Asbestos is a group of minerals that occur naturally as bundles of fibers.
These fibers, found in soil and rocks in many parts of the world, are made of
silicon, oxygen, and other elements. There are 2 main types of asbestos fibers:
Serpentine asbestos fibers are curly. The most common asbestos in industrial
use, known as chrysotile, or white asbestos, has curly fibers.
Amphibole asbestos fibers are straight and needle-like. There are several types
of amphibole fibers, including amosite, crocidolite, tremolite, actinolite, and
anthophyllite.
Amphiboles (particularly crocidolite) are considered to be more likely to cause
cancer, but even the more commonly used chrysotile fibers have been linked to
cancer.
Asbestos fibers are strong, resistant to heat and to many chemicals, and do not
conduct electricity. As a result, asbestos has been used as an insulating
material since ancient times. Since the industrial revolution, asbestos has
been used to insulate factories, schools, homes, and ships, and to make
automobile brake and clutch parts, roofing shingles, ceiling and floor tiles,
cement, textiles, and hundreds of other products.
During the first half of the 1900s, growing evidence showed that breathing in
asbestos caused scarring of the lungs. In the early 1900s, exposure to asbestos
dust in the workplace was not controlled. Beginning in England in the
1930s, steps were taken to protect workers in the asbestos industry by
installing ventilation and exhaust systems. However, in the huge shipbuilding
effort during World War II, large numbers of workers were exposed to high
levels of asbestos.
As asbestos-related cancers became better recognized in the second half of the
20th century, measures were taken to reduce exposure, including establishing
exposure standards. In addition to more careful handling, there has been a
dramatic decrease in the import and use of asbestos since the mid-1960s, and
alternative insulating materials have been developed. As a result, asbestos
exposure has dropped dramatically in the United States. However, it is still
used in some products, and there is still a potential for exposure to asbestos
in older buildings, water pipes, and other settings. Heavier asbestos use
continues in many other countries as well.
see full article at:
http://www.cancer.org/cancer/cancercauses/othercarcinogens/intheworkplace/asbestos