Pressure-Treated Lumber: Safest Options

Those who have built retaining walls or raised garden beds over the past few years may have used pressure-treated 4 ‘ to 8″ wood immersed with CCA, or copper chromium arsenate. A growing number of people have charged that this product, containing inorganic arsenic, can be toxic to people, pets, and even food grown in the garden.

Green PTL is now Red PTL

Ever wondered why green pressure treated lumber has been replaced by red PTL? Probably because copper replaced arsenate, or arsenic as an ingredient.

According to the U.S. EPA, as of December 31, 2003, the pressure treated wood industry discontinued the use of chromated copper arsenate (CCA) as the primary wood preservative used for most residential and general consumer construction. Existing CCA-treated stockpiles may be used until exhausted; however, the transition to CCA alternatives is well underway. There are several arsenic-free wood pressure treatment alternatives to CCA already on the market including ACQ, Borates, Copper Azole, Cyproconazole, and Propiconazole. There are also several alternative building materials to pressure treated wood that are available today.

Compared to the historic heavy-duty wood preservatives, ACQ and Copper Azole have been developed relatively recently and/or have been used infrequently, only limited research has been conducted on their potential leaching and environmental impact. Though slightly more expensive than the former CCA-treated wood, the appearance, strength properties, and handling characteristics of CCA alternatives are very similar to those of CCA.

As with any preservative treatment, hardware corrosion is a consideration in choosing appropriate fasteners. The industry has established guidance regarding the proper hardware to use with the alternatives that minimizes corrosivity concerns. Please refer the hardware portion of the Safety & Precautions page for hardware recommendations when working with the new wood treatments. Here you can also find handling and disposal recommendations.

For those wishing to know more, the New York Department of Environmental Conservation has written at length on the subject:

Lumber Pressure Treated With Chromated Copper Arsenate

What is chromated copper arsenate (CCA)?

Chromated copper arsenate (CCA) has been used extensively in this country as a wood preservative. CCA is composed of: copper, which acts as a fungicide; arsenate, a form of arsenic, which is an insecticide; and chromium, which binds the ingredients to the wood.

Is all pressure-treated lumber the same?

No, pressure-treating is one method of introducing a preservative into the lumber. The wood is immersed in a liquid preservative and exposed to high pressure. This process forces the chemical into the wood. The type of preservative used influences the properties of the pressure-treated lumber.

How do I know if my outdoor wood is pressure treated with CCA?

Most lumber pressure treated with CCA has a characteristic green tinge. However, as the wood weathers it becomes harder to distinguish from untreated wood. Most wood sold for outdoor use in the United States between 1975 and 2003 has been pressure treated with chromated copper arsenate.

Does CCA-treated wood present any health risks to me or my family?

The United States Environmental Protection Agency (USEPA) has not concluded that CCA-treated wood poses any unreasonable risk to the public or the environment. However, one of the components of CCA-treated wood, arsenic, is a known human carcinogen. Therefore, any reduction in the levels of potential exposure to arsenic is desirable.

When estimating the potential risks that a chemical may pose, the USEPA advises that one must consider two factors: toxicity and exposure. Toxicity is described as the harmful effects that the chemical may cause, which are often dependent on the amount or dose received. Exposure is the dose received, typically orally or through contact with the skin, or by inhaling, over a certain period of time. Therefore, any risk of toxic effects is dependent on both toxicity and exposure.

The USEPA is in the process of evaluating both the toxicity and potential exposure of CCA-treated wood. For more information visit USEPA’s CCA website (see Links Leaving DEC’s Website at right).

What precautions should be taken when working with CCA-treated wood?

The USEPA maintains that excessive exposure to inorganic arsenic can be hazardous to your health. Certain activities can facilitate the release of inorganic arsenic. According to USEPA, people working with CCA-treated wood should take the following precautions:

• Saw, sand, and machine CCA-treated wood outdoors, when possible. Wear a dust mask, goggles, and gloves.
• Clean up all sawdust, scraps, and other construction debris thoroughly and dispose of in the trash (i.e., municipal solid waste).
• Do not compost or mulch sawdust or remnants from CCA-treated wood.
• Do not burn CCA-treated wood, as toxic chemicals may be released as part of the smoke and ashes.
• After working with the wood, wash all exposed areas of your body, especially the hands, thoroughly with soap and water.
• Wash your work clothes separately from other household clothing before wearing them again.

These precautions will reduce your exposure from inhaling or ingesting sawdust, protect your eyes from flying particles, and prevent exposure to toxic smoke and ash. For more suggestions on avoiding unnecessary exposure while working with CCA-treated lumber, see link to USEPA’s Consumer Safety Information Sheet: Inorganic Arsenical Pressure-Treated Wood at right, under Links Leaving DEC’s Website

What can I do to limit exposure to CCA-treated wood?

USEPA does not recommend that consumers replace or remove existing structures made with CCA-treated wood or the soil surrounding those structures. Preliminary research results suggest that concerned citizens can take the following precautions to decrease the likelihood of exposure to chromated copper arsenate:

• At least once a year annually apply a penetrating-type coating.
• Oil or water-based stains that can penetrate wood surfaces are preferable to products such as paint. This is because paints and other film-formers can chip or flake, requiring scraping or sanding for removal which can increase a consumer’s exposure to arsenic.
• Periodically inspect coatings for wear.
• Inspecting the coating will allow you to determine if another application of the coating is required.
• Use a coating which is clearly visible after application.
• This will help make wear more apparent. Some coatings will change the surface properties of the wood, making added traction on floors and deck portions of playsets necessary.

