AskDefine | Define asbestos

Dictionary Definition

asbestos n : a fibrous amphibole; used for making fireproof articles; inhaling fibers can cause asbestosis or lung cancer

User Contributed Dictionary



From ἄσβεστος from ἀ- + σβέννυμι.


  • a UK /ˈæs.bɛs.tɒs/ /"

Extensive Definition

Asbestos is a group of minerals with long, thin fibrous crystals. The word "asbestos" is derived from a Greek adjective meaning inextinguishable. The Greeks termed asbestos the "miracle mineral" because of its soft and pliant properties, as well as its ability to withstand heat.
Asbestos became increasingly popular among manufacturers and builders in the late 19th century due to its resistance to heat, electricity and chemical damage, its sound absorption and tensile strength. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. Asbestos is used in brake shoes and gaskets for its heat resistance, and in the past was used on electric oven and hotplate wiring for its electrical insulation at elevated temperature, and in buildings for its flame-retardant and insulating properties, tensile strength, flexibility, and resistance to chemicals.
Unfortunately, this "miracle material" is now known to be highly toxic. The inhalation of asbestos fibers can cause serious illnesses, including mesothelioma and asbestosis. Since the mid 1980s, many uses of asbestos have been banned in many countries.

Types and associated fibres

Six minerals are defined as "asbestos" including: chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite.


Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks which are common throughout the world. Chrysotile fibers are curly as opposed to fibers from amosite, crocidolite, tremolite, actinolite, and anthophyllite which are needlelike. Chrysotile, along with other types of asbestos, has been banned in dozens of countries and is only allowed in the United States and Europe in very limited circumstances. Chrysotile has been used more than any other type and accounts for about 95% of the asbestos found in buildings in America. Applications where chrysotile might be used include the use of joint compound. It is more flexible than amphibole types of asbestos; it can be spun and woven into fabric. The most common use is within corrugated asbestos cement roof sheets typically used for outbuildings, warehouses and garages. It is also found as flat sheets used for ceilings and sometimes for walls. Numerous other items have been made containing chrysotile including brake linings, cloth behind fuses (for fire protection), pipe insulation, in floor tiles and in rope seals to boilers.


Amosite, CAS No. 12172-73-5, is a trade name for the amphiboles belonging to the Cummingtonite - Grunerite solid solution series, commonly from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for amosite is Fe7Si8O22(OH)2. It is found most frequently as a fire retardant in thermal insulation products and ceiling tiles.

Other materials

Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca2Mg5Si8O22(OH)2; actinolite asbestos (or smaragdite), CAS No. 77536-66-4, Ca2(Mg, Fe)5(Si8O22)(OH)2; and anthophyllite asbestos, CAS No. 77536-67-5, (Mg, Fe)7Si8O22(OH)2; are less commonly used industrially but can still be found in a variety of construction materials and insulation materials and have been reported in the past to occur in a few consumer products.
Other natural and not currently regulated asbestiform minerals, such as richterite, Na(CaNa)(Mg, Fe++)5(Si8O22)(OH)2, and winchite, (CaNa)Mg4(Al, Fe3+)(Si8O22)(OH)2, may be found as a contaminant in products such as the vermiculite containing zonolite insulation manufactured by W.R. Grace and Company. These minerals are thought to be no less harmful than tremolite, amosite, or crocidolite, but since they are not regulated, they are referred to as "asbestiform" rather than asbestos although may still be related to diseases and hazardous.

Production trends

In 2005, 2.2 million tons of asbestos were mined worldwide. Russia was the largest producer with about 40% world share followed by China and Kazakhstan.


