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Questions About Vermiculite: What It Is & How It Is Used

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What is Vermiculite?

Vermiculite is a naturally occurring flaky mineral that resembles mica. It was first described in Massachusetts early in the 19th century and was named for the Latin word vermiculare, “meaning to breed worms” because of the exfoliation process that occurs when it is heated. When the temperature reaches 900 degrees Celsius, the flakes expand and the vermiculite increases in size 8 – 30 times. The end product is an accordion-like shape that does not burn, has low thermal conductivity, is absorbent, lightweight, compressible, pH neutral, unaffected by all but the strongest acids, and mixes well with a wide variety of other products.

Where is Vermiculite Commonly Used?

Vermiculite has been, and still is used in a wide variety of applications such as in:

  • Home insulation
  • Building materials
  • Fire protection products
  • Insulation for high-temperature furnaces and kilns
  • Vehicular brake linings
  • Safety packaging material for shipping hazardous products
  • Horticultural applications such as mixing in potting soil, for germinating seeds, or distributing fertilizer

Contact RPF Environmental if you want to test for vermiculite insulation in your home or business. We offer asbestos testing in Maine, Massachusetts, New Hampshire, and throughout the country.

Is Vermiculite Safe?

The raw mineral vermiculite on its own is safe. The problem is that essentially the same geologic processes that produce vermiculite also are conducive to creating asbestos, so they can be found in the same locations whereby vermiculite can be contaminated with asbestos fibers. There is no safe level of human exposure to asbestos, and it cannot always be seen with the naked eye. Exposure to airborne asbestos can cause lung disease, even death, and the symptoms following an exposure may not show up for decades.

Most of the vermiculite that was used in the 20th century came from Libby, Montana; the same area where there was a huge mining operation for asbestos. The Libby vermiculite mine was closed in 1990 and vermiculite production nowadays is safer. Today, companies are expected to routinely test and sell vermiculite that is free of asbestos.

Where Am I Likely to Encounter Vermiculite and How Do I Stay Safe?

Vermiculite insulation and gardening products are the common uses of vermiculite that you might need to be careful of:

1. Vermiculite Insulation

While the Libby, Montana vermiculite mine was in operation, asbestos-contaminated vermiculite insulation was widely distributed throughout North America, most often under the company name Zonolite.

How Was Vermiculite Used in Insulation?

Loose-fill insulation of this type is poured into spaces between walls and in attics. It is in the shape of small nuggets, or pebbles, with the characteristic accordion-like shape and colored from silver-gray to gray-brown. In 2018, the United States Geological Survey (USGS) stated that approximately one million homes in the U.S. contain vermiculite insulation in the attic.

How to Protect Yourself from Asbestos-Contaminated Vermiculite Insulation

Any vermiculite insulation should be treated with caution, but insulation applied between 1920 and 1991 are at a high risk of containing asbestos fibers from the Libby, Montana mine.

If you suspect that your home has vermiculite insulation, assume that it does and do not disturb it.

If you suspect that your home has vermiculite insulation, the EPA and many states recommend that you assume that it does. Be careful not to disturb it causing microscopic asbestos fibers or any dust to become airborne. A dust mask will not prevent your inhalation of asbestos fibers. The Environmental Protection Agency (EPA) recommends that you leave vermiculite insulation undisturbed in your attic and walls.

Other things to keep in mind are:

  • Do not break walls open to see if vermiculite is there
  • Do not allow children to play in an attic with suspected vermiculite
  • Do not use an attic with vermiculite insulation for storage
  • Do not try to handle the vermiculite yourself
  • If you are concerned with asbestos fibers falling through the ceiling into living spaces, seal any openings
  • If you are concerned that you have been exposed to asbestos, contact your physician

If you plan to do any repairs or remodeling that would disturb the insulation, hire an accredited professional to assess the vermiculite for asbestos or assume there is asbestos. Normal bulk material analysis methods for other types of asbestos building materials are not sufficient for the assessment of vermiculite.

If you wish to have testing performed, only hire a qualified industrial hygiene firm that is independent of any abatement contractor firm and that can offer all the different testing and analytical methods. If removal of the vermiculite is necessary, be sure the material is safely handled or removed by a qualified asbestos removal contractor and ensure that 3rd party testing is completed afterwards by a qualified industrial hygiene firm.

2. Vermiculite in Home Gardening Products

In 2020, the EPA released the results of an investigation into how much asbestos could be found in gardening products containing vermiculite. While they did find low levels of asbestos in some products, they concluded that consumers face only minimal health risk from vermiculite in the home gardening setting. They were more concerned about gardening products containing vermiculite in occupational settings.

How to Use Vermiculite in the Garden

Vermiculite’s spongy, lightweight, and absorbent qualities are great for horticultural purposes. It can be used by itself for germinating seeds, growing root cuttings, flower arrangements, or for wicking moisture away from stored bulbs or root crops. When mixed with soil, peat, or compost, it helps to maintain moisture, provide anchorage for roots, eliminate packed-down soil, and allow aeration.

How to Protect Yourself from Asbestos-Contaminated Vermiculite Gardening Products

When handling vermiculite in a home gardening situation, the EPA recommends some ways to reduce the risk of exposure to airborne asbestos fibers:

  • Use the vermiculite outdoors or in a well-ventilated space
  • Keep it moist to avoid any asbestos fibers from becoming airborne
  • Consider using pre-mixed potting soil to reduce the amount of vermiculite and dust, and to increase the amount of moisture
  • Be careful to avoid bringing vermiculite dust inside your clothing
  • Try alternatives to vermiculite such as perlite, peat moss, or bark

In an occupational setting, vermiculite should be treated the same as any other suspected asbestos-containing material abiding by all OSHA, EPA, and state requirements.

Asbestos is what makes vermiculite unsafe.

Also Read:


What is vermiculite used for?

Vermiculite insulation is common in the construction industry due to its durability and fire-resistance properties. It is also popular in horticultural and agricultural applications where they are used as potting soil mixes.

Is vermiculite safe to use in potting soil?

Horticultural vermiculite that you can buy in stores today is generally safe and doesn’t contain asbestos. Vermiculite helps aerate the soil as well as increase nutrient and water retention.

Is vermiculite insulation any good?

Vermiculite insulation has a high chance of containing toxic asbestos and can harm your health once the material becomes friable. Any amount of exposure can cause serious health complications.

What are the side effects of vermiculite insulation?

Inhaling airborne asbestos fibers can increase your risk of developing asbestos diseases such as asbestosis, mesothelioma, and lung cancer. Minor asbestos poisoning symptoms include shortness of breath, wheezing, persistent dry cough, and fatigue.

Test for Vermiculite Insulation in Your Home or Business

At RPF Environmental, we have been dealing with asbestos every day since 1991. If you are concerned about vermiculite in your home or in an occupational setting, we can help you with assessing for asbestos, making plans to handle it safely, and testing for safe air after a project is completed. Click here to learn more.

Call us at 603-942-5432 today to find out how we can support your industrial hygiene control program. We serve clients throughout the United States.

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