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Asbestos is the name used for a group of six different fibrous minerals (amosite, chrysotile, crocidolite, and the fibrous varieties of tremolite, actinolite, and anthophyllite) that occur naturally in soil and rocks in several areas around the world, including the United States and Canada.
Asbestos fibers vary in length, and may be straight or curled. Asbestos fibers are strong, resistant to heat and most chemicals, do not dissolve in water, and do not conduct electricity. Because of these characteristics, asbestos is used in a wide range of manufactured goods, like roofing shingles, ceiling and floor tiles, paper products, insulation, cement products, heat-resistant fabrics, friction products (automobile clutches, brake pads, and transmission parts), textiles, packaging, gaskets, and coatings. Note: When found in homes, these products should be maintained in a condition that does not generate dust or release fibers. If these products become damaged or must be removed from the home an asbestos professional should evaluate them.
Four types of asbestos have been used commercially: chrysotile, or white asbestos; crocidolite, or blue asbestos; amosite, which usually has brown fibers; and anthophyllite, which usually has gray fibers. Chrysotile asbestos, with its curly fibers, is in the serpentine family of minerals. The other three types of asbestos, which all have rod-like fibers, are known as amphiboles. Asbestos fiber masses tend to break easily into a dust composed of tiny particles that can float in the air and stick to clothes. Asbestos fibers do not have any detectable odor or taste. The fibers may be easily inhaled or swallowed and can cause serious health problems.
All forms of asbestos are hazardous, and all can cause cancer, but the amphibole forms of asbestos are considered to be somewhat more hazardous to health than chrysotile fibers. Asbestos minerals consist of thin, separable fibers arranged in parallel Amphibole asbestos fibers are generally brittle and often have a rod- or needle-like shape, whereas chrysotile asbestos fibers are flexible and curved. Chrysotile is the predominant commercial form of asbestos; amphiboles are of minor commercial importance.
Nearly everyone is exposed to asbestos at some time during her/his life. Since asbestos fibers may cause harmful health effects in people who are exposed, the EPA attempted to ban all asbestos uses in 1989 but the courts overturned the rule in 1991 and now all new uses of asbestos are banned.
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Asbestos has been used in a broad variety of applications which draw upon its low cost and desirable properties such as heat and fire resistance, wear and friction characteristics, tensile strength, thermal, electrical and sound insulation, adsorption capacity, and resistance to chemical and biological attack.
At the peak of its demand, about 3,000 applications or types of products were listed for asbestos. In most applications, asbestos is bonded with other materials such as Portland cement, plastics, and resins. In other applications, asbestos is used as a loose fibrous mixture or woven as a textile. Consumption of asbestos in the United States has been declining for two decades. Domestic consumption of asbestos amounted to about 719,000 metric tons in 1973, but it had dropped to about 9,000 metric tons by 2002. Roofing products, gaskets, and friction products will continue to be the only significant domestic markets for asbestos in the foreseeable future. Chrysotile is the only form of asbestos currently used for manufacturing in the United States.
In 1973, EPA prohibited the spraying of asbestos-containing material on buildings and structures for fireproofing and insulation purposed. The ban on the use of spraying was later expanded to include applications for decorative purposes. The Consumer Product Safety Commission banned other uses including its inclusion in patching compounds and asbestos heat shields in hair dryers.
Substitutes for asbestos are constantly being developed, but no single substitute is as versatile and as cost effective as asbestos.
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The building and construction industry has used asbestos for strengthening cement and plastics as well as for insulation, fireproofing, and sound absorption. Asbestos is also used to insulate boilers, steam pipes and hot water pipes. The automotive industry still uses asbestos in vehicle brake shoes and clutch pads, however, the majority of auto manufacturers no longer manufactur asbestos containing brake and clutch pads.
More than 5,000 products contain or have contained asbestos. Some of them include:
Asbestos cement sheet and pipe products used for water supply and sewage piping, roofing and siding, casings for electrical wires, fire protection material, electrical switchboards and components, and residential and industrial building materials.
Friction products, such as clutch facings, brake linings for automobiles, gaskets and industrial friction materials.
Products containing asbestos paper, such as table pads and heat-protective mats, heat and electrical wire insulation, industrial filters for beverages, and underlying material for sheet flooring.
Asbestos textile products, such as packing components, roofing materials, and heat- and fire-resistant fabrics (including blankets and curtains).
Vermiculite-containing garden products and attic insulation.
Other products, including ceiling and floor tile; gaskets and packings; paints, coatings, and adhesives; caulking and patching tape; artificial ashes and embers for use in gas fireplaces; plastics; and some talc-containing crayons.
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Asbestos fibers do not evaporate into air or dissolve in water. The fibers can enter the air and water as a result of the weathering of natural deposits and manufactured asbestos products as well as the demolition or renovation of buildings that contain asbestos. Small diameter fibers and fiber-containing particles may remain suspended in the air for a long time, and can be carried long distances by wind or water currents before settling. Larger diameter fibers and particles tend to settle more quickly than smaller ones, but small asbestos fibers can remain airborne in the environment for decades or longer.
Asbestos fibers do not move through soil. They are generally not broken down by the environment and will remain virtually unchanged for long periods of time. Asbestos fibers may break down into smaller pieces or separate into a larger number of individual fibers as a result of physical processes, like cutting and sanding.
When asbestos fibers are inhaled, they may get trapped in the lungs or may be eliminated through the digestive tract.
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Asbestos - A Problem? - Discuss your encounters with asbestos and whether you think it is a major problem.
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