The unique properties of asbestos were first recognized by Finnish potters around 2500B.C. During Greek and Roman times asbestos was woven into cloth due to its fire resistant properties. Asbestos is a compound composed of magnesium and iron silicates, there are six varieties and although they all share a delicate fibrillar character, flexibility and crystalline nature, they all show distinct characteristics (acid resistance, insulating properties, fibre formation).
Due to its unique properties, asbestos has been incorporated into insulation and building materials.
Asbestos related diseases include:
- Benign asbestos pleural disease
- Pleural plaques
- Pleural thickening
- Pleural effusions
- Mesothelioma (often presents with a malignant effusion)
- Lung cancer
The risk of developing asbestosis, lung cancer and mesothelioma is linked to the degree and type of asbestos exposure. The risk of developing lung cancer increases greatly when the person is or has been a heavy smoker and has asbestosis rather than just asbestos pleural disease.
Benign asbestos pleural disease can include pleural plaques, pleural thickening and/or pleural effusions.
Plaques are localized thickenings of the parietal pleura; they vary between 1 to 2cm and may even be as large as 10cm. They are due to chronic irritation to the pleural surface. These plaques do not contain asbestos bodies. They rarely arise if there is no asbestos exposure history. The presence of pleural plaques is the hallmark of previous asbestos exposure.
Pleural thickening is defined as a smooth, non- interrupted sheet of pleural thickening more than 5cm wide, more than 8cm craniocaudal (up-down) extent and more than 3mm thick. Extensive diffuse pleural thickening can lead to restrictive lung disease.
Pleural disease may lead to pleural effusions (collection of fluid or blood in the pleural space). Recurrent pleural effusions may lead to diffuse pleural thickening.
Asbestosis leads to a reduction in lung size, the ability of the lung to exchange gas and increased lung stiffness. One of the most characteristic symptoms of asbestosis is breathlessness on effort and a dry cough.
Asbestosis is a scarring or fibrotic process that involves the lung itself and is sometimes loosely and incorrectly used to mean asbestos pleural disease. Asbestosis may take between 20 – 25 years to develop. Asbestosis may increase the risk of developing lung cancer or mesothelioma.