“ABOUT CHRYSOTILE”
Chrysotile and Amphiboles: Two Different Fibre Types
Chrysotile
Chrysotile fibre is a sheet silicate which is formed as a very thin
rolled sheet. The sheet is about 8 angstoms thick (0.8 nanometers thick). It is composed
of a sandwich of magnesium and silica. In the lung, the acid environment of the
macrophage scavenger cell quickly breaks apart the sheet structure causing the fiber to
decompose into small pieces. These pieces can then be readily cleared from the lung. If
the fiber is swallowed and ingested it is attacked by the even stronger acid environment
(hydrochloric acid, PH 2) in the stomach.
Chrysotile has been known for over 2000 years, being used initially for cremation cloths,
oil lamp wicks and other textiles. But, it is only in the 19th Century that Chrysotile was
first mined commercially in the Urals (Russia), Italy and Canada.
Amphiboles
This is in contrast to the amphibole fibers which are formed as solid rods/fibers. The
structure of an amphibole is a double chain of silicate tetrahedral which makes it very
strong and durable. The external surface of the crystal structures of the amphiboles is
quartz-like, and has the chemical resistance of quartz. The amphibole fibers have
negligible solubility at any pH that might be encountered.
All these fibres are non-flammable. The major difference between chrysotile and
amphiboles is related to its chemical composition, its acid-resistant properties and its
effects on health. In contrast with amphiboles, chrysotile does not persist in the lungs
after inhalation; it is quickly eliminated by the body. A prolonged exposure to high
concentrations of chrysotile fibres is required for a clinical manifestation of pulmonary
damage to appear. In the past, such high exposures were frequent; it is no longer the case
today. On the other hand, because of their toxicity and their high biopersistence,
amphiboles are mainly responsible for mesothelioma and pulmonary diseases even
caused after a short or moderate exposure.
Chrysotile
Today, chrysotile is the only asbestos fibre commercialized. The industry now only
markets dense and non-friable materials in which the chrysotile fibre is encapsulated in a
matrix of either cement or resin. These products include chrysotile cement building
materials, friction materials, gaskets and certain plastics.
Ends