Lungnet

A Brief History

Asbestos (from the Greek 'amiantus' meaning unquenchable) is a fibrous mineral which has been known and used for as long as 4,500 years. Many centuries before Christ, Finnish peasants mixed it in pottery and sealed cracks in their log huts with it. The ancient Romans wove asbestos fibres into fabrics to make towels, nets and even head coverings for women.

In medieval times, Emperor Charlemagne reportedly used an asbestos tablecloth to convince some Barbarian guests that he had supernatural powers - by throwing it into a fire and pulling it out unsinged! Some enterprising medieval merchants even sold asbestos crosses, citing their resistance to fire as evidence that they were made from wood from 'the true cross'.

Until the 19th Century, asbestos remained little more than a curiosity. This changed, however, with the advent of the Industrial Age in the 1800's when industry realised its potential uses. Before long, asbestos supported a flourishing global industry.

In the early 1900's, doctors in Europe knew that asbestos workers were dying from respiratory ailments. In 1924, Dr W E Cooke reported in the British Medical Journal cases of pulmonary fibrosis (asbestosis) in workers employed in the asbestos industry. Unfortunately it took many years for this information to be acted on.

Where is Asbestos mainly found?

Large deposits of asbestos have been discovered in the Ural Mountains of Russia, in the Alps of northern Italy, Canada, USA, South Africa and Rhodesia. In Australia, large deposits of blue asbestos were found in the north of Western Australia around Wittenoom Gorge in the Hammersley Ranges, and some deposits of white asbestos have been mined in Northern New South Wales. Asbestos is no longer mined in Australia.

Uses of asbestos have included fibro-sheeting, corrugated roofing, asbestos cement pipes, thermal insulation and fire proofing. It has also been used as an additive in paints and sealants, in textiles such as felts and theatre curtains, in gaskets, and in friction products like brake linings and clutches. During the peak post-war building years, ie 1950's, 60's and 70's, asbestos found its way into most public buildings, including hospitals, schools, libraries, office blocks and factories. Workplaces such as ships' engine rooms and power stations were heavily insulated with asbestos. With the recognition of its dangers there are now active programs in most areas to safely remove any asbestos where it remains a health risk, and all states have regulations to cover this..

Why was Asbestos so useful?

Asbestos is a term applied to some mineral silicates present in a fibre form. There are many members of the family: common among these are blue asbestos (crocidolite), white (chrysotile) and brown or grey asbestos (amosite). Other forms of asbestos include anthophyllite, used mainly in Finland, and tremolite, present in some commercial talcs.

Because of its unique properties - flexibility, tensile strength, insulation (from heat and electricity) and chemical inertness - asbestos is one of the most useful and versatile minerals known to mankind. It is the only natural mineral that can be spun and woven like cotton or wool into useful fibres and fabrics.

How does Asbestos enter the lungs?

Any particle gaining entry to the air passages must by-pass a number of protective mechanisms in order to reach the tiny air sacs or alveoli. These protective systems remove all but a very small number of the very finest inhaled particles. If asbestos fibres are inhaled, they must first pass the filtration mechanisms lining the nose and the upper airways down to the fine airways that lead to the small alveoli. Hence, only very small particles barely visible with a high powered microscope, may eventually reach the alveoli. Blue asbestos fibres are relatively long and thin and are more likely to reach the alveoli rather than the curlier fibres of white asbestos.

What happens to asbestos within the lungs?

Asbestos fibres reaching the alveoli are handled in different ways by the body. Scavenger cells may entirely engulf a very small fibre and carry it away out of the lung in the sputum or through the draining lymphatic system. Some fibres may also get covered with a yellowish-brown coating composed of iron and protein. These coated fibres are known as 'asbestos bodies'. Other fibres may, however, remain untouched by these mechanisms and can remain in the body over a lifetime with no apparent ill effect. Other fibres can lead to the lung changes listed below.

What sort of lung diseases can asbestos cause?

Asbestos-related diseases are believed to be caused more by the physical nature of asbestos fibres rather than their chemical properties, and the damage they inflict on the scavenger cells trying to engulf and ingest them.

