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Asbestos disease in Australia may not peak until sometime in the next decade. The average latency period, which refers to the period between first exposure to asbestos and development of disease, in the case of mesothelioma, is about 35 years. Asbestos related disease rarely develops earlier than 10 years after first exposure. Asbestos exposure may also increase the risk of developing lung cancer and cancer of the upper respiratory and gastrointestinal tracts in smokers.
Asbestos disease is not infectious.
The Lungs
The lungs are the main organs of the respiratory system, the body's system for breathing. The respiratory system also includes the nose, mouth, trachea (windpipe) and airways to each of the lungs. There are the large airways to the lungs, called the bronchi, and the small airways to the lungs, called the bronchioles.
When you inhale (breath in) air goes into the nose or mouth, down the trachea and into the bronchi and bronchioles. Tiny air sacks at the end of the bronchioles, called alveoli, pass oxygen into the blood and collect carbon dioxide, the waste gas. The carbon dioxide is released from the body and into the atmosphere when you exhale (breath out).
The lungs are like 2 large sponges which rest on the diaphragm - a wide, thin muscle which assists with breathing.
The pleura is a thin sheet of tissue which covers the lung. The inner layer of the pleura (called the visceral layer) is attached to the lungs and the outer layer (called the parietal layer) lines the chest wall and the diaphragm. The pleura is surprisingly tough and also well supplied by nerve fibres. There is normally a small amount of fluid between the 2 layers which facilitates the expansion of the lung and allows the lungs to move smoothly against the chest wall as the chest expands when you breathe.
The following is an overview of asbestos diseases, however anyone with an asbestos related disease should seek the advice of medical practitioners and be guided by them as to the appropriate investigation and treatment. The information that follows is not meant as a substitute for information from medical practioners but merely as a guide to the understanding of various asbestos related diseases.
Click here to view a video about "Asbestos Health Issues" - including Asbestosis, Mesothelioma and Lung Cancer.
Types of Asbestos Disease:-
Pleural Plaques (with or without chest pain)
Pleural plaques are patches of fibrous thickening on the pleural membrane which can progress slowly and can calcify. The calcification makes pleural plaques very apparent on x-rays and they appear radiologically generally at least 10 years after first exposure to asbestos with the extensiveness of plaqueing often related to duration and intensity of exposure. However, pleural plaques usually cause no measurable impairment of pulmonary function or of an individual’s general well-being. Many persons, often those who have only had brief exposure, develop pleural plaques. They are generally seen as a marker of past asbestos exposure but can in some instances cause chest pain and if extensive can restrict breathing capacity.
Pleural plaques are evidence of past exposure to asbestos and are the most common form of asbestos disease. Chest pain as a result of pleural plaques can be very severe and treatment may eventually involve the use of narcotic analgesics. As with many asbestos diseases there is no effective treatment. Of course chest pain can arise from various causes and the diagnosis of pleural plaque pain is a diagnosis of exclusion – other causes of the pain usually need to be excluded before plaques can be identified as the cause of pain. In addition, pleural plaques can be very extensive and interfere or restrict the function of the lung causing breathlessness or exertion.
It is important to remember that pleural plaques are generally a marker of past asbestos exposure and usually do not cause symptoms and do not develop into a more serious asbestos disease. Pleural plaques are evidence of past asbestos exposure and it is the asbestos exposure itself that can cause more severe disease. Pleural plaques do not become malignant.
Pleural Effusion
A pleural effusion may occur when the pleural becomes inflamed and fluid leaks into the space the visceral and parietal layers. Pleural effusion may cause chest pain and/or pleural thickening. A talc pleurodesis may be carried out to prevent further effusion which involves the insertion of talc or some other agent into the chest wall to adhere the parietal and visceral pleura, obliterating the pleural cavity and leaving no area for fluid to reaccumulate.
Asbestos Related Pleural Disease
Asbestos related pleural disease is generally referred to as benign asbestos related pleural effusion. Symptoms include shortness of breath and discomfort. When the pleural fluid eventually goes away, the pleura on the lung may become thickened which can compress the lung.
Asbestos Related Pleural Thickening
Asbestos related pleural thickening is a fibrous layer of tissue covering a significant portion of the pleura. The thickening can lead to restrictive disease which prevents the lung from inflating completely when a patient takes a breath. Other causes of pleural thickening include pleural and chest infections, chest trauma, previous surgery and tuberculosis.