Historic usage

Asbestos was named by the ancient Greeks who also recognized certain hazards of the material. The Greek geographer Strabo and the Roman naturalist Pliny the Elder noted that the material damaged lungs of slaves who wove it into cloth. Charlemagne, the first Holy Roman Emperor, is said to have had a tablecloth made of asbestos.
Wealthy Persians, who bought asbestos imported over the Hindu Kush, amazed guests by cleaning the cloth by simply exposing it to fire. According to Biruni in his book of Gems, any cloths made of asbestos (, āzarshast or , āzarshab) were called () shastakeh. Some of the Persians believed the fiber was fur from an animal (named samandar, ) that lived in fire and died when exposed to water.
Some archeologists believe that ancients made shrouds of asbestos, wherein they burned the bodies of their kings, in order to preserve only their ashes, and prevent their being mixed with those of wood or other combustible materials commonly used in funeral pyres. Others assert that the ancients used asbestos to make perpetual wicks for sepulchral or other lamps. By the mid 20th century uses included fire retardant coatings, concrete, bricks, pipes and fireplace cement, heat, fire, and acid resistant gaskets, pipe insulation, ceiling insulation, fireproof drywall, flooring, roofing, lawn furniture, and drywall joint compound. Thousands of metric tons of asbestos were used in World War II ships to wrap the pipes, line the boilers, and cover engine and turbine parts. There were approximately 4.3 million shipyard workers in the United States during WWII; for every thousand workers about 14 died of mesothelioma and an unknown number died from asbestosis.
The first documented death related to asbestos was in 1906. By the 1930s, England regulated ventilation and made asbestosis an excusable work related disease, about ten years sooner than the U.S. The term Mesothelioma was not used in medical literature until 1931, and was not associated with asbestos until sometime in the 1940s.

Specific products

Serpentine group

Serpentine minerals have a sheet or layered structure. Chrysolite is the only asbestos mineral in the serpentine group. In the United States, chrysotile has been the most commonly used type of asbestos. According to the U.S. EPA Asbestos Building Inspectors Manual, chrysotile accounts for approximately 95% of asbestos found in buildings in the United States. Chrysotile is often present in a wide variety of materials, including:
  • joint compound
  • mud and texture coats
  • vinyl floor tiles, sheeting, adhesives
  • roofing tars, felts, siding, and shingles
  • "transite" panels, siding, countertops, and pipes
  • fireproofing
  • caulk
  • gaskets
  • brake pads and shoes
  • clutch plates
  • stage curtains
  • fire blankets
  • interior fire doors
  • fireproof clothing for firefighters
  • thermal pipe insulation
In the European Union and Australia it has recently been banned as a potential health hazard and is not used at all. Japan is moving in the same direction, but more slowly. Revelations that hundreds of workers had died in Japan over the previous few decades from diseases related to asbestos sparked a scandal in mid-2005. Tokyo had, in 1971, ordered companies handling asbestos to install ventilators and check health on a regular basis; however, the Japanese government did not ban crocidolite and amosite until 1995, and a full-fledged ban on asbestos was implemented in October 2004. Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by the polymeric molecules lining up parallel with each other and forming oriented crystal lattices. These crystals thus have three cleavage planes, just as other minerals and gemstones have. But in their case, there are two cleavage planes that are much weaker than the third direction. When sufficient force is applied, they tend to break along their weakest directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring and one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers.
As asbestos fibers get smaller and lighter, they more easily become airborne and human respiratory exposures can result. Fibers will eventually settle but may be re-suspended by air currents or other movement.
Friability of a product containing asbestos means that it is so soft and weak in structure that it can be broken with simple finger crushing pressure. Friable materials are of the most initial concern due to their ease of damage. The forces or conditions of usage that come into intimate contact with most non-friable materials containing asbestos are substantially higher than finger pressure.

Environmental asbestos

Asbestos can be found naturally in the air outdoors and in some drinkable water, including water from natural sources. Studies have shown that members of general (non-occupationally exposed) population have tens of thousands to hundreds of thousands of asbestos fibers in each gram of dry lung tissue, which translates into millions of fibers and tens of thousands of asbestos bodies in every person's lungs.
Asbestos from natural geologic deposits is known as "Naturally Occurring Asbestos" (NOA). Health risks associated with exposure to NOA are not yet fully understood, and current US federal regulations do not address exposure from NOA. Many populated areas are in proximity to shallow, natural deposits which occur in 50 of 58 California counties and in 19 other U.S. states. In one study, data was collected from 3,000 mesothelioma patients in California and 890 men with prostate cancer, a malignancy not known to be related to asbestos. The study found a correlation between the incidence of mesotheliomas and the distance a patient lived from known deposits of rock likely to include asbestos, the correlation was not present when the incidence of prostate cancer was compared with the same distances. According to the study, risk of mesothelioma declined by 6 percent for every 10 kilometers that an individual had lived from a likely asbestos source.
Portions of El Dorado County, California are known to contain natural asbestos formations near the surface.
Large portions of Fairfax County, Virginia were also found to be underlain with tremolite. The county monitored air quality at construction sites, controlled soil taken from affected areas, and required freshly developed sites to lay of clean, stable material over the ground..
Early concern in the modern era on the health effects of asbestos exposure can be found in several sources. Among the earliest were reports in Britain. The annual reports of the Chief Inspector of Factories reported as early as 1898 that asbestos had 'easily demonstrated' health risks
At about the same time, what was probably the first study of mortality among asbestos workers was reported in France . While the study describes the cause of death as chalicosis, a generalized pneumoconiosis, the circumstances of the employment of the fifty workers whose death prompted the study suggest that the root cause was asbestos or mixed asbestos-cotton dust exposure.

