Asked by: Sanchez

Answered by: LAP

Mostly YES, in rare cases MAYBE NOT. (1.) MCA-treated wood is safe and the best choice, (2.) MCQ is also safe, (2.) ACQ-treated wood is probably safe but not as good as MCA/MCQ, and (3.) and CCA is potentially not-safe but hasn't been available commercially since 2003. Here is the background... the EPA phased out "CCA" wood preservation in 2003 because it contained arsenic which is a poison at high concentration and carcinogen at low concentrations. It also contained and a soluble form of copper that could leach into the environment easily (good for repelling things that rot wood), but copper can cause health problems at high concentrations for some people. Scientific studies actually measured how much arsenic and copper could leach into soil or water. Other studies showed that plants could take up these chemicals, however the amounts were very low, and if eaten the amounts transferred from food were so low that they were at "safe" levels or not even measurable at all. The EPA leaned towards safety and banned CCA from residential use but said what was already installed in homes could stay in place. Industry switched to ACQ, which got rid of the arsenic problem. Nowadays, ACQ is the most common form of "pressure-treated" wood and is best for indoor use because the form of copper can leach into soil when in contact with soil. Again, scientific studies have looked at this and the high amounts of copper that might cause problems to people and animals would kill the plants first, so you'd have to be eating dirt with copper in it for there to be problem (no joke). The MCA and MCQ are newer treatments in which the form of copper is more stable ("micronized"), so you will find these in pressure-treated wood rated as "ground contact." People who think pressure-treated wood is bad are probably reacting to old reputation of CCA, but unless you find pressure-treated wood that had been sitting around for 15+ years, it's not a factor nowadays. BOTTOM LINE: pressure-treated lumber rated as "ground contact" is safe for growing plants and vegetables that you will eat -- and MCA is slightly better than MCQ, if you can find it.