Asbestos exposure, both secondary and direct, is the only known cause of mesothelioma. Asbestos can also contribute to a variety of other illnesses including lung cancer, asbestosis and diffuse pleural thickening.

When a link between workplace asbestos exposure and mesothelioma was discovered, shipyard workers, miners, factory employees and construction workers became the most likely to develop this deadly cancer. If these at-risk employees disturbed asbestos, fibers would be released into the atmosphere. In addition, these employees could track home asbestos fibers on their hair, clohting and skin, leaving their family members susceptible to mesothelioma and other asbestos-related diseases.

When asbestos fibers are inhaled, they remain in the lungs for years. The body cannot extract these fibers unless they attach to mucous and are coughed up. While research still has not shown exactly how asbestos causes mesothelioma, scientists have a few theories:

• Asbestos irritates and inflames the mesothelial cells, which can lead to scarring, cell damage and cancer.
• When asbestos fibers enter the cells, they disrupt the function of cell division.
• Asbestos causes the production of free radicals, which damage DNA and cause cancer to develop.
• Asbestos causes cells to produce oncoproteins. Mesothelial cells then begin to ignore regular cell division restraints, which can result in cancer.

The common thread in all of these theories is that asbestos causes cell damage, which results in uncontrollable cell division. Healthy cells adhere to normal cycles of cell division to make sure organs and tissues do not grow past normal cells. However, in cancerous cells these restraints are lost.