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Vermiculite is a silver-gold to gray-brown mineral that is flat and shiny in its natural state. When heated to around 1000 degrees C, it pops (or puffs up) which creates pockets of air. This expanded form, and the fact that vermiculite does not burn, made the material suitable for use as insulation.
Vermiculite itself has not been shown to be a health problem. However, some vermiculite insulation contained asbestos fibres, which can cause problems if inhaled. As long as this kind of vermiculite-based insulation remains undisturbed behind intact walls or in attic spaces and does not become airborne, it should not be a concern.
Of concern is Zonolite® Attic Insulation; this insulation was sold in Canada under the name of Zonolite® and was extracted from the Libby Mine in Montana, USA. This mine had a natural deposit of asbestos which resulted in the vermiculite being contaminated with asbestos.
Vermiculite produced by the Libby Mine has not been on the market in Canada for more than 10 years. Not all vermiculite sold in Canada before 1990 contains asbestos fibres. However, if you believe that your home may contain vermiculite insulation, it is reasonable to assume that it may be contaminated with asbestos.
Asbestos can cause health problems when inhaled into the lungs. Breathing in very small, airborne asbestos fibres has been associated with diseases such as asbestosis, mesothelioma and lung cancer. (See OSH Answers web page How Do Particulates Enter the Respiratory System? for information about how small particles have to be to get into the lungs.)
The best way to minimize asbestos exposure from vermiculite is to NOT remove or disturb the insulation. Moving the vermiculite will cause fibres to become airborne. The following precautions will prevent releasing asbestos fibres into the air: