Asbestos: an introduction
Contents
- Introduction
- The hazards associated with asbestos
- How do fibres enter the lung?
- Asbestosis
- Lung cancer from asbestos exposure
- Mesothelioma
- Pleural plaques and other conditions of the pleura
- Chrysotile asbestos
- Amphibole asbestos varieties
- Uses of asbestos
- Synthetic mineral fibres
- References
1. Introduction
Asbestos is the term used for the fibrous form of a number of naturally occurring silicate minerals that have been exploited commercially for their useful properties of:
- flexibility
- high tensile strength
- incombustibility
- low thermal conductivity and
- resistance to chemical attack
There are six minerals included in this definition; one, chrysotile, is in the serpentine group of minerals, while the others, including amosite, crocidolite, anthophyllite, actinolite and tremolite belong to the amphibole group of minerals.
The three types of asbestos that have found significant industrial uses are amosite (brown asbestos), chrysotile (white asbestos) and crocidolite (blue asbestos). None of these minerals is found in commercial quantities in the UK, the bulk of the material that were used by industry were imported from Canada or South Africa.
In total, over 5 million tonnes of asbestos were imported into the UK.
The maximum importation of asbestos into the UK occurred between 1970 and 1975; thereafter importation has declined and for the amphiboles it has ceased completely. The figure shows the amount of the three common types of asbestos imported into the UK during the last century.
Figure 1 Importation of asbestos into Britain during the last century
The physical and chemical properties of asbestos determined its uses and commercial value. The very fine fibres of chrysotile and crocidolite were ideal for textile products. Their thermal stability made the asbestos minerals useful in friction products and, together with their low thermal conductivity, in insulation materials. Asbestos cements made with chrysotile asbestos were durable materials because of the chemical bonding of the lime with the surface of the fibres.
The use of asbestos was banned in Britain in 1999, but there are still a great deal of asbestos-containing materials in buildings and industrial plant.
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