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Asbestos is a naturally occurring group of minerals that can only be identified under a microscope. There are several types of these flexible, fire-resistant fibers.
The word asbestos is derived from a Greek adjective meaning inextinguishable. The "miracle mineral" as it was referred to by the Greeks, was admired for its soft and pliant properties as well as its ability to withstand heat. Asbestos was spun and woven into cloth in the same manner as cotton. It was also utilized for wicks in sacred lamps. Romans likewise recognized the properties of asbestos and it is thought that they cleaned asbestos tablecloths by throwing them into the flames of a fire.
From the time of the Greeks and Romans in the first century until its reemergence in - the eighteenth century, asbestos received little attention or use. It was not available -in large amounts until extensive deposits were discovered in Canada in the nineteenth century (late 1800's). . Following this discovery, asbestos emerged as an insulating component in thermal insulation for boilers, pipes and other high temperature applications and as a reinforcement material for a variety of products.
Asbestos is a naturally occurring mineral. It is distinguished from other minerals by the fact that its crystals form long, thin fibers. Deposits of asbestos are found throughout the world. The primary sites of commercial production are: Canada, the Soviet Union and South Africa. Asbestos is also mined commercially in the United States.
Asbestos minerals are divided into two groups -- serpentine and amphibole. The distinction between groups is based upon its crystalline structure -- serpentine minerals have a sheet or layered structure, amphiboles have a chain-like crystal structure.
Chrysotile, the only mineral in the serpentine group, is the most commonly used type of asbestos and accounts for approximately 95% of the asbestos found in buildings in the United States. Chrysotile is commonly known as "white asbestos" or named for its natural color.
Five types of asbestos are found in the amphibole group. Amosite , the second most likely type to be found in buildings, is often referred to as "brown asbestos". As you might assume, in its natural state amosite is brown in color.
Crocidolite , "blue asbestos" is also an amphibole. Crocidolite was used in high temperature insulation applications.
The remaining three types of asbestos in the amphibole group are: a nthophyllite, tremolite, and actinolite . These are extremely rare and of little commercial value. Occasionally they are found as contaminants in asbestos containing materials.
Once extracted from the earth, asbestos containing rock is crushed, milled (ground and graded. This produces long, thread-like fibers of material. What actually appears as a fiber is an agglomeration of hundreds or thousands of fibers, each of which can be divided even further into microscopic fibrils.
In the past, asbestos was added to a variety of products to strengthen them and provide heat insulation and fire resistance. In most products, asbestos is combined with a binding material so that it is not readily released into the air.
However, if asbestos should become airborne and is inhaled, it can remain in the lungs for a long period of time, producing the risk for severe health problems that do not appear until many years later.
More that 3,000 products in use today contain asbestos. Most of these are materials used in heat and acoustic insulation, fire proofing, and roofing and flooring. Collectively, produts with asbestos in them are frequently referred to as asbestos-containing material (ACM). Asbestos gained wide spread use because it is plentiful, readily available and low in cost. Because of its unique properties -- fire resistant, high tensile strength, poor heat and electric conductor, and generally impervious to chemical attacks, asbestos proved well-suited for many uses in the construction trades.
One of the most common uses for asbestos is as a fireproofing material. It was sprayed on steel beams, columns and decking that were used in construction of multi-storied buildings. This application prevented these structural members from warping or collapsing in the event of fire. Chrysotile was the most commonly used asbestos constituent in sprayed-on fireproofing. Asbestos comprised 5 - 95 percent of the fireproofing mixture and was used in conjunction with materials such as vermiculite, sand, cellulose fibers, gypsum and a binder such as calcium carbonate. These materials are soft and may be fluffy in appearance and to the touch. They vary in color from white to dark gray, occasionally they have been painted or encapsulated with a clear or colored sealant. The material may be exposed or concealed behind a suspended ceiling. Application to structural members (beams and columns) often resulted in some material being sprayed on walls and ceilings as well. This is referred to as overspray.
Asbestos is added to a variety of building materials to enhance strength. It is found in concrete and concrete-like products. Asbestos-containing cement products generally contain Portland cement, aggregate, and chrysotile fibers. The asbestos content may vary up to 50 percent by weight depending on the use of the product. Asbestos cement products are used as siding and roofing shingles; as wallboard; as corrugated and flat sheets for roofing, cladding, and partitions; and as pipes. Asbestos has also been added to asphalt, vinyl and other materials to make products like roofing felts, exterior siding, floor tile, joint compounds and adhesives.
Fibers in asbestos cement, asphalt and vinyl are usually firmly bound in the cement and will be released only if the material is mechanically damaged, for example by drilling, cutting, or sanding. Roofing shingles and siding may also show slow deterioration due to weathering.
As an insulator, asbestos received wide spread use for thermal insulation and condensation control. It was usually spray applied, trowel applied, or factory installed on or within equipment.
Asbestos proved valuable as a component of acoustical plaster. The material was applied by trowel or by spraying on ceilings and sometimes walls. It varies in color from white to gray - rarely was it painted as a noticeable loss of acoustical value occurs. Similarly as a decorative product, asbestos was mixed with other materials and sprayed on ceilings and walls to produce a soft, textured appearance.
Some of the more common products that may contain asbestos include:
Pipe and duct insulation. Building insulation. Wall and ceiling panels. Carpet underlays. Roofing materials. Artificial fireplaces and materials. Patching and spackling compounds. Brake pads and linings. Pot holders and ironing board pads. Hair dryers. Floor tiles. Electrical wires. Textured paints. Cements. Toasters and other household appliances. Furnaces and other furnace door gaskets.
