This may be a tough one.
Last year I had an ant problem in my house and was doing some research on pesticides. It appears Diatomaceous Earth ("DE") is one of the best and least hazardous methods of killing insects, (Beetles, ants, roaches, centipedes, etc.). Diatomaceous earth appears to be made of ground fossils of prehistoric fresh water diatoms. To insects DE is a lethal dust with microscopic razor sharp edges. These sharp edges cut through the insect's protective covering drying it out and killing them when they are either dusted with DE or if it applied as a wettable powder spray. If they ingest the DE it will shred their insides.
Based on my unscientific research, it appears that both swimming pool grade and natural diatomaceous earth come from the same fossil sources but are processed differently. The natural grades are mined, dried, ground, sled and bagged. The pool grade is chemically treated and partially melted and consequently contains crystalline silica which can be a respiratory hazard.
My question is; does anyone know if this is true or just another ploy to buy more expensive DE?
BTW For once, it appears to be cheeper for the pool then as an insecticide.