News Coverage
THE PRAIRIE GARDENER: Take Precautions with Treated Wood;
Changes for Treated Lumber on the Horizon
Published January 24, 2003
Wood is a natural in garden construction.
Whether building retaining walls on a sloped site, improving soil with raised beds or simply defining the edge of a planted area, wood has long been a favorite construction material for residential gardens. Wood is readily available, easily cut and fastened with common tools and blends with natural settings.
The drawback is that wood will eventually rot unless treated with a preservative. And the nation's most popular pressure-treated lumber will be phased out of use by the end of 2003 because it contains arsenic. Lumber alternatives for use outdoors include other chemical treatments that don't include arsenic, and redwood, cypress and cedar, which naturally repel insects and rot. Wood treated with the pesticide chromated copper arsenate (CCA) is not only used for garden construction purposes, but can be found in playgrounds, swing sets, decks and picnic tables. The main reason for the year-end ban, which also applies in Canada, is that the arsenic in the treated wood doesn't remain there and people are exposed to the poison. Arsenic, a known human carcinogen, can cause lung, bladder and skin problems, including cancer.
A special concern is children on play sets who can get arsenic in their mouths via their hands. Sanding, sawing or burning CCA-treated lumber also increases the risk of arsenic exposure. Even more alarming is a recent study warning that arsenic used to treat outdoor wood products doesn't dissipate with time and that children who play on decade-old playground equipment are likely to be exposed to high levels of the potential cancer-causing agent as those who play on structures manufactured recently.
According to experts surveyed, the phaseout marks the demise of the last consumer-marketed pesticide known to cause cancer. It also will dramatically reshape the pressure-treated wood industry, a $4 billion-a-year business that provides one of the nation's most widely used outdoor building products. An estimated 75 million board feet of pressure-treated lumber is in use nationwide, mostly in decks, play sets and fencing.
Most experts agree, however, that existing preservative-treated wood structures pose little threat and those threats can be reduced by taking these steps:
* Painters and sealers: Either will help contain arsenic leaching. The Environmental Protection Agency recommends conventional water sealer because more impervious coatings, such as paints and urethanes, can peel when they get old. Sanding peeling paint or urethanes off an arsenic-treated surface can be risky. Or, seal swing sets and decks annually with an oil-based product that doesn't require the wood to be sanded.
* Physical barriers: Plastic-and vinyl-based covers are available for many pressure-treated wood structures. These materials are made to fit over standard-size decking and structural members, such as conventional vinyl siding, and are available in various colors and textures. Simply covering a CCA wood table with a tablecloth will help.
* Wash up: Be sure and wash hands with soap and water after playing on or handling the preservative-treated wood. But avoid washing the treated wood, especially with cleaners that contain chlorine. Chlorine can convert the chromium in the wood into a more toxic chemical.
* Vegetable planting: If you raise vegetables in a treated-wood raised bed, keep your rows at least 15 inches away from the timbers. Studies show arsenic leaches into the surrounding soil, with the highest levels occurring within a couple inches of the treated timbers, but declining with distance. At about 15 inches away, levels drop to those found naturally in the soil. Vegetables can absorb these chemicals. Flowers can be planted next to treated timbers.
* Replacement: If you want to remove the CCA-treated lumber, there are a variety of substitutes on the market. Some companies offer wood treated with different federally approved chemicals. Other firms sell wood substitutes made of recycled plastic, rubber or other materials.
* Home test kits: To check arsenic levels in pressure-treated decks, play sets and other structures are available, at cost, from the Environmental Working Group, a non-profit research organization, through its Web site (www.ewg-org).