Vermiculite, a common moisture-retaining ingredient in potting soils, at one time contained unregulated amounts of asbestos prior to the discovery of the danger this could pose. Vermiculite potting soils sold now are regulated and labeled to show all ingredients.
At one time, many thousand tons of vermiculite contaminated by asbestos was shipped nationwide before the EPA (Environmental Protection Agency) began regulating and limiting allowable amounts of asbestos dust that vermiculite could contain.
Used to aid plant growth in some potting soils and having a shiny appearance, these metallic colored flakes absorb and hold water for slow release. To minimize your risk of asbestos exposure in the potting soil it is best to keep it moist.
From sometime in the 1920s until 1990, vermiculite contained a naturally occurring form of asbestos that was mined in Libby, Montana. The mine produced a large portion of the vermiculite for the world.
While vermiculite as a potting soil is considered safe, you may choose to purchase potting soils that do not contain vermiculite in order to avoid any asbestos exposure.
Although the EPA now bans products containing asbestos amounts of 1 percent or greater, these can still be hazardous especially if in dust form, as the asbestos fibers can float in the air making it possible for them to be inhaled.
- Illinois Department of Public Health: Asbestos in Vermiculite
- Asbestos: Potting Mixtures
- Earth Easy: Vermiculite and Asbestos
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