ASBESTOSIS

lung disease that is caused by the prolonged inhalation of asbestos fibres. A type of pneumoconiosis, it is found primarily among workers whose occupations involved asbestos, principally mining, construction, and the manufacture of insulation, fireproofing, cement products, and automobile brakes. The disease is not limited solely to asbestos workers but is also known among people living near mines, factories, and construction sites. Asbestos fibres that have been inhaled remain in the lungs for years and eventually cause excessive scarring and fibrosis, resulting in a stiffening of the lungs that continues long after exposure ceases. Greater effort is needed to make the stiffened lungs expand during breathing, and shortness of breath and inadequate oxygenation of the blood result. Persons with advanced cases of the disease have a dry cough, and the increased cardiac effort needed to expand the lungs may induce a secondary heart disease. An increased incidence of lung cancer and of malignant mesothelioma (a rare cancer of the membrane lining the lungs) is also associated with asbestos inhalation and asbestosis. There is no effective treatment for asbestosis. Asbestosis usually results only after at least 10 years' exposure to asbestos, and the first symptoms do not appear until many years after the initial exposure; shipyard workers exposed to asbestos during World War II began developing asbestosis in the 1960s and '70s. (Mesothelioma, by contrast, can develop after relatively little exposure to asbestos.) It is now known that cigarette smoking seriously aggravates the symptoms of asbestosis. The incidence of asbestosis increased after 1950, probably due to the increasingly widespread industrial use of asbestos. This use declined from the 1970s and had been prohibited in many countries by the 1990s owing to asbestos fibres' deleterious effects on the lungs.