ABC Health & Wellbeing

Fact File

Asbestos

by Peter Lavelle

Asbestos is highly toxic, causing a range of lung diseases that are slow to develop but in many cases deadly. Mining companies and other industries that used asbestos are now being sued by affected workers and a new wave of cases may be looming among home renovators. Are you at risk?

Published 29/04/2004

[Image source: sxhchange]

• Background
• Benign pleural disease
• Lung cancer
• Asbestosis
• Mesothelioma
• Renovators, beware
• More info

Background

It was the wonder building product of the post World War 2 years; strong, light, durable, waterproof and fireproof, and a good insulator. Chemists knew it as a group of fibrous hydrated mineral silicates (including chrysotile, amosite, anthophyllite, and crocidolite) mined from deep underground. But collectively, these substances were more widely known as asbestos.

Between 1945 and 1980 in Australia, asbestos was widely used in the construction industry, as well as in shipyards, power stations, boiler makers and plumbing. It was a staple of home building too – used in fibro cement, insulation, fireproofing, pipes, paint, floor coverings, ceiling tiles, and roofing materials. Such was the local – and global demand – for asbestos that it was mined in Australia and exported.

But there was a problem. Asbestos is highly toxic, causing a range of lung diseases, that are slow to develop but in many cases deadly. Inhaling the fibres can cause a fibrous stiffening and shrinking of the lung, as well as lung cancer, particularly the incurable, rapidly-growing lung cancer known as mesothelioma.

The link between asbestos and lung disease was known in the early 1900s. Yet, despite warnings from health authorities, mining companies allowed their workers to be exposed to it, and industries that used asbestos in their manufacturing processes did nothing to protect their workers from its dangers.

It wasn't until the mid 1970s that the wider public was alerted to the dangers of asbestos. Gradually asbestos mining was phased out, and industries replaced asbestos with alternative products like fibreglass.

Depending on how old it is, fibro contains mixtures of blue (crocidolite, the most dangerous), brown (amosite), and white (chrysotile, the least dangerous) asbestos fibres. Blue asbestos use in fibro was phased out in Australia in 1967, brown in 1984 and white asbestos in 1989.

But asbestos-related disease is slow to declare itself. There can be a lag period of 20 years or more after exposure before symptoms of lung disease appear. People are still getting asbestos-related lung diseases now from exposure 30 or even 40 years ago.

Currently there are hundreds of people in Australia suing mining companies and other industries that used asbestos. In many cases, deaths occur before cases are heard or compensation paid.

And now there's a new wave of cases of asbestos-related disease appearing in people who are renovating or working on homes built between 1945 and 1980, about a third of which contain asbestos. People working in the home building industry now account for the biggest percentage of new cases of the deadly cancer mesothelioma.

Why is asbestos so dangerous? There are other types of inorganic dusts like coal or silica that cause disease when inhaled into the lung. What makes asbestos fibres so risky is their size. They are so tiny, they become airborne very easily and when inhaled, are able to find their way into the smallest airways and air sacs of the lung where the critical transfer of oxygen into the blood takes place. There they can do extensive damage.

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Benign pleural disease

One of the effects of inhaled asbestos fibres is to irritate and inflame the pleura of the lung. The pleura is the double-sided lining of the outer part of the lung: one side lines the outside of the lung tissue itself, the other lines the inner part of the chest wall. The pleura helps the lung glide over the chest wall as it expands and contracts during breathing.

Asbestos fibres can irritate and thicken the pleura. This thickening can be widespread (known as diffuse thickening) or it can occur in patches, known as plaques. The inflamed pleura can also secrete fluid into the pleural cavity – the space between the two pleural layers. This is known as pleural effusion.

Benign plural disease is not dangerous or fatal, although it may interfere with the expansion and contraction of the lungs and restrict breathing. If there is pleural effusion, it can be drained to relieve the breathlessness. A doctor passes a needle through the chest wall into the pleural cavity under local anaesthetic and drains the fluid. The procedure may need to be repeated if the fluid gathers again.

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Lung cancer

Lung cancer is more likely in people who have been exposed to asbestos fibres – although overall it's still rare in those people. However, if the person has been exposed and is also a smoker, the chance of getting lung cancer increases dramatically – especially if they're a heavy smoker.

A person with lung cancer develops a cough, there may be blood in the sputum, weight loss and chest infections that don't seem to clear up. The diagnosis is made usually by x-rays (or scans such as CT or MRI scans) and by bronchoscopy. A narrow tube called a bronchoscope is passed through the mouth, down the windpipe and into the lungs where the cancer, if there is one, can be visualised and a specimen taken for analysis by a pathologist.

