Diatomaceous Earth (DE) is a naturally occurring, silica-rich powder derived from the fossilized remains of ancient, single-celled algae called diatoms. This fine, chalk-like powder is primarily composed of silicon dioxide, or silica, which provides its abrasive and absorbent qualities. DE is used widely, from filtering liquids in industrial settings to acting as a natural insecticide in homes and gardens. The central question for residential users remains whether this versatile material is safe for humans and household pets.
Understanding the Different Grades of Diatomaceous Earth
The safety of Diatomaceous Earth depends entirely on its grade, which is determined by processing methods. The two main types are Food Grade DE and Filter Grade, sometimes called Pool Grade DE. This distinction is necessary because of the difference in their silica structure.
Food Grade DE is largely uncalcined, meaning it is not treated with high heat, and consists primarily of amorphous silica. This form is safer and contains minimal crystalline silica, typically less than 2%. Filter Grade DE is calcined, or heat-treated up to 1000°C, converting the amorphous silica into crystalline silica. This industrial process results in a material that can contain around 60% crystalline silica, making it hazardous for residential use. Only Food Grade DE should be used for pest control, supplements, or any application involving contact with people or animals.
Safety Profile for Humans
For humans, the safety of Food Grade DE depends on the route of exposure, primarily ingestion or inhalation. When consumed as a dietary supplement, Food Grade DE is generally considered non-toxic. The Food & Drug Administration even recognizes it as “Generally Recognized as Safe” for specific uses. The material passes through the digestive system without being absorbed into the bloodstream. While ingestion is not expected to cause toxicity, some users may experience mild digestive side effects like constipation or stomach upset.
The primary safety concern is the inhalation of the fine powder, even the Food Grade variety. Any fine dust, including amorphous silica, can irritate the upper respiratory tract, causing coughing and nasal irritation. While this irritation is usually mild and reversible, the dust can be problematic for individuals with pre-existing respiratory conditions. Prolonged inhalation of the crystalline silica found in Filter Grade DE is linked to serious lung diseases like silicosis. Minimizing dust clouds during application is a necessary precaution for all users.
Safety Profile for Household Pets
Food Grade DE is widely used by pet owners for dogs, cats, and poultry, and is generally safe with proper precautions. It is often used internally as a purported dewormer or supplement, and externally for controlling fleas and ticks. When ingested in small amounts, the powder is non-toxic and passes through the digestive tract. Owners should consult a veterinarian before using it internally to determine the correct dosage.
DE works as a physical insecticide by rubbing against the insect’s exoskeleton, causing dehydration. When applied directly to a pet’s coat, the fine powder is effective against external parasites like fleas. Over-application should be avoided, as the drying properties that affect insects can also cause dryness or irritation to the pet’s skin. The most significant risk to pets is respiratory irritation from inhalation, similar to humans. Since animals are often closer to the ground where dust clouds linger, inhaling large amounts of the fine powder can lead to coughing or wheezing. Pet owners with existing breathing issues should be cautious about using DE around them.
Safe Application and Storage
To minimize the risk of inhalation for both people and pets, proper application methods are important. Applying DE in a thin, light layer is more effective for pest control than creating thick piles, which can deter pests. Using a dusting bulb or a shaker container helps reduce airborne powder during application. For large-scale applications or near sensitive individuals, wearing a simple dust mask and eye protection is recommended.
One method for reducing dust is applying DE when wet, such as mixing it into a slurry to be brushed onto surfaces. The material remains effective after the water evaporates, but it loses efficacy if it becomes wet again due to rain or dew. For storage, Food Grade DE should be kept in a sealed, airtight container in a cool, dry place. This prevents it from absorbing moisture, which renders it ineffective for pest control. Containers should be clearly labeled and stored away from children and pets to prevent accidental ingestion or inhalation.