Zonolite Insulation and Asbestos Lung Diseases

Zonolite, the brand name of attic insulation formerly manufactured by the W. R. Grace Company, contains asbestos. Significant exposure to asbestos increases the risk of lung cancer, mesothelioma and other lung disorders. As a result, the Environmental Protection Agency set limits on exposure to asbestos and is actively pursuing not only methods for reducing the exposure to asbestos of workers today but also cleaning up sites of former manufacturing operations with heavy asbestos usage (Super Fund sites).


Asbestos is the general term for a group of minerals exhibiting characteristic long, thin fibers that separate from each other. Working with or disturbing asbestos-containing materials has the potential of releasing these fibers into the surrounding air, where they can be inhaled and potentially lodge in the lungs. While the lungs are capable of clearing themselves of a variety of pollutants, the long fibers of asbestos cannot be cleared as readily as other substances or at all, setting the stage for lung malfunction and disease.

Asbestos occurs naturally in minerals in the environment but poses little threat to the average citizen in its natural form. However, throughout the 1900’s, asbestos-containing minerals were heavily utilized in construction and other materials because of their useful properties. Evidence of significantly increased rates of lung disease in miners and other workers exposed to asbestos brought the potential risks of asbestos to the forefront.

The Role of Vermiculite

While asbestos was purposely included in building products, for example in asbestos floor tile, asbestos was not intentionally included in the formulation of Zonolite attic insulation. Rather Zonolite was manufactured from vermiculite, another naturally occurring mineral, which was mined in Libby, Montana. Vermiculite mines are found around the world but the Zonolite product utilized only vermiculite from the Libby mine which, along with the insulation manufacturing facility, was owned by the W. R. Grace Company.

The mineral vermiculite has valuable chemical properties that arise when the mineral is heated to extremely high temperatures. Somewhat like popcorn, when appropriately heated, vermiculite expands to fluffy light granules which are fire resistant, chemically inert and lightweight, making vermiculite an excellent insulating material. Vermiculite’s light weight is especially useful in attic insulation applications.

The asbestos problems of Zonolite arose because the geological content in the area of the Libby mine included tremolite asbestos which was mined along with the vermiculite. Residual asbestos in the vermiculite of course was included in the Zonolite insulation that was sold as attic insulation for millions of homes across the Unites States from 1963 through 1984.

The Libby mine ceased operations in 1990 due to the effects of asbestos exposure on mine workers and residents. According to government estimates, approximately 1,800 residents of the town of Libby, Montana have died or become ill from the asbestos dust generated at the mine during its operations. An estimated 20 new cases of asbestos-related illnesses occur each month due to the long-term residual effects of the asbestos dust. To put these numbers into perspective, the town of Libby and a 10-mile radius around it have only 15,000 in population. The Libby mine and the surrounding area have been declared an EPA Superfund site.

Zonolite Insulation

One aspect of the Zonolite controversy is determining if the insulation installed in millions of homes poses a risk to occupants at all and if so, to what extent. Common sense dictates that miners were directly exposed to high levels of asbestos dust for an entire shift for years, resulting in a high level of risk for lung disease. However, local residents of the Libby area experienced only exposure to dust from the mine and are becoming ill as well.

Experts contend that any disturbance of Zonolite insulation, even through ordinary household activities like moving boxes that are stored on attic rafters or changing a ceiling light fixture, will release asbestos fibers which can then be inhaled. Others believe that homeowners are safe.

Another aspect of the discussion of Zonolite centers on how many homes across the United States currently contain Zonolite insulation. Zonolite was manufactured and installed from 1963 until 1984. According to figures from the U.S. Census Bureau, approximately 35 million homes were built from 1963 through 1984. Meanwhile, popularly available estimates for the number of homes with Zonolite insulation vary from 12 to 35 million. A closer estimate will probably never be known.

Homeowners can easily identify vermiculite attic insulation; vermiculite is a loose pebble-like substance that is lightweight. The product originally was golden or light brown in color but over the years has most likely changed to a shade of gray. Replacing Zonolite insulation requires the assistance of professionals and is an expensive undertaking.

After a study conducted in Vermont, the current EPA recommendation for homeowners with Zonolite vermiculite insulation is not to disturb the insulation and hire professionals for removal if replacement insulation is installed.


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