Vermiculite & Asbestos

plumbing image by Inger Anne Hulbækdal from

Vermiculite contaminated with asbestos was sold in the United States for more than 60 years. One mine supplied almost 70 per cent of all U.S vermiculite from 1919 to 1970, and stored product from the mine continued to be sold until 1984.

This contaminated substance was used for the majority of vermiculite insulation in attics and walls in the U.S. Vermiculite also has horticultural uses. The Environmental Protection Agency advises that all vermiculite insulation should be assumed to be contaminated with asbestos. The EPA also offers ways you can protect yourself and others from asbestos-contaminated vermiculite insulation.


From 1919 to 1970, a vermiculite mine in Libby, Montana, provided the majority of all vermiculite used in the United States. Vermiculite is lightweight, odourless and fire-resistant. The Montana mine also contained asbestos. This asbestos-contaminated vermiculite was sold as do-it-yourself home insulation in the 1970s and 1980s, usually under the brand name Zonolite. Before being taken off the market in 1984, it had been installed in almost 1 million homes across the nation.


Asbestos exposure can lead to lung cancer, another cancer called mesothelioma and a lung disease called asbestosis. In the article, "Protect Your Family from Asbestos-Contaminated Vermiculite Insulation," the EPA states plainly, "There is no known safe level of asbestos exposure." The Libby mine supplied so much of the nation's supply of vermiculite for so long that the EPA says that testing vermiculite insulation is not necessary. Instead, vermiculite insulation should be treated "as if it contained asbestos."


Most insulation found in homes is cellulose, fibreglass or rock wool. Rather than being soft and fluffy like these products, vermiculite is granular and slightly brown and can look like small pieces of popcorn. Between attic joists, vermiculite looks like a layer of sharp-angled small rocks has been poured in to a depth of a few inches. Some pieces are very fine particles, while others can be up to an inch long.


Do not disturb it. This is the EPA's main caution for any vermiculite insulation. Since the EPA cautions vermiculite insulation should be assumed to be contaminated, the agency does not recommend testing the insulation for asbestos. In order to cause a health risk through inhalation, asbestos particles must be airborne. Any disturbance puts more particles in the air. Removing or disturbing the vermiculite insulation increases the probability of inhaling asbestos fibres. If it is necessary to go into an attic containing vermiculite insulation, limit the number of trips and shorten the length of time in the attic.


The EPA has five recommendations for people living with vermiculite insulation: Do not disturb vermiculite insulation in the attic or in the walls. Do not store boxes or other items in an attic with vermiculite insulation. Do not let children play in attics containing this insulation. Even if you think of removing the insulation yourself, do not attempt to remove it yourself. If remodelling or renovating the structure will disturb the attic, wall spaces or other areas where vermiculite insulation might be located, hire a professional asbestos contractor to safely handle or remove the insulation.

Horticultural Vermiculite

With the closing of the Libby mine, the amount of asbestos contaminated vermiculite dropped sharply. Following a series of tests beginning in August 2000, the EPA recommended that gardeners who occasionally use vermiculite should limit the amount of dust produced during use. As summarised by the National Cancer Institute in its fact sheet, "Asbestos Exposure and Cancer Risk," gardeners should use vermiculite outdoors or in well-ventilated areas, wet the vermiculite before mixing to reduce airborne dust, avoid bringing vermiculite dust into the home on clothing, and use a premixed potting soil, since it is less likely to generate dust.