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Asbestos in Wiring Insulation

Asbestos in Wiring Insulation and Other Building Materials

In order to prevent fire as well as electrocution, insulation is used around electrical wiring to prevent sparks or electrical charges that could hurt people or their property.

There are many types of wiring insulation, rubber being one of the most effective. Ceramic is another inert material that possesses strong insulating properties. Both of these materials have their drawbacks, however. One is expense. During the Second World War, after the Japanese Empire invaded and occupied the rubber-producing regions of Southeast Asia, rubber became an expensive commodity.

By contrast, throughout the early and mid-20th century, asbestos was a cheap and easily accessible substance. Most asbestos was mined in the U.S., Canada, Russia, Australia and South Africa and so it was widely available for use in the United States. There are three types of asbestos used in commercial applications, but for electrical applications crocidolite, or "blue" asbestos, had properties that made it an especially effective insulator, and enormous quantities of crocidolite-based electrical insulation was produced and applied to residential and commercial wiring, power lines, and the power generation and transmission facilities of the major utility companies.

This changed in the late 1970s, as public awareness of the severe danger posed by asbestos inhalation became widespread, and for most applications in the United States asbestos is no longer legal to use. Other forms of insulation, such as ceramics and rubber, have taken its place.

Asbestos in Wiring Insulation Products Containing Asbestos

The following partial list of asbestos in wiring insulation products were known to contain asbestos:

Product Name Start Year End Year
United States Gypsum Thermalux (Generic) 1961 1965

Hazards Associated with Wiring Insulation Products

When the insulating material is intact or new, it is relatively safe to be around. Asbestos must be inhaled in order to cause disease in the body. However, when wiring becomes worn or damaged, the asbestos inside can easily become friable, meaning that it is delicate and will crumble at a touch. Friable asbestos can easily be inhaled, and the inhalation of asbestos fibers has been conclusively linked to the development of asbestosis, lung cancer, and malignant mesothelioma. Electrical workers, power plant employees, demolition workers, electricians, maintenance personnel, linemen, building engineers, and anyone else working with damaged or worn electrical insulation installed before 1980 is at risk of having been exposed to asbestos on the job.


Bowker, Michael. Fatal Deception: The Untold Story of Asbestos (New York: Touchstone, 2003)

N/A. "What? No Asbestos?" Commercial ad published in Fortune (February 1943).

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