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  Arsenic in Old Pressure-Treated Wood  l  6 Steps to Reduce Exposure  l

Should I Be Concerned?  l  Gardening & CCA-Treated Wood  l

How to Identify CCA-Treated Wood  l  Local Options for Purchasing Lumber  l

Disposal  l  Related Links & References

Arsenic in Old Pressure-Treated Wood

Pressure-treated woodMost pressure-treated lumber sold before January 2004 was treated with chromated copper arsenate (CCA for short), which contains arsenic. Swallowing arsenic is known to cause cancer in humans. Manufacture of CCA-treated wood for residential use was halted December 31, 2003, through an agreement between manufacturers and the Environmental Protection Agency (EPA).

Arsenic-treated lumber was used wherever outdoor wood was needed—decks, playgrounds, fences, docks, retaining walls, picnic tables, even treehouses. The arsenic was used as a pesticide to keep the wood from being consumed by termites and other wood-eating organisms.

6 Steps to Reduce Your Family's Exposure

  1. Children on playground equipmentWash up. Wash hands thoroughly with soap and water (not a waterless hand cleaner) after playing on or handling arsenic-treated wood.
  2. Keep children and pets from underneath decks. Do not store toys or tools under decks made of arsenic-treated wood.
  3. Avoid growing vegetables in beds lined with arsenic-treated wood. If you do raise vegetables in an old treated-wood raised bed, keep your rows at least 15 inches away from the timbers. You could plant flowers next to the wood, instead. You could also install a plastic liner between the boards and the soil.
  4. Place a tablecloth on picnic tables made of arsenic-treated wood to prevent food from taking up arsenic.
  5. Avoid pressure-washing arsenic-treated wood, and avoid using an acid deck wash or brightener that contains chlorine. These treatments speed up the leaching of arsenic out of the wood.
  6. Wear gloves, goggles, and a dust mask when sanding, sawing, or drilling arsenic-treated wood.

As an additional step, you may consider applying a sealant every year. Some studies suggest that applying a penetrating coating (such as a water or oil-based sealant or semi-transparent stain) at least every other year will limit the amount of arsenic that leaches out. It is not recommended to use paints or urethanes that will peel or that require the wood to be sanded. Keep children away when applying oil-based products.

The EPA is studying the effectiveness of 12 sealants to see whether they keep the arsenic from being rubbed or washed off the wood, and how often they need to be applied. Interim results show that a penetrating, water or oil-based sealant or stain should be applied at least once a year. (As of January 2007, full results from the EPA study had not been released.)

If you are thinking of using a sealant, note that sanding or pressure-washing the CCA-treated lumber may not be a good idea, even if it is recommended on the sealant label! Sanding will scatter particles of arsenic in the air. Pressure-washing could increase the leaching of arsenic out of the wood.

Should I Be Concerned About CCA Wood?

The major health concern is that daily, long-term contact with arsenic leached from CCA-treated wood might lead to an increased risk of lung, bladder, skin, and other cancers or other health effects.

According to a draft EPA study released in November 2003, young children who regularly contact CCA-treated wood have a risk of cancer that is greater than 1-in-1-million, which is the EPA's threshold of concern for the effects of toxic substances. Children in warm climates who play both at home and at school on treated decks and play structures have a risk of 1-in-100,000 of contracting cancer. The risk is also increased for children who frequently put their hands in their mouths as they play.

This study is still under scientific and public review. For additional information, see the EPA, Chromated Copper Arsenate (CCA): Questions and Answers.

Currently the EPA does not recommend that people remove existing structures made with CCA-treated wood or the soil surrounding those structures. However, they do recommend that people reduce their potential exposure to arsenic.

Touching arsenic-treated wood is not considered a significant health hazard; ingesting it is the main concern. Many children put their hands in their mouths, and their hands may have arsenic on them if they play on CCA-treated wood structures. Tests have shown that the arsenic comes off the wood, whether it is wet or dry. Even old playground equipment may still have high levels of arsenic. The soils below decks and play structures can also become contaminated. To be at risk of long-term health effects, a person would have to actually eat the soil or put wood chips in their mouth.

Gardening and CCA-Treated Wood

Another concern is for gardeners who have planted vegetables in raised beds built of arsenic-treated lumber. Fortunately, arsenic does not move far through soil. Tests show that while the level of arsenic is high in soil right next to the wood, by 15 inches it drops down to acceptable levels. It is unlikely that vegetables grown in raised beds will pick up enough arsenic to be a health concern. Arsenic-contaminated soil can stick to root crops such as carrots and potatoes. Peeling root crops or scrubbing with a brush and water helps remove this arsenic.

How Do I Identify Arsenic-Treated Lumber?

CCA lumber identification tagYou can usually recognize CCA pressure-treated wood by its greenish tint, especially on the cut end, and staple-size slits that line the wood. However, the greenish tint fades with time, and not all CCA pressure-treated wood has the slits. “Wolmanized” wood, which is treated with CCA (except for the Natural Select brand), looks like regular lumber.

If you are uncertain what your structure was made of, try contacting the manufacturer or builder. If your deck or swing set was built prior to 2003, unless it was made of cedar, it probably contains arsenic-treated wood. Most playset manufacturers switched to non-arsenic preservatives by 2003; Big Toys (in Tumwater), stopped using CCA to preserve playsets in September 2001.

What are My Options for Buying Lumber?

New, safer chemically treated woods are becoming available to replace the arsenic-treated lumber. One treatment is called ACQ, for alkaline copper quaternary. The wood meets the same standards for above ground and ground contact as arsenic-treated wood. It is sold under several names, including Nature Wood (by Osmose, Preserve and Preserve Plus (by Chemical Specialties Inc.), and Wolmanized Natural Select (by Arch Treatment).

Another option is wood treated with borates, such as Advance Guard Borate Pressure Treated Lumber (by Osmose). Copper borate azole (CA) is another formula, used on pressure-treated wood distributed in our area by McFarland-Cascade. Local lumber stores have replaced their stock of CCA-treated lumber with pressure-treated alternatives.

NOTE: The manufacturers of ACQ-treated lumber recommend using stainless steel fasteners with this lumber. Metal components made of aluminum will corrode when in contact with ACQ-treated lumber. Tests on corrosion of fasteners used in ACQ are underway. Ask at your lumber store for the latest recommendation.

Most lumber stores also sell wood substitutes made of 50% recycled plastic and 50% recycled wood fibers. This "plastic lumber" can be used for decking, but not for structural purposes such as posts and beams. Plastic lumber can be sawed and drilled, is extremely durable, and requires little maintenance. Two brands sold locally are Trex and ChoiceDek.

Other options are to use metal, concrete, or a wood that naturally repels insects such as cedar, juniper, or ironwood.

What About Disposal?

The Thurston County Waste and Recovery Center accepts treated lumber for disposal. Arsenic-treated lumber would be a hazardous waste except that a special state exemption allows it to be disposed of in lined landfills. Garbage brought to the Waste and Recovery Center is sent to the Roosevelt Regional Landfill in Klickitat County.

Do not bring arsenic-treated wood to the compost site!

Never burn treated lumber—the smoke and ash are highly toxic.
Do not chip it for use as mulch.


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This page last updated: 01/28/22