Pleural thickening is thought by some respiratory specialists to be caused by a pleural effusion which is the leakage of fluid into the space between the visceral and parietal pleura.
Rounded or Folded Actelectasis
Folded atelectasis is a less common condition caused by asbestos where the lung becomes entrapped by scar tissue from the pleura which rolls the lung up a bit like a jam roll, reducing lung function and often resulting in pain. This condition may be confused with lung cancer as it can look like a mass or a tumour. If this is not diagnosed corrected it may result in unnecessary procedures such as needle biopsies and even surgery.
Asbestosis
Asbestosis is a chronic fibrotic interstitial lung disease which is asbestos-induced. It is a non-cancerous condition. Fibrosis is a scarring of the lung. Interstitial refers to the lung tissue itself. In asbestosis it is the lung tissue, not the airways, that is damaged. The scarring results from asbestos fibres penetrating the lung tissue and causing inflammation. When this process continues then further scarring results. The alveoli (air sacks), where oxygen exchange occurs and oxygen diffuses into the blood stream, become scarred, damaged and obliterated. The scarring or fibrotic change within the lung tissue casues the lungs to be stiff and hence it is more difficult to breathe. The lung becomes very inelastic; hence the lung does not exchange oxygen and CO2 adequately because eventually the alveolar gas exchange units are markedly reduced in number and function. Dyspnoea (or shortness of breath on exertion) is one of the symptoms of asbestosis.
Fibrotic changes in the lungs can be associated with various causes other than asbestos such as silica dust, animal dust exposure, rheumatoid arthritis and many other causes. Exposure to silica dust, for instance arising from excavation work in rock with high silica content, can cause silicosis. Exposure to dusts from various birds can cause a fibrotic condition in the lung known as bird fanciers’ lung.
However, asbestosis refers exclusively to asbestos-induced fibrosis of the lung. Asbestosis is usually diffuse in that it is usually found throughout the lower sections of both of the lungs, and not isolated. The fibrosis associated with asbestosis is often roughly equal in both lungs. As the disease progresses, the upper lobes may be affected.
Asbestosis is usually a progressive disorder. Exertional breathlessness gradually worsens often over a period of years. As asbestosis progresses the scarring causes the lung to shrink and breathing becomes more difficult.
The damage to the lungs’ capacity may not be detected for many years due to the lungs’ reserve. As the disease progresses lung capacity reduces. Patients who suffer from asbestosis have an increased risk of developing bronchitis, pneumonia and heart disease. As a consequence asbestosis sufferers may present with heart-related symptoms such as abnormal heart rhythm and heart failure.
As well as arising from causes other than asbestos exposure interstitial fibrosis may also be idiopathic, meaning that no cause can be determined. This condition is known as idiopathic pulmonary fibrosis or cryptogenic fibrosing alveolitis. However, idiopathic pulmonary fibrosis tends to be a very rapidly progressive condition whilst asbestosis tends to involve gradual deterioration so the two conditions can usually be distinguished.
The diagnosis of asbestosis, however, may be difficult to make. The diagnosis is made by obtaining a history of exposure, typical x-ray signs, lung function studies and clinical signs such as inspiratory (respiratory) crackling. clubbing of the fingers and toes is rare.
The first modern evidence of fibrotic pulmonary disorder in an asbestos worker was discovered in an autopsy performed by Dr Montague-Murray in England in 1899, and reported on in 1907.
There is a popular misconception that asbestos-related disease is less of a problem because the exposure to the chemical is less than it was in the 1960’s and 1970’s. However, the number of cases of some forms of asbestos-related disease, namely mesothelioma, is increasing.
However, the advent of high resolution CT scanning in the 1990s which shows much more detail of the lung as compared to a simple chest x-ray has given respiratory specialists much more information to make the diagnosis of asbestosis and in fact the diagnosis of asbestosis is probably on the increase.
Mesothelioma
Asbestos Disease is increasing at an alarming rate in Australia, this is particularly so for mesothelioma. The following graph illustrates this:
The above graph is based on figures contained in the Australian Safety & Compensation Council
report "Mesothelioma in Australia - Incidence 1982 to 2004" dated March 2008
It is thought that the incidence of mesothelioma in Australia not peak until sometime between 2015 and 2020.
