Diatomaceous Earth (DE) is a naturally occurring, soft sedimentary rock that easily crumbles into a fine powder. This substance is composed of the fossilized remains of tiny, aquatic organisms called diatoms, whose skeletons are made primarily of silica. DE is widely utilized across many industries, including filtration, pest control, and as a food additive. The safety of physical contact with this fine powder depends almost entirely on how the material has been processed. This processing dictates the form of silica present.
The Two Essential Forms of Diatomaceous Earth
The safety profile of Diatomaceous Earth is determined by its processing, which results in two distinct forms: amorphous and crystalline silica. The raw material is composed of amorphous silica, a non-crystalline form that is considered low in toxicity. This is the form found in “Food Grade” DE, which is typically uncalcined and contains less than 1% crystalline silica.
The more hazardous form is crystalline silica, created when raw DE is heated, or calcined, at very high temperatures (often over 1,000°C). This high-heat process hardens the diatom exoskeletons, making the material a more effective filter. It also converts some amorphous silica into crystalline silica, primarily as cristobalite. This “Filter Grade” or “Pool Grade” DE can contain significantly higher concentrations of crystalline silica, sometimes ranging from 10% up to 75%.
Dermal and Gastrointestinal Contact
When handling Food Grade Diatomaceous Earth, direct contact with the skin (dermal exposure) is generally regarded as safe for incidental periods. The primary effect is localized dryness and mild irritation. This occurs because the fine powder is highly absorbent and wicks away moisture and oils from the skin’s outer layer. Simple rinsing with water after contact is usually sufficient to address this mild irritation.
Food Grade DE is also safe for ingestion in controlled amounts and is used as a dietary supplement or anti-caking agent. The body does not absorb a significant amount of the silica when swallowed, and it passes through the digestive tract without causing systemic toxicity. While non-hazardous in small quantities, consuming excessive amounts may potentially irritate the digestive tract.
The Primary Hazard: Inhalation Risks
The greatest safety concern with any form of Diatomaceous Earth is the risk associated with inhaling the fine dust particles. Both amorphous and crystalline silica can cause irritation to the nose and respiratory passages, leading to coughing and shortness of breath if a large amount is inhaled. This irritation stems from the dust’s abrasive nature and microscopic size.
The long-term danger is almost entirely due to inhaling the crystalline silica found in the calcined, Filter Grade material. These tiny crystalline particles can penetrate deep into the lungs and accumulate in the tissue and lymph nodes. Chronic or prolonged exposure to high concentrations of respirable crystalline silica has been linked to the development of serious, irreversible respiratory diseases.
The most severe condition resulting from prolonged crystalline silica exposure is silicosis, a fibrotic lung disease that causes scarring of the lung tissue. Amorphous silica, conversely, is associated only with mild, reversible lung inflammation and is not linked to these severe long-term diseases.
Safe Handling and Use Guidelines
The single most effective safety measure is to always verify the grade of Diatomaceous Earth being used. Only use Food Grade DE for applications involving human or animal contact, and reserve Filter Grade products for industrial or filtration purposes. For any use involving the dry powder, the primary goal is to minimize the generation of airborne dust.
Wearing appropriate Personal Protective Equipment (PPE) is recommended, especially when applying large quantities or working in poorly ventilated areas. A dust mask or respirator should be worn to prevent inhalation, and protective eyewear will prevent mechanical irritation to the eyes. When cleaning up spills, use a damp cloth or a vacuum with a high-efficiency filter instead of dry sweeping, which can easily aerosolize the dust.