One place I looked at online said that their food grade and their pesticide grade all come from the same mine, but due to EPA reg.s, if they're selling it as a pesticide, they have to do all the warning labels.
I started using it on some of the friendly barn kitties--one of them had HUGE open sores from scratching fleas and they started to heal up immediately. I am hoping that in grooming, they'll get enough into them to help with worms. It doesn't seem too dusty if you just scoop it up and place it on their back before you start rubbing it in.
It's good to see the nice kitties laying peacefully out in the sunshine while the not-nice kitties lay out there scratching and digging. It'll be interesting to see long term if we increase the ratio of nice kitties!