Intesting. Are you referring to the 'old' "salt-treated" wood - CCA - chromic copper arsenate, or the 'new' stuff, ACQ - ammonium copper quartenary? The old stuff was indeed bad - you couldn't even burn it to get rid of it, but the newer stuff doesn't have the same poisons/carcinogens. Supposedly, it can be used for direct human contact (benches and stuff) just not for food preparation (like cutting boards....)
The new stuff is fairly 'aggressive' WRT galvanic action on metal fasteners. You have to use hot dipped nails or specially-coated screws - or stainless - which gets expensive quick. Just finished a sizeable fencing project with the ACQ stuff, most everything 'shot' with a Paslode cordless nailer. Oh, if any of y'all need bulk fasteners, search out a company called NailZone. Best prices around.