asbestos

Fibrous asbestos on muscovite

Asbestos

Asbestos

Blue asbestos (crocidolite) from Wittenoom, Western Australia. The ruler is 1 cm.

Blue asbestos showing the fibrous nature of the mineral

Asbestos (pronounced  /æsˈbɛstəs/ or /æzˈbɛstəs/) is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties.^[1] They all have in common their eponymous, asbestiform habit: long, (1:20) thin fibrous crystals. The inhalation of asbestos fibers can cause serious illnesses, including malignant lung cancer, mesothelioma (a formerly rare cancer strongly associated with exposure to amphibole asbestos), and asbestosis (a type of pneumoconiosis). Long exposure to high concentrations of asbestos fibers is more likely to cause health problems.This is most common among the miners of asbestos, since they have the longest exposure to it. The European Union has banned all use of asbestos^[2] and extraction, manufacture and processing of asbestos products.^[3]

Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its sound absorption, average tensile strength, its resistance to fire, heat, electrical and chemical damage, and affordability. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement (resulting in fiber cement) or woven into fabric or mats. Commercial asbestos mining began in the Eastern Townships of Quebec, Canada and the world's largest asbestos mine is located in the town of Asbestos, Quebec.

Types and associated fibers

Chrysotile asbestos

Asbestos fibers

Six minerals are defined by the United States Environmental Protection Agency as "asbestos" including those belonging to the serpentine class chrysotile and those belonging to the amphibole class amosite, crocidolite, tremolite, anthophyllite and actinolite. There is an important distinction to be made between serpentine and amphibole asbestos due to differences in their chemical composition and their degree of potency as a health hazard when inhaled. However asbestos and all commercial forms of asbestos (including chrysotile asbestos) are known to be human carcinogens based on sufficient evidence of carcinogenicity in humans.^[4][5]

Serpentine

White

Chrysotile, CAS No. 12001-29-5, is obtained from serpentinite rocks which are common throughout the world. Its idealized chemical formula is Mg₃(Si₂O₅)(OH)₄. Chrysotile fibers are curly as opposed to fibers from amosite, crocidolite, tremolite, actinolite, and anthophyllite which are needlelike.^[6] 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.^[7] 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 and floors. Numerous other items have been made containing chrysotile including brake linings, cloth behind fuses (for fire protection), pipe insulation, floor tiles, and rope seals for boilers.^{[citation needed]}

Amphibole

Brown

Amosite, CAS No. 12172-73-5, is a trade name for the amphiboles belonging to the cummingtonite-grunerite solid solution series, commonly from South 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.^[7]

Blue

Crocidolite, CAS No. 12001-28-4 is an amphibole found primarily in southern Africa, but also in Australia. It is the fibrous form of the amphibole riebeckite. One formula given for crocidolite is Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂(OH)₂.

Crocidolite commonly occurs as soft friable fibers. Asbestiform amphibole may also occur as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that they are composed of fibers with breadths less than 1 micrometer that occur in bundles and have very great widths. Asbestos with particularly fine fibers is also referred to as "amianthus". Amphiboles such as tremolite have a crystal structure containing strongly bonded ribbonlike silicate anion polymers that extend the width of the crystal. Serpentine (chrysotile) has a sheetlike silicate anion which is bowed and which rolls up like a carpet to form the fiber.^[8]

Other materials

Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca₂Mg₅Si₈O₂₂(OH)₂; actinolite asbestos, 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.^{[citation needed]}

Producing nations

Asbestos output in 2005

In 2009, 2 million tonnes of asbestos were mined worldwide. Russia was the largest producer with about 50% world share followed by China (14%), Brazil (12.5%), Kazakhstan (10.5%) and Canada (9%).^[9]

History

Early uses

Asbestos use in human culture dates back at least 4,500 years, when evidence shows that inhabitants of the Lake Juojärvi region in East Finland strengthened earthenware pots and cooking utensils with the asbestos mineral anthophyllite.^[10] The word asbestos comes from the ancient Greek ἄσβεστος, meaning "unquenchable" or "inextinguishable".^[1][11] One of the first careful descriptions of the material is attributed to Theophrastus in his text On Stones, around 300 BC, although the naming of minerals was not very consistent at that time (the more consistent name of this material in both modern and ancient Greek is amiantos (undefiled, pure) whence the names of it in other languages like French amiante; the modern Greek word ἀσβεστος or ασβέστης stands consistently and solely for lime, not for the material known as asbestos in English). The term asbestos is traceable to Roman naturalist Pliny the Elder's manuscript Natural History, and his use of the term asbestinon, meaning "unquenchable".^[1][10][11] While Pliny is popularly attributed with recognising the detrimental effects of asbestos on slaves,^[12] examination of primary sources shows that this is not so.^[13] Charlemagne, the first Holy Roman Emperor (800–814), is said to have had a tablecloth made of asbestos.^[14]

