Pleural effusion is a build up of excess fluids in the space between an inner membrane, which covers the surface of the lungs and an outer layer which lines the rib cage and diaphragm. The weight of the fluid presses on the lung, restricting expansion and reducing air capacity, which may cause chest pain, coughing and increasing difficulty in breathing when active or at rest.

Although not a disease by itself, pleural effusion can indicate the presence of any number of medical conditions affecting the respiratory system, including asbestosis or mesothelioma, asbestos-related diseases.

Usually, the pleural membranes produce no more than 15 ml. of lubricant fluid in the space between the inner and outer pleural layers to allow the lungs to expand and move against other surfaces without irritation or discomfort. Pleural effusion occurs when more fluid is produced than the lymphatic system can absorb or is unable to function properly.

Pleural effusions are not unusual, often occurring because of infections such as pneumonia, or heart failure, when the heart is not pumping the blood efficiently around the body.

However, a pleural effusion can also be a symptom of several types of cancer, including mesothelioma, where the cancer cells have developed in the pleura, causing irritation and fluid to build up in 95 per cent of cases. Unfortunately, pleural effusion as an early symptom of a pleural mesothelioma is often confused with several other common complaints such as bronchitis or pneumonia, or even because of smoking.

Recognising the symptoms and the early detection of mesothelioma, still an incurable cancer, by confirmed diagnosis is crucial to extending survival for the patient from little more than 6 months to up to 18 months or possibly two years. The exceptionally long latency period from the initial exposure to asbestos and the emergence of asbestosis symptoms can be 15 to 50 years.

Lack of asbestos awareness and information to the fatal health risks meant that thousands of workers regularly breathed in asbestos fibre dust in traditional asbestos manufacturing industries throughout the twentieth century until banning regulations began to be introduced from the mid-1970s onwards.

However, forty to fifty years after employees were first exposed to asbestos, UK deaths from mesothelioma have continued to rise with a 100-fold increase between 1968 and just ten years ago with nearly 1,900 cases reported, and by 2006, the number had increased again to over 2,000, according to the Health and Safety Executive (HSE).