Arsenic in the Garden


I came across this interesting article in a local publication recently. It discusses the use of wood treated with chromated copper arsenate (CCA) in garden beds. Wood is treated with chemicals such as CCA to kill microorganisms and insects that can cause the wood to decay. The article discussed the possibility that people who build their vegetable gardens using wood treated with CCA might end up consuming arsenic that leached into the soil from the wood.

In 2004, the Department of Soil, Water, and Climate at the University of Minnesota published a study of vegetables grown near wood that has been treated with CCA. In the study, the researchers discovered that plants grown within a few centimeters of CCA treated wood absorbed significantly greater concentrations of arsenic than plants grown several feet away from the wood. Although they concluded that based on U.S. Public Health Service standards these vegetables would be safe for human consumption, they also stated that some of the vegetable crops may not be safe for sustained consumption based on the US EPA’s standard.

In 2004, the Environmental Protection Agency (EPA) in a voluntary agreement with industry began restricting the use of CCA in treated timber in residential and commercial construction, with some exceptions.

However, just a few weeks ago, I discovered a piece of lumber in my yard (see above picture) that had a yellow tag stapled onto it. The lumber was placed around a raised bed near our fence by the previous owners of our house. The yellow tag indicated that the wood had been treated with CCA. I had a rosemary bush growing next to that piece of lumber for years. I also have two orange bushes growing about 6 feet away from it. Based on the results of the University of Minnesota study, I think that our oranges are far enough away from the treated lumber to have avoided absorbing much arsenic from it. But I have pulled up the rosemary bush, and I plan on removing the treated piece of lumber soon.

September 19 2009 01:17 pm | Vegetables