1900s - 1910s

Further awareness of asbestos-related diseases can be found in the early 1900s, when London doctor H. Montague Murray conducted a post mortem exam on a young asbestos factory worker who died in 1899. Dr. Murray gave testimony on this death in connection with an industrial disease compensation hearing. The post-mortem confirmed the presence of asbestos in the lung tissue, prompting Dr. Murray to express as an expert opinion his belief that the inhalation of asbestos dust had at least contributed to, if not actually caused, the death of the worker.
The record in the United States was similar. Early observations were largely anecdotal in nature and did not definitively link the occupation with the disease, followed by more compelling and larger studies that strengthened the association. One such study, published in 1918, noted:
All of these processes unquestionably involve a considerable dust hazard, but the hygienic aspects of the industry have not been reported upon. It may be said, in conclusion, that in the practice of American and Canadian life insurance companies asbestos workers are generally declined on account of the assumed health-injurious conditions of the industry .

1920s and 1930s

Widespread recognition of the occupational risks of asbestos in Britain was reported in 1924 by a Dr. Cooke, a pathologist, who introduced a case description of a 33-year old female asbestos worker with the following: 'Medical men in areas where asbestos is manufactured have long suspected the dust to be the cause of chronic bronchitis and fibrosis...." Dr. Cooke then went on to report on a case in 1927 involving a 33-year old male worker who was the only survivor out of ten workers in an asbestos carding room. In the report he named the disease "asbestosis."
Dr. Cooke's second case report was followed, in the late 1920s, by a large public health investigation (now known as the Merewether report after one of its two authors) that examined some 360 asbestos-textile workers (reported to be about 15% of the total comparable employment in Britain at the time) and found that about a quarter of them suffered from pulmonary fibrosis . This investigation resulted in improved regulation of the manufacturing of asbestos-containing products in the early 1930s. Regulations included industrial hygiene standards, medical examinations, and inclusion of the asbestos industry into the British Workers' Compensation Act .
The first known US workers' compensation claim for asbestos disease was in 1927. In 1930, the first reported autopsy of an asbestosis sufferer was conducted in the United states and later presented by a doctor at the Mayo Clinic, although in this case the exposure involved mining activities somewhere in South America.
In 1930, the major asbestos company Johns-Manville produced a report, for internal company use only, about medical reports of asbestos worker fatalities. In 1933, Metropolitan Life Insurance Co. doctors found that 29% of workers in a Johns-Manville plant had asbestosis. Either in 1942 or 1943, the president of Johns-Manville, Lewis H. Brown, said that the managers of another asbestos company were "a bunch of fools for notifying employees who had asbestosis." When one of the managers asked, "do you mean to tell me you would let them work until they dropped dead?" the response is reported to have been, "Yes. We save a lot of money that way." In 1944, a Metropolitan Life Insurance Company report found 42 cases of asbestosis among 195 asbestos miners. In 1952, Dr. Kenneth Smith, Johns-Manville medical director, recommended (unsuccessfully) that warning labels be attached to products containing asbestos. Later, Smith testified: "It was a business decision as far as I could understand . . . the corporation is in business to provide jobs for people and make money for stockholders and they had to take into consideration the effects of everything they did and if the application of a caution label identifying a product as hazardous would cut into sales, there would be serious financial implications." In 1953, National Gypsum's safety director wrote to the Indiana Division of Industrial Hygiene, recommending that acoustic plaster mixers wear respirators "because of the asbestos used in the product." Another company official noted that the letter is "full of dynamite" and urged that it be retrieved before reaching its destination. A memo in the files noted that the company "succeeded in stopping" the letter, which "will be modified."