According to Tabari, one of the curious items belonging to Khosrow II Parviz, the great Sassanian king (r. 531–579), was a napkin that he cleaned by simply throwing it into fire. This is believed to be made of asbestos. (This is also mentioned in The New Encyclopædia Britannica, vol. 6, 2003, page 843). 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 (Persian: آذرشست, āzarshost) were called (Persian: شستكه) shostakeh.^[15] Some of the Persians believed the fiber was fur from an animal (named samandar, Persian: سمندر) that lived in fire and died when exposed to water,^[16][17] hence the old mistaken myth that the salamander tolerated fire.

While traveling to Siberia, Marco Polo described being offered garments that could not burn. He was told that the wool was from the salamander, but did not accept this explanation. At last he was told that these garments were made from a mineral from the mountains, which contained threads just like wool.^[18]

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.^[19] Others assert that the ancients used asbestos to make perpetual wicks for sepulchral or other lamps.^[16] In more recent centuries, asbestos was indeed used for this purpose. Although asbestos causes skin to itch upon contact, ancient literature indicates that it was prescribed for diseases of the skin, and particularly for the itch. It is possible that they used the term asbestos for soapstone, because the two terms have often been confused throughout history.^[19]

Industrial Era

The U.S. asbestos industry began in 1858 when fibrous anthophyllite was mined for use as asbestos insulation by the Johns Company, a predecessor to the current Johns Manville at a quarry at Ward's Hill on Staten Island, New York.^[20] Asbestos became more widespread during the industrial revolution; in 1866 it was used as insulation in the U.S. and Canada. Development of the first commercial asbestos mine began in 1874 in the Appalachian foothills of Quebec.^[21] 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.

Asbestos fibers were once used in automobile brake pads, shoes, and clutch discs. Since the mid-1990s, a majority of brake pads, new or replacement, have been manufactured instead with linings made of ceramic, carbon, metallic and aramid fiber (Twaron or Kevlar—the same material used in bulletproof vests).

Kent's filtered cigarette used crocidolite asbestos in its "Micronite" filter from 1952 to 1956.^[22]

Artificial Christmas snow, known as flocking, was previously made with asbestos.^[23]

In Japan, particularly after World War II, asbestos was used in the manufacture of ammonium sulfate for purposes of rice production, sprayed upon the ceilings, iron skeletons, and walls of railroad cars and buildings (during the 1960s), and used for energy efficiency reasons as well. Production of asbestos in Japan peaked in 1974 and went through ups and downs until about 1990, when production began to drop severely.^[24]

Discovery of toxicity

The first documented death related to asbestos was in 1906. In the early 1900s researchers began to notice a large number of early deaths and lung problems in asbestos mining towns. The first diagnosis of asbestosis was made in the UK in 1924. By the 1930s, the UK regulated ventilation and made asbestosis an excusable work related disease, about ten years sooner than the U.S.^[6] The term mesothelioma was first used in medical literature in 1931; its association with asbestos was first noted sometime in the 1940s.

Approximately 100,000 people in the United States have died, or will die, from asbestos exposure related to ship building. In the Hampton Roads area, a shipbuilding center, mesothelioma occurrence is seven times the national rate.^[25] Thousands of 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 fourteen died of mesothelioma and an unknown number died from asbestosis.^[26]

The United States government and asbestos industry have been criticized for not acting quickly enough to inform the public of dangers, and to reduce public exposure. In the late 1970s court documents proved that asbestos industry officials knew of asbestos dangers since the 1930s and had concealed them from the public.^[26] A similar situation had arisen in the 1920s with the careless handling of radium and the ensuing scandal of the Radium Girls.

In Australia, asbestos was widely used in construction and other industries between 1945 and 1980. From the 1970s there was increasing concern about the dangers of asbestos and its use was phased out. Mining ceased in 1983. The use of asbestos was phased out in 1989 and banned entirely in Dec 2003. The dangers of asbestos are now well known in Australia and there is help and support for sufferers from asbestosis or mesothelioma.^[27]

Specific products

Serpentine group

Serpentine minerals have a sheet or layered structure. Chrysotile 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 products and materials, including:

• drywall and joint compound
• plaster
• gas mask filters pre 1960s
• mud and texture coats
• vinyl floor tiles, sheeting, adhesives
• roofing tars, felts, siding, and shingles^[28]
• "transite" panels, siding, countertops, and pipes
• popcorn ceilings, also known as acoustic ceilings
• fireproofing
• caulk
• gaskets
• packing, a system for sealing a rotating shaft
• brake pads and shoes
• clutch plates
• stage curtains
• fire blankets
• interior fire doors
• fireproof clothing for firefighters
• thermal pipe insulation
• filters for removing fine particulates from chemicals, liquids and wine
• dental cast linings
• HVAC flexible duct connectors
• drilling fluid additives

