DE is not the same thing as the DE used in swimming pool filters. Pool grade DE is Diatomaceous Earth produced for pool filters and it is treated with heat, causing the formerly amorphous silicon dioxide to assume crystalline form. Pool grade DE should never be used for pest control. Swimming pool DE ranges from 60% to 70% free silica! Copyright Golden Harvest Organics LLC, 1996-2010 Learned this the hard way! Had never purchased DE and was having a hard time finding it. Somebody finally suggested a pool store so I thought I had lucked out. Short version...Nobody died but had blisters covering faces I later discovered a feed mill that carried DE. They call DE fossil flower.