What is asbestos?

What asbestos is

Asbestos materials have been used in buildings for the last hundred years or so. This is mainly because of the material’s natural properties, and because it could be mined and processed relatively cheaply.

The three main types of asbestos that occur naturally belong to two main fibre structures.

The main types of asbestos

White asbestos (chrysotile)

By far the most common type is chrysotile, usually called white asbestos. It has been imported for well over a hundred years.

Its fibres are unusual: very long and curly. This is known as a serpentine structure. It comes from the way the crystal lattice forms concentric bands radiating out from a central core, and it’s unique among the asbestos fibre types.

Brown and blue asbestos (the amphiboles)

The other types have a very different crystal structure, made up of parallel columns. This produces long, straight, fine, needle-like fibres.

This second class of fibre, known as the amphiboles, includes amosite, usually called brown asbestos, and crocidolite, usually called blue asbestos.

Asbestos and health

It has been accepted for many years that breathing in asbestos leads to a range of lung diseases, which are irreversible and in some cases fatal.

Pleural plaques and pleural thickening

Exposure to any type of asbestos fibre may first lead to a series of benign (non-cancerous) effects, generally known as pleural thickening and pleural plaques. These can also be seen in people with no asbestos exposure but, if present to a high degree, they’re usually a sign that some asbestos exposure has occurred.

Asbestosis

It has long been established that severe exposure, as was the case in the early asbestos processing factories, may also lead to a serious lung disease. Much of the lung tissue becomes consolidated by scar tissue, because of prolonged irritation from asbestos fibres retained in the lungs.

This condition, commonly called asbestosis, is in many ways similar to the disease of coal miners, and belongs to the group of lung diseases known as pneumoconiosis.

Asbestosis is not necessarily fatal. However, approximately fifty percent of people diagnosed with it go on to develop one or more lung tumours. When asbestosis is fatal, it’s usually indirectly so: the extra strain on the heart results in left-sided heart failure.

Even when someone is removed from exposure, the disease continues to progress. This is because of the large amount of fibre retained, which the lungs’ natural defences can’t readily remove. As it progresses, the lungs gradually lose their elasticity and breathing becomes extremely strenuous. As the tissue is obliterated, the body’s ability to absorb oxygen is badly affected. In its advanced state, asbestosis is severely disabling, with acute shortness of breath and weakness even after minimal exertion.

Lung cancer

Asbestos has long been associated with lung cancer (bronchial carcinoma), although it’s probably not as potent a cause of cancer as cigarette smoke. The disease does not have a high success rate for treatment.

Exposure to all asbestos fibre types has been shown to significantly increase the risk of lung cancer, with higher exposures resulting in a higher risk.

Mesothelioma

The third serious disease linked to breathing in asbestos is mesothelioma: a rare, incurable tumour that forms in the lining of the lungs.

Both mesothelioma and lung cancer take a long time to develop before they can be diagnosed. For lung cancer caused by asbestos exposure, the delay between first exposure and the onset of the disease is often 25 years or more. For mesothelioma, it may be more than forty years. From diagnosis of mesothelioma until death, the time is rarely more than eighteen months, and the disease’s progress is extremely distressing for both sufferers and carers.

Many schools of thought believe that asbestos exposure causes almost all mesothelioma cases, and that some occur after only minimal exposure to the fibrous dust.

Epidemiological studies show that the single most potent cause of mesothelioma is exposure to blue asbestos, with brown possibly a slight second, and white rarely associated with it on its own.

Where asbestos is found in buildings

Asbestos materials have been used almost everywhere in buildings. The mineral resists heat and chemicals, has great tensile strength and long, flexible fibres, and can be woven or mixed into plastic, bitumen and cement. As a result, it was used universally.

It’s commonly found in:

• spray coatings
• thermal insulation products for hot and cold water systems
• strong external weather boards and products
• insulation boards, used as fire protection cladding on structural steelwork, partitions, ceilings and soffits
• woven products, such as blankets, packings, gloves and fire break curtains

Asbestos and refurbishment work

Various treatments are available for making asbestos building products safe. During refurbishment, though, the only really sensible solution is to remove the materials, following a detailed survey of the building.

The costs on major contracts when “unknown asbestos” is discovered after the main contractor has started on site are well known. Wherever possible, it’s vital that all asbestos materials are removed before the main contract. This gives the main contractor free access to as much of the work area as possible from the start, more flexibility in where they can work, and fewer hold-ups if the removal work finishes behind schedule.

Where possible, it’s also desirable for the client, or their representative, to run the asbestos removal contract separately from the main contract, and to appoint an asbestos project manager to make sure the client’s duty of care is fully protected.