Vermiculite Insulation and Asbestos


Vermiculite is a mineral used in a number of consumer products, including home insulation. Some vermiculite produced at Libby Mine in Montana from the 1920s until 1990, sold primarily under the brand name Zonolite®, has been found to contain asbestos. While not all vermiculite produced before 1990 contains asbestos fibres, it is reasonable to assume that if a building has older vermiculite-based insulation, it may contain some asbestos.


Asbestos is the generic name for fibrous minerals found naturally in rock formations around the world. Because asbestos fibres are strong, durable and non-combustible, they were widely used by industry, mainly in construction and friction materials.

When inhaled in significant quantities, and over extended periods of time, exposure to asbestos can cause asbestosis (a scarring of the lungs which makes breathing difficult), mesothelioma (a rare cancer of the lining of the chest or abdominal cavity) and other types of lung cancer. Approximately 80 per cent of cases of mesothelioma are as a result of exposure to asbestos. Therefore, numbers of mesothelioma cases are often used as a marker for asbestos exposure in a population.

Cases of mesothelioma are rare, typically ranging between 5 and 20 cases per year in Manitoba (an approximate rate of one case per 100,000 Manitobans per year). This number of cases has gradually increased since the early 1970s, when surveillance for mesothelioma in Manitoba began. As there is a 30 to 40 year latency period (delay) between exposure to asbestos and the occurrence of mesothelioma, this increase in cases is believed to be due to exposures that occurred before the implementation of safety measures which reduced the risk for contact to asbestos in workplace environments. Improvements in disease surveillance systems have also increased the ability to accurately identify and report cases. With the introduction of measures to improve workplace safety, it is anticipated that the trend in mesothelioma and other asbestos-related diseases will begin to decline over the next one to two decades.

Vermiculite insulation

Of the 45,455 homes evaluated for energy efficiency across Canada as part of Natural Resource Canada's EnerGuide for Houses Program from June 1, 2004 to March 22, 2005, vermiculite insulation was observed in 1,674 (or 3.7 per cent) of houses. 3,184 of the homes evaluated were in Manitoba and 215 (6.6 per cent) of these homes contained vermiculite insulation.

In 2004, Indian and Northern Affairs Canada (INAC) conducted a national survey of First Nations homes. Of the 597 references to Zonolite® identified, 234 were in Manitoba.

Horticultural Vermiculite

Health Canada recently concluded national testing of horticultural (gardening) vermiculite products. This testing revealed mostly non-detected amounts of asbestos, with a few samples showing trace amounts of tremolite asbestos fibres. Based on these low levels, Health Canada has determined that the use of horticultural vermiculite, when used as directed by consumers, poses no additional risk of cancer. The United States’ Environmental Protection Agency has conducted similar testing and come to the same conclusion – that horticultural vermiculite is considered safe and does not pose an elevated risk of cancer to the user.

Minimizing your risk

According to the Health Canada advisory “Vermiculite Insulation Containing Amphibole Asbestos”, the best way to minimize your risk of asbestos exposure is to avoid disturbing vermiculite-based insulation. If vermiculite-based insulation is contained and not exposed to the home or interior environment, it poses very little risk.

If you know you have, or believe you may have, vermiculite-based insulation in your attic, the following precautionary steps are recommended:

  • Seal all cracks and holes in the ceilings of the rooms below the insulation (for example, apply caulking around light fixtures and the attic hatch) to prevent insulation sifting through.
  • Restrict access to the attic. Do not allow children to play in an attic with open areas of vermiculite-based insulation.
  • Make sure anyone working in the attic knows about the possible presence of asbestos.
  • Do not use the attic for storage if retrieving items from it may disturb the insulation.
  • If you must go into the attic, walk on boards in order to minimize disturbance of the insulation and use an appropriate respirator mask. Common dust masks are not effective protection against asbestos fibres. Half-face N, P, or R-100 respirators can be used and are available from retailers who sell safety equipment.
  • Do not remain in the attic any longer than is necessary.

If you suspect that you have vermiculite-based insulation in your walls, as a precautionary step, seal all cracks and holes. For example, apply caulking around window and door frames, along baseboards and around electrical outlets.

If you decide to have vermiculite-based insulation removed, or if you are planning renovations, speak to a professional qualified in dealing with asbestos. They can be found by looking under "asbestos abatement/removal” in the yellow pages. You should not attempt to remove the insulation yourself, unless you have been properly trained and have the necessary specialized equipment.

What to do if you are concerned that you may have been exposed to asbestos

Asbestos related illnesses are usually associated with frequent and prolonged exposure to asbestos. The time it takes to develop disease following exposure to asbestos is usually measured in decades. However, there are some steps you can take if you have concerns about exposure to asbestos:

  • Talk to your health care provider. Currently, there are no effective screening methods to determine if exposure to asbestos has occurred. For those with more frequent/prolonged exposure, your health care provider may recommend having a chest X-ray and/or refer you to a specialist.
  • Avoid or minimize further exposure to any form of asbestos. This includes making sure future work is done safely, as well as proper clean up of the area.
  • Don’t smoke, and avoid second hand tobacco smoke and other irritants that could affect your lungs. The combination of exposure to cigarette smoke and asbestos greatly increases the chance of developing lung cancer.

For information on this issue, Health Canada provides a toll-free contact number: 1-800-443-0395. You can also visit the Health Canada website to view the Health Risks of Asbestos page. Information can also be provided through your local public health office.

For workers and employers with questions related to a workplace, please contact the Workplace Safety and Health Division at 204-945-3446.

Public Health | Environmental Health
Manitoba Health

4th Floor - 300 Carlton St.
Winnipeg MB  R3B 3M9
Phone: 204-788-6735
Fax: 204-948-2040