It's generally considered safe. It's sold as an additive to livestock feed, though I don't know what the purpose there is.

It's very finely ground volcanic rock. The particulates have very sharp edges which shred insect exoskeletons. It doesn't hurt your skin though.

It might cause a problem if inhaled, similar to silicosis but that's mostly a guess.

Some people leave a line of it on windowsills or door thresholds to keep bugs out, but it's a fine powder that gets everywhere and makes a mess. Personally I wouldn't leave it around but that's up to you