Asbestos is a term used to name a number of different fibrous minerals with different properties. It is unfortunate that they are all named asbestos as there are 2 distinctly different fibres the serpentines, chrysotile, and the amphiboles, all the others.
As natural minerals they are being weathered into the air all the time and so there are small quantities of asbestos fibres in the air throughout the world.
I will not discuss in any depth the different chemical compositions of the different fibres but mention the basic differences between the 2 types and the different risks to human health from breathing in the different fibres.
Commercial use has mainly been made of the following fibres
These 3 fibres can be split into 2 distinct groups:
Chrysotile or white asbestos, are formed of several scrolls and could be said to have a curly, silky nature see diagram
Tthere is increasing evidence that the curly nature see picture of the fibres helps the human body to remove chrysotile fibres from the lung,
where as a proportion of any amphiboles fibres inhaled will never be removed from the human body.
all other asbestos types, These fibres are more rod like in nature with the cross section comprising a uniform stacked arrangement of structural units, see diagram of the amphibole crystal structure
they are generally straight and stiff, (see the magnified image below) , and so more able to penetrate the lung wall.
For more information on the geology and chemical composition of the different types of asbestos see: http://en.wikipedia.org/wiki/Asbestos
The following forms were not usually used on their own but are often contaminants of the commercially used fibres, they are amphiboles.
The 3 commercially used fibres have very different risk factors associated with them, If chrysotile is given a risk factor of 1 then amosite is likely to have a risk factor of 100 and crocidolite a factor of 200, the risk factor for the other 3 is likely to be similar to amosite.
Materials containing crocidolite were last manufactured in the UK in the mid 1960s and most will now have been removed from buildings.
Materials containing amosite were last manufactured in the UK in the late 1970s and as it was mainly used in asbestos insulating board, which was used for fire protection and insulation, much will still remain in buildings.
Materials containing chrysotile were the most commonly used of all the asbestos containing materials, with the largest percentage being asbestos cement which was last sold in the UK in 1999 when asbestos containing materials were finally prohibited and most will still be in use in buildings today.
It is still likely that the majority of buildings in the UK contain asbestos containing materials.
The diseases most commonly associated with asbestos inhalation are:
is a scaring of the lung similar to pneumoconiosis and is caused by inhaling large quantities of fibres over a considerable length of time. It is not a disease that is likely to be contracted without extensive exposure to free asbestos fibres over an extended period of time. It can indicate an increased risk of lung cancer or mesothelioma. To read more about this disease go to: http://en.wikipedia.org/wiki/Asbestosis
a cancer of the lungs the risk of which will be increased by exposure to large quantities of asbestos. Smoking and exposure to asbestos will markedly increase the risk. It usually takes many years from first exposure to the onset of the disease. To read more about lung cancer go to: http://en.wikipedia.org/wiki/Lung_cancer
a cancer of the chest lining or pleura, or peritoneum (the lining of the abdominal cavity); exposure to asbestos greatly increases the risk of catching this disease. It usually takes many years from first exposure to the onset of the disease. To read more about Mesothelioma go to: http://en.wikipedia.org/wiki/Mesothelioma
a thickening of the chest lining or pleura, which can cause shortness of breath and indicates exposure to high quantities of asbestos and might indicate an increased risk of cancers such as lung cancer or mesothelioma. It usually takes many years from first exposure to the onset of the disease. To read more about Pleural thickening go to: http://www.hse.gov.uk/statistics/causdis/pleural/
a thickening in spots of the Pleura or chest lining, with time they ossify, normally they do not cause any symptoms or problems, but they are an indication of asbestos exposure and so may indicate an increased risk of Mesothelioma or lung cancer in the future.
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