From Wikipedia

"Inhalation of crystalline silica is harmful to the lungs, causing silicosis. Amorphous silica is considered to have low toxicity, but prolonged inhalation causes changes to the lungs.[44] Diatomaceous earth is mostly amorphous silica but contains some crystalline silica, especially in the saltwater forms.[45] In a 1978 study of workers, those exposed to natural diatomaceous earth for over five years had no significant lung changes while 40% of those exposed to the calcined form had developed pneumoconiosis.[46] Today's common diatomaceous earth formulations are safer to use, as they are predominantly made up of amorphous silica and contain little or no crystalline silica."

Any type of dust isn't good for you but this stuff is wayyyy better than some chemical companies toxic aerosol, drop poison, or bait