Modern pressure-treated lumber (ACQ/Copper Azole)

Since 2004, residential pressure-treated lumber uses ACQ (alkaline copper quaternary) or copper azole instead of the banned arsenic-containing CCA. Multiple university extension services (Oregon State, Missouri, and others) confirm that modern treated lumber is safe for vegetable garden beds. A 2014 Oregon State University study found no elevated copper levels in root vegetables grown in copper azole treated Douglas fir beds compared to untreated wood beds. Treated lumber lasts 15-20+ years and costs only slightly more than untreated pine ($8-12 per 2x10x8-foot board). Micronized copper azole (MCA) formulations embed copper particles deeper into wood pores, further reducing leaching. For extra precaution, line interior walls with 6-mil polyethylene sheeting, though research suggests this is not strictly necessary. Important caveats: treated wood is NOT permitted in certified organic growing systems; always wash hands after handling; never burn treated wood scraps; wear a dust mask when cutting.