A household heat spreader for cooking on gas stoves, made of asbestos (probably 1950s; "Amiante pur" is French for "Pure Asbestos")

In the European Union and Australia it has recently been banned as a potential health hazard^[29] 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.^[30] 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.^[30]

Amphibole group

Five types of asbestos are found in the amphibole group: amosite, crocidolite, anthophyllite, tremolite, and actinolite. Amosite, the second most likely type to be found in buildings, according to the U.S. EPA Asbestos Building Inspectors Guide, is the "brown" asbestos.

Amosite and crocidolite were formerly used in many products until the early 1980s. The use of all types of asbestos in the amphibole group was banned in much of the Western world by the mid-1980s, and by Japan in 1995. These products were mainly

• Low density insulating board (often referred to as AIB or asbestos insulating board) and ceiling tiles;
• Asbestos-cement sheets and pipes for construction, casing for water and electrical/telecommunication services;
• Thermal and chemical insulation (e.g., fire rated doors, limpet spray, lagging and gaskets).

Health problems

Left-sided mesothelioma (seen on the right of the picture): chest CT

Amosite and crocidolite are the most hazardous of the asbestos minerals because of their long persistence in the lungs of exposed people. Tremolite often contaminates chrysotile asbestos, thus creating an additional hazard. Chrysotile asbestos, like all other forms of asbestos, has produced tumors in animals. Mesotheliomas have been observed in people who were occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos factories and mines.^[31] According to the NCI, "A history of asbestos exposure at work is reported in about 70 percent to 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos."^[32] The most common diseases associated with chronic exposure to asbestos include: asbestosis and pleural abnormalities (mesothelioma, lung cancer).^[33] Asbestosis has been reported primarily in asbestos workers, and appears to require long-term exposure, high concentration for the development of the clinical disease. There is also a long latency period (incubation period of an infectious disease, before symptoms appear) of about 12 to 20 years.^[34]

Studies have shown an increased risk of lung cancer among smokers who are exposed to asbestos compared to nonsmokers.^[35]

Asbestos exposure becomes a health concern when high concentrations of asbestos fibers are inhaled over a long time period.^[36] People who become ill from inhaling asbestos are often those who are exposed on a day-to-day basis in a job where they worked directly with the material. As a person's exposure to fibers increases, because of being exposed to higher concentrations of fibers and/or by being exposed for a longer time, then that person's risk of disease also increases. Disease is very unlikely to result from a single, high-level exposure, or from a short period of exposure to lower levels.^[36]

Mechanisms which might be triggering cancer development

Stanton and Layard hypothesized in 1977–78 that toxicity of fibrous materials is not initiated by chemical effects,^[37] that is any trigger-effects of asbestos must presumably be physical, such as (A) mechanical damage or (B) unwanted signal channels (a plausible property for slender transparent fibres) which might disrupt normal cell activity—especially mitosis.

(A) Mechanical Damage. There is experimental evidence that very slim fibers (<60 nm, <0.06 μm in breadth) do tangle destructively with chromosomes (being of comparable size).^[38][39] Clearly that is likely to cause the sort of mitosis disruption expected in cancer.

(B) Unwanted Signal channels. This has recently been explored theoretically, but not yet experimentally. The theory argues that this effect would only be feasible for asbestos fibers >100 nm in breadth (>150 nm in the case of chrysotile), which suggests that we should be on the look-out for a possible mixture of different mechanisms for the different fiber-diameter-ranges.^{[40] [41]}

One popular idea of the causal chain is (1) Asbestos fiber → → (3) inflammation → (4) other pathology. While that may be true, it does not explain "(2), the actual trigger":

"What is the physical property of asbestos which initiates any such inflammation?" (After all, inflammation is usually seen as caused by chemical-based processes: immunological &/or bacterial). So inflammation (&/or oxidation etc.) may well be part of the causal chain, but not the crucial first step.^[40]

Other asbestos-related diseases

• It is important to consult a doctor, particularly if the follow symptoms develop: shortness of breath, wheezing, or hoarseness, persistent cough that worsens over time, blood in fluid coughed up, pain or tightening in chest, difficulty swallowing, swelling of neck or face, decreased appetite, weight loss, fatigue or anemia.^[42]

• Asbestosis: Progressive fibrosis of the lungs of varying severity, progressing to bilateral fibrosis, honeycombing of the lungs on radiological view with symptoms including rales and wheezing. Individuals who have been exposed to asbestos via home, environment, work should notify their doctors about exposure history.
• Asbestos warts: caused when the sharp fibers lodge in the skin and are overgrown causing benign callus-like growths.
• Pleural plaques: discrete fibrous or partially calcified thickened area which can be seen on X-rays of individuals exposed to asbestos. Although pleural plaques are themselves asymptomatic, in some patients this develops into pleural thickening.
• Diffuse pleural thickening: similar to above and can sometimes be associated with asbestosis. Usually no symptoms shown but if exposure is extensive, it can cause lung impairment.

