Asbestos exists in its natural state in the air and water around the world. It is estimated that every day, the average person breathes thousands and ingests millions of asbestos fibres with no increased health risks. However, it is also known that under certain conditions, usually associated with heavy occupational exposures over prolonged periods of time, all forms of asbestos can lead to diseases such as asbestosis, mesothelioma and lung cancer. Based on both animal and human studies, all forms of asbestos have been classified as Class I "known human carcinogens" by the International Agency for Research on Cancer.
The nature of the risks of asbestos exposure vary according to the duration and intensity of exposure, the type of fibre and other critical factors. A detailed analysis of the health effects of exposure to different asbestos fibre types is presented in Modules 2, 3 and 4. Reviews of the nature and risks of environmental exposures to asbestos in drinking water and in the ambient air are presented in Modules 5 and 6 respectively.
Researchers now believe that the carcinogenicity of a fibrous substance is related to several physical and chemical characteristics. As a result, growing attention is being brought to the toxic potential of fibres other than asbestos. A review of the scientific data on the health effects of a wide range of natural and man-made fibres is presented in Module 10. The section of our Web site titled International Scientific Reviews provides an overview and summaries of the key international scientific reveiws which have dealt with the question of fibres and health.