Vermiculite May Pose Asbestos Hazard

by: Heather on 12/19/2008
Posted in: Guest Posts

The following post was submitted by James O'Shea, a reader concerned about potential soil contamination from vermiculite. Vermiculite is widely used in gardening for moisture retention. If you buy plant starts or potted plants from the garden center, the little whitish bits that you often find mixed in with the soil are vermiculite.

Vermiculite May Pose Asbestos Hazard

The mineral vermiculite is an extremely effective soil conditioner for moisture retention enhancement. Avid gardeners praise the material for being inexpensive and easy to incorporate into different garden arrangements. However, there may be a darker side to the mineral that is now becoming manifest. Unfortunately, many vermiculite deposits are known to contain not only the targeted mineral, but also hazardous asbestos.

Vermiculite occurs across the globe in mineral form and is mined not only for commercial and private gardening uses, but also for commercial insulation materials and industrial compounds. The origin of the mineral is another mineral known as biotite. Over millions of years of age and weathering, biotite will become vermiculite. Biotite would often be found in close proximity to another mineral known as diopsid, which over millions of years and the same weathering conditions would eventually become asbestos, a known carcinogen.

Most asbestos products were banned in the late 1970's by the Consumer Product Safety Commission and the Environmental Protection Agency. In 1989, a total phase out of asbestos was enacted but eventually overturned. Today, products which contain more than one percent asbestos are considered asbestos-containing materials (ACMs) and are banned.

When vermiculite is mined, often so too are trace amounts of asbestos dust. In Libby, Montana, W.R. Grace, a specialty chemical and mineral company was mining thousands of tons of vermiculite each year. When the mine's employees and residents of the town began to become ill with mesothelioma (an aggressive form of cancer known to be caused only by asbestos exposure) and other respiratory conditions, it became clear that asbestos contamination had become a major issue in commercial vermiculite mining. While W.R. Grace was mining vermiculite before existing regulations were in place, the fact is that even vermiculite which contains less than one percent asbestos is potentially hazardous to human health.

Asbestos, prior to being regulated, was used in a myriad of industrial capacities. It had unique insulation qualities and proved to be particularly adept at preventing temperature transfer. For this reason it was used in thousands of construction materials. When asbestos exists within a solid construction compound, it poses no true hazard as the fibers cannot be released. It is only when the compound is rendered "friable," or able to pulverized by human hand pressure, that the material is hazardous. Residual asbestos dust, as was found in the Libby vermiculite, is already friable as it is not in any stable compound.

For this reason, today most vermiculite manufacturers will label their product as "non dusty." It is important to use only vermiculite which is labeled as such. Those who encounter a great deal of residual dust in their vermiculite should likely dispose of the material and be careful not to disturb it. Asbestos cancer is among the most devastating malignancies known and mesothelioma treatment is typically limited to palliative therapies to ease symptoms. Fortunately, asbestos exposures due to vermiculite can now largely be avoided by being conscious of the material you are working with and identifying potentially hazardous vermiculite granules. Vermiculite can be used both safely and effectively if certain precautions are undertaken.

Environmental Protection Agency: Asbestos Regulations and History
Consumer Product Safety Commission: Asbestos: Risk and Assessment
Environmental Protection Agency: Libby Amphibole Asbestos


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