Asbestos

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Asbestos (a misapplication of Latin: asbestos "quicklime" from Greek ἄσβεστος: a, "not" and sbestos, "extinguishable") describes any of a group of minerals that can be fibrous, many of which are metamorphic and are hydrous magnesium silicates. These minerals, together with their occurrences, uses, and associated hazards, have been discussed in detail by Guthrie and Mossman (1993).

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, can cause a number of serious illnesses, including cancer. Many uses of asbestos are banned in multiple countries.

Contents 1 Types of asbestos and associated fibres 2 Uses 2.1 Historic usage 2.2 Modern usage 2.2.1 Serpentine group 2.2.2 Amphibole group 3 Asbestos-related diseases 3.1 Asbestos as a contaminant 3.2 Asbestos in the environment 3.3 Other asbestos-related diseases 4 Litigation 5 Removal of asbestos 6 Critics of safety regulations 7 Substitutes for asbestos in construction 8 See also 9 Footnotes 10 References 10.1 Regulatory and Government Links 10.2 Mineral & Mining links 10.3 Health & The Environment

[edit] Types of asbestos and associated fibres

"White" asbestos 

Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks. Chrysotile is the type most often used industrially. It is more flexible than other types of asbestos; it can be spun and woven into fabric. This is the kind of asbestos of which theatre curtains are made, as well as firefighters' suits, and possibly Charlemagne's tablecloth. There is 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.

"Brown" asbestos 

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. This type of asbestos is highly biohazardous.

"Blue" asbestos 

Riebeckite, CAS No. 12001-28-4, also known under the variety name of Crocidolite, is an amphibole from Africa and Australia. It is the fibrous form of the amphibole 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. This type of asbestos is highly biohazardous.

Notes: chrysotile 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 widths less than 1 micrometer that occur in bundles and have very long lengths. Amphiboles most commonly occur in nature in a safer nonfibrous form. Asbestos with particularly fine fibers is also referred to as "amianthus".

Other asbestos 

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)₅Si₈O₂₂(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 asbestos 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 contaminate in products such as the vermiculite containing Zonolite insulation manufactured by W.R. Grace and Company. These forms of asbestos are no less harmful than chrysotile, amosite, or crocidolite.

In 1989 the United States Environmental Protection Agency (EPA) passed 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 visit the EPA's clarification statement.^[1] Depending on the type of Asbestos, the cancer can be worse. It also depends on the amount inhaled. This is a welding occupational hazard.

[edit] Uses

[edit] Historic usage

Items made of asbestos were held in so great an esteem as to be of equal value with gold; none but emperors and kings had napkins made of it. Supposedly, Charlemagne had a tablecloth made of asbestos. Cleaning an asbestos cloth was simple- it was simply thrown into a fire. Some antiquaries have believed that ancients made shrouds of asbestos, wherein they burnt 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 building funeral pyres.^[2]

Others assert that the ancients used asbestos to make perpetual wicks for sepulchral lamps. 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 alumen plumosum, because the two terms have often been confused throughout history.^[2]

Asbestos fibers were once used in automobile brake pads and shoes. Since the mid-1990s, a majority of brake pads, new or replacement, have been manufactured with Aramid fiber (Twaron or Kevlar) linings (same material used in bulletproof vests).

Kent, the first filtered cigarette on the market, used crocidolite asbestos in its "Micronite" filter from 1952 to 1956.^[3]

[edit] Modern usage

[edit] 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, siding, and shingles
• "transite" panels, siding, countertops, and pipes
• acoustical ceilings
• fireproofing
• putty
• caulk
• gaskets
• brake pads and shoes
• clutch plates
• stage curtains
• fire blankets
• interior fire doors
• fireproof clothing for firefighters
• thermal pipe insulation

[edit] 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)

[edit] Asbestos-related diseases

[edit] Asbestos as a contaminant

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 in width.^[4] 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 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. The forces or conditions of usage that come into intimate contact with most non-friable asbestos containing materials are substantially higher than finger pressure. Non-friable asbestos products can release substantial quantities of asbestos fibers into their environments as well.^{[citation needed]}

[edit] Asbestos in the environment

Low levels of asbestos are in the air we breathe and some of the water we drink, including water from natural sources.^[5] Studies have shown that members of the general (nonoccupationally 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.^[6]

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). 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.^[7]

EWG Action Fund estimates that in the United States, about 10,000 people die each year of asbestos-related diseases, such as mesothelioma, asbestosis, lung cancer, and gastrointestinal cancer.^[8]

[edit] 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 become malignant or cause other lung impairment.

