BENTONITE - National Library of Medicine HSDB Database

Toxicity Summary: IDENTIFICATION: Bentonite is a rock formed of highly colloidal and plastic clays composed mainly of montmorillonite and produced in situ devitrification of volcanic ash. It may contain feldspar, cristobalite and crystaline quartz. Major uses of bentonite include binding foundry sand in molds, absorbing grease, oil and animal wastes; palletizing taconite iron ore and improving the properties of drilling muds. It is used as an ingredient in ceramics, water proofing and sealing in civil engineering projects such as landfill sites and nuclear waste repositories, serving as a filter, stabilizer or extender in adhesives, paints, cosmetics and medicines. It is used as a bonding agent in animal feed, carrier for pesticides, clarifying wine and vegetable oil and purifying waste water. HUMAN EXPOSURE: In the view of widespread distribution of bentonite in nature and its use in various consumer products, general population exposure to low concentrations is ubiquitous. Occupational exposure to bentonite dust from mining, processing and user industries is a factor. ANIMAL STUDIES: Single intratracheal injection into rodents of bentonite and montmorillonite with low quartz content caused dose and particle side dependent effects, as well as transient local inflammation, which included edema and increased lung weight. Single intratracheal exposures of rats to bentonite caused storage foci in the lungs. After intratracheal exposure of rats to this material with high quartz content, fibrosis is noted. Mice maintained on diets containing bentonite displayed slightly reduced growth rates. Mice treated with higher doses showed minimal growth and fatty livers and fibrosis of the liver and benign hepatomas. Bentonite increased the susceptibility of mice to pulmonary infection. In vitro studies of the effects of bentonite on a variety of mammalian cell types indicated a high degree of cytotoxicity. Limited studies did not demonstrate developmental toxicity in rats after oral exposure to bentonite. No adequate studies are available on the carcinogenicity of bentonite. [[World Health Organization/International Programme on Chemical Safety; Environmental Heath Criteriia 231 Bentonite, Kaolin and Selected Clay Minerals pp. 1-5 (2005)]] **PEER REVIEWED**