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Gardening with Vermiculite

I was taught to mix potting soil with vermiculite when preparing pots for planting for better drainage and I’m sure I inhaled some of the vermiculite dust along the way. Once I was even enveloped in a cloud of dust when I dropped the bag accidently.

These days my husband supplies me with dust masks to wear when performing nasty airborne chores like cleaning the litter box or mixing rocks with soil, but I’ve often wondered if my early stupidity would lead to lung problems decades later, the way asbestos exposure leads to mesothelioma cancer down the road.

Laura Hasha of Mesothelioma Info sheds some light on this subject in today’s guest post on vermiculite and mesothelioma:

Vermiculite is a versatile mineral commonly used in agriculture and home gardening as a soil aeration product. It is popular among gardeners, especially those who grow their own fruit or vegetables because it has a very low density and is extremely lightweight. Those two properties make it an ideal additive for soils that are very dense or highly compacted.

The addition of vermiculite to aerate such soils increases moisture and nutrient retention. In fact the material is one of the main components of the popular square foot gardening technique.


Vermiculite mines are typically large, open pit excavations from which rocks containing vermiculite are collected through the use of heavy machinery. These rocks are transported to a processing plant where they are then crushed and screened repeatedly until reaching a desired size. These flakes are then graded for size and type before being shipped to exfoliation plants where the material is heated in furnaces that reach temperatures of 1600-2,000 degrees F.

Similar materials

The most similar material to vermiculite is perlite which is produced by hydrating obsidian. When heated it expands and many companies that produce vermiculite produce perlite as well.

Vermiculite Controversy

In Libby, Montana a commercial vermiculite mine exposed people because the material was contaminated with a form of asbestos known as tremolite. The mine later sickened the town resulting in deaths from asbestos related diseases such as mesothelioma.

In 2000, the Environmental Protection Agency purchased 16 different vermiculite containing products from the Seattle area and found 5 of the products contained asbestos fibers.

Asbestos formations can occur within close proximity of vermiculite and four of the major formations in the United States have been confirmed to contain asbestos. But it is important to note that vermiculite is not a form of asbestos and exposure to vermiculite from a non-contaminated source poses no known health risks.

*** Thanks for the info, Laura! I wish it made me feel more confident that my previous vermiculite inhalation will not lead to cancer, but I guess it would depend on if that particular vermiculite product that I was using contained asbestos.

If there’s one thing I’ve learned from my journey into natural health and safe products it’s that there are so many things in our daily lives that can harm us that I should focus my attention on the things I can change in my life and not the things I can’t.

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