Vermiculite Products With Asbestos Can Be A Serious IAQ Concern

What vermiculite is and where it is found
Why vermiculite is an indoor air concern

What Vermiculite Is and Where It Is Found

Vermiculite is produced from ore mined throughout the world. Vermiculite ores from some mines have been found to contain asbestos. In the United States, vermiculite mines are located in Montana, South Carolina, and Virginia. Mines are also located in Australia, Brazil, China, Kenya, South Africa, and Zimbabwe.

When heated, the ore expands into a light, rather fluffy material. This material is fire resistant, absorbent, lightweight, odorless, and does not react with chemicals. The absorbent properties of the expanded vermiculite make it useful in lawn and garden, agricultural, and horticultural products. Other common uses are as thermal and sound insulation, construction material, and for lightweight, absorbent packaging material. It has been used in various industries for over 80 years.

Why Vermiculite Is An Indoor Air Concern

The concern is not with the vermiculite itself but rather the asbestos in some vermiculite products. The issue became known with reports of hundreds of deaths and lung diseases among workers and townsfolk in Libby, Montana near a mountain where asbestos-tainted vermiculite was mined for more than half a century. In addition, lawyers, doctors and family members say asbestos dust at two Minneapolis plants that processed Montana vermiculite killed or contributed substantially to the deaths of 21 workers and 3 neighborhood residents.¹

These incidents got people taking a closer look at vermiculite products. It was found that some vermiculite insulation, which is found in millions of attics and walls across the United States, contains asbestos in levels above what is considered to be safe. In August 2000 the assistant US surgeon general warned that handling Zonolite insulation could expose people to the hazards of asbestos. Recent studies of Zonolite insulation have shown that even casual handling of the insulation can expose workers or homeowners to 150 times the asbestos level considered safe under federal law.

Zonolite insulation was made with ore from the vermiculite mine in Libby, Montana. The brownish-pink vermiculite from Libby was sold for use in garden products, fireproofing, cement mixtures, and more than a dozen other consumer products. However, most of it was heat-treated until it expanded; it was then marketed as Zonolite insulation that was stuffed between rafters and inside walls. Tests have shown that even installing a light fixture or ceiling fan through an attic floor insulated with Zonolite can produce dangerous levels of airborne asbestos.¹ If piles or bags of vermiculite are disturbed, it could cause tiny asbestos particles to get into the air. The US Environmental Protection Agency (EPA) recommends the following:

• Limit your exposure to any vermiculite dust, including remodeling

• Use vermiculite outdoors or in a well-ventilated area

• Keep vermiculite damp while using it to reduce the amount of dust created

• Avoid bringing dust from vermiculite use into the home on clothing

• Use premixed potting soil, which usually contains more moisture and less vermiculite than a pure vermiculite product, and is less likely to generate dust

• Use other soil additives such as peat, sawdust, perlite or bark

1. Gordon G. EPA: Asbestos in gardening products poses little risk; After tests on vermiculite products from around the country, the EPA recommended buying premixed potting soil, and raised questions for workers who use such products often. Minneapolis Star Tribune. August 23, 2000; page 9A.