Types of Asbestos
Once mined in many places throughout the world but now mostly in Canada, Russia, Africa, and China, asbestos is a naturally-occurring mineral that was used for decades as an insulator for a host of products, many used in homes throughout the world.
Six different types of asbestos have been identified. These types are divided into two groups:
- Serpentine – This variety of asbestos has a layered structure and curly fibers. Chrysotile asbestos is the only type in this category and was the kind of asbestos most often used in buildings in the United States.
- Amphibole – This kind of asbestos is characterized by a long chain-like structure of fibers that are sharp and straight and easy to inhale. Found in this category are the remaining 5 types of asbestos – amosite, crocidolite, anthophyllite, tremolite, and actinolite. The first two were widely used in products until the 1980s and amosite is the 2nd most likely type to be found in buildings.
These kinds of asbestos are also often categorized by their color, though tremolite, anthophyllite, and actinolite remain unclassified.
- White – chrysotile
- Brown – amosite
- Blue – crocidolite
The commercial production of amosite or “brown” asbestos ended within the last 10 years and it is no longer mined. It was at one time, however, the second-most commonly used form of asbestos and many individuals were exposed to it during its use. It was employed as insulation in factories and buildings and also as acoustical material and anti-condensation material. Its use has been banned in most countries for about the last 30 years.
Crocidolite accounted for about 4 percent of all asbestos once used in the United States. This “blue” asbestos is harder and more brittle than other types of the mineral and can break easily, releasing dangerous needle-like fibers that are easily inhaled. This is undoubtedly the most lethal form of asbestos and was often used in making yarns and rope lagging and as reinforcement materials for plastics.
Crocidolite was generally mined in Western Australia, Bolivia, and South Africa and the percentage of miners who developed asbestos cancer due to crocidolite exposure stands at a staggering 18 percent. In the town of Wittenoom, Australia (population 20,000), where blue asbestos was mined for many years, more than 1,000 people have died of mesothelioma with officials estimating that another 1,000 will eventually perish from asbestos-related diseases. The town is now a ghost town, with 8 residents remaining, and has literally been erased from the map.
The most common type of asbestos and the only kind that is still mined, chrysotile was the most widely used in the world’s developed countries. Estimates show that about 90-95 percent of all asbestos that remains in buildings in the U.S. and Canada is of this variety. Obviously, because it was the most widely used, it accounts for the most health problems, though the companies that mine it continue to attest to its safety.
Chrysotile is most often used in fireproofing and in insulation products and was widely used aboard U.S. Navy ships during World War II and the Korean War. It can also be woven into cloth and was once used in theater curtains and – ironically – to make protective clothing for those who worked with high temperature equipment or liquids. It was also an ingredient in cement and was helpful in the manufacture of friction products because of its heat-resistant properties. These included brake shoes, clutches, and disk pads. Its most recent uses were in the nuclear energy industry.
Today, the Canadian Chrysotile Institute maintains that the asbestos they mine is much safer these days and claims that they only market dense and non-friable products in which the chrysotile fiber is “encapsulated in a matrix of either cement or resin.” Previously, the chrysotile that was sold in the marketplace crumbled easily and was quite toxic.
Nonetheless, most experts maintain that ALL asbestos can cause cancer, even chrysotile, and even when exposure is minimal. This has been demonstrated by the fact that those who live near chrysotile mines have a much higher incidence of mesothelioma than the general public.
Anthophyllite asbestos, also known as “brown” asbestos is composed predominantly of iron and magnesium. The fibers are known to be long and flexible. Of the amphibole asbestos sub-classification, brown asbestos can be found in many talc mines and has been associated different respiratory disorders, though is not conclusively associated with mesothelioma as other varieties of asbestos are.
As an amphibole variety of asbestos fiber, tremolite asbestos is indeed associated with the development of mesothelioma and other asbestos-related cancer. Like other varieties of asbestos, tremolite asbestos is composed predominantly of magnesium and can range from off-white to a dark green in color. Tremolite asbestos is particularly common in vermiculite and vermiculite deposits.
Actinolite asbestos is a variety of the sub-classification of amphibole asbestos and, as such, its makeup and consistency is similar to other forms of this subset. Made predominantly of magnesium, actinolite asbestos is extremely rare and ranges in color from white to dark brown. Actinolite was not known to be used in asbestos products because of its rarity, but is known to be found in metamorphic rock.