Boron (boric acid, borax, etc.) is a poison. Years ago it was a common ingredient in baby powders until that was banned because it all too often caused babies to turn nicely bright red with their reactions to the stuff. There is a commonly used "homemade" cockroach killer made with 1 part each of corn meal, sugar, and boric acid powder. People are told to place the mixture into jar cap lids and place the lids around so that cockroaches can eat the stuff, head back for their nests, die, be eaten by other cockroaches, which themselves will then die -- but to be sure to keep the bait out of the reach of pets and children. The lesson may be: If it does not grow as a vegetable or an animal, people should not eat it. You can eat a lot of salt before it kills you, but, boric acid - not so much !