Asbestos as a contaminant

Asbestos fibers (SEM micrograph)

Most respirable asbestos fibers are invisible to the unaided human eye because their size is about 3–20 µm wide and can be as slim as 0.01 µm. Human hair ranges in size from 17 to 181 µm in breadth.^[43] 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, and in this case, there are two cleavage planes which are much weaker than the third. 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. When fibers or asbestos structures from asbestos containing materials(ACM) become airborne, the process is called primary release. Primary release mechanisms include abrasion, impaction, fallout, air erosion, vibration, and fire damage. Secondary release occurs when settled asbestos fibers and structures are resuspended as a result of human activities. In unoccupied buildings or during unoccupied periods, fiber release typically occurs by fallout or is induced by vibration or air erosion.^[44]

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 because of 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.

It is important to note that asbestos containing building materials were not as widely used in residences as it was in larger institutional and commercial buildings. Most products manufactured today do not contain asbestos, but until the 1970s many building materials used in homes contained asbestos. Asbestos containing building materials in residences includes a variety of products like thermal system insulation (TSI) around hot or cold water lines, asbestos paper wrap around heating ducts, cement board around furnaces/wood-burning appliances, cement board roofing materials and so on. Other sources of asbestos containing materials include deteriorating, damaged, or disturbed insulation, fireproofing, acoustical materials, and floor tiles.^[45]

Asbestos Exposure: Various individuals may be exposed to airborne asbestos fibers. Among these people are general building occupants such as teachers, students, office workers, and visitors; housekeeping/custodial employees who may come in contact with or disturb asbestos containing building materials (ACBM) or contaminated settled dust during their work activities, and maintenance/construction workers who may disturb ACBM during repair or installation activities. Asbestos abatement/remediation workers and emergency personnel such as firefighters may also become exposed.^[46]

Environmental asbestos

Asbestos can be found naturally in the air outdoors and in some drinkable water, including water from natural sources.^[47] Studies have shown that members of the 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.^[48]

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% for every 10 km that an individual had lived away from a likely asbestos source.^[49]

Portions of El Dorado County, California are known to contain natural amphibole asbestos formations at the surface.^[49][50] The USGS studied amphiboles in rock and soil in the area in response to an EPA sampling study and subsequent criticism of the EPA study. The EPA study was refuted by its own peer reviewers and never completed or published. The study found that many amphibole particles in the area meet the counting rule criteria used by the EPA for chemical and morphological limits, but do not meet morphological requirements for commercial-grade-asbestos. The executive summary pointed out that even particles that do not meet requirements for commercial-grade-asbestos may be a health threat and suggested a collaborative research effort to assess health risks associated with "Naturally Occurring Asbestos."

However, the main criticism pointed at EPA was that their testing was conducted in small isolated areas of El Dorado where there were no amphibole asbestos deposits, thus the language regarding amphibole, nonfibrous "particles". Actual surface amphibole deposits in residential areas were ignored for testing purposes. Thus no final findings were published by ATSDR since the criticism was correct and the effort of combined EPA/ATSDR teams were wasted time and money.^[51]

Great deals 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 6 inches (150 mm) of clean, stable material over the ground.^[49]

Globally, collected samples from Antarctic ice indicate chrysotile asbestos has been a ubiquitous contaminant of the environment for at least 10,000 years. Snow samples in Japan have shown ambient background levels are one to two orders of magnitude higher in urban than in rural areas. Higher concentrations of airborne asbestos fibers are reported in urban areas where there is more ACM (asbestos containing materials) and mechanisms of release (vehicles braking and weathering of asbestos cement materials); concentrations in the range of 1–20 ng/m^3 have been reported. Fibers longer than 5μm are rarely found in rural areas. Ambient concentrations using TEM analysis have been based on mass measurements.^[44]

For environmental samples, one must normally resort to electron microscopy for positive identification.^[52] Today, gravimetric and PCM/PLM techniques are employed. However, the latter techniques cannot readily identify the smallest, most hazardous, fibers, because they are limited to PM10 particulate size evaluation, which completely ignores ultrafine particles (UFPs).

