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Air: Asbestos in Vermiculite Insulation

Vermiculite is a naturally occurring mineral used in construction, insulation, and gardening products. Some vermiculite insulation in homes can contain asbestos.

Answers to frequently asked questions

Below are answers to common questions about asbestos and vermiculite insulation.

Asbestos is a mineral fiber that, until the 1970s, was commonly added to a variety of building materials. Asbestos fibers are long, thin, and strong, but flexible enough to be woven together. For this reason, the fibers were used to provide heat insulation to building materials and make them resistant to fire.

Although most building materials produced today don’t contain asbestos, some older materials in your home may, including:

  • Floor tiles.
  • Pipe and sprayed-on insulation.
  • Roofing.
  • Siding materials.

Vermiculite looks like shiny, small pieces of popcorn and is usually gold or light brown in color. The mineral is mined for several uses, including insulation.

Before it was closed in 1990, a mine in Libby, Montana, produced more than 70% of the world’s vermiculite. Much of it was used as attic insulation and sold under the product name Zonolite. In 1985, the Environmental Protection Agency estimated that 940,000 U.S. homes contained this type of attic insulation.

We now know that the ore from the mine in Libby also included a natural deposit of amphibole/tremolite asbestos, and that much of the vermiculite from the mine was contaminated.

Because asbestos fibers are invisible to the eye and can only be professionally detected, you should understand that vermiculite used for home insulation may contain asbestos. You should avoid disturbing it if you’re unsure whether your insulation contains vermiculite until you or a professional can confirm it.

Today, vermiculite that’s mined for insulation use is from an asbestos-free source.

Vermiculite is used for attic insulation because of its properties as a lightweight, fire-resistant, absorbent, and odorless material. In insulation, vermiculite is pebble-like, blown-in, and usually gold or light brown in color. The sizes of vermiculite products range from very fine particles to large (coarse) pieces nearly an inch long.

Consider these points:

  • Due to the physical characteristics of vermiculite and where it’s installed, such as the attic, the contamination potential for air in your home may be low.
  • If the insulation won’t be disturbed and isn’t contaminating the air in the home (if it’s sealed behind tight walls, floors, or in an unfinished attic that’s vented outside, for example), you may be able to leave it alone. However, you should post signs nearby that warn people that the insulation contains asbestos, and they should be careful not to disturb it or create dust. This can ensure electricians, plumbers, and others doing work on the home are warned and can take steps to protect themselves.
  • You may need to take extra precautions and hire a trained and certified professional if you’re conducting renovation work on your home that involves removing walls or in other areas that contain vermiculite insulation.

These steps can help reduce asbestos exposure during minor home renovations, such as installing a ceiling light, bathroom fan, or computer cable:

  • Hire a professional, state-certified, asbestos removal contractor if your renovation involves more extensive removal or exposure to asbestos-containing insulation.
  • Keep the vermiculite damp to prevent spreading dust.
  • Keep the windows open to ensure good ventilation.
  • Wipe up all dust and debris using wet cleaning methods like wet wipes and wet mops.
  • Tape off rooms with plastic sheeting to prevent contaminating other areas of the home.
  • Use a high-efficiency particulate air (HEPA) vacuum, not a home/shop vacuum, to clean up minor dust and debris.
  • Wear gloves, eye protection, and a HEPA respirator (not just a dust mask).

Unless you take precautions, you risk asbestos exposure if you disturb vermiculite insulation or dust that contains the fiber. When this happens, asbestos fibers are released into the air. If you inhale them, it can damage your health.

In general, the more you’re exposed to asbestos, the greater your risk of developing health problems. Exposure doesn’t always have immediate health consequences, either. In many cases, people exposed to asbestos don’t develop related diseases for years or even decades.

People at highest risk for asbestos exposure and related diseases are those who work at vermiculite processing plants long term, as well as those who regularly install or handle products containing asbestos without wearing proper protection.

People at lower risk are those who occasionally disturb attic insulation during minor “handyman” jobs. The lowest risk is for people who live in a home where the vermiculite insulation is isolated, and they have no direct contact with the materials.

Asbestos exposure is the only known cause of mesothelioma, a rare cancer type that begins in the tissue surrounding the lungs, stomach, and heart. The disease can develop in people who have prolonged exposure to the fibers. However, it also can develop in people who were only exposed once to asbestos decades earlier.

In addition, people who are exposed to asbestos over a long period of time can develop asbestosis, which is permanent lung damage. Asbestosis causes shortness of breath and raises the risk of serious lung infections. Smoking also increases a person’s risk of developing asbestos-related disease.

More information

Contact your local health department for more information. You can also call 608-261-6876 or visit our Asbestos Program page for a list of state-certified contractors and consultants.

The Environmental Protection Agency also includes information on its webpage about how to protect your family from asbestos-contaminated vermiculite insulation.

Last revised April 18, 2023