A major risk factor for mesothelioma is working with asbestos. A history of asbestos exposure at work is reported in about 70 to 80 percent of all cases.
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 cancer of the air passageways in the lung.
National Cancer Institute Mesothelioma Risk Factors Information