Information about asbestos exposure
What is asbestos?
Asbestos is a mineral. It is mined in much the same way that other minerals, such as iron, lead, and copper, are. Asbestos is composed of silicon, oxygen, hydrogen, and various metal cations (positively charged metal ions). There are many varieties of asbestos: the three most common are chrysotile, amosite, and crocidolite. Chrysotile fibers are pliable and cylindrical, and often arranged in bundles. Amosite and crocidolite fibers are like tiny needles. The first commercial asbestos mine -- a chrysotile mine -- opened in Quebec, Canada, in the 1870's. Crocidolite asbestos was first mined in South Africa during the 1980's. Amosite asbestos also comes from Africa and was first mined in 1916. Unlike most minerals, which turn into dust particles when crushed, asbestos breaks up into fine fibers that are too small to be seen by the human eye. Often individual fibers are mixed with a material that binds them together, producing asbestos containing material (ACM).
Why has asbestos been so widely used?
Asbestos appealed to manufacturers and builders for a variety of reasons. It is strong yet flexible, and it will not burn. It conducts electricity poorly, but insulates effectively. It also resists corrosion. Asbestos may have been so widely used because few other available substances combine the same qualities.
How many products contain asbestos?
One study estimated that 3,000 different types of commercial products contained asbestos. The amount of asbestos in each product varied from as little as one percent to as much as 100 percent. Many older plastics, paper products, brake linings, floor tiles and textile products contain asbestos, as do many heavy industrial products such as sealants, cement pipe, cement sheets, and insulation.
How long has asbestos been in use?
Asbestos was first used in the United States in the early 1900's, to insulate steam engines. But until the early 1940's, asbestos was not used extensively. However, after World War II, and for the next thirty years, people who constructed and renovated schools and other public buildings used asbestos and asbestos -containing materials (ACM) extensively. They used ACM primarily to fireproof, insulate, soundproof, and decorate. The Environmental Protection Agency (EPA) estimates that there are asbestos containing materials in most of the nation's approximately 107,000 primary and secondary schools and 733,000 public and commercial buildings.
How are people exposed to asbestos?
When asbestos fibers are in the air, people may inhale them. Because asbestos fibers are small and light, they can stay in the air for a long time.
People whose work brings them into contact with asbestos -- workers who renovate buildings with asbestos in them, for example -- may inhale fibers that are in the air: this is called occupational exposure. Workers' families may inhale asbestos fibers released by clothes that have been in contact with ACM: this is called paraoccupational exposure. People who live or work near asbestos- related operations may inhale asbestos fibers that have been released into the air by the operations: this is called neighborhood exposure.
The amount of asbestos a worker is exposed to will vary according to
- The concentration of fibers in the air
- Duration of exposure
- The worker's breathing rate (workers doing manual labor breathe faster)
- Weather conditions
- The protective devices the worker wears
It is estimated that between 1940 and 1980, 27 million Americans had significant occupational exposure to asbestos. People may also ingest asbestos if they eat in areas where there are asbestos fibers in the air.