Mesothelioma is an incurable malignancy which affects the parietal layer (lining) of the pleura. It may also affect the abdominal cavity (the peritoneum). The majority of cases affect the pleura. As the disease progresses the pleura or the peritoneum thickens from the calibre of a cigarette paper to form a hard tumour mass often between 0.5 and 1.0cm thick. This tissues compresses the lung and the gastrointestinal tract. This may cause intestinal obstruction.
Cigarette smoking is not related to the development of mesothelioma. Exposure to Erionite, a fibrous mineral found in Turkey, may also casue mesothelioma.
Mesothelioma is the most lethal of all asbestos disease. Unfortunately it is also one of the most prevalent. Of claims filed in the Dust Diseases Tribunal of NSW, a specialist court handling asbestos compensation claims, mesothelioma claims historically account for approximately fifty per cent of total claims filed.
The latency period between first exposure to asbestos and the onset of mesothelioma is rarely less than 20 years from first exposure and may be more than 50 years. Diagnosis of mesothelioma is usually made by biopsy by either a needle biopsy or through key-hole surgery.
Of the various commercial types of asbestos, mesothelioma is predominantly associated with exposure to the blue asbestos, crocidolite and brown asbestos, amosite. White asbestos, chrysotile has also been linked to the incidence of mesothelioma. All asbestos exposure should be avoided given the potential of developing mesothelioma which is also often associated with quite brief or low level of asbestos exposure.
Recently there has been some progress in the treatment of mesothelioma particularly with the chemotherapy drug Alimta which has been found to extend life expectancy in some cases.
Some people who have been treated with Alimta are still alive years after diagnosis with mesothelioma. Other treatments are also being trialled.
Another option for treatment of mesothelioma is a pleuropneumonectomy which is surgical removal of the lung, the pleura and the diaghragm. It is a major operation. Whether it extends life span is unclear. Recently there has been an increased effort to find a cure for mesothelioma and an example of this is the establishment of the Asbestos Diseases Research Institute in Sydney.
The Australian Mesothelioma Registry (AMR) includes information about each person diagnosed with mesothelioma on or after the 1st of July 2010 in Australia. The Society encourages participaton in the AMR which involves completing a postal questionnaire with information about residential, school and occupational histories. Patients are also asked about their family history of mesothelioma. This is followed by a telephone interview tailored to the participant. The information colleced is used to assess the participant's past exposure to asbestos throughout their lifetime. This will help the Australian Government develop policies to best deal with the asbestos still present in Australia's buildings and environment and to prevent mesothelioma in the future.
If you are a mesothelioma patient or a medical professional and are approached to participate in the AMR, we encourage you to become involved. Click here to visit the AMR website.
Lung Cancer
Diagram of Lung Cancer (carcinoma) and Mesothelioma
(image used courtesy of Lilly Alimta)
Lung cancer is a cancer originating in the airways of the lung or in the parenchyma, which is the tissue of the lung. Lung cancer is often fatal although in some cases can be successfully treated. Cigarette smoking is generally thought to be the major risk factor although there are potentially other causes such as asbestos exposure. The casual link between asbestos and lung cancer was identified by the publication in 1955 of the report of Richard Doll, “Mortality from Lung Cancer in Asbestos Workers” in the British Journal of Industrial Medicine.
Cigarette smoke and asbestos are often stated to play a synergistic or multiplicative role in the development of lung cancer. Some studies have shown that those who smoke cigarettes and have been exposed to asbestos have a fifty fold increased risk of lung cancer over the non asbestos and cigarette exposed population while those who have smoked cigarettes but who have had no exposure to asbestos have only an eleven fold increased risk. Regardless of the precise increase risk there does seem to be some interaction between cigarette smoke and asbestos in the development of lung cancer.
The latency period between exposure to asbestos and development of lung cancer is generally believed to be about 15 to 25 years.
Lung cancer caused by asbestos exposure is undernotified. The popular conception is that lung cancer is invariably related to cigarette smoking, but in those patients who have also been exposed to asbestos, the risk of developing lung cancer is much higher. There are various types of lung cancer including Adenocarcinoma and squamous cell carcinoma and asbestos exposure has been implicated in virtually all types of lung cancer.
Asbestos exposure has also been implicated in other cancers such as oesophageal cancer, kidney cancer, laryngeal cancer as well as other cancers.
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