Pleural mesothelioma occurs primarily in three groups of people exposed to asbestos. First, those who were occupationally exposed to asbestos, particularly mining and milling workers who were directly exposed to blue asbestos. Some authors have studied in great detail those exposed to blue asbestos at the Wittenoom mine in Australia. The site was one of the most horrific industrial disasters in history. Not only were the miners severely exposed to asbestos, but asbestos residue was used to replace grass on school playing fields and town squares, resulting in a massive outbreak of malignant pleural mesothelioma, many young patients due to playing on asbestos waste as children. Second, asbestos-related diseases were also found in indirectly occupationally exposed populations, i.e., workers who used asbestos products, such as plumbers, carpenters, defense personnel, and asbestos insulator installers. Third, the environmentally exposed population, those who are in industrialized countries and unconsciously exposed to asbestos, account for 20-30% of malignant pleural mesothelioma cases. The phenomenon of familial aggregation of malignant pleural mesothelioma has been reported in several articles, including one from the Cappadocia region of Turkey suggesting that familial aggregation of malignant pleural mesothelioma may be autosomal related.