Inhaling asbestos fibers can cause scar tissue (fibrosis) to form inside the lung. Scarred lung tissue does not expand and contract normally, and cannot perform gas exchange. The severity of the disease depends upon the duration of exposure to asbestos and the amount inhaled. Asbestos fibers were commonly used in construction before 1975. Asbestos exposure occurs in asbestos mining and milling industries, construction, fireproofing, and other industries. In families of asbestos workers, exposure can also occur from particles brought home on the worker's clothing. Asbestos-related disease includes pleural plaques (calcification), malignant mesothelioma, and pleural effusion. Mesotheliomas may develop 20 - 40 years after exposure. More than 9 million workers are at risk of developing this disease. Cigarette smoking increases the risk of developing the disease. The incidence is 4 out of 10,000 people.
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