Vermiculite is a naturally occurring mineral composed of shiny flakes of a similar appearance to mica. While not dangerous if untainted, in many cases vermiculite is nested closely in the ground to asbestos. Manufacturers are not always careful to ensure the vermiculite they sell is pure. From 1919 to 1990, almost 70% of all vermiculite sold in the United States was from a mine in Libby, Montana. In this mine, there was also asbestos in the ground. Vermiculite from the mine in Libby became infamous because of this asbestos. The vermiculite from Libby was often sold under the brand name Zonolite.
If your home or building contains vermiculite, assume the vermiculite is contaminated with asbestos. Then make sure you know the steps to protect those in the building from asbestos and implement them.
When vermiculite is heated to a high temperature, flakes of the mineral can expand from 8 to 30 times their original size. The expanded vermiculite is lightweight, odorless, and fire-resistant. It has been used in multiple products, including wall and attic insulation. The size of vermiculite products can range from very small, fine particles to large particles almost an inch long.
Vermiculite is a pebble-like, pour-in product. It is usually silver-gold or gray-brown in color. It is a good idea to assume that vermiculite installation is from the Libby mine, and to treat the insulation as if it contains asbestos. If you remove the vermiculite, make sure to have a trained professional do the work. Because such a high percent of vermiculite in the United States came from Libby, and vermiculite from Libby contained asbestos, it is not necessary to test vermiculite for asbestos before assuming the vermiculite is indeed contaminated. You could have a professional test vermiculite in your attic, but depending on the methods used, the outcome could be wrong. Opening a wall to test for vermiculite is not recommended.
The first step to asbestos avoidance is to not disturb the material, since asbestos only poses a danger when airborne. Disturbing the material can easily make fibers airborne and possible to be inhaled. Even if you disturb insulation to remove it, asbestos fibers can be released. If the insulation of concern is in an attic, and you do not enter the attic, the chances of being exposed to asbestos are greatly diminished. If asbestos-contaminated vermiculite in an attic is disturbed, exposure may then occur throughout the whole building or at least more of it than just the attic.
Being exposed to asbestos does not mean you will, later on in life, have an asbestos-caused disease. More asbestos exposure simply increases the risk of asbestos-caused disease. Most asbestos-caused diseases have latency periods decades long. Disease risk increases with level, length, and frequency of exposure. Asbestos disease risk is also made higher by smoking.
If you have vermiculite in your home, you should assume it contains asbestos and not touch or otherwise disturb it. This is extremely important, as any disturbance, no matter how slight, could possibly release carcinogenic asbestos fibers into the air. Wherever you have vermiculite, leave it undisturbed. If your attic has vermiculite insulation, do not store boxes there, or allow children to play there. Do not remove vermiculite yourself. If you wish to remodel or do some renovations that may disturb some vermiculite, hire a professional asbestos removal contractor to make sure the vermiculite is safely handled (or removed).