asbestos

Description

Asbestos is a fibrous silicate of magnesium and calcium. However, the “extender”, known as “asbestine”, that has come to the forefront in paint making, is really a ring silicate of magnesia and slightly alkaline, but without the fibrous texture of asbestos or amianth. Asbestine pulp (as a certain variety of the material mined at the foot of the Adirondack mountains is known to the trade), although it is sold in the dry powdered form, belongs really to the soapstone or talc variety. But it is not as unctuous as either of those, has a harder texture, and is of whiter color than either soapstone or talc.

Chemical Properties

TREMOLITE, the mineral tremolite is a calciummagnesium silicate corresponding to the formula Ca2Mg5Si8O22(OH)2, belonging to the amphibole group. The replacement of magnesium by ferrous iron causes tremolite to approach actinolite in composition. Tremolite is monoclinic, developing bladed prismatic crystals, but it is frequently found in compact columnar, granular, or fibrous masses. The perfect prismatic cleavage at angles of 56° and 124° typical of this group is to be noted; hardness, 5–6; specific gravity, 2.9–3.1; luster, vitreous to silky; color, varies from white or whitish-gray through shades of green or greenish-yellow; transparent to opaque. Tremolite is formed as a result of contact metamorphism and occurs in marbles, dolomites, and schists. It may alter to talc.

Chemical Properties

Asbestos, a naturally occurring fibrous mineral, is widespread in nature. Asbestos is noncombustible, resistant to heat, and features a low conductivity and is insoluble in water. Asbestos is classified into two groups: (i) serpentine and (ii) amphibole. The serpentine group includes: (i) chrysotile: molecular formula: Mg3Si2O5(OH)4; and (ii) crocidolite: molecular formula: Na2Fe2(Fe,Mg)3Si8O22(OH)2. The amphibole group includes (i) amosite: molecular formula: Na2Fe2(Fe,Mg)3Si8O22(OH)2; (ii) anthophyllite: molecular formula: Mg7Si8O22(OH)2; (iii) tremolite: molecular formula: Ca2Mg5Si8O22(OH)2; and (iv) actinolite: molecular formula: Ca2(Mg,Fe)5Si8O22(OH)2. Asbestos fi bers can be very small—up to 700 times smaller than a human hair. Because it is fire resistant, resists many chemicals, and is an excellent insulator, asbestos was added to a variety of building materials and other products. The most important deposits are to be found in the former Soviet Union, Canada, and South Africa. Natural emissions are produced, for example, by the weathering of serpentine rocks.

Asbestos is not a chemical element, but rather an umbrella term for two groups of minerals, namely, serpentine and amphibole asbestos. Asbestos is a fibrous, impure mineral and its color varies between pure white and green, brown or gray, depending on the iron-oxide content. Crocidolite is blue or blue asbestos with fibers between 20 and 25 nm long that are smooth and greasy to the touch. Asbestos, because of its heat resistance, suppleness, and its capacity for being incorporated into inorganic and organic binders, is used in industry for thermal insulation, fi reproofing, and sealing, in addition to acting as a filler in the production of countless composites (more than 3000). Economic exploitation is centered on chrysotile asbestos from the serpentine group (95%). Five percent of amphibole asbestos is used for asbestos fi ber production.
Spun asbestos is used for fireproof, chemical-resistant clothing. When mixed with cement, asbestos is cast to form panels and pipes (70%–90% of the world’s production is used in the construction industry in Western Europe; acc. WHO, 1987). Asbestos has also been used as a filter material in the drinks and pharmaceutical industry and for the manufacture of brake and clutch linings for motor vehicles.

Physical properties

White or greenish (chrysotile), Blue (crocidolite), or gray-green (amosite) fibrous, odorless solids; freezing/ melting point5600 C (Decomposes). Hazard identification (based on NFPA-704 M Rating System): Health 2; flammability 0; reactivity 0. Insoluble in water. Asbestos is a generic term that applies to a number of naturally occurring, hydrated mineral silicates incombustible in air and separable into filaments. The most widely used in industry in the United States is chrysotile, a fibrous form of serpentine. Other types include amosite, crocidolite, tremolite, anthophyllite, and actinolite.

Uses

Asbestine pulp or asbestine in its various varieties has been used for many years by manufacturers of paints, not so much as an adulterant, but rather to make the paint more buoyant in order to keep it from settling to any extent, as this compound is of very low-specific gravity and a great oil absorber.

