Asbestos, a Greek-derived word, is the commercial name given to a group of mineral fibres. It is not a man-made material, but a naturally occurring, fibrous mineral rock, formed over millions of years in the earth’s crust. Despite once being branded the ‘miracle mineral’, asbestos is now universally recognised as a dangerous, life threatening substance.
What is Asbestos?
The asbestos mineral rock is a silicate material, owing its fibrous nature to its silicon and oxygen content. Despite the fact that individual asbestos fibres are so fine they are invisible to the naked eye, asbestos is a very tough, durable material, which is also soft and flexible.
Asbestos is heat-resistant, incombustible, weather-proof and resistant to chemicals. It does not rot and it does not rust. These qualities make asbestos an ideal building material, and up until the 1980s, it was used in abundance for this very purpose. The use of asbestos has now been restricted or banned in many places around the world.
The problem with asbestos is that if its fibres are disturbed, they become airborne and can be inhaled or swallowed. This is potentially hazardous, for asbestos fibres are carcinogenic. If large enough amounts of asbestos fibres enter the body, especially the lungs, they can cause diseases such as lung cancer and mesothelioma. Thousands of people have died due to asbestos-related diseases.
What are the Different Types of Asbestos Fibres?
There are six recognised types of asbestos, and each type is either an amphibole or serpentine mineral. Amphibole asbestos has straight, needle-like fibres and consists of the silicates of aluminium, calcium, iron, magnesium and sodium, while serpentine asbestos has curled fibres and contains hydrated magnesium silicate. Amosite, crocidolite, tremolite, actinolite, and anthophyllite asbestos all consist of amphibole fibres, while chrysotile asbestos has serpentine fibres.
The three types of asbestos with the most commercial importance include:
- Chrysotile Asbestos (White Asbestos) - Chrysotile asbestos is made of white, fine, flexible, silky fibres, but can also be green or grey. Found in abundance in Canada, the United States, China, Russia, Rhodesia and Italy, chrysotile is the most commercially important of the asbestos minerals, used widely in heat-resistant materials.
- Amosite Asbestos (Brown Asbestos) - Amosite asbestos has brown, straight, brittle fibres. Once commonly used as an insulation material, it occurs mainly in South Africa and India.
- Crocidolite Asbestos (Blue Asbestos) - Crocidolite asbestos has straight, blue fibres. Once often used to make cement products and pressure piping, it is found mainly in South Africa, Western Australia, Bolivia and Rhodesia.
The other three types of asbestos have comparably less commercial or industrial significance, but were sometimes found as contaminants in other products such as talc and vermiculite. They are: actinolite asbestos, mainly found in South Africa and India; tremolite asbestos, which occurs mainly in Greece, Cyprus, Italy, Turkey, Pakistan and South Korea; and anthophyllite asbestos, mostly found in the United States and Finland.
Resources:
- Oury, T., Roggli, V., and T. Sporn. Pathology of Asbestos-Associated Diseases, 2nd Ed. New York: Springer, 2004.
- Asbestos.com. “Types of Asbestos.” (Accessed 27th November 2009)
- Mesothelioma Research Foundation of America. “Types of Asbestos.” (Accessed 27th November 2009)
Sharon Kirby - Sharon is a freelance health writer and contributes to various print and online publications. Writing credits include Nursing Times, Good ...
