University of Wisconsin - Extension

MADISON, Wis.-The insulation found in the attics and walls of most homes is either fiberglass, rock wool or cellulose. These are all soft, fluffy and somewhat fibrous. There is another type of insulation in some homes that is granular, similar in appearance to small pieces of popcorn, and light brown in color. This is vermiculite. Vermiculite is a naturally occurring mineral that expands to a lightweight insulating material when heated. It was widely marketed under the brand name Zonolite as a do-it-yourself insulation in the 1970s and early 1980s. You may be familiar with vermiculite as a soil conditioner sold in gardening centers.

Most of the world's supply of vermiculite insulation came from a mine in Libby, Montana operated by the W.R. Grace Company. The company processed the mineral into insulation at facilities in Minneapolis, so it is likely that it was available to consumers in Wisconsin. After noting unusually high levels of asbestos related deaths among people who lived and worked near the Libby mine, the U.S. Environmental Protection Agency (EPA) determined that the vermiculite from the mine might be contaminated with asbestos and began investigating the extent of the hazard. Even if asbestos makes up only one percent of a product it is classified as an asbestos hazard. Zonolite insulation went off the market in 1984, but prior to that it had been installed in nearly a million homes across the United States. The vermiculite for sale today comes from a different mine and does not appear to be contaminated with asbestos.

Asbestos exposure can lead to lung cancer, another lung disease known as asbestosis and another type of cancer know as mesothelioma. The type of asbestos fiber found in vermiculite from the Libby mine is particularly dangerous. Asbestos is only considered hazardous when it is airborne. The particles are very small and very light so that once they become air borne they can remain in the air almost indefinitely where they can be breathed into the lungs.

If you do have Zonolite insulation in your home, here is what the EPA recommends. First, if it isn't disturbed, it is not dangerous; leave it alone. This means you should not store items in the attic if they will be in contact with the vermiculite. Second, even though it is still not certain how general the asbestos contamination was, it is best to assume that if you have any type of vermiculite insulation it contains asbestos. Testing is not recommended.

Third, if you are planning any remodeling that will require substantial disturbance of the Zonolite, hire certified professionals to remove it. They will have the skills and equipment to remove it safely so asbestos-containing dust does not contaminate your home.

Fourth, for projects that will only disturb small amounts of the vermiculite, such as installing a bath fan, you can minimize the amount of asbestos to which you and your family will be exposed by taking some precautions. To reduce the amount of asbestos you breathe, wear a HEPA respirator; ordinary dust masks are ineffective. Seal off the work area from the rest of the house so dust does not spread. When the work is completed, clean all surfaces in the work area with wet wiping or mopping. Remember that your outer layer of clothing may be contaminated and should be removed before leaving the work area, bagged and put directly in the laundry. For more information on dealing with vermiculite insulation and for the names of certified contractors, contact the staff of the Asbestos and Lead Section of the Wisconsin Division of Public Health at 608-261-6876.

If you have a housing question, you may send it to John Merrill, 1300 Linden Dr., Madison, WI 53705, or visit the UW-Extension housing web site at http://www.uwex.edu/house .