Uses

Although asbestos use dates back at least 2,000 years, modern industrial use began around 1880. Use of asbestos peaked in the late 1960s and early 1970s, when more than 3,000 industrial applications or products were listed. Asbestos has been used in roofing, thermal and electrical insulation, cement pipe and sheets, flooring, gaskets, friction materials, coatings, plastics, textiles, paper, and other products (ATSDR 2001, HSDB 2009). The U.S. Consumer Product Safety Commission banned use of asbestos in general-use garments, but asbestos may be used in fire-fighting garments if they are constructed to prevent release of asbestos fibers (HSDB 2009). Domestically used asbestos fibers are classified into seven quality categories or grades. Grades 1, 2, and 3 include the longer, maximum-strength fibers and generally are used in the production of textiles, electrical insulation, and pharmaceutical and beverage filters. Grades 4, 5, and 6 are medium-length fibers used in the production of asbestoscement pipes and sheets, clutch facings, brake linings, asbestos paper, packaging, gaskets, and pipe coverings. Grade 7 includes short fibers generally used as reinforcers in plastics, floor tiles, coatings and compounds, some papers, and roofing felts (OSHA 1986).
The four commercially important forms of asbestos have been chrysotile, amosite, anthophyllite, and crocidolite (IARC 1973); however, commercial use of anthophyllite was discontinued by the 1980s (IPCS 1986, HSDB 2009). Chrysotile, amosite, and particularly crocidolite all have extremely high tensile strengths and are used extensively as reinforcers in cements, resins, and plastics. Although chrysotile is most adaptable to industrial use, crocidolite and amosite are particularly useful in combination with chrysotile for adding specific properties, such as rigidity (OSHA 1986). By the 1990s, chrysotile accounted for more than 99% of U.S. asbestos consumption (ATSDR 2001). By 2008, chrysotile was the only type of asbestos used in the United States (Virta 2008); 64% of chrysotile used was categorized as grade 7 asbestos (with fiber lengths less than 3 mm), followed by grades 4, 5, and 3 (Virta 2002a, 2009).
In 1973, when U.S. consumption of asbestos was at its peak, the major markets included asbestos cement pipe (24%), flooring (22%), roofing (9%), friction products, such as automobile brakes and clutches (8%), and packing and gaskets (3%) (Virta 2002a). In 2009, roofing products accounted for about 65% of U.S. consumption; the remaining 35% was attributed to “other uses” (USGS 2010).

Uses

Thermal and electrical insulation; fireproofing; cement products

Definition

A fibrous variety of various rock-forming silicate minerals, such as the amphiboles and chrysotile. It has many uses that employ its properties of heat-resistance and chemical inertness. Prolonged exposure to asbestos dust may cause asbestosis – a form of lung cancer.

Definition

A group of impure magnesium sil- icate minerals that occur in fibrous form.

General Description

Any of a group of impure magnesium silicate minerals that occur as slender, strong, flexible fibers. Colors range from white to gray, green, brown. Resistant to fire and most solvents. Breathing of ASBESTOS dust causes ASBESTOSis and lung cancer. Used as a heat resistant material, in cement, furnace bricks, and in brake linings.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

ASBESTOS minerals are generally unreactive.

Hazard

Inhalation of dust or fine particles is dangerous. Carcinogenic.

Health Hazard

Various asbestos-induced illnesses are known from the industrial-medicine sector in which the size of the fi bers plays a crucial role. Generally speaking, fi bers with a diameter of <2 m and a length of >5 μm are considered to be hazardous to health (diameter:length = 1:3). Such a fi ber size is capable of entering the lungs, accumulating and becoming encapsulated. Fibers have also been found to have a certain migration capability in the organism and the cell metabolism. Accumulation in the lungs causes sclerosis of the pulmonary alveoli, thereby impairing oxygen exchange. The inhalation of large quantities of fi ber can cause asbestosis, which increases the risk of bronchial cancer. In particular, dusts <200 μm are highly toxic and are suspected of being a direct cause of tumors. Exposure to asbestos irritates the eyes and the respiratory tract. Direct penetration into damaged skin produces excessive hornifi cation. Fibers in the lungs cause chronic bronchitis, irritation of the pleura and pleurisy. Distension of the lungs can result in lung cancer. Workplace exposure may produce periods of latency in the gastrointestinal tract lasting up to 40 years. To date, there are no known characteristic toxicology data (DVGW, 1988).
Asbestos fi bers are released into the environment by natural and anthropogenic processes. The liberation of asbestos during the manufacture and processing of materials containing asbestos must be signifi cantly reduced, especially in confi ned areas and at workplaces because of the great hazard to the respiratory organs, in particular the lungs. There is increasing speculation that the oral intake of asbestos can cause tumors. Therefore, there is no justifi cation for the further use of asbestos cement in drinking water pipes. Numerous products containing substitute materials are now making it possible to dispense with the use of substances containing asbestos.

