What is Asbestosis?
Asbestosis is a scarring of the spongy part of the lung. It is a non-cancerous condition. The scarring results from asbestos fibres penetrating the lung tissue and causing inflammation. If this process continues then further scarring results from the body’s attempt to repair itself. The scarring also causes stiffness in the lungs which can make them less able to transfer oxygen. The immediate effect is breathlessness usually with exertion, but later, even minimal amounts of exercise can cause breathlessness. The disease tends to progress and severe cases result in death from respiratory failure or even heart failure since the heart has to work harder to force blood through the lungs.
The first modern evidence of asbestosis in an asbestos worker was discovered in an autopsy performed by Dr Montague-Murray in England in 1899 and reported on in 1907.
Causes of Asbestosis
The development of asbestosis is a function of dose which is related to exposure. One could get asbestosis if one is exposed to a low dose for a long time or higher dose for a shorter time. It is unlikely that asbestosis will develop outside an occupational setting. The intensity of exposure will determine how soon after first exposure the disease will present. The cases being diagnosed now have had low dose exposure over a long time and thus there is a long lag period.
There remains debate over the amount of exposure to asbestos that is required to develop asbestosis. A Canadian Royal Commission determined that the cumulative dose required to develop it was 25 fibre/ml years. For example, somebody exposed to 5 fibres per ml over a normal working day over a normal working year would be exposed to 25 fibre/ml years in 5 years. Another person could be exposed to 2 fibres/ml over 12.5 years and would accumulate 25 fibre/ml years of exposure. It is possible to be exposed to asbestos at these levels and not develop asbestosis. However, there have been cases where people have developed asbestosis with substantially smaller exposures to asbestos.
Symptoms of Asbestosis
The pulmonary fibrosis resulting from asbestos exposure presents in a similar manner to other causes of pulmonary fibrosis. The symptoms of dry cough and breathlessness will be the same; the signs of bilateral end-inspiratory crepitations and perhaps clubbing will be the same; the lung function abnormalities which are those of lung restriction will be the same as will be the radiological changes typical of this form of pulmonary fibrosis. There could be a difference here in that the patient may have other radiological changes of asbestos exposure for example pleural plaques. The presence of these does not automatically mean the diagnosis is asbestosis.
The differentiating feature will be the occupational exposure to asbestos. From this the treating physician with experience in the field will endeavour to ascertain if this exposure was sufficient to cause asbestosis. The condition can be differentiated from other causes of pulmonary fibrosis by the presence of asbestos bodies in the microscopic section of lung tissues being examined. It is usually not justifiable to subject the patient to a lung biopsy to make this diagnosis.
In most cases asbestosis will present 10 or more years after first exposure. Its rate of progression is variable. The extent of disease when diagnosed may be minimal. It is a condition we should expect to be diagnosing much less frequently from now on because of the improvements in occupational hygiene and the absence of any asbestos mining or manufacturing facilities in this country.
There is no treatment for asbestosis.