Asbestosis can develop as a result of prolonged exposure to asbestos, usually more than 20 years. Symptoms include progressive shortness of breath, clubbing of fingertips and abnormal chest sounds (known as basal crackles). The sufferer will have been exposed to heavy amounts of asbestos fibres before contracting this condition. Investigation is by means of a combination of chest x-ray, high resolution CT scan, pulmonary function tests and a bronco alveolar lavage. The condition progresses slowly and it can be very disabling, but few patients die from asbestosis.

Asbestos is a naturally occurring fibrous mineral often found in insulation materials around pipes and tanks, in tiles and other building materials. It was used extensively in the 1970s because of its strength and heat resistance. White, blue and brown asbestos are all potentially dangerous and have all been banned in the UK.

This is become if asbestos is damaged, the fine fibres become airborne and can be inhaled. When these fibres penetrate the lung tissue, they trigger an inflammatory reaction. The body recognises there's a problem and sends defensive white blood cells to engulf and attack the fibres.

The fibres usually resist and destroy these blood cells, promoting further inflammation and irreversible scarring of the lungs, called fibrosis. There's no known safe level of asbestos exposure. However, it's thought the higher the levels of asbestos and the longer the time someone is exposed to it, the greater their risk of developing problems.

Anyone who's exposed to asbestos may develop an asbestos-related illness. Particularly at risk are those involved in the building and demolition industry, the manufacture of asbestos products and asbestos spraying.

Asbestos fibres are also carried on clothing, so the families of those working with asbestos and those involved in the laundering of an asbestos worker's clothing may be at risk.

Asbestos is now used less and working practices have been developed to protect people from asbestos exposure.

The effects of asbestosis don't tend to appear for many years, often between 25 and 40 years later.

The main symptom is shortness of breath, initially on exertion but later even at rest. Others include tiredness, a cough, chest tightness and chest pain.

Asbestos can cause thickening of the pleura, the membrane that lines the outside of the lung. Often this will only be noted when an x-ray is performed for another reason. If the thickening is severe and widespread, it restricts lung function causing shortness of breath.

Mesothelioma is a rare form of cancer that's only caused by exposure to asbestos. It can occur in the pleura, where it may cause shortness of breath or chest pain, or the peritoneum (the lining of the abdominal wall), where it may cause intestinal obstruction.

A history of exposure to asbestos, the pattern of symptoms experienced, a chest x-ray and lung function tests are usually all that's needed to make the diagnosis of asbestosis.

People who've been exposed are often advised to have regular check-ups because it may take years before lung damage becomes apparent.

Although there's no cure for asbestosis, it's important to prevent the symptoms becoming worse by avoiding further exposure to asbestos.

Medication can be prescribed to relieve symptoms and improve breathing. Some people with severe problems are given oxygen

The lungs are the place in the body where air comes in direct contact with blood cells. In order to ensure an efficient transfer of oxygen from the air into the blood, the innermost layers of the lungs must be kept highly sterile. The sterilization of air occurs through a matrix of filtration systems, starting with the nose and the other air passages leading into the lungs. The reason asbestos is hazardous is because asbestos particles are able to bypass the lungs filtration systems and become imbedded in the innermost layers of the lungs.

Asbestos particles are long, extremely thin, microscopic fibers. When asbestos is in the air, these particles are inhaled by those in close proximity. The fibers are so thin and light that they cannot be properly filtered by the lungs. The asbestos becomes embedded in the alveoli, the innermost layer of the lungs where the transfer of oxygen to the blood takes place.

Once embedded, the asbestos particles are attacked by the body's immune system. The immune system releases digestive molecules called macrophages, which target and devour foreign objects in the body. Unfortunately, because asbestos is a hard, fibrous mineral, the macrophages are unable to eliminate them from the lungs. As the macrophages attempt to wipe out the asbestos, they create scar tissue in the area where the asbestos is embedded. But since the macrophages are unable to remove the asbestos, the body's immune system sends more and more macrophages, creating more scar tissue. This creates a chain reaction that cannot be stopped. People who are exposed to airborne asbestos particles inhale hundreds or thousands of asbestos fibers, which means that hundreds or thousands of these chain reactions occur, all of which create scar tissue.

When the scar tissue becomes advanced and there is large-scale injury to lung tissue, this is called fibrosis; or, more specifically, asbestosis. The first onset of asbestosis symptoms sometimes takes place years after asbestos exposure. Manifestations of asbestosis rarely occur less than 10 years following first exposure and are more common after 20 years or more. Anyone who has come in contact with asbestos is at risk for developing asbestosis, not just the workers who directly handled the fibers.

The most common symptom of asbestosis is shortness of breath. In fact, asbestosis has been called a monosymptomatic disease because shortness of breath is consistently reported and is the most distressing symptom. Breathing occurs with heavy effort and becomes more difficult as the disease progresses. Asbestosis is also associated with persistent and productive cough, and sometimes with distressing spasms. Chest tightening, chest pain, ill feeling, fitful sleep and appetite loss have also been associated with asbestosis, but not as commonly as shortness of breath.

The fibrosis associated with asbestosis is normally detected with an X-ray. There is no treatment for asbestosis, and once symptoms appear, they rarely subside. A patient's prognosis depends upon several factors, including the type of asbestos fiber the patient is exposed to, the level and duration of exposure to asbestos and (sometimes) the status of the X-ray at the time of detection. Progression continues even without additional exposure and is thought to accelerate with additional exposure.

Shortness of breath becomes more and more pronounced as the disease progresses. The end result is failure of the lungs and eventual heart failure resulting from the stress placed on the heart. Most patients do not die of asbestosis, but perish due to other ailments of the lungs brought about by asbestosis, such as mesothelioma and other lung cancers