Asbestos or Asbestosis

(a misapplication of Latin: asbestos "quicklime" from Greek ἄσβεστος: a-, "not"; sbestos, "extinguishable") describes any of a group of fibrous metamorphic minerals of the hydrous magnesium silicate variety. The name is derived for its historical use in lamp wicks; the resistance of asbestos to fire has long been exploited for a variety of purposes. It was used in fabrics such as Egyptian burial cloths and Charlemagne's tablecloth, which, according to legend, he threw in a fire to clean. Asbestos occurs naturally in many forms (see below); it is mined from metamorphic deposits.

When asbestos is used for its resistance to fire or heat, the fibers are typically mixed with cement or woven into fabric or mats. It is used in brake shoes and gaskets for its heat resistance, and in the past was used on electric oven and hotplate wiring for its electrical insulation at elevated temperature, and in buildings for its flame-retardant and insulating properties, its tensile strength, flexibility, and resistance to chemicals. However, the inhalation of some kinds of asbestos fibers causes various serious illnesses, including cancer, and thus most uses of asbestos are banned in many countries. Fiberglass has been found to be a suitable substitute for thermal insulation and woven ceramic fiber performs as well or better as an insulator of high-temperature electrical conductors.

Most respirable asbestos fibers are invisible to the unaided human eye because their size is about 3.0-20.0 µm in length and can be as thin as 0.01 µm. Human hair ranges in size from 17 to 181 µm.[1] Fibers ultimately form because when these minerals originally cooled and crystallized, they formed by the polymeric molecules lining up parallel with each other and forming oriented crystal lattices. These crystals thus have three cleavage planes as other minerals and gemstones have. But in their case, there are two cleavage planes that are much weaker than the third direction. Thus when sufficient force is applied they tend to break along their weakest directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring over and over until they have been broken down to their smallest unit dimensions. For this reason, one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers in a normal environment over the course of time. As they get smaller and lighter, they become more mobile and more easily entrained (wafted) into the air, where human respiratory exposures typically result.