"Diatomaceous earth is an abrasive and an absorbent. These properties make it effective in controlling slugs and certain insects. To control ants, fleas, roaches, lice, mites, and ticks indoors, vacuum the infested area, then dust it with a small amount of diatomaceous earth. Repeat every few weeks until resolved." Diatoms are microscopic jagged particles that irritate soft tissue of insects. It's a anti clumping agent. It is harmless enough, but I wouldn't want to breathe it. Jagged and spikey particles are not what I want in my lungs. Maybe an irritant that lets some of the other chems break through natural defenses. https://geology.com/rocks/diatomite.shtml