What to Do About Pressure-Treated Wood
I have pressure treated wood in my garden. Should I be concerned? If so, what do I do about it? –Sam, GA
Yes, sadly, you do need to be concerned about it. Hopefully your garden beds are for flowers and not food. Even then you need to be concerned about arsenic leaching into the surrounding soil. Pressure-treated wood is mostly treated with chromated copper arsenate (CCA), made of chromium, copper, and arsenic. Having been used since the 1940s, there has been increasing concern since the 1990s that the lumber will exude toxic amounts of arsenic.
If you have raised beds for vegetables I’d start from scratch and remove the pressure treated wood and call your local hazardous waste pickup about removing it. Even sealing in the wood (see below) doesn’t feel safe enough to me for food. All the soil needs to be removed from the old beds and replaced with new. Replace the wood itself with something non-toxic, such as recycled plastic lumber or Timbersil.
For flower beds and decks, seal the stuff in using a water-based penetrating sealant every six months. The EPA recommends either an oil or water-based penetrating sealant every year, but I’d not suggest an oil-based sealant unless the oil was from soy or other plant and not petroleum, so as not to pollute the area further, and to reseal every six months to be on the safe side. With arsenic readily found in pesticides, we don’t need additional sources of arsenic in our own homes and gardens. Read about the EPA’s sealant studies to help you determine what option is best for you.
Make sure not to burn CCA-treated wood as the fumes would be full of arsenic. Also make sure to use a mask if you need to cut it.