Sodium Bentonite Dangers

Sodium bentonite powder can be an inhalation hazard.

Used in cat litter and industrial sealants as well as feeds, foods and personal-care products, sodium bentonite has earned its long-standing title as the “clay of a thousand uses.” Sodium bentonite can absorb up to five times its weight in water and capture charged particles from solutions. Its safety has not been exhaustively studied, but its primary hazards appear to be as a lung and eye irritant and--depending on its history--a potential source of toxins. Knowing the properties of the bentonite used for a particular application is key to using it safely.

Composition

Sodium bentonite is a naturally occurring mineral.

Sodium bentonite is a naturally occurring clay material made of very thin sheets of alternating aluminum and silicon oxides. The sheets are held loosely together by sodium and other atoms sandwiched between the sheets that help neutralize electrostatic repulsion. Like any other natural mineral, it is mined from the earth, where it can be contaminated with other mineral forms, water-borne toxins, such as lead and arsenic, or man-made chemicals. After extraction from the ground, sodium bentonite is processed to various degrees of purity, depending on the final application. These impurities must be considered in any analysis of sodium bentonite hazards. A more detailed description of sodium bentonite structure and composition can be found in "Sealing of Boreholes and Underground Excavations in Rock."

Mechanisms of Action

Clumping cat litter gets its properties from sodium bentonite.

Sodium bentonite is able to absorb large amounts of water by accepting layers of water molecules between each layer of clay, swelling--but not entirely dissociating--the structure. This property is most often used in applications such as cat litter and sealants. As described in "Clay Geosynthetic Barriers," sodium bentonite's other distinctive property is its capacity for ion exchange. The clay can absorb unwanted positively charged particles, including proteins, from liquid solutions, exchanging its loosely held sodium ions into solution in return.

Powder

Sodium bentonite's absorbant properties make it a good pond sealant.

Industrial-grade sodium bentonite powder is used as a clumping agent in many cat litters and in some other farm and garden uses, including pond sealants and feed additives. Sodium bentonite and its impurities have been implicated in inflammation of the lungs in industrial workers, and although laboratory tests indicate that the clay itself has a low carcinogenic potential, the fine impurities that remain in the industrial-grade bentonite sold for these applications can represent a hazard to the lungs, eyes or sensitive parts of the skin. The materials safety data sheet for sodium bentonite, available online from ILC resources, provides additional safety information on industrial sodium bentonite, as does Reade Advanced Materials, a bentonite supplier.

In Foods

Some wines have higher sodium after processing with sodium bentonite.

Food-grade bentonite is used to remove particles that cause cloudiness from liquids like white wine and vinegar, and also as a sealant for wine barrels. Since bentonite works by exchanging its sodium ions for other charged particles in the solution, its use increases the sodium level of the treated liquid. However, according to Christian Butzke, professor at Purdue University, wine is still considered a “very low sodium” beverage even after extensive bentonite treatment. In food-grade bentonite, the level of impurities is more tightly controlled than in industrial-grade bentonite, and according to Reade Advanced Materials, arsenic and lead content specifically must be below accepted levels. The FDA finds sodium bentonite to be “generally regarded as safe” as a food additive, according to "Bentonite, Kaolin, and Selected Clay Minerals."

As a Detoxicant

Livestock feed is often supplemented with sodium bentonite, without apparent adverse effects.

Only trace amounts of the sodium bentonite clay itself are likely to be found in foods like wine and vinegar that are processed with it. However, sodium bentonite is widely used in feed for meat animals as up to two percent of the total feed weight. Certain alternative medicine regimes also promote the direct consumption of sodium bentonite as a “detoxifying agent” for humans, although it is not FDA approved for this purpose. According to a 2001 review in “Toxicological Sciences,” the addition of sodium bentonite appears to help livestock absorb certain toxins present in mold-contaminated feed. No adverse effects on the animals' nutrient absorption or growth rates have been reported from the addition of sodium bentonite to animal feed, although the review's author adds that “the main disadvantage...may be the significant hidden risks associated with the indiscriminate inclusion of nonselective clays (or other absorbant materials) in the diet of humans or animals.”

In Cosmetics

Sodium bentonite is considered "safe as currently used in cosmetic formulations."

Sodium bentonite is a common ingredient in facial cleansers, makeup, and other personal care products. A 2003 review in “The International Journal of Toxicology” concluded that sodium bentonite and other clay-like materials are “safe as currently used in cosmetic formulations,” with the caveat that cosmetic sprays could represent the same kind of inhalation hazard as industrial bentonite. Sodium bentonite is most commonly used in facial masks and other liquid-based formulations, in which particulate inhalation is not a likely problem.

Summary

The history of a batch of sodium bentonite must be considered when planning its use.

An analysis of the safety of sodium bentonite requires an understanding of its nature. As a highly absorbent naturally derived clay, sodium bentonite can be contaminated in the ground or during processing, and those contaminants can be--although often are not--released during its use. The source and grade of any sodium bentonite used in homemade cosmetics or food products should be carefully considered, since not all commercially available sodium bentonite is suitable for these uses. An expert should be consulted for these applications.

References

• Purdue University: Fining with Bentonite
• Sage Journals: Report on the Safety Assessment of Aluminum Silicate, Calcium Silicate, Magnesium Aluminum Silicate, Magnesium Silicate, Magnesium Trisilicate, Sodium Magnesium Silicate, Zirconium Silicate, Attapulgite, Bentonite, Fuller's Earth, Hectorite, Kaolin, Lithium Magnesium Silicate, Lithium Magnesium Sodium Silicate, Montmorillonite, Pyrophyllite, and Zeolite
• Google books: Bentonite, Kaolin, and Selected Clay Minerals
• Toxicological Sciences: Dietary Clay in the Chemoprevention of Aflatoxin-Induced Disease
• Google books: Sealing of Boreholes and Underground Excavations in Rock

Resources

• Ilcresources.com: “ILC Resources: Sodium Bentonite Material Safety Data Sheet.”
• reade.com: "Reade Advanced Materials: Bentonite Powder."
• “Clay geosynthetic barriers: Volume 1”; Helmut Zanzinger; 2002.