Answer: Pressure treated lumber is treated with chromium copper arsenate (CCA) to prolong the life of the wood. It's always best to wear gloves when handling, and wear a dust-mask while you're cutting the timbers. As far as safety is concerned when used around vegetables, there are two sides to the story. One says they are safe, citing studies showing little or no leaching of arsenate. The other side has its own studies and says it does leach at dangerous levels. I prefer to err on the cautious side and recommend gardeners not use pressure treated wood around food plants. Try cedar, redwood, plastic timbers, or even cement blocks instead. If you already have the pressure treated wood in place, you can line it with heavy plastic to keep chemicals from leaching into the bed and you can be careful to plant only above ground veggies (tomatoes, corn, etc.) nearest the edges of the bed, saving the center for underground veggies such as beets and carrots.
Best wishes with your vegetable garden!
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