Is vermiculite carcinogenic: Should I be using it in potted plant material?
Here is what the Health Canada webpage on garden safety suggests in regards to this soil amendment:
Chemicals and Soil Amendments
- Although processed vermiculite, found in some potting soils, is considered safe, use vermiculite outdoors, keep it damp to avoid dust, and do not bring dust into your home on clothing. Premixed potting soils contain less vermiculite than pure vermiculite products and are less likely to generate dust.
- Use peat moss, sawdust, pearlite or bark as an alternative to vermiculite when amending the soil.
As well as the Canadian Centre for Occupational Health & Safety has the following information:
Vermiculite Insulation Containing Asbestos
What is vermiculite?
Vermiculite is a silver-gold to gray-brown mineral that is flat and shiny in its natural state. When heated to around 1000 degrees C, it pops (or puffs up) which creates pockets of air. This expanded form, and the fact that vermiculite does not burn, made the material suitable for use as insulation.
Is all vermiculite a health concern?
Vermiculite itself has not been shown to be a health problem. However, some vermiculite insulation contained asbestos fibres, which can cause problems if inhaled. As long as this kind of vermiculite-based insulation remains undisturbed behind intact walls or in attic spaces and does not become airborne, it should not be a concern.
Vermiculite is a naturally occurring mineral whose thin, shiny layers and appearance resembles mica. This mineral compound is formed by the weathering and transformation of the minerals biotite and phlogopite. Like many micaceous compounds, vermiculite layers can expand up to 30 times their original size when subjected to intense heat. In its post-heated form, vermiculite is light weight, absorbent and versatile.
From 1925 to 1990, vermiculite ore mined near Libby, Mont., accounted for more than half of the global production and supply. During the mining process, asbestos and asbestos fibers were mined and mixed with vermiculite. It is primarily the asbestos-contaminated vermiculite that has posed the greatest health concern. Though the Libby mine is no longer in operation, two companies with three operations in the United States, two in South Carolina and one in Virginia, mine vermiculite. There are still vermiculite deposits in Texas, Colorado, Nevada, North Carolina and Wyoming. In the United States, imported vermiculite comes primarily from two countries–South Africa and China. Less amounts come from Russia, Australia, Zimbabwe, Brazil and Japan.