Types of Asbestos

What Are the Types of Asbestos?

Asbestos is a group of silicate-based minerals that form naturally underground. The Asbestos Hazard Emergency Response Act (AHERA) identifies six varieties of the mineral:

• Chrysotile asbestos
• Amosite asbestos
• Crocidolite asbestos
• Actinolite asbestos
• Anthophyllite asbestos
• Tremolite asbestos

Many health agencies, including the World Health Organization (WHO), classify all six varieties of asbestos as carcinogenic to people. While generally considered safe when encapsulated or sealed, the mineral becomes dangerous when it is disturbed.

Asbestos fibers can easily become airborne when disturbed. This situation may happen when using asbestos products, mining for asbestos or performing normal job duties in industries where asbestos was used. Fibers can also become airborne during natural disasters, renovations or demolition.

Once airborne, individuals are susceptible to inhaling the dangerous asbestos fibers. This can lead to serious diseases, such as mesothelioma and lung cancer.

Efforts to ban the mineral began in the 1980s. In 1989, the Environmental Protection Agency (EPA) attempted to ban all asbestos-containing products, but the ban was overturned. However, asbestos mining in the United States has stopped. The last U.S. asbestos mine, located in California, closed in 2002.

As of 2023, chrysotile asbestos was the only type still actively used in the United States. In 2024, the EPA finalized a rule to ban chrysotile asbestos nationwide. The rule does not amount to a full ban but is a step in the right direction.

Serpentine Asbestos vs. Amphibole Asbestos

The types of asbestos are categorized into two main families: amphibole and serpentine. All types of asbestos are fibrous and composed of hundreds of small silica fibers. The shape of these fibers determines their family.

Serpentine asbestos is recognized by its wavy or curly form, shaped much like a serpent. The fibers are also long and pliable. Serpentine asbestos may also be classified as “sheet silicates” as the fibers form layered sheets. The only member of this family is chrysotile asbestos.

Amphibole asbestos features straight, stiff, needle-like fibers. Some studies suggest these features make amphibole asbestos more dangerous than serpentine asbestos. This is because the fibers are easier to inhale. Asbestos types that fall under the amphibole category include amosite, crocidolite, actinolite, anthophyllite and tremolite.

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Chrysotile Asbestos

Chrysotile is the only type of asbestos in the serpentine group. Its long, curly fibers can weave together to form sheets. It is also called “white asbestos” because of the color of the asbestos fibers.

Chrysotile is the most commonly used type of asbestos in the United States. It can be found in many buildings, including homes and schools, and accounts for an estimated 90% – 95% of asbestos used in construction. In previous decades, it was also widely manufactured and used in Canada. This form of asbestos was popular in construction products and automotive parts, such as brake shoes.

Amosite Asbestos

Amosite asbestos has straight, brittle fibers that are often needle-like. As an amphibole asbestos, it is generally considered more hazardous than chrysotile. Its light brown color gives it the name “brown asbestos.”

Because it has high heat resistance, amosite was used in products such as insulation and ceiling tiles. It was the second-most common type used in the United States, after chrysotile. Research suggests around 5% of asbestos building materials used in the United States contained amosite asbestos.

Crocidolite Asbestos

Crocidolite asbestos is also known as “blue asbestos.” Studies have linked it to a higher mesothelioma risk than amosite or chrysotile. Its thin, durable fibers can reach deep into the lungs and remain there for a long time.

This mineral has lower heat resistance than other major types of asbestos, so it was used less often. However, it was occasionally found in some construction and consumer materials. One of its most notable uses was in Kent Micronite cigarette filters from 1952 to 1956.

Actinolite Asbestos

Actinolite is a rare form of amphibole asbestos. It features long, sharp fibers that may be easily inhaled. It is also typically darker than other common types of asbestos, ranging from white or pale yellow to dark gray or green.

This type of asbestos contains other minerals including iron, magnesium, calcium and silicon. It is not found as often in consumer products. However, trace amounts have been found in vermiculite. Zonolite insulation made from vermiculite was popular in attics.

Anthophyllite Asbestos

Anthophyllite features long, needle-like fibers that are easily inhaled, like other amphibole asbestos. It is yellowish-brown and composed primarily of magnesium and iron.

Anthophyllite asbestos is rarer than other types of asbestos and much less common in consumer products. It has occasionally been found in some cement and insulation materials.

Tremolite Asbestos

Tremolite asbestos can range in color from white to dark green and features long, sharp fibers. This type of asbestos was commonly used in insulation and other construction materials.

Testing of talc and vermiculite has often shown trace amounts of tremolite asbestos. For instance, testing of various cosmetic products sold at Claire’s© found tremolite asbestos contamination. This sparked concern as these makeup products are marketed to children.

Tremolite asbestos also contaminated the vermiculite mines in Libby, Montana. This led to widespread exposure in the city and risks at other sites that used its vermiculite. This type of asbestos may also be referred to as Libby Asbestos or LA.

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Other Minerals That May Contain Asbestos

Asbestos may be found in other minerals, including talc and vermiculite. When mining these minerals, their proximity to naturally occurring asbestos can result in contamination. This poses a potential health risk to workers and consumers.

Are All Types of Asbestos Dangerous?

Exposure to any type of asbestos is dangerous. Researchers have found even one-time or minimal exposure poses health risks. Various organizations and health agencies have classified asbestos as carcinogenic, including the EPA and the International Agency for Research on Cancer (IARC).

Exposure to any type of asbestos can cause a number of asbestos-related diseases, including mesothelioma, asbestosis and lung cancer.

All types of asbestos are made up of microscopic fibers. The small, sharp fibers may embed in different parts of the body, including organs and the tissues surrounding them. Because the body can’t get rid of the fibers, they remain embedded. The resulting inflammation may eventually lead to mesothelioma or another disease.

Anyone who believes they have been exposed to asbestos in the past should speak to their doctor. A healthcare professional can help monitor for any signs or symptoms of mesothelioma.