What to know
- Asbestos refers to a class of minerals that naturally form long, thin, very strong fibers.
- It occurs naturally in the environment and from breakdown or disposal of old asbestos products.
- Exposure to asbestos can lead to serious and sometimes fatal disease.
Overview
Asbestos is a commercial and legal term referring to a class of minerals that naturally form long, thin, very strong fibers. Asbestos has been mined and used in many products worldwide, mostly during the 20th century. In the United States, mining asbestos has ended. However, asbestos is still present in older homes and buildings, and some products still contain it.
Properties
Asbestos occurs naturally in certain types of rock. Large amounts of asbestos in rocks can look like long fibers. Each asbestos fiber, though, is too small to see with the naked eye. Asbestos fibers
- do not dissolve in water or evaporate
- resist heat and fire
- cannot be broken down easily by chemicals or bacteria
- can be found near the ground surface in certain areas of the country
Types
The legal definition of asbestos applies to six fibrous minerals in two general classes:
- Serpentine class: chrysotile (also known as white asbestos)
- Amphibole class: amosite (brown asbestos), crocidolite (blue asbestos), anthophyllite, tremolite, and actinolite
Exposure to either chrysotile or amphibole asbestos increases the risk of disease. However, amphiboles remain in the lung for a longer period of time. Exposure to amphiboles may result in a higher risk of developing mesothelioma than exposure to chrysotile.
Some studies have suggested that other durable, fibrous silicate minerals can have health effects similar to asbestos. These minerals are called “asbestiform” minerals and include winchite or richterite.
Where it's found
Asbestos occurs in the environment, both naturally and from the breakdown or disposal of old asbestos products.
Because of its sturdy properties, asbestos was mined and used in making many products, including
- insulation and roofing shingles
- fireproofing and acoustic materials
- wallboard
- plaster
- cement
- floor tiles
- brake linings
Beginning in the 1970s, the United States banned many uses of asbestos. However, asbestos is still present in old materials and is still used in products such as automobile brakes and roofing materials. Asbestos may also be present in other commercial products, such as vermiculite (especially vermiculite from Libby, Montana) and talc.