In the 1930's, scientists developed a process to treat wood under pressure with copper (toxic to the fungi that cause rot) and arsenic (an insecticide). Chromium was added, which triggered a chemical reaction that locked the treatment into the wood. This is the standard pressure treated wood, chromated copper arsenate (known as CCA), which has been so popular since the 1970's.
The product works well, but safety concerns are now being raised. For example, an 8 foot by 10 foot deck has about four pounds of toxic material in its 1½-inch-thick platform.
Studies are underway to determine if the chemicals can leach from the wood, particularly if exposed to acids such as the oxalic acid or citric acid in chemical deck brighteners. The natural acids in compost may also increase leaching from a compost bin into compost.
In 2002, the U. S. Environmental Protection Agency (EPA) announced a voluntary decision by industry to move away from using CCA to treat wood used in residential settings. As of the end of 2003, CCA products cannot be used to treat lumber intended for most residential settings, including play structures, decks, picnic tables, landscaping timbers, residential fencing, patios and walkways/boardwalks. The intent of the phase out was to reduce the potential exposure risk to arsenic, a known human carcinogen, thereby protecting human health, especially children's health and the environment.
An alternative treatment for lumber, alkaline copper quaternary (ACQ) is now being sold. The active ingredients in ACQ are copper oxide and a quaternary ammonium compound. ACQ is registered for use on lumber, timbers, landscape ties, fence posts, building and utility poles, pilings for use on land, decking, wood shingles, and other wood structures.
Although the formulation has changed, the U.S. EPA still publishes the following handling and disposal recommendations.
Do not use pressure-treated wood where it may come into direct or indirect contact with drinking water.
Do not use pressure-treated wood where the preservative may become a component of food, such as a compost bin or vegetable bed, or animal feed.
Do not use pressure-treated wood for mulch.
Use pressure-treated wood with caution:
X Wear a dust mask, gloves, and goggles when cutting or handling pressure-treated wood.
X Do all sawing and machining outdoors over a tarp that can be emptied into the trash or thrown away with the sawdust.
X After handling, wash exposed skin thoroughly.
X Wash work clothes separately.
X Never burn it—the resulting ash concentrates the toxic substances. The only current disposal solution is burial in a landfill.
When working on projects, consider the following options:
X For existing decks and structures, seal the wood regularly with a moisture repellent. It will help lock in the toxic chemicals and prolong the life of the wood.
X For new work, use pressure-treated wood only on structural parts near the ground, such as posts and framing under decks.
X Off the ground, use poplar for vertical features such as balusters. Apply paint or stain.
X For decking, cedar and redwood look better than pressure-treated wood, but cost more.
For more information: Arsenic and Old Wood, This Old House Magazine, March/April, 1998.
For more information on the discontinuance of CCA: http://www.epa.gov/oppad001/reregistration/cca/cpsc.htm
For more information on ACQ: http://www.epa.gov/oppad001/reregistration/cca/acq.htm
The Lakewood Heritage Advisory Board was established to serve in an advisory capacity for the purpose of educating, informing and making recommendations to City officials, departments, boards and commissions, and the community on matters relating to historic preservation
The Lakewood Heritage Advisory Board may be contacted through the City of Lakewood Department of Planning and Development (216/529-6630). Information in this publication may be reprinted. Please credit the Lakewood Heritage Advisory Board, Lakewood, Ohio.