Vermiculite Toxicity

Vermiculite, a mineral used in gardening, insulation and a variety of industrial applications, has been associated with the cancer-causing properties of asbestos because it shares similar properties and has been found to be contaminated with asbestos-like materials. Vermiculite's toxicity has not been studied completely, and no research has linked it to to significant adverse-health effects, according to the Centers for Disease Control (CDC). Miners and factory workers exposed to it in dust form should take precautions because exposure to any mineral dust can cause respiratory problems.

What is Vermiculite?

• Vermiculite is a group of minerals with a flaky texture that looks like mica. It is surface-mined all over the world, including in Australia, Brazil, China, Kenya, Russia, South Africa, Uganda, U.S. and Zimbabwe, according to the Vermiculite Association. The name Vermiculite comes from a Latin word, "vermiculare," meaning to breed worms, a visual description of one of the properties of the substance. When heated, vermiculite expands or pops, forming a lightweight material that is noncombustible, compressible, highly absorbent and nonreactive.

Uses

• Most home gardeners are familiar with vermiculite as an additive to improve soil retention, increase aeration and reduce fertilizer leeching in soil. But vermiculite is found in many other parts of a home, including in the insulation, the plaster and swimming pool lining. Vermiculite is also used to make concrete more lightweight for roofing, in sprays and boards that increase a building's fire resistance, in brake and clutch lining, and as a heat-resistant insulator in kilns, furnaces and boilers. Perhaps one of its more surprising uses is in animal feed, where the trade organization The Vermiculite Association claims it can support and carry a wide range of nutrients, fat concentrates, vitamins and molasses.

Concerns

• The discovery that asbestos could cause cancer led scientists to consider whether similar materials might pose the same health risks, according to the Environmental Protection Agency (EPA). Vermiculite in its natural form contains a range of other materials that formed with it in the rock, and vermiculite from certain mines contains some asbestos-like material. The two materials are also associated with each other because they are both extremely heat resistant, so they were used in many of the same applications before asbestos became highly regulated.

Research

• Unlike asbestos, vermiculite is not a fiber. It cannot be absorbed through the skin the way asbestos can, meaning the only way it can be introduced to the body is through inhalation. It can form fibers when its flakes break and curl, but exposure to vermiculite fibers does not cause any adverse health effects other than what would typically be seen after exposure to any kind of silica dust, according to the CDC and the EPA, which also report that vermiculite toxicity has not been studied completely. Studies of miners and residents near vermiculite mines, however, have found high concentrations of cancer and respiratory diseases in populations exposed to vermiculite that contained asbestos or asbestos-like materials.

Vermiculite and Asbestos

• The CDC indicates that high-profile studies of a mine in Montana where the vermiculite contained asbestos-like minerals contributed to the popular perception that the two were linked. The mine, in Libby, Montana, was active for more than 60 years until it was closed in 1990. Residents of the town, which was six miles away, were exposed to the dust when the vermiculite was loaded onto trucks at a transfer facility three miles away and from several in-town facilities that heated the vermiculite to expand its crystals, one of which was adjacent to a baseball field. These processes released the asbestos-like fibers, including tremolite, actinolite, winchite, richterite and ferro-edenite, into the air, exposing residents to air concentrations of asbestos levels of up to 15 times current occupational limits, according to the CDC. Air concentrations have since returned to more normal levels. High numbers of asbestos-related lung diseases have been reported among residents and miners in the town.

Future Problems

• The Vermiculite Association reports that the Montana mines are the only ones where workers have been found to have asbestos-related diseases. The organization also points out that the industry is subject to a wide range of regulations in the United States and Europe, and manufacturers, producers and suppliers are required to provide health and safety data sheets.