" Pressure treating does make wood rot resistant. But — it doesn’t make wood water resistant. Pressure treated wood still soaks and looses moisture. And as a result, the wood moves, cracks, twists, bends, cups and virtually tears itself apart."
I'm not sure of the toxicity... I built my first...
If you are not planning to paint the wood, you should still seal it... Thompson's waterseal...
think of an exposed patio deck..won't last too long without water protection