The Q&A Archives: Arsenic in Treated Wood

Question: I work at a childcare center and have been working to create a children's garden. My goal is to have a community garden eventually, but I have been working in stages to acheive that goal. Currently we have an 18x24 ft. raised plot with rails around the border. Unfortunately, one of the parents volunteered to purchase and place the rails and he built a the garden with pressure treated lumber.....which contains arsenic. My opinion is that we shouldn't grow anything we intend to eat. The director of the center feels that it is safe. What are the facts? Has research been done in a case like this?

Answer: Wood treated with CCA contains chromated copper arsenate. There have been numerous studies on whether the chemicals leach from the wood, and whether they will taint edible crops. At this point, the jury is still out. To be on the safe side, place a sheet of plastic between the wood and the soil, and don't plant root crops or leafy vegetable crops in close proximity to the wood. How about growing edibles near the center of your bed and bordering the bed with flowers? For a complete discussion on using treated timbers in vegetable gardens, visit the following Oregon State University website:

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