Posted: 19/05/2012 at 20:26
The horticultural vermiculite on sale now is not thought to pose a health risk but to give a potted history to some of the information that you find on the internet...
The vermiculite/asbestos connection comes from a public health emergency caused by a vermiculite mine at Libby, Montana. The public health emergency is well documented in both US Environmental Protection Agency documents and in medical literature. Being a natural product, vermiculite can contain lots of different minerals and other substances and the composition varies between different deposits. This particular mine was found to have high levels of amphibole (a type of asbestos) contamination. The mine closed down in 1990 before the contamination was identified. The vermiculite from this mine was largely used for insulation so is still present in many buildings.
There doesn't seem to be any need to be concerned with the vermiculite that gardeners use but with any dusty product, it's never going to be a good idea to shake the bag and breath it in.