The most common diseases associated with chronic exposure to asbestos are asbestosis and mesothelioma. Mesothelioma can be prevented in most cases by preventing exposure to asbestos. Asbestosis is caused by breathing in asbestos fibers. The duration of exposure to asbestos causing mesothelioma can be short. A history of exposure to asbestos may increase clinical suspicion for mesothelioma. Nevertheless, mesothelioma may be related to brief, low level or indirect exposures to asbestos. Other carcinogens include asbestos and radioactive materials. Pleural contamination with asbestos or other mineral fibers has been shown to cause cancer. Government agencies also worked to control other carcinogenic substances such as asbestos and pesticides. Workplace exposure to silica dust or asbestos is also associated with pulmonary heart disease. Sometimes corrugated asbestos cement sheeting was used. The first lawsuits against asbestos manufacturers occurred in 1929. The first lawsuits against asbestos manufacturers were in 1929. In 2002 the import of chrysotile (white) asbestos was also banned. Initially, the risks associated with asbestos exposure were not publicly known.