Pressure Treated Lumber

Until 2003, 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.
...Extensive studies were done since the mid 1980's concerning the potential dangers of pressure-treated wood. And rightfully so! Large volumes of CCA were being used, and the treated wood products were beginning to be widely distributed, justifying the need for some hard research.
The research was mixed, but the typical hysteria ensued as attorneys and plaintiffs lined up to claim damages from exposure to CCA. In the end, the industry agreed to voluntarily eliminate use of CCA for residential use. Your local home store or lumberyard is now selling lumber treated with (hopefully) less toxic alternatives... amine copper quat (ACQ) and copper azone (CA)... though you may find other chemical combinations in specific areas. CCA is still being used in certain marine and industrial applications since it is still the best preservative available at the present time.
Whether these new chemicals will turn out to be less hazardous in the long term is anyone's guess.

So how much arsenic leaches into the soil from CCA lumber? More to the point, how much gets taken up by vegetables? And how much winds up in the mouths of children? There have been a lot of studies looking at the first two issues, but in trying to organize the facts into meaningful information, I discovered definitive answers can be elusive. I can’t tell you whether or not you should use pressure-treated wood. What I can do is explain the results of pertinent studies and give you the information you need to decide for yourself.