The main cause of mesothelioma is exposure to asbestos. Doctors first suspected the connection between asbestos and mesothelioma in the 1890s. Research in the 1960s confirmed asbestos exposure as the most important risk factor for the disease.
Pleural mesothelioma develops after a person inhales asbestos. The long, thin fibers pass through the lungs, and they get trapped in the pleura, which is the lining of the lung. The heavier the asbestos exposure and the longer a person is exposed throughout their lifetime, the higher the risk for mesothelioma.