Asbestos

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Content from Wikipedia article: Asbestos

Asbestos (a misapplication of Latin: asbestos "quicklime" from Greek ἄσβεστος: a-, "not"; sbestos, "extinguishable") describes any of a group of fibrous metamorphic minerals of the hydrous magnesium silicate variety. The name is derived for its historical use in lamp wicks; the resistance of asbestos to fire has long been exploited for a variety of purposes. Asbestos was used in fabrics such as Egyptian burial cloths and Charlemagne's tablecloth which according to legend, he threw in a fire to clean. Asbestos occurs naturally in many forms (see below); it is mined from metamorphic rocks.

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. The inhalation of some kinds of asbestos fibers, however, causes a number of serious illnesses, including lung cancer and [mesothelioma]. Because of the hazards, most uses of asbestos are banned in 60 countries. Fiberglass has been found to be a suitable substitute for thermal insulation, and woven ceramic fiber performs as well as or better than asbestos as an insulator of high-temperature electrical conductors.

Most respirable asbestos fibers are invisible to the unaided human eye because their size is about 3.0-20.0 µm in length and can be as thin as 0.01 µm. Human hair ranges in size from 17 to 181 µm.[1] 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. Thus, 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 over and over until they have been broken down to their smallest unit dimensions. For this reason, one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers in a normal environment over the course of time.

As they get smaller and lighter, they become more mobile and more easily entrained (wafted) into the air, where human respiratory exposures typically result. The released fibers being heavier than air will eventually settle in quiescent conditions only to be resuspended over and over again by any kind of activity or air currents over a period of time. This cyclic re-entrainment has consequences. Consistent with the tenets of the Second Law of Thermodynamics, the smallest sizes of easily mobile asbestos fibers move away from their initial source location in an ever-broadening manner. They disperse both by simple spontaneous airborne diffusion and through mass transport of the fibers. This latter is an energy-driven process that can occur through directed air currents or by "pickup and release" along a pathway of directed movement by persons, mechanical equipment or vehicles.

For these reasons, asbestos contamination does not tend to remain localized at its initial release point but will eventually spread throughout all available accessible areas of buildings, even into areas that don't have their own asbestos-containing products. Eventually asbestos from virtually all products that were manufactured from this mineral will invade each and every space within an affected building. This is because during the lifecycle of each asbestos product, microscopic fibers and larger particles or pieces of these products are typically produced during their residency. The lifecycle of an asbestos containing product begins from the initial delivery of the product to the building, followed by its installation, normal usage forces, age-related deterioration, physical or chemical damage that often occurs, to finally its removal either for replacement or demolition. Any small impact or damage to a typical asbestos containing product can easily release billions to trillions of fibers of asbestos into the immediate environment which then add to the pool of similar fibers and particles from other asbestos containing products within that building.

Friability of an asbestos containing product 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. But non-friable asbestos containing materials are not necessarily safe. The forces or conditions of usage that come into intimate contact with most non-friable asbestos containing materials are substantially higher than finger pressure. Because of this, non-friable asbestos products can and do release substantial quantities of free asbestos fibers into their environments as well. During normal usage, initially non-friable products slowly change into a quasi-friable condition. Asphalt asbestos floor tiles are typically worn down through a sanding action of the normal floor grit under foot traffic on such floor coverings. Asbestos shingles, siding and roofing materials are eroded through drying, weathering, embrittlement, acid rain leaching and other deteriorative changes to their binder matrix resulting in release of asbestos fibers ("chalk dust") when simple contact is made with their surface or when the wind blows across them. Most government regulations treat such products with much less care than they do when addressing more friable products.

Confusingly, the Modern Greek word άσβεστος means quicklime.

Contents

Types of asbestos

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Chrysotile asbestos
  • Chrysotile, or white asbestos, CAS No. 12001-29-5, is obtained from serpentine rocks. It is less friable (and therefore less likely to be inhaled) than the other types and is the type most often used industrially. Chrysotile should not be confused with chrysolite, a synonym of olivine. There is some evidence that this form of asbestos is not as harmful when inhaled. However it should be noted that there is also evidence that this type of asbestos is harmful, although not perhaps as harmful as other forms (refer to UK Health & Safety Commission report Asbestos: Effects on health of exposure to asbestos, 1985). One formula given for Chrysotile is Mg3(Si2O5)(OH)4.
  • Amosite, CAS No. 12172-73-5, also known as Grunerite or brown asbestos, is an amphibole from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for Amosite is Fe7Si8O22(OH)2.
  • Crocidolite, or blue asbestos, CAS No. 12001-28-4, is an amphibole from Africa and Australia. It is the fibrous form of riebeckite. Blue asbestos is commonly thought of as the most dangerous type of asbestos (see above and below). One formula given for Crocidolite is Na2Fe2+3Fe3+2Si8O22(OH)2.