Some uses of asbestos have been banned: the spraying of asbestos-containing materials (1973); certain pipe coverings (1975); certain patching compounds and artificial fireplace logs (1977); sprayed-on asbestos decorations (1978); and
asbestos-containing hair dryers (1979). Remember that just because it is banned in the U.S. does not mean that products made elsewhere are free of asbestos. Canada, for example, has been notrious for contnuing to mine and produce asbestos.
The production of all asbestos-containing materials for home construction and use was banned, in three stages over seven years, beginning in 1990. Once again, remember that older homes often still contain asbestos, especially in siding, floor tiles and pipe insultation. And some materials being sold today may come from warehouse supplies of materials made prior to the ban.
Products containing asbestos are often not labeled as such. Contact the manufacturer to find out if asbestos is present. Or call the U.S. Consumer Product Safety Commission (800-638-2772) for information about whether a product contains asbestos.
Friable vs. Nonfriable Asbestos
The U.S. Environmental Protection Agency (EPA) and others distinguish between friable and nonfriable forms of ACM. Friable ACM contains more than 1% asbestos and can be "crumbled or reduced to powder by hand pressure". Other things being equal, friable ACM is thought to release fibers into the air more readily; however, many types of nonfriable ACM can also release fibers if disturbed.
CATEGORIES OF ASBESTOS-CONTAINING BUILDING MATERIALS
EPA identifies three categories of ACM used in buildings:
Surfacing Materials -- ACM sprayed or troweled on surfaces (walls, ceilings, structural members) for acoustical, decorative, or fireproofing purposes. This includes plaster and fireproofing insulation.
Thermal System Insulation -- Insulation used to inhibit heat transfer or prevent condensation on pipes, boilers, tanks, ducts, and various other components of hot and cold water systems and heating, ventilation, and air conditioning (HVAC) systems. This includes pipe lagging, pipe wrap; block, batt, and blanket insulation; cements and "muds"; and a variety of other products such as gaskets and ropes.
Miscellaneous Materials -- Other, largely nonfriable products and materials such as floor tile, ceiling tile, roofing felt, concrete pipe, outdoor siding, and fabrics.
While it is often possible to "suspect" that a material or product is or contains asbestos by visual determination, actual determinations can only be made by instrumental analysis. The EPA requires that the asbestos content of suspect materials be determined by collecting bulk samples and analyzing them by polarized light microscopy (PLM). The PLM technique determines both the percent and type of asbestos in the bulk material.
However, some of these materials do not have to be inspected and inventoried under the Asbestos Hazard Emergency Response Act (AHERA) Rule. Asbestos-containing building materials (ACBM) as defined by the Rule exclude materials installed outside a building (e.g., roofing felt and siding) and all fabric materials.
Asbestos fibers can have serious effects on your health if inhaled. There is
known safe exposure to asbestos. The greater the exposure, the greater the risk of developing an asbestos-related disease.
The amount of time between exposure to asbestos and the first signs of disease can be as much as 30 years. It is known that smokers exposed to asbestos have a much greater chance of developing lung cancer than just from smoking alone.
Asbestos can cause asbestosis, a scarring of the lungs that leads to breathing problems and heart failure. Workers who manufacture or use asbestos products and have high exposures to asbestos are often affected with asbestosis.
Inhalation of asbestos can also cause lung cancer and mesothelioma, a rare cancer of the lining of the chest and abdomen lining. It may be linked to cancer of the stomach, intestines, and rectum, as well.
Asbestos is rarely used alone, and it is generally safe when combined with other materials with strong bonding agents. As long as the material remains bonded so that fibers are not released, it poses no health risk. But occasionally asbestos fibers become loose and airborne, most often when contained in soft, easily crumbled materials.
Even in such well-bonded materials as floor tiles and painted surfaces, asbestos can become loose and airborne when these materials are cut, scraped, filed, sanded, or removed. Remodeling or demolition often cause the release of asbestos fibers.
To discover whether you have an asbestos problem, you must first determine whether the material in question is releasing asbestos fibers. The best way to have this done is to have a state health agency or a reliable testing company take a sample for you and
have it analyzed.
You may have asbestos-containing substances in your home or office, especially those built before 1978. If the material is in good condition, LEAVE IT ALONE! To be certain, however,you may want to have the materials inspected, and, if necessary, repaired or
removed. You may want to read Asbestos in the Home - A Homeowner's Guide .
Repair usually involves either sealing or covering asbestos material. Sealing (or encapsulation) involves coating materials so that asbestos is sealed in. This process is only effective for undamaged asbestos-containing substances. Repair is, at best, a temporary measure. All asbestos will eventually have to be removed. And maintaining the sealing and continuing the inspections can be expensive.
If materials are soft or crumbly or otherwise damaged, sealing is not appropriate. Covering involves placing something over or around the material that contains asbestos to prevent release of fibers.
Asbestos removal is an expensive and hazardous process. Situations where removal may be required including remodeling, major structural changes, and if the asbestos material is damaged and can not be otherwise repaired.
Removal is complex, and should (in many cases, legally must ) be done only by a contractor with special training and licenses. Improper removal may increase the health risks to those exposed! In addition, the asbestos removed must be managed according to the state and federal TSCA asbestos disposal regulations.
Of course, any demolition or extensive remodeling will involve some removal and disposal. And you should be forewarned that a notification to the EPA is required PRIOR to demolition or disposal.
Finally, if you think that you may have been exposed to any amount of loose asbestos in any degree, no matter how long ago, see your doctor. Don't smoke! It synergistically increases many times your chances of being affected by asbestos.