A combination of methods such as light microscopy, electron microscopy, and energy dispersive X-ray analysis are used to offer the most accurate approach to identify asbestos and to estimate concentrations that may become airborne upon disturbance. For the purposes of counting asbestos fibers in these samples, regulatory agencies commonly count as fibers those particles of asbestos minerals at least 5 micrometers in length and with length:width ratios of 3:1. For detecting fibers in bulk building materials, asbestos particles with length:width ratios of 5:1 are counted. Air concentrations of asbestos fibers in ambient (typical) air are 0.00001 to 0.0001 fibers per milliliter (fiber/mL). The recently established exposure limit for U.S. workplaces is 0.1 fiber/mL.^[53]

History of health concerns and regulation

Until 1900

By the first century AD, Greeks and Romans are claimed to have observed that slaves involved in the weaving of asbestos cloth were afflicted with a sickness of the lungs,^[54] although this is not confirmed by examination of primary sources.^[13]

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.^[55]

At about the same time, what was probably the first study of mortality among asbestos workers was reported in France.^[56] 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

Micrograph demonstrating asbestosis of the lung (ferruginous bodies). H&E stain.

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.^[57]

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.^[58]

1920s–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, Nellie Kershaw, 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..."^[59] 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".^[60]

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.^[61] 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.^[62]

The first known U.S. workers' compensation claim for asbestos disease was in 1927.^[63] 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.^[64]

In 1930, the major asbestos company Johns-Manville produced a report, for internal company use only, about medical reports of asbestos worker fatalities.^[65] In 1932, a letter from U.S. Bureau of Mines to asbestos manufacturer Eagle-Picher stated, in relevant part, "It is now known that asbestos dust is one of the most dangerous dusts to which man is exposed."^[66]

In 1933, Metropolitan Life Insurance Co. doctors found that 29% of workers in a Johns-Manville plant had asbestosis.^[65] Likewise, in 1933, Johns-Manville officials settled lawsuits by 11 employees with asbestosis on the condition that the employees' lawyer agree to never again "directly or indirectly participate in the bringing of new actions against the Corporation."^[66] In 1934, officials of two large asbestos companies, Johns-Manville and Raybestos-Manhattan, edited an article about the diseases of asbestos workers written by a Metropolitan Life Insurance Company doctor. The changes downplayed the danger of asbestos dust.^[66] In 1935, officials of Johns-Manville and Raybestos-Manhattan instructed the editor of Asbestos magazine to publish nothing about asbestosis.^[66] In 1936, a group of asbestos companies agreed to sponsor research on the health effects of asbestos dust, but required that the companies maintain complete control over the disclosure of the results.^[65]

1940s

In 1942, an internal Owens-Corning corporate memo referred to "medical literature on asbestosis… scores of publications in which the lung and skin hazards of asbestos are discussed."^[65] Testimony given in a federal court in 1984 by Charles H. Roemer, formerly an employee of Unarco, described a meeting in the early 1940s between Unarco officials, J-M President Lewis H. Brown and J-M attorney Vandiver Brown. Roemer stated, "I’ll never forget, I turned to Mr. Brown, one of the Browns made this crack (that Unarco managers were a bunch of fools for notifying employees who had asbestosis), and I said, ‘Mr. Brown, do you mean to tell me you would let them work until they dropped dead?’ He said, ‘Yes. We save a lot of money that way.'" ^[67] In 1944, a Metropolitan Life Insurance Company report found 42 cases of asbestosis among 195 asbestos miners.^[65]

1950s

In 1951, asbestos companies removed all references to cancer before allowing publication of research they sponsored.^[68] 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."^[69]

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 was "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."^[70]

1960s–1980s

Through the 1970s, asbestos was used to fireproof roofing and flooring, for heat insulation, and for a variety of other purposes. The material was used in fire-check partitioning and doors on North Sea Oil Production Platforms and Rigs.

During mid-to late 1980s, public health concern focused on potential asbestos fiber exposures of building occupants and workers in buildings containing asbestos containing building materials (ACBM) and their risks of developing lung cancer or mesothelioma. As a consequence, the Health Effects Institute (Cambridge, MA) convened a panel to evaluate the lifetime cancer risk of general building occupants as well as service workers.^[71]

Modern regulation

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. EPA, 947 F.2d 1201 (5th Cir. 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.^[72] In 2010, Washington State banned asbestos in automotive brakes starting in 2014.^[73]

The EPA has proposed a concentration limit of seven million fibers per liter of drinking water for long fibers (lengths greater than or equal to 5 µm). The Occupational Safety and Health Administration (OSHA), has set limits of 100,000 fibers with lengths greater than or equal to 5 µm per cubic meter of workplace air for eight-hour shifts and 40-hour work weeks.^[74]

OSHA regulations regarding asbestos are covered in 29 C.F.R. 1926.1101. Such work is divided into four categories.

