Asbestos is mined, milled and used in a variety of industrial and commercial products. Asbestos was used in insulations, textile industry, heat protectors, filters, and construction industry. Occupational exposure to asbestos may have occurred to asbestos miners, millers and producers of asbestos products, and workers who install plumbing, boilers and heating equipment in ships factories and homes. It is not necessary for the worker to handle the asbestos products directly to have a higher risk of developing mesothelioma, but working in the environment in proximity to asbestos may be sufficient. Carpenters, electricians, welders and many other workers who may have worked in the shipyard may have been exposed to asbestos and could be in the high-risk category for mesothelioma.
Mesothelioma exposure puts grave risk to the workers. One study has suggested that up to 10% asbestos workers may have died as the direct result of mesothelioma development. The time period between the initial exposure to a disease causing agent and development of disease known as lag period. Mesothelioma is a disease with a very long lag period. Average lag period associated with the development of mesothelioma is around 30 to 40 years and it could be as long as 65 years or more. Different subtypes of asbestos are associated with varying risk of development of mesothelioma. A subtype of asbestos, namely crocidolite is shown to be associated with higher risk of mesothelioma in miners, manufacturers and workers who install asbestos products. Another subgroup, amosite is associated with intermediate risk of development of mesothelioma. Chrysolite, which is currently the major form of asbestos in production, probably has the weakest association with the development of mesothelioma. Prior to restrictions imposed on asbestos use, a variety of workers were exposed to asbestos. The high-risk workers included asbestos minors, insulators, asbestos producers and asbestos manufacturers. Heating and construction workers also had very high risk of exposure to asbestos. People in this occupation with history of exposure to asbestos during early adulthood have a very high risk of development of mesothelioma. It is estimated that such workers have a lifetime risk of about 20 percent for the development of mesothelioma. The risk of mesothelioma development is not confined to workers who directly handle asbestos products as in the case of workers mentioned above. Other workers who work in close proximity to these occupational groups in construction sites, but had no direct contact with asbestos, have a high risk of development of mesothelioma. Workers who had no direct contact with asbestos have a relatively lower risk of development of mesothelioma compared to those who worked in direct contact. Exposure to asbestos may also increase the risk of other cancers. These cancers include lung cancer (about 4 to 5 fold increase) and pancreatic cancer.