Carl your absoulutey right ......up until the mid 2000's the preservative most commonly used in residential pressure-treated lumber was chromated copper arsenate (CCA), an extremely toxic chemical. Remember "Arsenic and Old Lace"? How about that old box of rat poison you have lurking in the garage? CCA is so toxic that the Environmental Protection Agency, over 20 years ago, imposed strict guidelines regarding the manufacturing practices of companies using CCA. They have made a more mild solution....and in CA it is very well regulated and you can find a stamp on the lumber itself.Agree with everyone else Charlie.
One word of caution...if you use pressure treated wood, be sure that water doesn't drip into food or water pans after rains, sprinkling, and so on.
I highly suspect that I lost some yearlings years ago to this after I constructed a pen with overhead beams for screening made of new pressure treated wood.
Every time I watered or it rained the water would drip into the tortoises food and water dishes.
Within a month they all suddenly started getting sick and then they died a few weeks later.