Types of Asbestos Insulation

Asbestos is a naturally occurring mineral found almost everywhere on earth. It is odorless, non-conductive to heat or electricity, and fire-retardant, making it a valuable, yet dangerous, building tool. While the United States Bureau of Mining recognizes over 100 “asbestos-like” fibers, the United States government has regulations on only six types of asbestos. They include chrysotile, amosite, crocidolite, anthophyllite, tremolite, and actinolite. Chrysotile, amosite, and crocidolite are the most common forms of asbestos used in commercial and industrial settings, with chrysotile being the most readily used of the three, although the others have in the past been used often as well.

These six asbestos fibers are broken into two groups, the serpentine group and the amphibole group. The serpentine group is defined by its curly fibers and layered form, and of the six regulated types of asbestos, chrysotile is the only member of this group. The other five fibers are in the amphibole group and have straight fibers. Their structure is chain-like.

Of the six types of asbestos we are focusing on, chrysotile, or “white asbestos”, and its most common form used in products in the U.S., making up around 95% of asbestos use. It is a more flexible fiber than its cousins in the amphibole group, and can be spun into fabric. Common uses include ceiling and wall panels, brake linings, and roof sheets used in warehouses and outbuildings. Of all types of asbestos, chrysotile is the least likely to be inhaled, and therefore deemed to be the safest. Although it may be the safest to use, chrysolite asbestos is used so much more frequently than other types that it is considered to be the leading cause of asbestos related health problems. Quebec, Canada is the main source of chrysotile, but there are deposits throughout Europe and North America. It is a curly, white fiber and a magnesium silicate.

Amosite is commonly referred to as “brown asbestos” because of its gray to brown hue. It’s name is an acronym derived from the South African mines in which it was found (Asbestos Mines of South Africa). Previously, it was the second-most used form of asbestos but has since been banned in many countries, and commercial and industrial usage has dwindled. It is made up of brittle, linear fibers, and is most commonly found in ceiling tiles, and formerly used as an insulation. Amosite fibers can easily become airborne, and can cause significant health risks if inhaled. Inhalation of these fibers has been known to cause lung cancer as well as pleural and peritoneal mesothelioma. Amosite contains iron and magnesium.

Crocidolite, or “blue asbestos”, is the common name for the amphibole riebeckite in fibrous form. It is generally considered to be the most deadly form of asbestos, and, like amosite, is known to cause lung cancer and mesothelomia. Because of its strength, it is commonly used to reinforce plastics. It consists of straight blue fibers, and is found mostly in South Africa, but can be found in Australia and Canada. Crocidolite is a sodium iron magesium silicate.

Anthophyllite has a white to gray color, and is formed by talc breakdown in ultramafic rocks. Because of this, anthophyllite can commonly be found contaminating talc. It has no common industrial uses, but can be found in heat expansive minerals such as vermiculite, a mineral sometimes added to gardening soil. Its fibers are brittle, and as a member of the amphibole group, are chain-like. Anthophyllite is a magnesium iron silicate hydroxide and can be found in places in the eastern United States and also in the Gravelly Range and Tobacco Root Mountains of Montana.

Tremolite is a white to dark green mineral found in most metamorphic rocks. It is formed when dolomite and quartz metamorphose. Tremolite has been sparingly used industrially, and can be found as an ingredient in household products, talcum powder included. It is a calcium magnesium iron silicate. In 1999, the Agency for Toxic Substances and Disease Registry began investigating health problems in Libby, Montana caused by a tremolite contaminated vermiculite mine. They found that mortality in the time studied (1978-1998) was approximately sixty times higher than the rest of the United States.

Actinolite is gray, white or green and very similar to tremolite, but contains more iron in proportion to magnesium. It is not commonly used in commercial settings, yet can be found as a contaminant in other asbestos products.

This is just a brief explanation of the types of asbestos. For a more thorough understanding, talk to your local house builder, visit the public library, or do a Google or Yahoo search under “asbestos types.”

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