What additional precautions can I take to maintain my play structure?

In addition to the precautions described in the previous section, applying a ground cover around a play structure (swing set or other outdoor playset) will provide additional protection from potential exposure to arsenic.

The ground near play structures built with CCA-treated wood can contain higher levels of arsenic than the surrounding soil as some arsenic leaches out of the wood over time. Applying a ground cover around the play structure such as pea gravel, sand or tire chips will help provide a buffer against direct contact with the soil. Since arsenic readily washes through these ground covers, the amount of arsenic will be less in these ground covers than in the underlying soil. Bark mulch is not as effective a ground cover for limiting arsenic exposure since arsenic binds to the mulch.

Does CCA-treated wood pose any environmental risks?

Studies have shown that CCA-treated lumber does leach chromium, copper and arsenic into the surrounding soil. The migration of these elements appears to be limited. In addition, research has not clearly shown a long term negative impact upon plants or animals.

How do I dispose of CCA-treated wood?

In New York State, CCA-treated wood may be disposed of in construction & demolition (C&D) debris landfills and municipal solid waste landfills which are authorized to accept construction and demolition debris. If you have any questions, contact your landfill or waste hauler to make sure they accept construction & demolition debris, or contact the appropriate DEC regional office for information on disposing of CCA-treated wood. CCA-treated wood should not be chipped into mulch or burned in fireplaces, stoves, outdoor wood-fired boilers or open fires.

What steps has New York State taken to limit exposure to CCA-treated wood?

In 2002, New York State enacted legislation that added Section 37-0109 to the Environmental Conservation Law (ECL), which became effective on March 16, 2003. This Section addresses playground lumber pressure treated with chromated copper arsenate. On August 5, 2003 the Governor signed legislation that expanded ECL 37-0109, which became effective on February 1, 2004, to include picnic tables on public property. Section 37-0109 does the following:

• prohibits certain entities from constructing new structures on public playgrounds made with lumber that has been pressure treated with CCA;
• requires that public picnic tables and existing public playground structures, made with lumber pressure treated with CCA, be maintained in a manner that minimizes leaching of CCA; and
• requires that the ground cover surrounding public picnic tables and existing public playground structures be maintained to minimize exposure to potential CCA contamination.

In addition, on February 12, 2002, the United States Environmental Protection Agency (USEPA) announced a voluntary decision by industry to move consumer use of treated lumber products away from a variety of pressure-treated wood that contains arsenic by December 31, 2003, in favor of new alternative wood preservatives. This transition affects virtually all residential uses of wood treated with CCA, including wood used in play-structures, decks, picnic tables, landscaping timbers, residential fencing, patios and walkways/boardwalks. As of January 1, 2004, USEPA will not allow CCA products to be used to treat wood intended for any of these residential uses.

The remaining stock of CCA-treated lumber was sold out in most stores by the fall of 2004.

What are some alternatives to using CCA pressure-treated lumber?

There are many types of less toxic alternatives to CCA-treated wood such as plastic lumber, metal, wood which is naturally resistant to insects and decay, and wood that is pressure treated with less toxic ingredients.

• Plastic lumber is an increasingly popular building material. Plastic lumber, which is most frequently composed of high density polyethylene (HDPE), does not release hazardous materials into the ground. An additional benefit of using this material is that it is often manufactured with recycled plastic. Therefore, using plastic lumber conserves natural resources. In addition, plastic lumber usually requires less maintenance.
• Composite lumber – Wood and plastic combined into one lumber product is called composite lumber. Wood/plastic composites generally exhibit low moisture absorption and high resistance to decay, insect, and UV ray damage. The wood component provides the composite with greater dimensional stability than plastic lumber, but not as much as wooden lumber. Like plastic-only lumber, wood/plastic composite lumber is often made with recycled materials.
• Metal-constructed playground equipment is another option for a durable non-polluting structure.
• Naturally decay-resistant wood offers another alternative to CCA-treated wood. Untreated wood such as redwood and cedar contain natural wood preservatives which protect the wood from decay.
• Lumber pressure treated with non-arsenic wood preservatives is available in the marketplace. Many of these wood preservatives are copper-based such as ACQ (ammoniacal copper quaternary) compound or CA (copper azole). For additional information about alternatives to CCA-treated lumber, visit USEPA’s CCA website or contact your local hardware store or lumberyard

So has The Home Depot, which sells PTL impregnated with  Micronized Copper Quaternary (MCQ):

To withstand the elements, wood is chemically protected through a process called pressure treating, which wards off insects, microorganisms and fungal decay.  The most common types of chemical used to treat wood are Alkaline Copper Quaternary (ACQ), Copper Azole (CA), and, the newest type, Micronized Copper Quaternary (MCQ). Pressure treated lumber can last 20 years or more, and most pressure treated wood comes with a limited lifetime warranty.

 Photo: Pressure treated lumber from Shutterstock

Sources: US EPA, New York Department of Environmental Conservation,The Home Depot