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What Is Asbestos?General DefinitionAsbestos is the name of a group of highly fibrous minerals with separable, long, and thin fibers. Separated asbestos fibers are strong enough and flexible enough to be spun and woven. Asbestos fibers are heat resistant, making them useful for many industrial purposes. Because of their durability, asbestos fibers that get into lung tissue will remain for long periods of time. For more information on asbestos, see ATSDR's Toxicological Profile on Asbestos. Other ATSDR resources include the Public Health Statement on Asbestos, which is the summary chapter from the Toxicological Profile, and the ToxFAQs for Asbestos, which is a shorter question and answer version. Types of AsbestosThere are two general types of asbestos, amphibole and chrysotile. Some studies show that amphibole fibers stay in the lungs longer than crystotile, and this tendency may account for their increased toxicity (harmfulness to the body).
Regulatory agencies such as the U.S. Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) recognize six asbestos minerals: chrysotile, a serpentine mineral with long and flexible fibers; and five amphibole (with relatively brittle crystalline fibers) minerals, actinolite asbestos, tremolite asbestos, anthophyllite asbestos, crocidolite asbestos, and amosite asbestos. How Are People Exposed to Asbestos?We are all exposed to low levels of asbestos in the air. These "ambient" - or typical - air concentrations of asbestos fibers are 0.00001 to 0.0001 fibers per milliliter (fiber/mL). Much more concentrated levels of exposure are known to cause health effects in humans. For more information on asbestos exposure, see the Public Health Statement on Asbestos, "How might I be exposed to asbestos?" Asbestos Exposure and Your WorkAsbestos exposure can occur in the workplace, particularly if you work or have worked as a(n):
Individuals who have worked in the above industries should consult with a physician with expertise in the evaluation and management of asbestos-related lung disease. Information on Asbestos from OSHA NIOSH Information on Asbestos Exposure in the Workplace NIOSH Fact Sheet on Contaminated Vermiculite Chrysotile Asbestos ExposureThe asbestos fibers detected in the samples taken at the World Trade Center sites were chrysotile asbestos. Click here to link to more World Trade Center information. Amphibole Asbestos Exposure
Detecting AsbestosThe combined use of detection methods called light microscopy, electron microscopy, and energy dispersive X-ray analysis offer the most accurate approach to identify asbestos and to estimate concentrations that may become airborne upon disturbance. For the purposes of counting asbestos fibers in these samples, regulatory agencies commonly count as fibers those particles of asbestos minerals at least 5 micrometers in length and with length:width ratios of 3:1. For other purposes, such as detecting fibers in bulk building materials, asbestos particles with length:width ratios of 5:1 are counted. Air concentrations of asbestos fibers in ambient (typical) air are 0.00001 to 0.0001 fibers per milliliter (fiber/mL). The recently established exposure limit for U.S. workplaces is 0.1 fiber/mL. |
This page last updated on October 9, 2003
Joanne Cox / Robert Searfoss ATSDR-OpeaMail@cdc.gov
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