Serious lung disorders that develop as a result of inhaling asbestos fibres many years earlier
- Rare under the age of 40; more common with increasing age
- More common in males due to increased risk of occupational exposure
- Caused by exposure to asbestos in the workplace or at home
- Genetics is not a significant factor
Asbestos is a fibrous mineral that can cause serious lung damage if inhaled. Inhaling even very small numbers of asbestos fibres can lead to problems decades later, but those with the heaviest exposure are at greatest risk. The damage caused by inhaling asbestos fibres is irreversible, and preventing exposure to the dust is very important. The families of people who are exposed to asbestos at work may also be at risk of developing asbestos-related diseases because fibres from the workplace may be brought into the home on clothing.
Over the past 25 years, there has been a general decline in the use of asbestos and safer working practices have been introduced. However, the number of people with asbestos-related diseases is continuing to rise because there is a time lag of up to 50 years between first exposure to asbestos and the development of lung disease.
What is the cause?
Asbestos fibres are needle-shaped. They are therefore drawn deep into the lungs when inhaled, where they can penetrate the lung tissue. The asbestos fibres then trigger a reaction from the defensive white blood cells in the lungs, which try to engulf the fibres. However, the fibres usually destroy the white blood cells, and inflammation and eventual scarring of the lung tissue may follow.
Asbestos fibres are divided into three main types: white, blue, and brown, all of which are dangerous. White asbestos is the type most commonly used for commercial purposes. Blue and brown asbestos fibres are less common, but they are particularly dangerous and are the most likely to trigger the development of asbestos-related diseases.
What are the types?
The inhalation of asbestos fibres can result in three different types of disease: asbestosis; diffuse pleural thickening, in which the pleura (the membrane that separates the lungs from the chest wall) becomes abnormally thickened; and mesothelioma, a cancerous tumour of the pleura. Often, more than one type of asbestos-related disease occurs simultaneously in one person.
In this condition, widespread fine scarring occurs in the lung tissue. The disease may progress even when exposure to asbestos is discontinued. Asbestosis tends to develop among people who have been heavily exposed to asbestos, such as asbestos miners, people who work in asbestos factories, and workers who regularly handle insulation materials that contain asbestos.
The period of time between first exposure to asbestos and development of symptoms is usually at least 20 years and is often longer. The main symptom is shortness of breath on exertion, which may eventually become disabling. Other symptoms include a dry cough, an abnormal shape to the fingernails known as clubbing (see Nail abnormalities), and a bluish tinge to the complexion. Some people with asbestosis develop primary lung cancer.
Diffuse pleural thickening
Pleural thickening may develop after only a brief exposure to asbestos. Usually, the condition produces no obvious symptoms and is detected only if a chest X-ray is performed for another reason. However, in some cases, pleural thickening is severe and widespread, and the ability of the lungs to expand is restricted, causing shortness of breath.
This disorder is a cancerous tumour of the pleura or less often of the peritoneum (the thin membrane that lines the abdominal cavity). Mesotheliomas most commonly result from working with blue or brown asbestos. It may take 30–50 years from the initial exposure for symptoms to first appear. Mesotheliomas that affect the pleura usually cause chest pain and shortness of breath. In the peritoneum, they may cause an intestinal obstruction, resulting in symptoms such as abdominal pain and vomiting.
Are there complications?
People with asbestos-related diseases are particularly susceptible to developing primary lung cancer. People who smoke and who also have an asbestos-related disease are considered 75–100 times more likely to develop lung cancer than people with neither factor. Asbestos-related diseases may also increase a person’s susceptibility to other serious lung conditions, including tuberculosis and chronic obstructive pulmonary disease.
How is it diagnosed?
If your doctor suspects that you have an asbestos-related disease, he or she will ask you about your current occupation and work history. Asbestos-related disease is usually diagnosed using a chest X-ray to look for signs of thickening of the pleura. Your doctor may also listen to your chest for abnormal sounds and may arrange for lung function tests to assess the extent of your breathing problems. A sample of sputum from the lungs may be examined for evidence of asbestos fibres. If a mesothelioma is suspected, CT scanning or MRI may be performed. To confirm the diagnosis of mesothelioma, a sample of tissue may be taken from the pleura under local anaesthesia to check for cancerous cells.
What is the treatment?
No treatment can reverse the progress of an asbestos-related disease. However, further exposure to asbestos may cause the condition to worsen more rapidly and should therefore be avoided. If you have asbestosis, you may be given oxygen (see Home oxygen therapy) to relieve shortness of breath. Diffuse pleural thickening re-quires no specific treatment because the condition rarely causes severe symptoms. Mesothelioma cannot be treated effectively, but radiotherapy may relieve pain.
Can it be prevented?
The only way to prevent asbestos-related diseases is to minimize your exposure to asbestos fibres in the workplace and at home. Since the 1970s, the use of asbestos has been severely restricted, and industries that use asbestos have improved fibre-control measures. Most cases of asbestos-related diseases now being diagnosed are the result of working practices that were in effect before the 1970s. If you are carrying out repair work on a house that was constructed before 1970, you should check for the presence of asbestos. If you find asbestos, you should seek professional advice before you continue the work.
What is the prognosis?
About 4 in 10 people with asbestosis or diffuse pleural thickening will eventually die of lung cancer, and smoking should be avoided to lower this risk. Only a few people with asbestos-related mesothelioma survive for longer than 2 years after the diagnosis.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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