|
What is Asbestos?
Asbestos is a collective term for a group of magnesium silicate materials (MgSiO4).
It is a fibrous mineral of variable length with excellent resistance to fire, heat and chemical attack.
It has been widely used in building products, gaskets, brake linings and roofing materials.
What are the different types and their former uses?
There are three main forms of asbestos:
1. Blue asbestos or Crocidolite, which is so dangerous that its use is virtually banned now in the UK.
It causes mesothelioma (malignant tumours) in the chest wall.
It is still present in old buildings, boiler plants, ships, etc., and this presence is a substantial threat to renovation or demolition workers.
2. Brown asbestos, or Amosite, is a type of Crocidolite used chiefly in insulation.
3. White asbestos, or Chrysotile, can be readily spun or woven into tape.
Other varieties of minor commercial importance are tremolite, actinolite and anthophyllite.
What are the harmful effects?
The dangers associated with asbestos are grave.
Asbestosis, a scarring of the lung, & cancers of the bronchi, pleura and peritoneum may result from breathing in the minute fibres.
Asbestosis may result from exposures as short as six weeks in heavy dust concentrations.
Brief exposure to blue asbestos can manifest itself later in life as mesothelioma, a specific and invariably fatal form of cancer.
UK legislation for asbestos control:
The current legislation is under Control of Asbestos Work Regulations 1987.
Its recommendations are:
1. Substitute asbestos with a different material where possible.
2. Use exhaust ventilation to reduce atmospheric contamination to below the control limits. Monitoring is mandatory and is enforced by the Health and Safety Executive.
The current control limits for asbestos dust are:
Crocidolite, amosite and tremolite: 0.2 fibres per millilitre of air.
Chrysotile: 0.5 fibres per millilitre of air.
The above control limits are based on measurements averaged over any continuous period of 4 hours, where the fibres measured are five millionths of a metre in length or greater.
The sample is taken by a prescribed membrane filter, which is then scanned by a microscope at 400-450 times magnification.
The Control of Asbestos in the Air Regulations 1990 imposes an emission limit of 0.1 mg/m3 for asbestos emission to the air by industrial installations.
Respiratory Problems
Asbestosis: This causes scarring and shrinkage of the lungs, and is thought to increase the risk of lung cancer by five times.
Mesothelioma: This is a cancer of the inner lining of the chest wall & abdomen, associated primarily with exposure to asbestos. There is no cure and patients usually die within a year of diagnosis.
The Lancet, (March 1995) stated that this material is a major hazard to health and no concentration of asbestos dust may be presumed safe.
|
|
