Asbestos is not a recognized (International Mineralogical Association) mineral name. It is a term for six naturally occurring silicate minerals exploited commercially for their desirable physical properties. They all have in common their asbestiform habit, long, (1:20) thin fibrous crystals. Asbestos in some forms can be toxic. The inhalation of asbestos fibers can cause serious illnesses, including malignant lung cancer, mesothelioma (a type of malignant neoplasm dependent mostly from exposure to asbestos), and asbestosis (a type of pneumoconiosis). Since January 1 2005 the European Union has banned all types of utilization of asbestos Directive 1999/77/EC and extraction, manufacture and processing of asbestos products Directive 2003/18/EC
For environmental samples, one must normally resort to electron microscopy for positive identification. However today gravimetric and PCM/PLM techniques are employed, which cannot readily identify the smallest, most hazardous, fibers. These techniques being limited to PM10 particulate size evaluation which completely ignores UFPs.
Asbestos became increasingly popular among manufacturers and builders in the late 19th century because of its resistance to heat, electrical and chemical damage, sound absorption and tensile strength. When asbestos is used for its resistance to fire or heat, the fibers are often mixed with cement or woven into fabric or mats. Asbestos was used in some products 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, tensile strength, flexibility, and resistance to chemicals.
Types and associated fibres
Six minerals are defined as "asbestos" including: chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite.
White
Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks which are common throughout the world. Serpentine rock is also the state rock of California. Its idealized chemical formula is Mg 3 (Si 2 O 5 )(OH) 4 . Chrysotile fibers are curly as opposed to fibers from amosite, crocidolite, tremolite, actinolite, and anthophyllite which are needlelike. Chrysotile, along with other types of asbestos, has been banned in dozens of countries and is only allowed in the United States and Europe in very limited circumstances. Chrysotile has been used more than any other type and accounts for about 95% of the asbestos found in buildings in America. Applications where chrysotile might be used include the use of joint compound. It is more flexible than amphibole types of asbestos; it can be spun and woven into fabric. The most common use is within corrugated asbestos cement roof sheets typically used for outbuildings, warehouses and garages. It is also found as flat sheets used for ceilings and sometimes for walls and floors. Numerous other items have been made containing chrysotile including brake linings, cloth behind fuses (for fire protection), pipe insulation, floor tiles, and rope seals for boilers.
Brown
Amosite, CAS No. 12172-73-5, is a trade name for the amphiboles belonging to the Cummingtonite - Grunerite solid solution series, commonly from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for amosite is Fe 7 Si 8 O 22 (OH) 2 . It is found most frequently as a fire retardant in thermal insulation products and ceiling tiles.
Blue
Crocidolite, CAS No. 12001-28-4 is an amphibole found primarily in southern Africa, but also in Australia. It is the fibrous form of the amphibole riebeckite. One formula given for crocidolite is Na 2 Fe 2+ 3 Fe 3+ 2 Si 8 O 22 (OH) 2 . Notes: chrysotile commonly occurs as soft friable fibers. Asbestiform amphibole may also occur as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that they are composed of fibers with widths less than 1 micrometer that occur in bundles and have very long lengths. Asbestos with particularly fine fibers is also referred to as "amianthus". Amphiboles such as tremolite have a crystal structure containing strongly bonded ribbonlike silicate anion polymers that extend the length of the crystal. Serpentine (chrysotile) has a sheetlike silicate anion which is curved and which rolls up like a carpet to form the fiber.
Other materials
Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca 2 Mg 5 Si 8 O 22 (OH) 2 ; actinolite asbestos (or smaragdite ), CAS No. 77536-66-4, Ca 2 (Mg, Fe) 5 (Si 8 O 22 )(OH) 2 ; and anthophyllite asbestos, CAS No. 77536-67-5, (Mg, Fe) 7 Si 8 O 22 (OH) 2 ; are less commonly used industrially but can still be found in a variety of construction materials and insulation materials and have been reported in the past to occur in a few consumer products.
Other natural and not currently regulated asbestiform minerals, such as richterite, Na(CaNa)(Mg, Fe ++ ) 5 (Si 8 O 22 )(OH) 2 , and winchite, (CaNa)Mg 4 (Al, Fe 3+ )(Si 8 O 22 )(OH) 2 , may be found as a contaminant in products such as the vermiculite containing zonolite insulation manufactured by W.R. Grace and Company. These minerals are thought to be no less harmful than tremolite, amosite, or crocidolite, but since they are not regulated, they are referred to as "asbestiform" rather than asbestos although may still be related to diseases and hazardous.
Producing nations
In 2006, 2.3 million tons of asbestos were mined worldwide, in 11 or 12 countries. Russia was the largest producer with about 40.2% world share followed by China (19.9%), Kazakhstan (13.0%), Canada (10.3%), and Brazil (9.9%).
Uses
Historic usage
Asbestos was named by the ancient Greeks, although the naming of minerals was not very consistent at that time (the modern Greek word ἀσβεστος stands for lime, not for the material known as asbestos in English). The ancients already recognized certain hazards of the material. The Greek geographer Strabo and the Roman naturalist Pliny the Elder noted that the material damaged lungs of slaves who wove it into cloth. Charlemagne, the first Holy Roman Emperor, is said to have had a tablecloth made of asbestos.
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 , āzarshast or Persian: آذرشب , āzarshab ) were called (Persian: شستكه ) shastakeh . 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.
While traveling to China, Marco Polo described observing miraculous garments that were cleaned by being placed in fires. These garments were likely made from asbestos.
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 alumen plumosum, because the two terms have often been confused throughout history.
Recent usage
Asbestos became more widespread during the industrial revolution; in the 1860s it was used as insulation in the U.S. and Canada. Development of the first commercial asbestos mine began in 1879 in the Appalachian foothills of Quebec. By th
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