Asbestos refers to six unique minerals — chrysotile, amosite, crocidolite, anthophyllite, tremolite and actinolite — belonging to the serpentine and amphibole families.
Technically speaking, “asbestos” is a commercial and legal term encompassing multiple types of minerals. The Asbestos Hazard Emergency Response Act (AHERA) classifies the asbestiform varieties of the following minerals as asbestos:
Chrysotile (white asbestos) is the most commonly used form of asbestos and can be found today in the roofs, ceilings, walls and floors of homes and businesses. Manufacturers also used chrysotile asbestos in automobile brake linings, gaskets and boiler seals, and insulation for pipes, ducts and appliances.
Amosite (brown asbestos) was used most frequently in cement sheets and pipe insulation. It can also be found in insulating board, ceiling tiles and thermal insulation products.
Crocidolite (blue asbestos) was commonly used to insulate steam engines, and it was also used in some spray-on coatings, pipe insulation, plastics and cement products.
Anthophyllite was used in limited quantities for insulation products and construction materials, and it also occurs as a contaminant in chrysotile asbestos, vermiculite and talc. It may have a grey, dull green or white color.
Tremolite and actinolite are not used commercially, but they can be found as contaminants in chrysotile asbestos, vermiculite and talc. The chemically similar minerals can be brown, white, green, gray or transparent.
The AHERA granted the U.S. Environmental Protection Agency (EPA) permission to regulate these six types of asbestos 1986, and more than 50 countries have banned them completely.
However, the U.S. Bureau of Mines and the National Institute for Occupational Safety and Health (NIOSH) have since recognized a number of other asbestos-like minerals that are not yet restricted or regulated. For example, winchite, richterite, erionite and taconite are all minerals containing asbestiform fibers with the potential to cause serious health problems.
While some types of asbestos may be more hazardous than others, all are dangerous. Leading health agencies, including the U.S. Department of Health and Human Services, the EPA and the International Agency for Research on Cancer, classify all types of asbestos as cancer-causing substances.
All the identified forms of asbestos can cause asbestosis, malignant mesothelioma, lung cancer, ovarian cancer, laryngeal cancer and other serious diseases.
Some agencies, such as the Health Protection Agency in the U.K., claim amphibole varieties of asbestos are the most dangerous forms. The EPA has abandoned projects aiming to identify which asbestos fiber types are the most toxic, citing the overall regulation of asbestos and asbestiform minerals as a more pressing priority.
The Two Mineral Families of Asbestos
Serpentine asbestos has curly fibers made up of sheets of crystals. The single type of asbestos from the serpentine family, chrysotile, has historically accounted for more than 95 percent of all asbestos used around the world. As a result of asbestos-industry lobbying, some countries that have banned other types of asbestos still permit the “controlled use” of chrysotile.
Amphibole asbestos has needle-shaped fibers, and studies suggest it takes much less exposure to amphibole asbestos to cause cancer, compared to serpentine asbestos. Amosite and crocidolite are the most commercially valuable types of amphibole asbestos, while anthophyllite, tremolite and actinolite are considered noncommercial forms.
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Chrysotile, commonly referred to as “white asbestos,” was used in the vast majority of the myriad asbestos-containing products manufactured in the United States during the 20th century, and the United States and Canada were once major producers of the toxic mineral.
Naturally occurring deposits of chrysotile are often accompanied by trace amounts of amphibole types of asbestos, which increase its toxicity. However, exposure to chrysotile asbestos fibers alone still creates a serious risk of developing a life-threatening illness, and the NIOSH has concluded people should treat chrysotile asbestos with virtually the same level of concern as all other forms of asbestos.
Chrysotile asbestos-containing products include:
The U.S. Environmental Protection Agency determined amosite, or “brown asbestos,” to be the second most commonly used type of asbestos in the United States. In its natural state, amosite is known as grunerite, and it was mainly mined in South Africa. According to the American Cancer Society, exposure to amosite asbestos creates a higher risk of cancer in comparison with common chrysotile asbestos.
Amosite asbestos-containing products include:
Crocidolite may be responsible for more deaths than any other type of asbestos, because its fibers are extremely thin, causing them to lodge more easily in lung tissue. The most common mining sites for this type of asbestos were Bolivia, Australia and South Africa.
Crocidolite asbestos-containing products include:
Anthophyllite is one of the rarest types of asbestos and does not have a long history of commercial use. The mining of this mineral began in Finland, and smaller deposits were mined in various other countries around the world.
Anthophyllite asbestos-containing products include:
Unlike with the commercial forms of asbestos, manufacturers rarely intended to include tremolite or actinolite in their products. Instead, traces of these types of asbestos were extracted when other minerals were being mined. However, even incidental contamination by amphibole forms of asbestos is still hazardous enough to cause asbestos-related illnesses.
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Asbestiform minerals naturally occur in many types of geological formations. Generally, businesses mined asbestos intentionally to make use of its unique properties, but there have also been cases where companies mined other types of mineral resources that naturally contained a small percentage of asbestos. The most significant cases of this contamination center on talc and vermiculite products.
Talc is the softest known mineral on earth and is used in numerous products including chalk, crayons, paint, rubber, cosmetics, ceramics and pharmaceuticals. Most famously, manufacturers use this mineral for making talcum powder (commonly marketed as “baby powder”), and consumers have filed several mesothelioma lawsuits over asbestos exposure from personal hygiene products. Since 1973, U.S. laws have required all commercial talcum powder products to be asbestos-free.
Vermiculite is a mineral that can be “popped” like popcorn when heated in a process called exfoliation. This results in a light-weight material useful for insulation, packaging and soil improvement. Vermiculite itself is harmless, but unfortunately much of the vermiculite mined in the United States during the 20th century contained highly toxic tremolite asbestos.
More than 70 percent of the vermiculite sold in the United States between 1919 and 1990 came from mining operations near the town of Libby, Montana — now the site of the longest running environmental cleanup operation in the EPA’s history. W.R. Grace and Company sold the tremolite-contaminated vermiculite from these mines as Zonolite attic insulation, putting millions of American homeowners at risk of asbestos exposure.
Matt Mauney is an award-winning journalist with nearly a decade of professional writing experience. He joined Asbestos.com in 2016, and he spends much of his time reading, analyzing and reporting on mesothelioma research articles to ensure people in the mesothelioma community know the latest medical advancements. Prior to joining Asbestos.com, Matt was a reporter at the Orlando Sentinel. Matt also edits some of the pages on the website. He also holds a certificate in health writing from the Centers for Disease Control and Prevention.
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