The main risk factor for mesothelioma is asbestos exposure. The use of the material has been banned in the United States since approximately 1975, but about 8 million Americans may already have been exposed through various jobs.
Jobs such as miners, ship builders, factory and railroad workers, mechanics and construction workers (particularly those responsible for installing brakes in automobiles and insulation in buildings) are at risk. Many men who served in the Navy were exposed to significant amounts of asbestos on their ships.
It takes about twenty years after exposure to develop mesothelioma.
Asbestos is not only found in the workplace. It may still be found in 10-15% of schools (about 110,000) throughout America. The asbestos fibers have also been known to be picked up through clothing or other articles. After exposure to the airborne fibers, the risk of lung cancer is 7 times greater than that of the general population (smokers who are exposed to asbestos have a risk 50-90 times greater yet).
Not all workers exposed to asbestos will develop diseases related to their exposure. In fact, many will experience no ill effects.
Asbestos that is bonded into finished products such as walls, tiles, and pipes poses no risk to health as long as it is not damaged or disturbed (for example, by sawing or drilling) in such a way as to release fibers into the air.
When asbestos particles are set free and inhaled, however, exposed individuals are at risk of developing an asbestos-related disease. Once these fibers work their way into body tissues, they may stay there indefinitely.
The risk of developing asbestos-related diseases varies with the type of industry in which the asbestos exposure occurred and with the extent of the asbestos exposure. In addition, different types of asbestos fibers may be associated with different health risks.
For example, results of several studies suggest that exposure to amphibole forms of asbestos are more likely than exposure to chrysotile asbestos form to cause lung cancer, asbestosis, and, in particular, mesothelioma.
Even so, no fiber type can be considered harmless, and proper safety precautions should always be taken by people that work under asbestos exposure.