Answer: There are two sides to the story concerning the safety of pressure treated wood in gardens. One says they are safe, siting studies showing little or no leaching of arsenate for years. The other side has its own studies and says it does leach at dangerous levels. So, I lean to the cautious side and recommend gardeners not use pressure treated wood, especially for food plants. Try cedar, redwood, hemlock, plastic wood or cement blocks as alternatives. You could line the inside with plastic to reduce the risk of the chemicals leaching into the soil. Or use this wood for beds for flowers, and make other beds for your vegetables.
There is an article covering the topic in detail at the followng site:
It states that recent research shows that more arsenic is leaching out of the wood treated with CCA (chromated copper arsenate) than previously thought.
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