Diatomaceous Earth question

Today when I visited the Dollar Tree, they had bags of Cat Litter for $1- (4.5 lbs). When I read the bag, it suggested using it as a soil additive for moisture retention. The only ingredient is Diatomaceous Earth-100% natural. Now- my question--- years ago I used Diatomaceous Earth in trying to control slugs- it is sharp crystals which pierce the soft bodied slugs, and they supposedly die. If this is in the same form, I am thinking it would also harm my precious earthworms- any opinions from the experts? Maybe I will only use it in containers-

I have heard it had no adverse effect on earthworms.