Class I asbestos work means activities involving the removal of TSI and surfacing ACM and PACM.

Class II asbestos work means activities involving the removal of ACM which is not thermal system insulation or surfacing material. This includes, but is not limited to, the removal of asbestos-containing wallboard, floor tile and sheeting, roofing and siding shingles, and construction mastics.

Class III asbestos work means repair and maintenance operations, where "ACM", including TSI and surfacing ACM and PACM, is likely to be disturbed.

Class IV asbestos work means maintenance and custodial activities during which employees contact but do not disturb ACM or PACM and activities to clean up dust, waste and debris resulting from Class I, II, and III activities.^[75]

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.^[76]

Australia

A complete ban on asbestos-containing material in Australia was introduced in 1991 although some building materials in storage were still being used in the years that followed. Queensland began regulation of asbestos removal and disposal in 2005. Handlers of asbestos materials must have a B-Class license for bonded asbestos and an A-Class license for friable asbestos.

The town of Wittenoom, in Western Australia was built around a (blue) asbestos mine. The entire town continues to be contaminated, and has been disincorporated, allowing local authorities to remove references to Wittenoom from maps and roadsigns.

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.^[77] 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.^[78] The EPA has determined that harmful asbestos is released from the mine as well as through other activities that disturb soil in the area.^[79]

Asbestos and talc

Talc is sometimes contaminated with asbestos.^[80] In 2000, tests in a certified asbestos-testing laboratory found the tremolite form of amphibole asbestos in three out of eight bigger brands of children's crayons that are made partly from talc: Crayola, Prang, and RoseArt.^[81] 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.^[81] In May 2000, Crayola said tests by a materials analyst, Richard Lee, whose testimony has been accepted in lawsuits over 250 times on behalf of the asbestos industry, showed two of its crayons were negative for asbestos.^[82] In June 2000, Binney & Smith, the maker of Crayola, and the other makers agreed to stop using talc in their products, and changed their product formulations in the United States.^[82] 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",^[83] but a news article claimed that the United States Mine Safety and Health Administration (MSHA) did find asbestos in four talc samples that it tested in 2000.^[81] At the time, however, the Assistant Secretary for Mine Safety and Health informed the news reporter that his article was in error and that the reporter had misquoted him stating that “In fact, the abbreviation ND (non detect) in the laboratory report – indicates no asbestos fibers actually were found in the samples.”^[84] Further supporting the claim of Vanderbilt that asbestos is not found in this industrial grade talc (composed of a very complex mineral mixture) is a decades old record of analytical work that does not find asbestos in this talc by mineral scientists in academia, government and contract laboratories.^{[85][86][87][88][89][90][91][92][93]}

Human, animal and cell health studies conducted on Vanderbilt’s controversial talc also lend no support for the presence of asbestos in this talc.^[94][95][96] Several non fully peer-reviewed health reports concerning Vanderbilt talc do exist and suggest a "same as" asbestos risk, some of which were referenced in the previously cited news articles.^[97][98]

Asbestos in construction

Asbestos construction in developed countries

Older decorative ceilings, like this one, often contain small amounts of white asbestos.

1929 newspaper advertisement from Perth, Western Australia, for asbestos sheeting for residential building construction.

The use of asbestos in new construction projects has been banned for health and safety reasons in many developed countries or regions, including the European Union, Australia, Hong Kong, Japan, and New Zealand. A notable exception is the United States, where asbestos continues to be used in construction such as cement asbestos pipes. The 5th Circuit Court prevented the EPA from banning asbestos in 1991 because although EPA research showed it would cost between $450 and 800 million and save around 200 lives in a 13-year length, the EPA did not provide adequate evidence for the safety of alternative products. ^[99] Until the mid-1980s, small amounts of white asbestos were used in the manufacture of Artex, a decorative stipple finish,^[100] however, some of the lesser-known suppliers of Artex were still adding white asbestos until 1999.^[101] Removing or disturbing Artex is not recommended, as it may contain white asbestos.

