I've volunteered on Habitat For Humanity crews for decades, doing electrical
wiring.
I also am pretty good at reading the detail sheets and sorting out the
framing metal joist hangers and the fasteners, and the fasteners have been
directly impacted by the move away from "CCA" in pressure-treated wood.

The arsenic in CCA was the concern, so there are now a bunch of new
alternatives:

ACQ-C (Alkaline Copper Quaternary Type C), 
ACQ-D Carbonate (Alkaline Copper Quaternary Type D, Carbonate formulation), 
CA-B/ CA-C (Copper Azole Types B and C), 
Chlorpyrifos/IBPC,
Copper Naphthenate,
Pentachlorphenol,
µCA-C (Azole Biocide), 
SBX/DOT (Sodium Borate),
Zinc Borate 

All of them are said to be more corrosive to metal than CCA was, so now you
need Hot-Dipped Galvanized fasteners for Pressure-Treated stock.  Not
electroplated, not electro galvanized, gotta have the dipped.  You want the
nails driven and bolts tightened to outlive you, not corrode.

I have no idea if any of these new preservatives are harmless or toxic to
bees, but with the names, they can be looked up.  The arsenic in CCA was a
PR issue, never an actual risk to human health. I've heard that CCA can be
still found in wood sold for fenceposts.

A pressure-treated set of "skids" screwed to the underside a standard bottom
board might be the best apiary use of pressure-treated.  

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