• diffuse pleural thickening – similar to above and can sometimes be associated with asbestosis. Usually no symptoms shown but if extensive can cause lung impairment.

[edit] Litigation

Main article: Asbestos and the law

Asbestos litigation is the longest, most expensive mass tort in U.S. history, involving more than 6,000 defendants and 600,000 claimants.^[9] Current trends indicate that the rate at which people are diagnosed with the disease will likely increase through the next decade. Analysts^{[attribution needed]} have estimated that the total costs of asbestos litigation in the USA alone is over $250 billion^[10]. Due to the prevalence of asbestos, it is normally part of the scope of a Phase I Environmental Site Assessment to inspect for potential asbestos in a building which is being sold.

The volume of the asbestos liability has alarmed the manufacturers and insurance industry. 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.

[edit] Removal of asbestos

Main article: asbestos abatement

[edit] Critics of safety regulations

Asbestos regulation critics include Junkscience.com author and Fox News columnist Steve Milloy and the asbestos industry.^[11] They sometimes argue that the ban does more harm than good and that replacements to asbestos are inferior. An example is the suggestion 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 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.^[12][13]

Scott Bass suggests that the World Trade Center towers could still be standing or at least would have stood for longer had a 1971 ban not stopped the completion of the asbestos coating above the 64th floor.^[14] 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 and subsequent explosion.^[15][16][17]

[edit] Substitutes for asbestos in construction

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.

See also a report by the Australian government, Hazardous Substances-Chrysotile Asbestos: Technical Assessment of Alternatives.

[edit] See also

• Ambler, PA
• Asbestine
• Asbestos and the law
• Asbestosis
• Asbestos, Quebec
• Brominated flame-retardant
• Eternit
• Fireproofing
• List of minerals
• Mesothelioma
• Vermiculite
• Wittenoom, former asbestos mining town

[edit] Footnotes

1. ^ EPA clarification statement on asbestos (PDF format.
2. ^ ^{a b} History of science This article incorporates content from the 1728 Cyclopaedia, a publication in the public domain.
3. ^ Cancer Research 55, 1 June 1995
4. ^ Physics factbook on asbestos
5. ^ Centre for disease control article on asbestos
6. ^ Medscape article on asbestos
7. ^ Agency for toxic substances and disease registry article on asbestos
8. ^ Asbestos and cancer
9. ^ American Bar Association article on asbestos litigation
10. ^ [The Economist - The war on tort, 26 Jan. 2005]
11. ^ Multinational Monitor article on Corporate junk science, retrieved December 16th, 2006
12. ^ MSNBC article on myths of the Challenger disaster, retrieved December 16th, 2006
13. ^ Asbestos and the Challenger disaster, retrieved December 16th, 2006
14. ^ Fox News - Asbestos could have saved the World Trade Center, retrieved December 16th, 2006
15. ^ Asbestos and the WTC collapse, retrieved December 16th, 2006
16. ^ Center for Fire Research PDF, retrieved December 16th, 2006
17. ^ Why Did the World Trade Center Collapse? Science, Engineering, and Speculation, retrieved December 16th, 2006

[edit] References

• 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

[edit] Regulatory and Government Links

• U.S. EPA Asbestos Home Page
• Directory of Accredited Laboratories - Asbestos Fiber Analysis (TEM Test Method)
• Congressional Research Service (CRS) Reports regarding asbestos
• Health History Source: Article by the SafetyLine Institute - WorkSafe - Western Australian state government
• Asbestos and Occupational Health in the World
• British Government Health and Safety Executive (HSE)

[edit] Mineral & Mining links

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

[edit] Health & The Environment

• About Your House — General Series — Asbestos
• Hazards.org
• Case Studies in Environmental Medicine: Asbestos Toxicity
• The Miracle Mineral Fiber - Asbestos A gruesome industrial crime story by: Dr. Noel Kerin
• Management of Asbestos in the UK A. H. Allen
• CBC Digital Archives - Asbestos: Magic mineral or deadly dust?
• An article on the health impact of asbestos from Liverpool's 'Nerve' magazine
• The Wittenoom Tragedy, Asbestos Diseases Society of Australia.
• Health and Safety - Asbestosis (TUC Resources, UK)
• UK asbestos news Thames Laboratories
• "According to Plan: The beauty and functionality of asbestos sidewalls" - A 1952 Asbestos Commercial featuring footage of scientists handling asbestos in several forms without gloves
• International Asbestos Victims Memorial
• About Asbestos European Agency for Safety and Health at Work (OSHA)
• Asbestos contamination near abandoned mine