Asbestos related disorders

What is asbestos?

Asbestos is a family of naturally occurring silica compounds (similar to, but not the same as, the silica of window glass and computer chips). These substances form fibres with varying shapes and sizes and are found throughout the earth. There are three commonly available types of asbestos; chrysotile (white asbestos), amosite (brown asbestos), and crocidolite (blue asbestos). All three have been associated with cancerous and non-cancerous lung disease.

Asbestos has been used frequently in a variety of building materials for insulation and as a fire retardant. Today, it is found most commonly in older homes - in pipes, furnaces, roof tiles, textured paints, coating materials, and floor tiles.

What are the types of asbestos-related lung disease?

Lung disease from exposure to asbestos can be divided into four main types; mesothelioma, asbestosis, diffuse pleural thickening, and lung cancer. Mesothelioma is a formerly rare form of cancer which affects the pleura (lining of the lungs) and peritoneum (surrounding the lower digestive tract). Asbestosis is a process of widespread scarring of the lungs. Disease of the lining of the lungs, called the pleura, has a variety of signs and symptoms, and is the result of inflammation and the hardening (calcification) and/or thickening of the lining tissue. The fourth type of lung disease is cancer, either of the internal portions of the lungs or the outer lining (pleura). All of the commonly available commercial forms of asbestos have been linked to cancerous and non-cancerous lung disease.

Asbestos-related lung disease occurred at very high rates towards the middle of the 20th century, when patients who were exposed decades earlier eventually developed the disease. British asbestos workers were among the first who were observed to have lung cancer related to asbestos. Most current patients were once exposed to asbestos in mines, mills, factories, or homes with asbestos, either in the process of carrying, installing, or removing asbestos, or while cleaning items laden with asbestos dust. Some workers in car repair, boiler making, construction, and pipefitting, as well as launderers of asbestos-containing clothing, have been exposed to high concentrations of asbestos. Continuing sources of exposure are the asbestos removal and general construction industries. The delay between exposure to asbestos and the development of cancer is generally 20 or more years.

The number of deaths from asbestosis has increased over the past two decades, but is felt to have plateaued - probably because of increased awareness of the risks.

Size is everything.

Depending on their shape and size, asbestos fibres deposit in different areas of the lung. Fibres less than 3 mm easily move into the lung tissue and the lining surrounding the lung (pleura). Long fibres, greater than 5 mm, cannot be completely broken down by scavenger cells (macrophages) and, therefore remain in the lung tissue. These asbestos fibres can cause inflammation. Substances damaging to the lungs are then released by the cells of inflammation that are responding to the foreign asbestos material. Furthermore, the continued existence of these long fibres in the lung tissue and the resulting inflammation seem to initiate the process of cancer formation.

As inflammation and tissue damage around the asbestos fibres continues, the resulting scarring can extend from the small airways to the larger airways and the tiny air sacs (alveoli) at the end of the airways. Some of these fibres can move to the surface of the lung where they form plaques (white-grey regions of scarred tissue) in the tissue lining of the lung (pleura). In severe cases of asbestosis, scarring of both the lung and its lining tissue can occur.