Fibers and fibrous minerals, for example, the asbestos minerals, erionite (one of the many natural and synthetic zeolite species), fiberglass, or other silica forms (diatoms) have been shown to be extremely hazardous. Their airborne character is paramount, and the specific gravity of the species, the size, and an appropriate morphology that permits suspension are of primary consideration.
Asbestos as a ubiquitous natural resource refers to several types of fibrous minerals formed by earth processes and made up of microscopic bundles of fibers. The dangers associated with inhalation of asbestos fibers haveeen known for more than 30 years. Asbestos is known as a group A human carcinogen. The potential hazards of exposure to asbestos materials are of concern worldwide.
There are several modes of exposure to airborne fibers including occupational exposure and the erosion of natural deposits in asbestos-bearing rocks. Asbestos may also be dispersed in water from a number of sources, including erosion of natural deposits, corrosion, and disintegration of asbestos materials. Governments and industries have introduced regulatory measures requiring safety controls throughout the product life cycle to limit asbestos exposure to the general public and workers.
Although asbestos materials have been well documented as to their physical and chemical characteristics, they remain under investigation both by mineralogists studying geologic aspects and by pathologists/epidemiologists studying medical aspects. The term asbestos may be well known, but the precise definition, safe level of exposure, duration of exposure, and asbestos types of these fibrous materials still raise questions and often lead to differences of opinions and arguments as well as legal disputes.
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