Vermiculite insulation is way worse than I previously thought. I’ve known that vermiculite insulation can contain asbestos, and my advice to homeowners has always been to assume it contains asbestos and leave it alone, which is also the advice of the EPA. If the insulation needs to be removed or disturbed, my advice has previously been to recommend first having it tested for asbestos. When vermiculite is tested for asbestos and is found to contain less than 1% asbestos, it is considered to NOT be asbestos containing. The EPA defines asbestos-containing material or “ACM” as having >1% asbestos. The problem is that this can be a misleading diagnosis because it seems to imply that the product is safe. The photos below show an attic that still had several unopened bags of vermiculite insulation.
Somewhere between 75% – 85% of all vermiculite insulation sold in the U.S. came from a mine in Libby, Montana, and was sold under the name Zonolite. Nearly all of this insulation contained asbestos which could be easily released into the air. As part of a major class-action lawsuit against WR Grace, numerous studies were conducted. One of these studies determined that exposure to vermiculite attic insulation with less than 1% asbestos is still a potential health hazard when performing typical homeowner activities such as cleaning, maintenance, and remodeling activities. The conclusion of this study was that vermiculite insulation containing less than 1% asbestos should not be considered non-asbestos containing. Reinforcing this conclusion is the fact that the type of asbestos found in Libby vermiculite is “amphibole” asbestos, which is even more hazardous than the chrysotile asbestos that was most widely used in the US. It’s still really bad stuff.