What is mesothelioma?

Mesothelioma is cancer of the mesothelium. Like most cancers, mesothelioma involves the abnormal dividing of cells of a particular part of the body -- in this case, the mesothelium. Mesothelioma is so deadly because it remains dormant for many years and then begins to rapidly expand. The cancer then begins to invade and damage nearby tissue, including the vital organs.

What is the mesothelium?

Many of the internal organs of the body are protected by a membrane called the mesothelium. This membrane actually consists of two layers of cells. The inner layer surrounds the organs, and the second is a sac surrounding the inner layer. When organs within this membrane must move, expand or contract -- such as the heart, lungs, bladder, and so on, they are able to do so because the mesothelium produces a lubricating fluid between the two layers.

Mesothelioma most often begins in the pleura or peritoneum. The pleura surrounds the lungs and covers the chest cavity. The peritoneum covers most of the organs in the abdominal cavity. Other mesothelium tissue is also vulnerable to mesothelioma. These include the pericardium that surrounds and protects the heart; the tunica vaginalis testic which surrounds the internal male reproductive organs; and the tunica serosa uteri which is the membrane covering the internal reproductive organs in women.

Who is at greatest risk to develop mesothelioma?

Mesothelioma has a very specific cause - exposure to asbestos. During the first half of the previous century, right up until the mid 1970s asbestos was an important material used to insulate buildings, machines, heavy equipment, and a broad range of commercial applications. Because it was plentiful and inexpensive to mine, asbestos was used in many building products such as home insulation, floor, ceiling and roof tiles. It was also used in commonly found commercial products such as brake linings and pipe insulation.

This meant that millions of people were coming in contact with asbestos on a daily basis. And since the effects of exposure to asbestos fibre often do not become apparent for 30 or 40 years after prolonged exposure, companies and health officials were slow to recognize the dangers of asbestos. As a result, shipyard workers, men and women working in asbestos mines and mills, workers producing asbestos products, workers in the heating and construction industries, and virtually all other tradespeople were exposed to asbestos fibres for extended periods of time.

Today it is understood that anyone working with or near asbestos has an increased risk of developing mesothelioma, so there are strictly controlled limits of exposure in the work place. But since the dormancy period of mesothelioma can often be 30 or 40 years, there are millions of workers who are at risk because of their exposure in the decades before the safety controls were put in place.