Vermiculite is a nonfibrous silicate mineral with multiple consumer uses that has been shown to contain various concentrations of asbestiform fibers. Vermiculite is a micaceous hydrate of magnesium-iron-aluminum silicates with the ability to exfoliate or expand up to 20 times its original size at high temperatures. It has high-cation-exchange capacity and a very low thermal conductivity. Most of the vermiculite mined and beneficiated is exfoliated and used in construction aggregates, insulation, and agricultural applications. Exposure to vermiculite occurs mainly via the inhalation route. Nonoccupational exposure to vermiculite is high. In 1979, approximately 13 million persons were estimated to have been exposed to vermiculite. The carcinogenicity classification for vermiculite is D. However, the weight of evidence for asbestos-contaminated vermiculite is sufficient to show a causal relationship for increased lung cancer in miners and millers.

"Office of Health and Environmental Assessment." "Office of Research and Development." "September 1991." "EPA/600-8-92-037." "EPA/600-8-91-037." Includes bibliographical references.