Working with asbestos is the major risk factor for mesothelioma. A history of asbestos exposure at work is reported in about 70 to 80 percent of all cases. However, mesothelioma has been reported in some individuals without any known exposure to asbestos.

There is some evidence that family members and others living with asbestos workers have an increased risk of developing mesothelioma, and possibly other asbestos-related diseases. This risk may be the result of exposure to asbestos dust brought home on the clothing and hair of asbestos workers. To reduce the chance of exposing family members to asbestos fibers, asbestos workers are usually required to shower and change their clothing before leaving the workplace.

Smoking does not appear to increase the risk of mesothelioma. However, the combination of smoking and asbestos exposure significantly increases a person's risk of developing lung cancer (see Causes of Lung Cancer).

Mesothelioma and Asbestos
Asbestos is the name of a group of minerals that occur naturally as masses of strong, flexible fibers that can be separated into thin threads and woven. Asbestos has been mined and used commercially since the late 1800s; its use greatly increased during World War II. Asbestos has been widely used in many industrial products, including cement, brake linings, roof shingles, flooring products, textiles, and insulation. Since the early 1940s, millions of American workers have been exposed to asbestos dust.

If tiny asbestos particles float in the air, especially during the manufacturing process, they may be inhaled or swallowed and can cause serious health problems. In addition to mesothelioma, exposure to asbestos increases the risk of lung cancer, asbestosis (a noncancerous, chronic lung ailment), and other cancers, such as those of the larynx and kidney.

Initially, the risks associated with asbestos exposure were unknown. However, an increased risk of developing mesothelioma was later found among:


* Shipyard workers
* People who work in asbestos mines and mills
* Producers of asbestos products
* Workers in the heating and construction industries
* Other tradespeople.


Today, the US Occupational Safety and Health Administration (OSHA) sets limits for acceptable levels of asbestos exposure in the workplace. People who work with asbestos wear personal protective equipment to lower their risk of exposure.

The risk of asbestos-related disease increases with heavier exposure to asbestos and longer exposure time. However, some individuals with only brief exposures have developed mesothelioma. On the other hand, not all workers who are heavily exposed develop asbestos-related diseases.