Notes: Serpentine rocks are those with curled fibres. Amphiboles have straight, needle-like fibres.

The amphiboles, in their fibrous form, are friable and therefore the most carcinogenic, although they also exist in safer non-fibrous forms. Asbestos with particularly fine fibers is also referred to as "amianthus".

Other asbestos minerals, such as tremolite, CAS No. 77536-68-6, Ca2Mg5Si8O22(OH)2; actinolite (or smaragdite), CAS No. 77536-66-4, Ca2(Mg, Fe)5Si8O22(OH)2; and anthophyllite, CAS No. 77536-67-5, (Mg, Fe)7Si8O22(OH)2; are less-used industrially but can still be found in a variety of construction materials and insulations and occur in a few consumer products, such as talcum powders and vermiculite. In 1989, In the United States, the Environmental Protection Agency (EPA) passed the Asbestos Ban and Phase Out Rule which was subsequently overturned in 1991. This ruling leaves many consumer product that can still legally contain asbestos. For a clarification of products which legally contain asbestos visit the EPA's clarification statement: http://www.epa.gov/asbestos/pubs/asbbans2.pdf

Uses

Serpentine group

Chrysotile is the form of asbestos from the serpentine group that has been used commercially.

In the United States, chrysotile has been the most commonly used type of asbestos. Chrysotile is often present in a wide variety of materials, including but not limited to:

  • sheetrock taping
  • mud and texture coats
  • vinyl floor tiles, sheeting, adhesives and ceiling tiles
  • plasters and stuccos
  • roofing tars, felts, and shingles
  • "transite" panels, siding, countertops, and pipes
  • acoustical ceilings
  • fireproofing
  • putty
  • caulk
  • gaskets
  • brake pads and shoes
  • clutch plates
  • stage curtains
  • fire blankets

Amphibole group

Amosite and crocidolite were used in many products until the early 1980s. The use of all types of asbestos in the amphibole group was banned in the mid-1980s. These products were mainly:

  • Low density insulation board and ceiling tiles
  • asbestos cement sheets and pipes for construction, casing for water and electrical/telecommunication services
  • thermal and chemical insulation (i.e., fire rated doors, limpet spray, lagging and gaskets)

Asbestos-related diseases

Asbestosis and cancer

Alarm about the health hazards associated with asbestos had been described many times over the years. As early as 1898 the Chief Inspector of Factories of the United Kingdom reported to Parliament in his Annual Report about the "evil effects of asbestos dust". He reported the "sharp, glass like nature of the particles" when allowed to remain in the air in any quantity, "have been found to be injurious, as might have been expected" (Report of the Select Committee 1994). In 1906 a British Parliamentary Commission confirmed the first cases of asbestos deaths in factories in Britain and recommended better ventilation and other safety measures. In 1918 a US insurance company produced a study showing premature deaths in the asbestos industry in the United States and in 1926 the Massachusetts Industrial Accidents Board processed the first successful compensation claim by a sick asbestos worker. Many American injuries from asbestos exposure came from shipbuilders working during World War II.[2]

The fine asbestos fibres are easily inhaled, and can cause a number of respiratory complaints, including a potentially serious lung fibrosis called asbestosis. Exposure to asbestos has also been determined to cause a very serious form of cancer, mesothelioma, that occurs in the chest and abdominal cavities. This aggressive disease is improperly referred to as a lung cancer, as the malignant cells are derived from the mesothelium, a tissue found on the inner walls of the chest and abdominal cavities and on the outer surface of the lungs rather than in the lung itself.

When inhaled, asbestos is carcinogenic (i.e. promotes cancer). In the United States alone, it is estimated that ten thousand people die each year of asbestos-related diseases, such as mesothelioma, asbestosis, lung cancer, and gastrointestinal cancer. Asbestos has a synergistic effect with tobacco smoking in the causation of lung cancer.

Other asbestos-related diseases

  • asbestos warts – caused when the sharp fibres 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. They do not generally become malignant, but do reflect damage to the lungs.
  • diffuse pleural thickening – similar to above and can sometimes be associated with asbestosis. Usually no symptoms shown but if extensive can cause lung impairment.

