Pressure treated wood picnic table?

Pressure treated lumber should have a water seal applied to it but there is a catch. Most of the treated lumber now has a waxy coating on it to slow down the drying from the treatment process. The current rule of thumb is to sprinkle a little water over the surface of the wood. If the water beads up and doesn't soak in right away do not apply anything to it yet. Normally it takes from 60-90 days for the wood to dry enough for the water to soak in. At that point apply the water seal to the wood. While modern AC2 treated lumber is safe for food contact you'll also have to make sure that the coating you apply is also safe. This same rule applies to any other treated lumber your trying to protect outdoors including decks.