Tip of the Week

Arsenic and Old Decks

For nearly 70 years, wooden decks, storage sheds, playground sets, and other outdoor structures were commonly made with pressure-treated wood infused with chromated copper arsenate (CCA) to make it insect- and rot-resistant. CCA contains known carcinogens and has been shown to migrate to the wood surface, where it can come into contact with skin or leach into the surrounding soil. Children are often more susceptible to toxicity exposure than adults. In late 2003, the industry voluntarily stopped using CCA in residential products after an agreement was reached with the U.S. Environmental Protection Agency (EPA), but many people still own CCA-treated wood structures. Additionally, existing supplies of the lumber may still be sold.

What are the symptoms of CCA exposure?

The component of CCA-treated wood that is of primary concern is known as inorganic arsenic, it is the most toxic form of arsenic and a known carcinogen. Possible symptoms resulting from short-term exposure to high levels include nausea and vomiting. Long-term exposure to lower levels has been shown to increase the risk of lung, bladder, and skin cancer. The EPA recommends that people who believe they may be suffering from adverse effects from CCA-treated wood immediately contact their medical provider or local poison control center.

What to do if your deck is made of CCA-treated wood?

Take precautions. While replacing CCA-treated wood is the best long-term solution, it is also costly. There are several intermediate steps you can take to minimize risk.

Consider applying a sealant. Studies by the EPA and the CPSC suggest that applying a sealant at least once a year can reduce the amount of CCA that leaches from treated wood. Preliminary results show that oil- or water-based stains that penetrate wood surfaces are preferable to regular paint. That's because thicker paints and other film-formers can chip or flake, requiring scraping or sanding for removal, which may increase exposure to CCA. More information on these studies is available on the EPA Web site.

Note that if the structure is indoors, it's important to apply sealant or paint in a well-ventilated area to minimize exposure to volatile organic compounds (VOCs), the main component in forming ground-level ozone. Exposure to ground-level ozone can damage lung tissue and potentially cause serious respiratory illness.

Are there good alternatives?

If you're looking to buy less toxic construction materials, furniture, or a play set for outdoor use, there are a number of alternatives currently available, including products made from recycled plastics, recycled composite materials (plastic resin and wood fiber), and aluminum.

If you want to use wood, there are non-arsenic containing preservatives that have been registered by the EPA that are used to treat wood for consumer applications. Common alternatives include ACQ (ammonium copper quaternary) and CA-B (copper azole). Since these are not necessarily non-toxic, however, wood preserved with these compounds should still be coated regularly.

Another option is to look for untreated, cedar, redwood, or Southern Cyprus, which have natural pest- and rot-resistant properties; the more costly higher grades are typically more durable. But for both wood and wood-fiber based materials applying a deck treatment can extend the life and maintain the look of the material, regardless of whether they were treated with a preservative. For a list of companies offering alternatives backyard play sets, see The Green Guide's Product Report.

Wood to the wise. Be sure to check the label before buying any wood product for outdoor use. Although CCA-treated wood is no longer being manufactured, stocks produced prior to 2004 may still be on the shelves. Products containing CCA should be labeled or come with safety information sheets per the EPA's Consumer Awareness Program.

© The Green Guide, 2008

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