What is Asbestos?
Asbestos (Greek a-,”not”; sbestos, “extinguishable”), is the collective name for a group of naturally occurring minerals in their fibrous form, and hydrous silicates of magnesium. The fibres are strong, durable and resistant to fire. They are long, thin and flexible so they can be woven into cloth. The Romans made cremation cloths and wicks from it.
Due to these qualities, asbestos has been used in thousands of consumer, industrial, maritime, automotive, scientific and building products. During the twentieth century some 30 million tons of asbestos has been used in industrial sites, homes, schools, shipyards and commercial buildings.
Asbestos is of two principal classes, the amphiboles and the serpentines, the former of relatively minor importance. Chrysotile, in the serpentine class, constitutes about 95 percent of the world supply of asbestos, of which three-fourths is mined in Québec. Other large deposits exist in South Africa. In the United States, California, Vermont, and Arizona are the leading asbestos-producing states; however, the majority of United States deposits are of no commercial value.
Types of asbestos fibres:
Asbestos Procedures and Methods
Asbestos is obtainable by various underground mining methods, but the most common method is open-pit mining. Only about 6 percent of the mined ore contains usable fibres.
The fibres are separated from the ore by crushing, air suction, and vibrating screens, and in the process are sorted into different lengths, or grades. The most widely used method of grading, the Québec Standard Test Method, divides the fibres into seven groups, the longest in group one and the shortest, called milled asbestos, in group seven. The length of the fibres, as well as the chemical composition of the ore, determines the kind of product that can be made from the asbestos. The longer fibres have been used in fabrics, commonly with cotton or rayon, and the shorter ones for molded goods, such as pipes and gaskets.
In 1986 the Environmental Protection Agency proposed an immediate ban on the major uses of asbestos and the complete ban on all asbestos products within the next decade.
Common to many asbestos-containing products is that they are used to contain heat (thermal insulation). It is impossible to list all the products that contain asbestos. Some of the common asbestos-containing products are:
Why is Asbestos still a Problem?
A great deal of it has been widely used and currently remain in buildings, ships, industrial facilities and other environments. The fibres become airborne and pose serious human health hazards.
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