The presence of bilateral calcified pleural plaques is fairly specific for the diagnosis of chronic asbestos exposure. Pleural plaques per se do not cause disability. Patients with asbestos exposure are at a five-fold greater risk of developing lung cancer. There is a synergistic effect between asbestos exposure and smoking with a 55-fold increase in risk for lung cancer. Mesotheliomas are malignancies of the pleura that are associated with asbestos exposure and are rarely found in people not exposed. Occupations with high risk of exposure to asbestos include shipyard workers, auto mechanics, construction workers (including plumbers, electricians etc.), and asbestos miners.