permissible exposure limit, reflecting the ACGIH analysis of best available peer-reviewed research data concerning how little airborne beryllium is required to cause sensitization and CBD. Because it can be difficult to control industrial exposures to beryllium, it is advisable to use any methods possible to reduce airborne and surface contamination by beryllium, to minimize the use of beryllium and beryllium-containing alloys whenever possible, and to educate people about the potential hazards if they are likely to encounter beryllium dust or fumes.[55]
On 29 January 2009, the Los Alamos National Laboratory announced it was notifying nearly 2,000 current and former employees and visitors that they may have been exposed to beryllium in the lab and may be at risk of disease. Concern over possible exposure to the material was first raised in November 2008, when a box containing beryllium was received at the laboratory's short-term storage facility.[56]
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