Asbestos containing products are often thought to be solely in the industrial sector of an occupation. What is more uncommonly known is that gardening should be done cautiously because some potting mixtures contain asbestos.
Asbestos is a long thin fiber that is utilized for its resistance to heat, chemical, and electric damage. When inhaled, however, it may lead to various asbestos-related diseases such as mesothelioma.
Asbestos remains in one popular and organic fertilizer - vermiculite. Vermiculite is a naturally occurring mineral that expands up to 15 times its normal size when exposed to heat and is very absorbent. Its water retaining qualities make it usable in gardens that have significant clay content, loosening the soil.
Vermiculite must be mined from the ground, where it is then distributed for various purposes. While this mineral does not contain asbestos, it is mined in almost all cases, directly in the vicinity of asbestos deposits.
A vast majority, upward of 80 percent, of the commercially available vermiculite came from Libby until 1990 when the plant, then owned by W.R. Grace, was closed down due to asbestos-related illnesses. Most environmental experts agree that the amount of asbestos currently found in potting soil is likely to be minimal - such that it may not pose a significant health risk to gardeners.
You can never be too cautious. When buying in bulk ensure that it is labeled "non-dusty" as the dust is non-vermiculite inert matter that will very likely contain microscopic asbestos fibers.
If you use vermiculite, the EPA recommends these steps to reduce exposure to the dust:
If you are using vermiculite to condition soil use caution with stored bags because they will likely contain higher proportions of asbestos. Even newer bags that seem to incorporate large quantities of dust alongside the vermiculite pellets may have residual asbestos and should be used with caution, or discarded.
The current EPA standard of one percent or less of asbestos does not guarantee your safety, as even minute portions of asbestos can lead to asbestos-related disease such as mesothelioma, which is a deadly form of cancer whose incidence is known to be higher among commercial gardeners.
It is possible for asbestos fibers to be released into the air during use, creating the potential for the consumer to inhale them. Since no one knows exactly how much exposure it takes to cause cancer, some consumers may decide to avoid potting mixtures that contain vermiculite altogether.
Reference: The Asbestos Cancer and Mesothelioma Support Center at Asbestos.Net