Friday, February 9, 2007

Asbestos Types

Individuals who don’t know a lot about asbestos but have heard much about its many dangers may be surprised to learn that asbestos is a natural substance, found in various places on the planet, not a man-made substance developed for commercial use. Indeed, asbestos is mined in many countries throughout the world and was, at one time, widely used in many commercial products, usually for a number of reasons including its high resistance to heat and chemicals, its low electrical conductivity, and its strength and flexibility.

AsbestosThis natural material was first used in 1828 as a lining material for steam engines. For many years, vinyl-asbestos tiles were used for floor coverings and automobile clutch facings and brake linings also contained asbestos. Alarmingly, asbestos was even used in toothpaste, as artificial snow for Christmas trees, and as incision thread for surgery patients.

A total of six different types of asbestos are found in the earth and they’re categorized into two separate groups: 1) serpentine, with a layered form and curly fibers, and 2) amphibole, with straight fibers and a chain-like structure. The latter has been determined to be the most dangerous type of asbestos to which human beings can be exposed.

The serpentine group has just one member…Chrysotile. This is the most common type of asbestos, still found in buildings in nearly every developed country throughout the world. As a matter of fact, figures show that between 90% and 95% of all asbestos found in buildings and other commercial products that contain asbestos is of the Chrysotile variety. Furthermore, this is the only type which is still mined, primarily in Canada, Africa, and the former Soviet Republic. Because of its rampant use, Chrysotile accounts for most asbestos-related health problems.

Chrysotile is usually white or green in color and is most often used in insulation and fireproofing products. It can also be woven into asbestos tapes and clothes and is used in the manufacture of cement in the form of sheets, shingles, and pipes. This type of asbestos is also used in a number of friction materials, largely due to its high resistance to heat. These products include automobile brake shoes, disk pads, clutches and elevator brakes. In addition, roof sealants, textiles, plastics, rubbers, door seals for furnaces, high temperature caulking, paper, and components for the nuclear industry contain Chrysotile.

Five kinds of asbestos are members of the amphibole variety. Only two of them were consistently used in commercial applications – Amosite and Crocidolite. These two forms, possessing strong and stiff fibers, are highly dangerous when airborne fibers are inhaled or ingested.

The commercial production of Amosite, also known as “brown asbestos”, was halted within the last decade. Most often used as an insulating material, the use of Amosite has been banned in most countries for several decades. However, at one time, it was the second most-commonly used type of asbestos, accounting for about 5% of the asbestos used in factories and buildings and was sometimes included for anti-condensation and acoustical purposes.

Crocidolite is a rare form of asbestos, bluish in color, and is highly resistant to chemicals. It’s believed to be the most lethal form of asbestos and was often used as a reinforcement material for plastics. In the mid-twentieth century, Crocidolite was also used in pre-formed thermal insulation and, prior to that, some yarns and rope lagging contained this form of asbestos.

Though the use of most asbestos products has long been banned in most developed countries, many buildings may still contain some form of this dangerous mineral. To learn more about the various types of asbestos and their uses, be sure to sign up for a free information packet, available from this site.