Diatomaceous Earth (DE) is a naturally occurring, fine, white powder sourced from the fossilized remains of ancient aquatic life. This sedimentary rock material is widely used across various industries, including as an insecticide, a filtering agent for liquids, and an anti-caking additive in feed. Due to its common use in homes and industrial settings, understanding the composition of DE and the specific safety considerations necessary when handling the material is important.
Understanding Diatomaceous Earth Composition
Diatomaceous earth is composed primarily of the skeletal remains of diatoms, which are single-celled algae that secrete a shell made of silica. These microscopic fossils are mostly silicon dioxide, existing in an amorphous, or non-crystalline, state. Under a microscope, these particles appear as tiny, porous, and highly structured cylinders.
The sharp, abrasive nature of these particles makes DE an effective insect control agent. When insects contact the powder, the fine particles scratch their protective outer waxy layer (the cuticle). The highly absorbent silica then draws moisture and oils from the insect’s body, leading to death by desiccation. This mechanical action, while effective against pests, necessitates caution during human handling.
The Crucial Distinction: Food Grade Versus Filter Grade
The safety of handling diatomaceous earth depends entirely on its processing, which defines its commercial grade. The key difference between grades lies in the form of the silica, which can be either amorphous or crystalline. While most naturally occurring DE is amorphous silica, high-heat processing can change this structure dramatically.
Food Grade
Food Grade DE is minimally processed and remains largely in its natural amorphous state, containing less than one to two percent crystalline silica. This grade is approved for use in food storage, animal feed, and as a natural insecticide, making it the safer option for home use. The amorphous structure is considered much less hazardous to mammals, though inhalation should still be minimized.
Filter Grade
Filter Grade, often called Pool Grade, is subjected to extreme heat treatment (calcining) to improve its filtration properties. This intense heat converts the amorphous silica into crystalline silica, which can make up 35 to 70 percent of the final product. This crystalline form is highly abrasive and classified as a significant respiratory hazard. Filter Grade DE must only be used for industrial purposes like water filtration and should never be used for pest control or food-related applications.
Safety of Physical Contact and Inhalation
Direct skin contact with diatomaceous earth is not toxic, but its highly absorbent nature can lead to mild physical irritation. The fine particles readily absorb moisture and oils from the outer layer of the skin. Prolonged exposure, especially for individuals with dry or sensitive skin, may result in dryness, redness, or mild irritation. Washing the exposed area thoroughly with soap and water after use is sufficient to mitigate this effect.
If the dust contacts the eyes, it will cause irritation and discomfort due to its abrasive texture. Like any fine particle, DE can cause redness and tear formation. If this occurs, flush the eyes with water for several minutes and remove any contact lenses.
The most significant health concern with diatomaceous earth is the risk of inhalation. Breathing in any fine dust can irritate the nasal passages and throat, leading to coughing and temporary shortness of breath. The danger is amplified, however, with the crystalline silica found in Filter Grade DE. Chronic inhalation of crystalline silica can lead to serious and irreversible lung damage, including silicosis, a condition where the lungs develop scar tissue. Even when using Food Grade DE, minimize dust cloud creation and work in a well-ventilated area. When handling large quantities of any grade, or when dealing with Filter Grade, wearing an N95 respirator mask is a necessary precaution.