1960s-early 80s

Modern regulation

See main article at Asbestos and the law

United States

In 1989 the United States Environmental Protection Agency (EPA) issued the Asbestos Ban and Phase Out Rule which was subsequently overturned in the case of Corrosion Proof Fittings v. U.S. Environmental Protection Agency, 1991. This ruling leaves many consumer products that can still legally contain trace amounts of asbestos. For a clarification of products which legally contain asbestos read the EPA's clarification statement.
The EPA has proposed a concentration limit of 7 million fibers per liter of drinking water for long fibers (lengths greater than or equal to 5 µm). The OSHA, (Occupational Safety and Health Administration) has set limits of 100,000 fibers with lengths greater than or equal to 5 µm per cubic meter of workplace air for 8-hour shifts and 40-hour work weeks.

New Zealand

In 1984 The import of raw amphibole (blue and brown) asbestos into New Zealand was banned. In 2002 the import of chrysotile (white) asbestos was banned.

Contamination of other products

Asbestos and vermiculite

Vermiculite is a hydrated laminar magnesium-aluminum-iron silicate which resembles mica. It can be used for many industrial applications and has been used as a replacement for asbestos. Some ore bodies of vermiculite have been found to contain small amounts of asbestos. One vermiculite mine operated by W. R. Grace and Company in Libby, Montana exposed workers and community residents to danger by mining contaminated vermiculite, in 1999 the EPA began cleanup efforts and now the area is a superfund cleanup area. The EPA has determined that harmful asbestos is released from the mine as well as through other activities that disturb soil in the area.

Asbestos and talc

Talc is sometimes contaminated with asbestos. In 2000, tests in a certified asbestos-testing laboratory found the tremolite form of amphibole asbestos in three out of eight major brands of children's crayons (oil pastels) that are made partly from talc — Crayola, Prang, and Rose Art. In Crayola crayons, the tests found asbestos levels from 0.05% in Carnation Pink to 2.86% in Orchid; in Prang crayons, the range was from 0.3% in Periwinkle to 0.54% in Yellow; in Rose Art crayons, it was from 0.03% in Brown to 1.20% in Orange. Overall, 32 different types of crayons from these brands contained more than trace amounts of asbestos, and eight others contained trace amounts. The Art and Creative Materials Institute, a trade association which tests the safety of crayons on behalf of the makers, initially insisted the test results must be incorrect, although they later said they do not test for asbestos. The mining company, R T Vanderbilt Co of Gouverneur, New York, which supplied the talc to the crayon makers, insists there is no asbestos in its talc "to the best of our knowledge and belief", but tests by the United States Mine Safety and Health Administration found asbestos in all four talc samples that it tested in 2000., and at least one defendant reported claim counts in excess of 800,000 in 2006.
Current trends indicate that the worldwide rate at which people are diagnosed with the disease will likely increase through the next decade. Analysts have estimated that the total costs of asbestos litigation in the USA alone is over $250 billion.
The Federal legal system in the United States has been faced with numerous counts of asbestos related suits, which often included multiple plaintiffs with similar symptoms. The concern with these court cases are the staggering numbers, which in 1999 recorded a whopping 200,000 cases pending in the Federal court system of the United States . Further, it is estimated that within the next 40 years, cases may balloon to seven hundred thousand cases. These numbers help explain how there are thousands of current pending cases.
Litigation of asbestos materials has been a difficult entity to muster due to the multiple factors which play a role in every case. The company that often is being exposed for their negligence of working conditions and the worker or in many cases, workers who were exposed to asbestos and did not know that they were, or knew and now fear future medical problems, have current symptoms or were upset for the negligence of the company. Companies sometimes counter saying that health issues do not currently appear in their worker or workers, or sometimes are settled out of court. The Research and Development (RAND) think-tank has appropriated certain legal information which is readily available for proclaimed victims of natural resource accidents. This information, although sometimes deemed radical, has helped many workers, regardless of health condition, earn compensation through companies. RAND, along with the Institute for Civil Justice (ICJ) have been proponents of the organization of past cases in order to determine one aspect of fair compensation for workers. 1999 saw the introduction of the Fairness in Asbestos Compensation Act. This Act was used as a tool in order to determine which of the numerous federal cases were true, and if the plaintiff’s were actually suffering from asbestos related illness. This process was necessary as thousands of false insurance claims were costing companies billions and ultimately many companies were forced to file for bankruptcy. While companies filed for bankruptcy, this limited payouts to those who were actually affected by the material. What the 1999 Act ultimately determined was “a judgment that those resources should be spent on delivering full and prompt compensation to those who are, and will become, impaired by asbestos disease, and not dissipated on payments to those who are not sick and may never become sick, on punitive damages that seek retribution for the decisions of long-dead executives for conduct that took place decades ago and on the extraordinary transaction costs (Professor Christopher Edley, Jr.).” . The amounts and method of allocating compensation have been the source of many court cases, and government attempts at resolution of existing and future cases.
One notable asbestos lawyer, Peter Angelos, used the vast fortune he gained from asbestos lawsuits to buy the Baltimore Orioles.

