Q: In a wine tour through the Okanagan region of Canada, I was surprised to see that vines are supported with pressure-treated lumber. Will the chemicals meant to preserve the wood go to the grapes and from there in my wine? Can I avoid this by buying organic wines? —Daniela
A: Pressure-treated wood is treated with inorganic chemicals, such as arsenic, chromium and copper to protect the wood from insect attack , fungus or moisture. While some of the elements may leach into the surrounding soil when planted, the amount varies widely, depending on factors such as soil type, age of wood, and the amount of wood exposed to the soil. How much of these chemicals a plant absorbs also varies depending on the plant itself. Most studies have shown that these chemicals tend to stay in the root system of plants with little movement to the edible parts. Few studies exist that analyze plants grown in close proximity to treated-wood, but one study, conducted in the 1970s, showed that in grapes grown adjacent to treated-stakes, there was no increase of these chemicals beyond a naturally-occurring level.
Matthew Holmes, executive director of Canada Organic Trade Association, explains that the organic regulations in Canada prohibit the use of pressure-treated wood in new construction. Older structures made with treated-wood can be grandfathered in and used on organic-certified farms, although no new treated-wood would be allowed, even for repairs.
According to Holmes, in situations where older wood is used, the amount of chemicals the wood leaches is reduced and "growers can mitigate accumulation of copper, chromium and arsenic in soil by lining with sleeves or plastic barriers to limit contact with soil."
In the United States, regulations also prohibit the use of pressure-treated wood in organic vineyards, except in situations with pre-existing structures.
As far as buying organic, Holmes believes that "any chemicals and preservatives end up in soil, water, air and bodies. Yes, you can definitely avoid most of the chemicals by buying organic."
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