Green Building:
Proper Use and Disposal of Treated Lumber

Outdoor wood, used widely in home landscape projects, is protected from moisture, rot and insect damage with chemical preservatives (pesticides) to inhibit fungal decay and extend the life of the wood. The wood treating industry estimates that treated wood will last 20 to 30 times longer than untreated wood in challenging outdoor environments. The benefits of treated wood include longer useful life and conservation of trees. However, the chemicals used to preserve it are toxic which present environmental problems especially when the wood is taken out of service requiring disposal. To prevent treated wood from causing adverse health and environmental impacts, it makes good sense to select, use and dispose of treated wood products appropriately.

There are three broad categories of preservative treatments for wood currently in use:

  • creosote,
  • oilborne chemicals,
  • and waterborne chemicals.

Creosote is a highly complex mixture of chemicals distilled from coal tar, which is a by-product of producing coke from bituminnous coal in coking ovens. Creosote is essentially an oil-based compound. The most common oilborne preservative is pentachlorophenol, generally known as penta. Penta has been shown to cause birth defects and fetal damage, among other health problems. Both creosote and penta have been a restricted-use pesticide since 1986. Copper naphthenate is the other fairly common oilborne preservative.

Today, waterborne preservatives are widely used in building applications. These waterborne chemicals are used in pressure-treating only and include chromated copper arsenate (CCA), ammoniacal copper zinc arsenate (ACZA), ammoniacal copper quaternary compound (ACQ), and several others. CCA accounted for 94% of the waterborne chemicals used in 1995. By themselves, the primary CCA chemicals are highly toxic and are regulated as pesticides by the EPA. However, in treated wood, they become tightly bonded to the wood during fixing, so leaching from the wood is minimal under normal usage conditions.

ACQ is the most popular copper based alternative to CCA. This alternative eliminates the toxic components of arsenic and chromium.

Using Treated Lumber

A number of factors should be considered before using treated lumber. For instance, where will it be used; indoors or outdoors? Will people or animals come into direct contact with the wood? Will the wood come into contact with any drinking water source, any water body (such as a lake or stream), or with ground water? Is there a less toxic or nontoxic option to using treated lumber? Never inhale the sawdust when cutting treated wood. Always wear a dusk mask.

Consumer Information Sheets are published as federal guidelines by the U.S. Environmental Protection Agency and the wood-treating industry. Sellers of treated lumber will have these sheets available to the consumer.

Some of the important federal guidelines for using treated lumber include:

  • Refrain from using any type of treated wood where the wood will come into direct or indirect contact with drinking water supplies. Incidental contact, such as with docks or bridges, is acceptable under the federal guidelines.
  • Avoid using treated wood where the wood will come into contact with human or animal food or with beehives.
  • Avoid using Penta- and creosoted-treated wood for structural uses inside homes, on decks, in playground equipment, or in areas where wood will come in contact with drinking water for domestic animals and livestock.

Follow these additional precautions:

  • Do not use treated wood for cutting boards or countertops
  • Only treated wood that is visibly clean and free of surface residue should be used for patios, decks and walkways.
  • When power-sawing and machining, wear goggles to protect eyes from flying particles.
  • Wash exposed areas thoroughly after working with the wood and before eating, drinking and use of tobacco products.
  • If preservatives or sawdust accumulate on clothes, launder before reuse.  Wash work clothes separately from other household clothing.

Disposal Options for Treated Lumber

The first priority in keeping treated wood out of the waste stream should be salvage and reuse. If such wood does not enter the waste stream, it will not be considered waste. Therefore, whenever possible, try to reuse treated wood that has been taken out of service, as long as it still meets the design requirements. If you must dispose treated wood, follow these recommendations:

  • State statute prohibits open burning of treated lumber. Typically, open burning of any kind can only occur at town transfer stations, by permit, involving only clean (untreated) wood and brush. Other limited open burning situations can occur at other sites, but only under a permit from local authorities, and typically only for clean wood and brush, not treated lumber.
  • Treated wood of all types can be most responsibly disposed of as follows: Homeowners engaged in small projects should take treated wood to their local landfill or transfer station and place it in the designated location (i.e., the non-clean wood pile). Contractors, utilities, and manufacturers should contract directly with a DEEP permitted bulky waste landfill, or send it to an out-of state wood burner facility appropriately equipped and permitted to burn treated wood.
  • Sawdust, chips, and small wood scraps should never be composted. Treat these items as stated above.

As much as possible, avoid specifying or using CCA-treated wood. Use construction details that minimize use of wood in locations where rot or insect infestation is likely. If wood must be used, go with one of the newer, copper-based products, such as ACQ Preserve. Naturally rot-resistant species such as cedar are an option, especially if available from certified, well-managed forests. Avoid rot-resistant species from domestic old-growth or tropical rain forests.

  • Other alternatives include using recycled plastic lumber such as TREX or Choicedek by Weyerhauser. Use landscape blocks for retaining walls instead of treated wood. For structures in or around water, use metal for some applications such as dock materials and steel pilings filled with concrete in place of creosote-treated underground construction pilings.

Additional Information

This information is provided as a service to those professionals in the construction industry. This information does not include all available references and does not constitute an endorsement by DEEP. Use of this information does not in any way lessen your responsibilities for compliance with applicable federal, state, and local laws. 

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Content Last Updated  May 19, 2020