Asbestos is a naturally occurring fibrous silicate mineral. It has been used since Roman times, and at its peak was used in over 3000 products. It occurs throughout the world including Africa, Australia, Canada, China Russia, and the United States of America. It is estimated that over 6 million tonnes of asbestos has been mined worldwide. Asbestos is a commercial term rather than a scientific or geological one. It comes in three main forms: crocodilite (blue asbestos) amosite (brown) and chrysotile (white) although the colour is not significant in identification. There are other forms, such as actinolite, anthophyllite and tremolite, although these are much less common in buildings. Asbestos is a very versatile building material. As a result, it was extensively used in a variety of applications, including cement, sprayed coatings, lagging, insulating board, textiles, floor tiles and roofing felt. Unfortunately, the physical properties which give it these qualities, the long, flexible fibres, have been found to be the cause various diseases such as lung cancer, asbestosis and mesothelioma, making asbestos the biggest single occupational health problem ever encountered. Although the use of asbestos has been prohibited for some time, there is usually a substantial delay between the first exposures of asbestos to the first symptoms of any asbestos related disease, varying from between 10 to 60 years.
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