someone dips their box boards in this green stuff. (copper napalate with diesel fuel)
A paper on the relative safety of copper naphthenate is available: http://128.104.77.228/documnts/pdf1984/kalni84a.pdf
Less than 1 ppm of Cu is added to honey and wax using the Cu preservative. The paper does caution on using fuel oil as the diluting agent, as it does migrate into the hive. Paper is older (in that Penta and other bad things were still on the market), but appears to be very responsibly researched.
My boxes are highly rot-resistant redwood and latex. (Redwood fence boards converted to mediums)
ya from the article: "Few, if any, adverse findings resulted from treatments
of beehives with (1) a preservative-free water-repellent
solution, (2) copper naphthenate, (3) copper 8-
quinolinolate, and (4) ACC. Winter survival with these
treatments was better than or comparable to that in controls. Of these four treatments, only copper naphthenate
gave a slight increase in copper content of honey (less than
1 ppm)"