What is asbestos, exactly? Unlike many chemicals and substances that have been found to be harmful, asbestos is not a specific mineral or substance, and has no defined chemical structure. The word itself doesn’t refer to a specific mineral. Instead, it’s a commercial term for a group of minerals that form strong, flexible, durable fibers rather than the crystalline structure we usually associate with minerals. The Toxic Substances Control Act of 1976 defines six types of asbestos, based on the mineral from which they are manufactured. The six minerals are chrysotile, amosite, crocidolite, tremolite, anthophyllite and actinolite. These minerals are not themselves “asbestos.” Rather, they are minerals that can form into fibers which can then be woven into asbestos for commercial use. Each of them has been used in various ways throughout history, and some are more toxic than others.
Asbestos is further classified as falling under two types – serpentine and amphibole. The only one of the six regulated forms of asbestos to form serpentine fibers is chrysotile asbestos, which accounts for most of the asbestos used commercially in the U.S. and throughout the world.
Chrysotile – White Asbestos
Chrysotile asbestos is the most widely used type of asbestos, accounting for nearly 95% of asbestos used commercially throughout the world. It was incorporated into paint, wall boards, roofing tiles and floor tiles as an element of fireproofing, and is still found in many residential and commercial buildings. Chrysotile asbestos is also found in pipe insulation, automobile brake linings and in seals for boilers and gaskets. Because of its wide use, even countries that ban other types of asbestos often allow the use of chrysotile asbestos under certain conditions. That doesn’t mean it’s safer than other types of asbestos – it’s a known carcinogen, as has been proven by multiple studies. The reason that it’s exempted from most bans is that the asbestos industry has a long history of lobbying for its use.
Of all known types of asbestos, chrysotile is the only one in the serpentine family. It forms long, curly fibers that are finer than amphibole asbestos, and is more suitable for most applications than other types of asbestos. It is also commonly known as white asbestos.
Chrysotile Asbestos – Toxicity
Exposure to chrysolite asbestos has been linked to lung cancer, mesothelioma, ovarian cancer and laryngeal cancer. It is often contaminated with trace amounts of tremolite, which is considered more toxic, but some reports show that exposure to chrysotile alone can be just as toxic as exposure to amphibole asbestos. The National Institute for Occupational Safety and Health has stated that chrysolite asbestos should be treated with the same concern and caution as amphibole asbestos.
Chrysotile Asbestos Uses
Chrysotile asbestos has been used (and in some cases continues to be used) in:
- Brake pads
- Brake linings
- Roofing materials
- Joint compound
The remaining five types of asbestos used commercially all fall under the amphibole classification. Amphibole fibers are more brittle, and can break off with sharp edges. Traditionally, amphibole forms are considered more toxic than chrysotile.
Amosite – Brown Asbestos
Amosite is a commercial name for asbestos that was mined in Africa. In fact, its name comes from the acronym Asbestos Mines of South Africa, the company that mined most of the amosite in use. It is commonly known as brown asbestos, and was most frequently used in cement sheet and pipe insulation. The Environmental Protection Agency names amosite as the second most commonly used type of asbestos in the United States.
Amosite – Toxicity
Numerous studies have found that amosite, like most amphibole asbestos, is more dangerous than chrysolite, and requires far less exposure to cause harm than other forms. The American Cancer Society says that exposure to amosite carries a higher risk of cancer than exposure to other types. It has been associated with lung cancer, mesothelioma and asbestosis.
Amosite – Uses
Amosite was used in:
- Thermal, plumbing and chemical insulation
- Insulation boards
- Cement sheets
- Electrical insulation
- Roofing tiles, ceiling tiles, floor tiles
- Roofing products
- Fire protection
Crocidolite – Blue Asbestos
Crocidolite, also known as blue asbestos, is also found in South Africa, as well as in Bolivia and Australia. It is widely considered to be the most deadly form of asbestos, with some reports estimating that up to 18% of crocidolite miners died of mesothelioma, and some studies suggest that people living near crocidolite mines have a higher risk of asbestos-related illnesses.
Crocidolite – Toxicity
Crocidolite forms fibers about the diameter of a strand of hair. Because of their fineness, the fibers can be inhaled and lodge in the linings of the lungs more easily than other types of asbestos. Many studies suggest that because of this, exposure to crocidolite may be more deadly than other exposures. Crocidolite has been associated with mesothelioma, lung cancer and asbestosis.
Crocidolite – Uses
Crocidolite is less heat resistant than other types of asbestos, which limited its industrial uses, but it still made its way into many products used in construction.
- Spray-on insulation
- Ceiling tiles
- Chemical insulation
- Insulation boards
- Water encasement
- Cement sheets
- Electrical wires
Tremolite is not mined on its own, but can be found in other minerals, including vermiculite and talc. The amphibole fibers are strong and heat-resistant, and can be woven into cloth. It was extensively used in household and industrial products through the 1970s.
Tremolite – Toxicity
Like other amphibole forms, tremolite is considered to be more hazardous than chrysolite. Exposure to tremolite increases the risk of lung cancer, mesothelioma, asbestosis, laryngeal cancer and ovarian cancer. Tremolite is often found in minerals like vermiculite and talc. One of the most notorious asbestos-related cases in U.S. history occurred at the vermiculite mines in Libby, Montana, where dozens of miners and local residents were exposed to tremolite over a period of decades.
Tremolite – Uses
Tremolite was widely used in heat-proof and insulating products, including:
- Roofing materials
- Plumbing materials
Non-commercial Asbestos – Anthophyllite, Actinolite
The remaining types of asbestos have never been mined or used commercially, but exist as contaminants in commercial asbestos where they can contribute to the exposure risk.
Anthophyllite occurs largely as a contaminant in other minerals, such as talc or vermiculite. Studies have shown that it can cause lung cancer and other asbestos-related diseases. A study of miners in Finland suggested that exposure to anthophyllite increases the risk of lung cancer more than it does of mesothelioma.
Actinolite is usually used alongside other materials, such as talc and vermiculite. When used together with vermiculite, for example, it makes a lightweight, effective insulation material, and was frequently used that way until the early 1970s. Because of its widespread use for insulation and fireproofing, actinolite can still be found in many residences and commercial buildings in the United States.
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