Pleural Plaques

Unrelated to the appearance of any scar tissue within the lung themselves, discrete patches of thickening may appear on the lining of the chest wall and over the diaphragms in the pleural membranes that surround the lungs. It usually takes over fifteen years before they can be seen on a chest x-ray and are better seen on a CT or CAT scan. They usually do not produce any symptoms and do not lead to lung cancer or mesothelioma (see below). They are a marker of previous asbestos exposure.

Benign Asbestos-Related Pleural Effusion

In this condition, fluid called an effusion appears between the lung and the chest wall. Many other diseases, such as cancer and tuberculosis, can also give rise to an effusion, so they all have to be excluded before this diagnosis can be made. Typically, a benign pleural effusion occurs a long time after asbestos exposure but is sometimes seen within ten years of exposure. It can begin with symptoms such as breathlessness and chest pain (called pleurisy) or more commonly without any symptoms at all. It is sometimes associated with pleural plaques, but not always. The amount of fluid is usually small compared with other causes, and it goes away without any treatment. However, in a number of cases, it may recur sometime later.

Diffuse Pleural Thickening

This is different from pleural plaques and affects a bigger area of lung surface. It may result from the presence of pleural effusion. The thickening can be seen on chest x-ray and CT. Although most people don't have any symptoms, a dull chest ache and breathlessness can occur if the thickening becomes extensive.

Asbestosis

With the passage of time, inhaled asbestos fibres if present in very large numbers, can sometimes cause inflammation to occur in the lung tissues leading to scar tissue or fibrosis. This is often called 'interstitial fibrosis'. It causes the lungs to stiffen and it cuts down on the passage of oxygen between the air and the blood. Such reduced size and oxygen movement in the lungs may be measured by pulmonary function testing. On chest x-rays, fibrosis is seen as fine spots and linear shadows, called reticulation.

Asbestosis is usually slowly progressive and does not reverse. It leads to respiratory disability and sometimes death from respiratory failure. Symptoms include shortness of breath, coughing, and bluish skin discoloration called cyanosis, which occurs when the body's oxygen is too low.

Lung Cancer

Lung cancers occur more frequently amongst workers who have been exposed to asbestos of any kind. However, heavily asbestos-exposed workers and those who smoke cigarettes are particularly prone to develop lung cancer. If diagnosed early, such cancers may be totally removed by surgery. Chemotherapy and radiotherapy are also often used in treating lung cancer.

Current research is being done to see if there are any links between laryngeal and bowel cancer, and asbestos exposure.

Malignant Mesothelioma

Malignant Pleural Mesothelioma - Persons exposed to asbestos either within or outside the asbestos industry may, after many years, develop malignant mesothelioma. This cancer occurs in the cells of the pleura covering the surface of the lung and lining the inside of the chest wall and diaphragm. Crocidolite (blue asbestos) has the most potent effect in producing this cancer. This tumour may eventually totally envelope the lung, with a malignant growth sometimes several centimetres thick. The tumour is irreversible, poorly responsive to any current cancer treatments, and often fairly rapidly fatal. It may be accompanied by chest pain, fluid in the chest cavity (pleural effusion) and breathlessness. In rare cases combined surgery and chemotherapy may prolong life. Mesothelioma tumours have no relationship with tobacco smoking.

Peritoneal Mesothelioma - Around the outside of the coils of intestine and also lining the abdominal cavity is a membrane (the peritoneum) similar in character and thickness to the pleura. It is similar tissue to the pleura and, like it, can give rise to a malignant tumour called peritoneal mesothelioma, which is also related to previous asbestos exposure. This disease usually progresses slower then pleural mesothlioma..

What should I do if my exposure to Asbestos occurred in the workplace?

Some exposure to asbestos can be quite trivial but may be highlighted by the media in such a way it could elevate people's concern. When an asbestos-related problem is first diagnosed, discuss all concerns with your doctor including whether you should seek further information from a respiratory physician.

It may be appropriate to seek advice from your union, or employer.

There are several patient support groups around Australia catering for the needs of patients with an asbestos related condition. Phone 1800 654 301 for more information and a referral to a group near you.

Please Note: 

This information is intended by The Australian Lung Foundation to be used as a guide only and is not an authoritative statement. Please consult your family doctor or specialist respiratory physician if you have further questions relating to the information provided here.

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For details of patient support groups in Australia please call 1800 654 301

Content updated July 2002