Prior to the ban, asbestos was widely used in the construction industry in thousands of materials, some are judged to be more dangerous than others due to the amount of asbestos and a materials friable nature. Sprayed coatings, pipe insulation and Asbestos Insulating Board (AIB) are thought to be the most dangerous due to their high content of asbestos and friable nature. Many older buildings built before the late 1990s contain asbestos. In the United States, there is a minimum standard for asbestos surveys as described by ASTM Standard E 2356-04. The U.S. Environmental Protection Agency includes some but not all asbestos-contaminated facilities on the Superfund National Priorities list (NPL). Renovation and demolition of asbestos contaminated buildings is subject to EPA NESHAP and OSHA Regulations. Asbestos is not a material covered under CERCLA's innocent purchaser defense. In the UK, the removal and disposal of asbestos and of substances containing it are covered by the Control of Asbestos Regulations 2006^[102]

In older buildings (e.g. those built prior to 1999 in the UK, before white asbestos was finally banned), asbestos may still be present in some areas e.g. old bath panels, concrete water tanks and many other places. Being aware of asbestos locations reduces the risk of disturbing asbestos.^[103] See the asbestos image gallery (external link) to see some common asbestos locations.

Removal of asbestos building components can also remove the fire protection they provide, therefore fire protection substitutes are required for proper fire protection that the asbestos originally provided.^[103][104]

Asbestos construction in developing countries

Some developing countries, such as India and China, and also Russia, have continued widespread use of asbestos. The most common is corrugated asbestos-cement sheets or "A/C Sheets" for roofing and for side walls. Millions of homes, factories, schools or sheds and shelters continue to use asbestos. Cutting these sheets to size and drilling holes to receive 'J' bolts to help secure the sheets to roof framing is done on-site. There has been no significant change in production and use of A/C Sheets in developing countries following the widespread restrictions in developed nations.

Asbestos and 9/11

As the towers collapsed, Lower Manhattan was blanketed in a mixture of building debris and combustible materials. This complex mixture gave rise to the concern that thousands of residents and workers in the area would be exposed to known hazards in the air and in the dust, such as asbestos, lead, glass fibers, and pulverized concrete.^[105] More than 1,000 tons of asbestos are thought to have been released into the air during the destruction of the Twin Towers in New York on 9/11.^[106] Inhalation of a mixture of asbestos and other toxicants is thought to be linked to the unusually high death rate of emergency service workers from cancer since the disaster.^[106] Many thousands more are now thought to be at risk of developing cancer due to this exposure with those who have died so far being only the 'tip of the iceberg'.^[106] Some commentators have criticised authorities for using asbestos in the Towers' construction (see 'Other criticism' below).

In May 2002, after numerous cleanup, dust collection, and air monitoring activities were conducted outdoors by EPA, other federal agencies, New York City and New York State, New York City formally requested federal assistance to clean and/or test residences in the vicinity of the WTC site for airborne asbestos.^[105]

Litigation

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Asbestos litigation is the longest, most expensive mass tort in U.S. history, involving more than 8,400 defendants and 730,000 claimants as of 2002 according to the RAND Corporation,^[107] and at least one defendant reported claim counts in excess of 800,000 in 2006.^[108]

Current trends indicate that the worldwide rate at which people are diagnosed with asbestos-related diseases will likely increase through the next decade.^[109][110] Analysts have estimated that the total costs of asbestos litigation in the USA alone is over $250 billion.^[111]

The federal legal system in the United States has dealt with numerous counts of asbestos related suits, which often included multiple plaintiffs with similar symptoms. In 1999 there were 200,000 related cases pending in the federal court system of the United States.^[112] Further, it is estimated that within the next 40 years, the number of cases may increase to 700,000. These numbers help explain how there are thousands of current pending cases.

Litigation of asbestos materials has been slow. Companies sometimes counter saying that health issues do not currently appear in their worker or workers, or sometimes are settled out of court.^[113] 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 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.^[114] Ultimately many asbestos companies were forced to file for bankruptcy. While companies filed for bankruptcy, this limited payouts to those who were actually affected by the material. Christopher Edley said what the 1999 Act ultimately did was "limit punitive damages that seek retribution for the decisions of long-dead executives for conduct that took place decades ago (Professor Christopher Edley, Jr.).” ^[114]

Litigation exists outside the United States in England, Scotland, Ireland, the Netherlands, France, Australia, and Japan among other nations. See the companion article for further information.

The volume of the asbestos liability has concerned manufacturers and insurers and reinsurers.^[115] 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.

Critics of safety regulations

Canada-EU dispute

Natural Resources Canada states chrysotile, one of the fibres that make up 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".^[116]

In May 1998, Canada requested consultations before the WTO and the European Commission concerning France's 1996 prohibition of the importation and sale of asbestos. Canada said that the French measures contravened provisions of the Agreements on Sanitary and Phytosanitary Measures and on Technical Barriers to Trade, and the GATT 1994. The EC claims that substitute materials have 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 claimed 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 (the EC) was in the process of submitting substantial scientific data in favour of the asbestos ban.^[117]

The Canadian federal government has in response claimed that chrysotile is much less dangerous than other types of asbestos, and Canada does not export the other asbestos fibre.^[118] Chrysotile continues to be used in new construction across Canada, in ways that are very similar to those for which chrysotile is exported.^[119] The Chrysotile Institute, an asbestos industry funded organization, said that the use of chrysotile does not pose an environmental problem and the inherent risks in its use are limited to the workplace.^[120] The Canadian government continues to draw both domestic and international criticism for its stance on chrysotile, most recently in international meetings on the Rotterdam Convention hearings regarding chrysotile.

