Horticultural grade DE is not carcinogenic but it should NOT be inhaled. It could be damaging to the mucus tissues and lungs of animals (including us). POOL grade DE does have a different chemical makeup, and should not be handled at all. But you wouldn't be using pool grade DE, anyway. Horticultural grade DE is also the same stuff that is dusted all over cats, dogs, chickens, horses, cattle and other animals, as well as put into their food to prevent and get rid of intestinal parasites. Stored grains and nuts are dusted with it to prevent weevils and other insects from devouring everything.....thus, we are eating DE with our peanut butter and cereal! Horticultural DE and Food grade DE are the same thing.

Boric acid is the product that must be handled with more caution. It should not be placed anywhere where pets or people will be chronically exposed to it, and they must not ingest it. It should be considered toxic.

I have used the Terro liquid boric acid baits for ant control in my home. I was THRILLED with the rapid response. However, I do not have pets. The baits would have to be placed where the animals cannot possibly get to them, as they will find them a tasty treat, I suspect.

I have also used boric acid powders, but only in tiny nooks and crannies. I have an aerosol boric acid, also. I've used to prevent access of critters from my garage into the kitchen. But I wouldn't use it if I had pets.

Does all of this make sense? Be sure to let me know if there is still some confusion.

Here is a link that might be useful: Boric acid fact sheet

I need to correct myself about the DE. If inhaled, it CAN cause cancer. It is the silica dust that is the responsible ingredient. However, it is still safe to use as long as it is not INHALED! We all eat it every day.

Diamotaceous Earth is the shells of a sea dwelling animal left behind when the sea retreated and now dried out. the shells normally are sharp and are left that way for FOOD grade DE, sometimes refered to as horticultural grade, because of that. Research has also found DE can be a good filter medium if it is processed and smoothed out and that is all of the processing it goes through but that makes it not usable in the garden.
Generally ants in the garden are not a problem since they help clean up our environment as do many other insects. However, ants do not belong in our living quarters although they will visit to see what goodys might be available for them to eat. Once ants visit your living quarters they leave a trail for others to follow and if you eliminate or hide that trail others won't follow it. The best method of eliminating that trail is with lemon juice, or peppermint juice, which will also repel the wee buggers. If ants are coming in the house you need to find out where and plug those points of entry, because that is how other even less desireable critters can enter.