Litigation

Main Article on Wikipedia: Asbestos and the law

In the United States, asbestos was one of the first hazardous air pollutants regulated under Section 112 of the Clean Air Act of 1970. One estimate says that, in the 20th century, more than 100 million Americans were exposed to asbestos in the workplace.[3]

Today, lawsuits claiming that asbestos caused plaintiffs' diseases form a large part of the total amount of lawsuits pending in American courts, with a cost of tens of billions of dollars for expenses, settlements, and judgments to date. The original asbestos manufacturers were driven into Chapter 11 bankruptcy; plaintiffs have moved to suing corporations who had more peripheral connections to asbestos; the original plaintiffs have gone from those who had mesothelioma and other serious asbestos-related health problems to include those who merely were exposed to asbestos and wished to recover for their fear of future injury.[4] Nearly every American industry has had asbestos defendants, and over 70 corporations have filed Chapter 11 bankruptcy in the face of heavy liability claims.[5], [6] Since the late 1970s, approximately 6% of all filings in American courts each year were related to asbestos, leading to its perception as a sort of poster child of tort reform and the rampant lawsuit excesses of the United States. As of 2004, asbestos cases result in about 600 to 700 appellate opinions per year (that is, including both federal and state courts); this number does not include other cases that were not appealed, or were settled or otherwise abandoned before trial. Estimates of total American deaths attributable to asbestos range from 200,000 to 265,000 (according to the March 1991 Report of the Judicial Conference Ad Hoc Committee on Asbestos Litigation). The number of suits has increased, although the leading epidemiological study, cited by attorneys on both sides, suggests that deaths peaked in the 1990s. However, others contend that deaths from asbestosis and mesothelioma have not yet peaked.[7]

The Tort Reform Argument

"Asbestos litigation today is, for the most part, a massively fraudulent enterprise that can rightfully take its place among the pantheon of such great American swindles as the Yazoo land frauds, Credit Mobilier and Teapot Dome," said Lester Brickman, a professor at Cardozo Law School, in a recent speech on the phenomenon.[8] For example, Baron & Budd, P.C., a renowned Dallas plaintiff's firm, is alleged to have coached clients how to provide winning testimony against asbestos defendants.[9] In recent years, there have been many scandals over asbestos litigation because of the number of cases involving plaintiffs who had suffered no injury other than asymptomatic pleural plaques. An investigation into claims filed for alleged silicosis found that 65% of the plaintiffs claiming to be suffering from silicosis had previously recovered from asbestos defendants by alleging that they had asbestosis.[10], [11] Many attorneys, including Peter Angelos, have become rich because they established lucrative relationships with unions that steered potential asbestos plaintiffs to their law firms in exchange for questionable financial relationships with union executives.[12], [13] In the mass screenings that would take place, it is alleged that asbestos-related ailments were systematically overdiagnosed.[14]

Because many companies filed for Chapter 11 bankruptcy in view of claims from plaintiffs (some of whom may have been uninjured), and because some of the earlier manufacturer bankruptcy proceedings underestimated future asbestos liability, many seriously injured workers received as little as ten cents on the dollar of the compensation due them.[15], [16]

Asbestos-related cases were a rare sight on the U.S. Supreme Court docket prior to 1980, but since then, the Court has dealt with asbestos-injury cases in 1986, 1993, 1995, 1997, 1999, and 2002. The 1997 and 1999 cases both involved giant settlement class actions that were designed to stabilize the liability of the largest defendants. Both settlements were ultimately overturned by the Court because they resolved the rights of future claimants who, because they were currently unknown, could not be given the notice that due process requires.

Texas passed a reform bill requiring neutral medical screening in asbestos claims. Georgia passed a reform bill that requires an out-of-state plaintiff to provide "prima facie evidence of physical impairment" that shows "to a reasonable degree of certainty" that exposure to asbestos was "a substantial contributing factor" to the plaintiff's injuries. Plaintiffs' attorneys in the state complain that this would foreclose "98%" of the pending claims, and that the law is unconstitutional.[17]

Congress is considering legislation, the Fairness in Asbestos Injury Resolution Act of 2005, that would establish a $140 billion trust fund to supplant litigation as a means to compensate victims of asbestos. Trial lawyers protest that the trust fund would undercompensate injured workers, while some conservatives argue that the trust fund does not do enough to prevent fraud; would override state reforms in Texas, Ohio, and Georgia; and would be too "leaky" to prevent future litigation problems.

Asbestos liability is one of the largest issues facing the global insurance industry today, with the industry contending that many are suing because they have been exposed but have not as yet contracted asbestos-related lung diseases, which have latency periods of 10-40 years, and because lawyers spend millions each year advertising to promote such lawsuits.[18], [19], [20]

In Australia, public attention was drawn in mid-2004 to James Hardie's handling of its asbestos injury liabilities, following the revelations of a New South Wales government-sanctioned inquiry.

In Brazil, prohibition of extraction and use of asbestos is currently under consideration.

In Japan too, recently there has been a spurt of lawsuits involving actual or potential damage due to the use of asbestos in schools and public places, following public outcry over asbestos-related deaths.