The earlier the diagnosis is made, the better the outcome of treatment. Early lung cancer can sometimes be cured by surgery. If cancer has spread outside the lung to lymph nodes in the chest or to other organs via the bloodstream, a cure isn't possible. Radiotherapy will often help the symptoms of advanced cancer.

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Asbestosis

Asbestosis is fibrosis, or scarring, of the lungs due to asbestos exposure. In this condition, and a similar condition called pulmonary interstitial fibrosis, the airways become so inflamed and scarred that oxygen is no longer able to pass from the lungs into the blood. The lungs become stiff and inelastic, and breathing becomes progressively difficult. The affected person feels a tightness in the chest, has a dry cough, and in the later stages, a bluish tinge to the skin caused by lack of oxygen.

Lung fibrosis usually takes at least ten years to develop after exposure to asbestos, but once it does, the symptoms get progressively worse. Asbestosis requires a great deal of exposure to asbestos to develop. It is usually seen in former asbestos miners, asbestos manufacturing workers and insulation workers.

Now that high exposure to asbestos in the workplace no longer takes place, it's becoming increasingly rare. There is no cure, although oxygen supplied via mask at home helps.

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Mesothelioma

Mesothelioma is a cancer of the pleura, the lining of the lung, as described above. Very little asbestos exposure is required to develop a mesothelioma; the wives of asbestos miners have developed it through contact with contaminated overalls while doing laundry. And those renovating homes built using fibro or other asbestos-containing products can develop it, even if the period of renovation is short. However, there is usually a very long lag period between exposure and development of the disease – at least 20 years and sometimes as long as 50. Fortunately only a very small percentage of people exposed to asbestos develop mesothelioma.

When it appears, mesothelioma grows and spreads quickly into the lung and the chest wall. Someone with mesothelioma has difficulty breathing and may get chest pain. They may lose weight, they may cough up sputum and blood, and in the later stages may have difficulty swallowing and a hoarse voice.

The condition may be quite advanced before it is finally diagnosed with the aid of a chest x-ray, CT and MRI scans. An instrument called a thorascope is also used. This is inserted into the chest wall under general anaesthetic. It can visualise the tumour and allows a tissue sample to be taken to confirm the diagnosis.

There is no proven effective treatment for mesothelioma. Removal of the pleura (pleurectomy) is sometimes attempted if the cancer is small enough but it's a difficult and dangerous operation. Sometimes all or part of the lung on the affected side is also removed. Chemotherapy is an option if surgery can't be done, or if the cancer has recurred after surgery. Mesothelioma often causes fluid on the lungs (pleural effusion), and this can be treated with needle aspiration which gives temporary relief, or surgery, which is more effective in the long term.

Sometimes mesothelioma can occur in the lining of the abdomen (the peritoneum). Peritoneal mesothelioma can't usually be cured – the average time between diagnosis and death is only about eight months. But the quality of life can be sometimes improved with surgery, radiotherapy or chemotherapy.

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Renovators, beware

Asbestosis is no longer used in Australia. Mining ceased in Australia in 1983. It was finally phased out in building products like fibro in 1989, though it was still used in gaskets and brake linings until recently. It was banned entirely from the beginning of 2004 – it can't be used (nor recycled) or imported.

However, it's still possible to be exposed to asbestos. In fact Australia is experiencing a big jump in new cases of mesothelioma. It now has the highest per capita incidence of mesothelioma in the world.

An increasing number of new cases are renovators who have been exposed to asbestos fibres whilst renovating homes built during the period when asbestos-containing products were widely used (between 1945 and 1980).

About one third of homes built in this period used asbestos-containing products in walls, ceilings, eaves, kitchens, bathrooms, and in vinyl floor tiles, and in sheds and garages.

There's negligible risk in living in these homes. Installed, undisturbed asbestos-containing products are safe because the asbestos fibres are bound together in a solid matrix. But if they are tooled, cut, drilled, sanded or otherwise abraded or machined they can release asbestos fibres into the air.

Unfortunately, through ignorance, many home renovators, home maintenance and building workers don't realise the dangers of exposure and may only learn of it – if at all – once the building work is finished. Prolonged exposure, where the building work goes on for months or years, carries the greatest risk. For home renovators, a brief one-off exposure is very low risk.

Before renovating or demolishing, it's essential to identify asbestos-containing products. It's usually difficult for a layperson to tell which products contain asbestos and which don't. Potentially any type of board building material over 20 years old could contain asbestos. The only way to be sure is to have the material identified and removed by a licensed asbestos removal contractor.

Unfortunately many workers on building sites are being needlessly exposed because of negligent building contractors who don't want to incur the additional expense of safe demolition, removal and disposal.

For a list of licensed contractors, consult the WorkCover Authority in your state.