What is Asbestos?
Asbestos is the name for a group of six different fibrous minerals which occur naturally in the environment. These fibers are impervious to heat, fire, chemicals, and biological degradation; they do not dissolve in water or evaporate, and they have no detectable odor or taste. Because of these properties, asbestos has been widely used by industry in manufactured products such as building materials, friction products, and heat resistant fabrics.
Chrysotile, or white asbestos, belongs to the serpentine family of minerals, and accounts for 95 per cent of all asbestos used in the United States. The other five, amosite, crocidolite, and the fibrous varieties of tremolite, actinolite, and anthophyllite, belong to amphibole family. While all forms of asbestos are dangerous and may cause cancer, the amphiboles are considered to be the most dangerous.
Chrysotile asbestos fibers are flexible and curved, while amphibole fibers are most often brittle and have a rod or needle-like shape. Asbestos fiber masses break apart easily, and become tiny airbourne particles that may easily be inhaled or swallowed and cause serious health problems many years later.
How is Asbestos Used?
Asbestos has been mined and used commercially in North America since the late 1800s, but its use increased dramatically during and after World War II. The building and construction industry uses it for strengthening cements and plastics as well as for insulation, fireproofing, and sound absorption; the shipbuilding industry has used asbestos to insulate boilers, steampipes, and hot water pipes; the automotive industry uses asbestos in vehicle brake shoes and clutch pads. Some other applications 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); and
- 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; and plastics.
In the late 1970s, the U.S. Consumer Product Safety Commission banned the use of asbestos in wallboard patching compounds and gas fireplaces because these products released excessive amounts of asbestos fibers into the environment. Asbestos was voluntarily withdrawn by the manufacturers of electric hair dryers. In 1989, the Environmental Protection Agency (EPA) banned all new uses of asbestos, however, uses established prior to 1989 are still allowed. Asbestos is currently used most frequently in gaskets and in roofing and friction products.
Who Is at Risk?
Since the early 1940s, millions of Americans have been exposed to asbestos in the course of their jobs in the construction trades and in military service. Although it is known that the risk to workers increases with heavier exposure and longer exposure times, asbestos-related illnesses have been found in individuals with only brief exposures. Because of the long latency period, no signs of illness may be apparent for 20 to 50 or more years.
Family members of workers heavily exposed to asbestos also face an increased risk of developing mesothelioma. This is most often the result of asbestos dust being brought into the home on the shoes, clothing, skin, and hair of workers. This type of exposure is referred to as paraoccupational or household exposure. (See page on particulate air pollution.)
It is important to remember that not everyone exposed to asbestos will develop diseases related to their exposure. In fact, many will experience no ill effects whatsoever. Asbestos that is bonded into finished products such as walls, tiles, and pipes poses no risk to health as long as these products are not damaged or disturbed in such a way that fibers are released into the air. It is when asbestos fibers are released and inhaled or digested that individuals are at risk for developing asbestos disease. Once these fibers work their way into body tissues, they may stay there indefinitely.
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