The CFMEU pointed out that most exports go to developing countries. Canada has pressured countries, including Chile, and other UN member states to avoid chrysotile bans.^[121]

Other criticism

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Asbestos regulation critics include the asbestos industry^[122] and Fox News columnist Steven Milloy. Critics sometimes argue that increased government 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 disintegrated because the maker of O-ring putty was pressured by the EPA into ceasing production of asbestos-laden putty.^[123][124] However, the putty used in Challenger's 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.^[124][125]

Asbestos was used in the first forty floors of the World Trade Center north tower causing an airborne contamination among lower Manhattan after the towers collapsed in the attacks on September 11th, 2001.^[126] 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.^[127] This was not considered in the National Institute of Standards and Technology's report on the towers' collapse. All fireproofing materials, regardless of what they are made of, are required to obtain a fire-resistance rating prior to installation. All fiber-based lightweight commercial spray fireproofing materials are vulnerable to kinetic energy impacts that are outside of the fire testing upon which their ratings are based, including asbestos-based materials, and may have been removed in large areas by the impact of the planes.^{[128][129][130]}

Substitutes for asbestos in construction

Fiberglass insulation was invented in 1938 and is now the most commonly used type of insulation material. The safety of this material is also being called into question due to similarities in material structure.^[131] However, the International Agency for Research on Cancer removed fiberglass from its list of possible human carcinogens in 2001. ^[132]

In 1978, a highly texturized fiberglass fabric was invented by Bal Dixit, called Zetex. This fabric is lighter than asbestos, but offers the same bulk, thickness, hand, feel, and abrasion resistance as asbestos. The fiberglass was texturized to eliminate some of the problems that arise with fiberglass, such as poor abrasion resistance and poor seam strength^[133]

In Europe stone- and glasswool are the main insulators in houses.

Many companies that produced asbestos-cement products that were reinforced with asbestos fibers have developed products incorporating organic fibers. One such product was known as Eternit and another "Everite" now use "Nutec" fibers which consist of organic fibers, portland cement and silica. Cement-bonded wood fiber is another substitute. Stone fibers 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. Because of its exceptional thermal and chemical stability, it is often used by fire departments and space agencies.

Old Wailuku Post Office sealed off for asbestos removal

Asbestos alternatives for industrial use include sleeves, rope, tape, fabric, textiles and insulation batt materials made from fiberglass and silica.

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.^[134] 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.^[135][136]

See also

Mineralogy

• Asbestine
• List of minerals

Other asbestos-related topics

References

Bibliography

• Castleman, Barry I. Asbestos: Medical and Legal Aspects, 4th edition, Aspen Law and Business, Englewood Cliffs, NJ, 1996.

Further 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.

External links

Find more about Asbestos on Wikipedia's sister projects:
	Definitions and translations from Wiktionary
	Images and media from Commons
	Learning resources from Wikiversity
	News stories from Wikinews
	Quotations from Wikiquote
	Source texts from Wikisource
	Textbooks from Wikibooks

Independent links

• The Asbestos Information Centre Independent site with information about asbestos and its use in buildings

Regulatory and government links

• U.S. EPA Asbestos Home Page
• ATSDR Case Studies in Environmental Medicine: Asbestos Toxicity U.S. Department of Health and Human Services
• British Government Health and Safety Executive (HSE)
• National Institute for Occupational Safety and Health: Asbestos
• World Health Organization – Asbestos page

Mineral and mining links

• Parachrysotile (asbestos) at the webmineral.com Mineral Database
• Univ. of Minn.: Asbestos
• White Gold Pioneers: Asbestos Mining—The origins of asbestos mining, illustrated with many early photographs

Health and the environment

• About Your House — General Series — Asbestos
• British Government Health and Safety Executive (HSE) essential guides
• Hazards magazine's comprehensive asbestos resource pages
• The Miracle Mineral Fiber – Asbestos
• Asbestos: Magic mineral or deadly dust?, CBC Digital Archives
• About Asbestos (2006), European Agency for Safety and Health at Work (OSHA)
• A USGS map of "Naturally Occurring Asbestos" in Eastern America
• Occupational exposure to asbestos and man-made vitreous fibres and risk of lung cancer: a multicenter case-control study in Europe, Rafael Carel et al.

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