Asbestos in Vermiculite Attic Insulation (VAI)

Libby Montana "Vermiculite" [EPA site info]

Sampling VAI(pdf)

HealthCanada Vermiculite Insulation

Vermiculite is a naturally occurring mineral that has the unusual property of expanding into “books” or worm-like accordion shaped pieces when heated. (the name vermiculite is derived from the Latin 'vermiculare' - to breed worms)  The expanded vermiculite is a light-weight, fire-resistant, absorbent, and odorless material.  These properties allow vermiculite to be used in numerous applications, including attic insulation.  Vermiculite Attic Insulation (VAI) is a pour-in-product, fragments of which are generally approximately 5mm to 1cm in dimension, and usually light-brown or gold in colour.  Asbestos is not intrinsic to vermiculite and only a few ore bodies have been found to contain more than tiny trace amounts  Deposits of Vermiculite usually contain other mineral phases and some ore bodies may contain fibrous amphibole.

Predominant commercial mines are in Australia, Brazil, China, Kenya, South Africa, USA and Zimbabwe.  Prior to 1990, a large proportion of North America’s consumption of vermiculite originated from the mine at Libby, Montana.  Depending on the date of production, this material may have contained several percent of fibrous amphibole, down to a fraction of a percent shortly before the mine was closed in 1990.

Asbestos is a Class A human carcinogen that commonly enters the body through inhalation of asbestos fibres, this action increases the risk of nonmalignant interstitial and pleural lung disease, lung cancer, and mesothelomia.  Several studies have implicated the fibrous amphiboles, such as those found in Libby vermiculite, and in cases of asbestos related disease.  These studies provide evidence that mineral forms of asbestos not specifically regulated in North America can cause diseases such as asbestosis, lung cancer, and mesothelomia.  The risk of developing these diseases depends upon many factors, including the chemistry and shape of fibre, level of exposure, duration of exposure, the individual’s physiological response to fiber exposure, and the smoking history of the exposed individual.

Health Canada’s concern is that VAI products can cause health risks if disturbed during maintenance, renovation or demolition. However, there is currently no evidence of risk to your health if the insulation is sealed behind wallboards and floorboards, isolated in an attic, or otherwise kept from exposure to the interior environment. The best way to minimize your risk of asbestos exposure is to avoid disturbing vermiculite-based insulation in any way. If vermiculite-based insulation is contained and not exposed to the home or interior environment, it poses very little risk