October 7, 2011

Asbestos meaning

Asbestos is a set of six naturally occurring silicate minerals exploited commercially for their desirable physical properties. They all have in common there, eponymous, asbestiform habit, long, (1:20) thin fibrous crystals. The inhalation of asbestos fibers can cause serious illnesses, including malignant lung cancer, mesothelioma (a formerly rare cancer strongly associated with exposure to amphibole asbestos), and asbestosis (a type of pneumoconiosis). Long exposure to high concentrations of asbestos fibers is more likely to cause health problems. The European Union has banned all use of asbestos and extraction, manufacture and processing of asbestos products. 

Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its sound absorption, average tensile strength, and its resistance to fire, heat, electrical and chemical damage. It was used in such applications as electrical insulation for hotplate wiring and in building insulation. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement (resulting in fiber cement) or woven into fabric or mats. Commercial asbestos mining began in the Eastern Townships of Quebec, Canada and the world's largest asbestos mine is located in the town of Asbestos, Quebec.

Asbestos use in human culture dates back at least 4,500 years, when evidence shows that inhabitants of the Lake region in East Finland strengthened earthenware pots and cooking utensils with the asbestos mineral anthophyllite. Asbestos was named by the ancient Greeks. One of the first careful descriptions of the material is attributed to Theophrastus in his text On Stones, around 300 BC, although the naming of minerals was not very consistent at that time (the more consistent name of this material in both modern and ancient Greek is amiantos (undefiled, pure) whence the names of it in other languages like French amiante; the modern Greek word σβεστος or ασβέστης stands consistently and solely for lime, not for the material known as asbestos in English). 

The term asbestos is traceable to Roman naturalist Pliny the Elder's manuscript Natural History, and his use of the term asbestinon, meaning "unquenchable". While Pliny is popularly attributed with recognising the detrimental effects of asbestos on slaves, examination of primary sources shows that this is not so. Charlemagne, the first Holy Roman Emperor (800-814), is said to have had a tablecloth made of asbestos. 

According to Tabari, one of the curious items belonging to Khosrow II Parviz, the great Sassanian king (r. 531-579), was a napkin that he cleaned by simply throwing it into fire. This is believed to be made of asbestos. (This is also mentioned in The New Encyclopedia Britannica, vol. 6, 2003, page 843). Wealthy Persians, who bought asbestos imported over the Hindu Kush, amazed guests by cleaning the cloth by simply exposing it to fire. According to Biruni in his book of Gems, any cloths made of asbestos (Persian: آذرشست, āzarshost) were called (Persian: شستكه) shostakeh. Some of the Persians believed the fiber was fur from an animal (named samandar, Persian: سمندر) that lived in fire and died when exposed to water, hence the old mistaken myth that the salamander tolerated fire.

While traveling to Siberia, Marco Polo described being offered garments that could not burn. He was told that the wool was from the salamander, but did not accept this explanation. At last he was told that these garments were made from a mineral from the mountains, which contained threads just like wool.

Some archeologists believe that ancients made shrouds of asbestos, wherein they burned the bodies of their kings, in order to preserve only their ashes, and prevent their being mixed with those of wood or other combustible materials commonly used in funeral pyres. Others assert that the ancients used asbestos to make perpetual wicks for sepulchral or other lamps. In more recent centuries, asbestos was indeed used for this purpose. Although asbestos causes skin to itch upon contact, ancient literature indicates that it was prescribed for diseases of the skin, and particularly for the itch. It is possible that they used the term asbestos for soapstone, because the two terms have often been confused throughout history.

source wikipedia asbestos