Fire Hazard

Some may burn but none ignite readily. Containers may explode when heated. Some may be transported hot.

Industrial uses

Any of six naturally occurring minerals characterizedby being extremely fibrous (asbestiform),strong, and incombustible. They areutilized in commerce for fire protection; asreinforcing material for tiles, plastics, andcements; for friction materials; and for thousandsof other uses. Because of a great concernover the health effects of asbestos, many countries have promulgated strict regulationsfor its use. The six minerals designated asasbestos also occur in a nonfibrous form. Inaddition, there are many other minerals thatmorphologically mimic asbestos because oftheir fibrous nature.
The important characteristics of the asbestosminerals that make them unique are theirfibrous form; high strength and surface area;resistance to heat, acids, moisture, and weathering;and good bonding characteristics withmost binders such as resins and cement.
Asbestos is used for many types of products because of its chemical and thermal stability, high tensile strength, flexibility, low electrical conductivity, and large surface area. Past uses of asbestos, such as sprayed-on insulation, where the fibers may become easily airborne, have been generally abandoned. Asbestos is used predominantly for the construction industry in the form of cement sheets, coatings, pipes, and roofing products. Additional important uses are for reinforcing plastics and tiles, for friction materials, and packings and gaskets.

Safety Profile

Confirmed human carcinogen producing lung tumors. Experimental neoplastigenic and tumorigenic data. Human pulmonary system effects by inhalation. Usually at least 4 to 7 years of exposure are required before serious lung damage (fibrosis) results. Mutation data reported. A common air contaminant.

Potential Exposure

Most asbestos is used in the construction industry. Much of it is firmly bonded, i.e., the asbestos is “locked in” in such products as floor tiles, asbestos cements, and roofing felts, and shingles; while the remaining 8% is friable or in powder forms present in insulation materials, asbestos cement powders, and acoustical products. As expected, these latter materials generate more airborne fibers than the firmly bonded products. The asbestos used in nonconstruction industries is utilized in such products as textiles; friction material including brake linings and clutch facings; paper, paints, plastics, roof coatings; floor tiles, and miscellaneous other products. Significant quantities of asbestos fibers appear in rivers and streams draining from areas where asbestos-rock outcroppings are found. Some of these outcroppings are being mined. Asbestos fibers have been found in a number of drinking water supplies, but the health implications of ingesting asbestos are not fully documented. Emissions of asbestos fibers into water and air are known to result from mining and processing of some minerals. Exposure to asbestos fibers may occur throughout urban environments perhaps resulting from asbestos from brake linings and the flaking of sprayed asbestos insulation material. In recent years, much effort has been put into removal of asbestos insulation, particularly from schools and other public buildings where worn or exposed asbestos causes public exposure. Incompatibilities: None

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water.

Carcinogenicity

Asbestos and all commercial forms of asbestos are known to be human carcinogens based on sufficient evidence of carcinogenicity from studies in humans.

storage

Color Code—Blue: Health Hazard/Poison: Store ina secure poison location. Prior to working with asbestosworkers must be, by law, trained in its proper handling andstorage. Asbestos should be stored wet with special surfactants and water. Keep asbestos in closed, impermeable,sealed containers. Protect against physical damage. A regulated, marked area should be established where this chemicalis handled, used, or stored in compliance with OSHAStandard 1910.1045.

Shipping

UN2212 Blue asbestos (Crocidolite) or Brown asbestos (amosite, mysorite), Hazard class: 9; Labels: 9-Miscellaneous hazardous material. UN2590 White asbestos (chrysotile, actinolite, anthophyllite, tremolite), Hazard class: 9; Labels: 9-Miscellaneous hazardous material.

Incompatibilities

None.

Toxics Screening Level

The asbestos initial risk screening level (IRSL) is being set at 2.2 E-5 μg/m3.

Waste Disposal

Asbestos may be recovered from waste asbestos slurries as an alternative to disposal. Landfilling is an option for disposal if carefully controlled.