Critics of safety regulations

According to Natural Resources Canada, chrysotile asbestos is not as dangerous as once thought. According to their fact sheet, "...current knowledge and modern technology can successfully control the potential for health and environmental harm posed by chrysotile". In May of 1998, Canada requested consultations with the European Commission concerning France's 1996 prohibition of the importation and sale of asbestos.
The EC said that substitute materials had been developed in place of asbestos, which are safer to human health. It stressed that the French measures were not discriminatory, and were fully justified for public health reasons. The EC said that in the July consultations, it had tried to convince Canada that the measures were justified, and that just as Canada broke off consultations, it was in the process of submitting substantial scientific data in favour of the asbestos ban.
Asbestos regulation critics include author and Fox News columnist Steven Milloy and the asbestos industry. Critics sometimes argue that increased regulation does more harm than good and that replacements to asbestos are inferior. An example is the suggestion by Dixy Lee Ray and others that the shuttle Challenger exploded because the maker of O-ring putty was pressured by the EPA into ceasing production of asbestos-laden putty. However, scientists point out that the putty used in Challengers final flight did contain asbestos, and failures in the putty were not responsible for the failure of the O-ring that led to loss of the shuttle. Steven Milloy suggests that the World Trade Center towers could still be standing or at least would have stood longer had a 1971 ban not stopped the completion of the asbestos coating above the 64th floor . This was not mentioned in the National Institute of Standards and Technology's report on the towers' collapse. Insulation that replaced asbestos is believed to have equivalent fire resistance, and any sort of sprayed-on insulation, including asbestos-based material, would have been removed in large areas by the impact of the planes.

Substitutes for asbestos in construction

Fiberglass insulation was invented in 1938 and is now the most commonly used type of insulation material. In Europe stone- and glasswool are the main insulators in houses.
Many companies that produced asbestos-cement products that were reinforced with asbestos fibres have developed products incorporating organic fibres. One such product was known as Eternit and another "Everite" now use "Nutec" fibres which consist of organic fibres, portland cement and silica. Stonefibres are used in gaskets and friction materials.
Another potential fiber is Polybenzimidazole or PBI fiber. Polybenzimidazole fiber is a synthetic fiber with high melting point of 760 °C that also does not ignite. Due to its exceptional thermal and chemical stability, it is often used by fire departments and space agencies.

Recycling and disposal

In most developed countries, asbestos is typically disposed of as hazardous waste in landfill sites.
Asbestos can also be recycled by transforming it into harmless silicate glass. A process of thermal decomposition at 1000-1250 °C produces a mixture of non-hazardous silicate phases, and at temperatures above 1250 °C it produces silicate glass. Microwave thermal treatment can be used in an industrial manufacturing process to transform asbestos and asbestos-containing waste into porcelain stoneware tiles, porous single-fired wall tiles, and ceramic bricks.

See also


Other internal links


Additional reading

  • George B. Guthrie and Brooke T. Mossman, editors, Health Effects of Mineral Dusts, Mineralogical Society of America Reviews in Mineralogy v. 28, 584 pages (1993) ISBN 0-939950-33-2

Mineral and mining links

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Synonyms, Antonyms and Related Words

act drop, amianthus, asbestos board, asbestos curtain, backdrop, batten, border, cloth, coulisse, counterweight, curtain, curtain board, cyclorama, decor, drop, drop curtain, earth flax, fire break, fire curtain, fire line, fire resistance, fire retardant, fire wall, fireproofing, flat, flipper, hanging, mountain flax, rag, scene, scenery, screen, side scene, stage screw, tab, tableau, teaser, tormentor, transformation, transformation scene, wing, wingcut, woodcut
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