Medical Matters/Dr Muiris Houston: Recent industrial-relations difficulties in the ESB have brought the medical consequences of exposure to asbestos into the limelight.
Workers at Rhode power station in Co Offaly, which the ESB wishes to close, have been slow to agree a redundancy and transfer package in part because of concerns for their future health. Like many buildings of its vintage, the Rhode plant contained asbestos.
In addition, a number of court cases about asbestos disease have highlighted the considerable time lag between exposure and the development of asbestos-related health problems.
Asbestos is a mineral that was commonly used in construction until the 1970s. A fibrous material, it is heat resistant to a temperature of 800 degrees. As an insulating and fireproofing substance it is used extensively in roofing tiles, insulation products and friction materials such as brake linings and clutch pads.
The principal reason for recent concern about asbestos is related to the maintenance and demolition of buildings and ships built in the 1960s and 1970s. Left alone, asbestos is not a hazard to humans, but problems arise as buildings and ships of this vintage are repaired and demolished - especially when the presence of asbestos has not been considered by those carrying out the work.
The dust released by such operations can enter the lungs and cause disease. Depending on their size and shape, asbestos fibres can penetrate deep into the lung.
Asbestos causes three distinct disease processes: asbestosis, cancer of the bronchus - or principal air passages in the lungs - and mesothelioma.
Asbestosis is a non-malignant lung disease in which the asbestos fibres set up a fibrosis, or scarring of lung tissue. This occurs principally in the lower parts of the lung, and it leads to a loss of elasticity. Symptoms develop quite slowly and may not become apparent for years after exposure.
As the lungs progressively stiffen, breathlessness occurs. Cough and chest tightening are less common. The presence of calcified plaques on a chest X-ray indicate exposure to asbestos and help to distinguish the condition from other forms of lung fibrosis. Lung-function tests are also helpful.
The risk of developing cancer of the bronchus - similar to the type of cancer we associate with cigarette smoking - is much greater in a worker who is both a smoker and exposed to asbestos dust. Symptoms include persistent cough, chest pain, shortness of breath, recurrent lung infections, loss of appetite, fatigue and weight loss.
Mesothelioma is a rare form of cancer that occurs in the lining of the lungs and in the peritoneum, a structure that lines the abdominal cavity. It is almost exclusively caused by asbestos exposure. Mesothelioma has been linked to even a small exposure to blue (crocidolite) or brown (amosite) asbestos fibres. The tumour develops between 20 and 40 years after inhaling asbestos dust, so deaths from the disease will continue to rise for another 15-20 years. There is no specific treatment.
Symptoms can be vague, and the cancer is often not detected until it is well established. Shortness of breath, chest discomfort and weight loss occur. Patients often have a pleural effusion - a build-up of fluid in the periphery of the lung - by the time the diagnosis is made.
Unfortunately, most people with mesothelioma die within a year of diagnosis. Treatment, in the form of radiotherapy, chemotherapy and surgery, is aimed at palliation rather than cure.
Brown and blue asbestos have been banned for several years, and there are proposals to introduce an EU-wide ban on the remaining, white form of the material.
Because of the time lag between exposure and the development of health problems, it has been estimated that the number of deaths from asbestos-related disease in Britain will rise to 10,000 a year by 2020.
The key to preventing further health problems is for builders, demolition workers and their employers to exercise extreme caution when adding extensions to schools or demolishing old buildings.
You can e-mail Dr Muiris Houston at mhouston@irish-times.ie. He regrets he cannot answer individual queries