Removal of asbestos

Image:Asbestos-warning.jpg
Structures containing asbestos are marked

Many buildings contain asbestos, which was used in spray-applied flame retardant, thermal system insulation, and in a variety of other materials. Typically, asbestos was "flocked" above false ceilings, inside technical ducts, and in many other small spaces where firefighters would have difficulty gaining access. Structural components like asbestos panels were also used. In residences, it was often a component of a type of flocked acoustic ceiling called "popcorn ceiling", until its production was banned in the U.S. in 1978. However, the ban allowed installers to use up remaining stocks, so houses built as late as 1986 could still have asbestos in their acoustic ceilings. The only way to be sure is to remove a sample and have it tested by a competent laboratory.

Depending on how and where asbestos was applied, it might not pose any risk to most users of the building. If the fibers cannot dislodge themselves, they cannot be inhaled, and thus the risk is absent.

However, with certain ways of applying asbestos, particularly flocking, asbestos fibers may gradually drop off into the air. Furthermore, in all cases, asbestos poses special hazards to maintenance personnel who have to drill holes in walls for installation of cables or pipes.

Also, even if the workers are protected, such maintenance operation may release fibers into the air, which may be inhaled by other users later. As a consequence, interventions in areas where asbestos is present often have to follow stringent procedures.

The removal of asbestos from a building is quite difficult because of the above constraints. If removal is to be performed when users are still present in the building, it is usually necessary to relocate some of them temporarily. Typically, the part of the building from which asbestos is being removed has to be sealed off in order to prevent contamination of the other areas.

Even if the building is closed to normal users, it is necessary to seal it off from outside atmosphere so that no accessible air is contaminated. Accordingly, asbestos removal projects are long and costly. Examples of long asbestos removal enterprises include the Jussieu Campus (begun circa 1996 and still going on as of 2005) and the Tour Montparnasse (in 2005, projected duration was 3 years if the tower was emptied of its users, and 10 years if it was not).

An asbestos-containing building that is to be torn down may have to be sealed, and to have its asbestos safely removed first before ordinary demolition can be performed. The asbestos removal may take longer and cost more than the actual tearing-down of the building. For example, the former seat of parliament of East Germany, the Palast der Republik was stripped of most of its asbestos between 1998 and 2001, before it was finally decided to tear it down starting in 2006. The demolition process alone is expected to cost between 20 and 60 million Euros.

Regarding the automotive industry, asbestos linings were once used in brake pads and shoes. Since the mid-1990s, a majority of brake linings, new or replacement, have been manufactured with kevlar linings (the same material used in bulletproof vests).

Controversy

As with some other environmental prohibitions like DDT and CFCs, the movement to ban asbestos has many critics, some of whom claim either that the substance in question is not harmful, or that the ban does more harm than good [21].

Among the arguments around asbestos prohibition are:

  • The view that the shuttle Challenger exploded because the maker of O-ring putty was pressured by the EPA into ceasing production of its more temperature-resistant, asbestos-laden putty, prompting replacement with an inferior putty, which had continual problems of a sort which could have caused the O-ring leak and subsequent explosion. Note: see Jim Norton for a discussion of this idea. According to that source, and others quoted there, 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.
  • The "Amphibole Hypothesis" states that Chrysotile asbestos is not as harmful as asbestos from the amphibole group. Several studies have been conducted which support this conclusion. Criticisms have been raised about the methodology used in these studies. Several other studies have been conducted which contradict the "Amphibole Hypothesis" [22].
  • Some countries, notably Canada, still use Chrysotile asbestos [23]. Canada has a significant economic interest in the mining of Chrysotile.
  • The question of why asbestos is also banned in circumstances where inhalation is nearly impossible, such as when it's being included in sealed areas already dangerous to human beings, instead of simply when it might be used as insulation in a ventilated area, or other similar cases which actually expose it to people against their will.
  • Critics argue that where asbestos has been banned, its roles were taken by products which are often either inferior, or far more expensive. They argue that this has a negative impact on society as a whole, which (especially if the previous arguments are true in whole or part) may be greater than the benefit of its removal.
  • There are suggestions that the World Trade Center towers could still be standing or at least would have stood for longer had asbestos lagging not been removed in the years prior to 2001. Others refute this idea, noting that the insulation that replaced asbestos had equivalent fire resistance, and that any sort of sprayed-on insulation, including asbestos-based material, would have been removed in large areas by the impact of the planes and subsequent explosion (Jim Norton, Cryptome.org).

Substitutes for asbestos in construction

Many companies that produced products that were reinforced with asbestos fibres have developed products incorporating alternative fibres, such as Eternit.

See also


External links

Mineral links

Health

Cleanup and the environment

  • U.S. EPA Asbestos Home Page
  • Health and Safety - Asbestosis (TUC Resources, UK)
  • White Gold Pioneers: Asbestos Mining — The origins of asbestos mining, illustrated with many early photographs
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