In 1975, a study of three small villages in central Cappadocia—Tuzköy, Karain and Sarıhıdır—found that mesothelioma was causing 50% of all deaths. Initially, this was attributed to erionite, a zeolite mineral with similar properties to asbestos, but detailed epidemiological investigation demonstrated that the substance causes the disease mostly in families with a genetic predisposition to mineral fiber carcinogenesis. The studies are being extended to other parts of the region.