Treated wood waste

Treated wood waste commonly comes from demolition sites. To encourage proper disposal of this material, there are exemptions for managing this waste in the dangerous waste regulations. We offer guidance for both commercial generators and homeowners.

What is dangerous about treated wood?

Treated wood is full of chemicals. Outdoor and structural wood is preserved from deterioration and natural decay caused by insects, fungi, and marine borer worms by dipping, spraying, or pressure-treatment with pesticides that contain harmful chemicals. Since dangerous levels of pesticides are hard to see, it is important that wood waste from commercial sites is properly designated.

What do I need to do?

Commercial or industrial businesses

  • Determine if your treated wood is conditionally excluded from the dangerous waste regulations.
    • Read our focus sheet on the treated wood exclusion.
    • If the waste doesn't meet the conditions of the exclusion, you must designate the waste to determine if it is a regulated dangerous waste and manage it accordingly.
    • Do not burn treated wood. Only creosote-treated wood can be burned.
    • You can only burn creosote-treated wood wastes in a commercial/industrial incinerator or boiler in accordance with state and federal regulations.


Household wastes are excluded from the dangerous waste regulations. If you have treated wood waste from your household:

  • Dispose of treated wood in your trash collection.
  • Do not burn treated wood waste in open fires, stoves, fireplaces, or residential boilers. Toxic chemicals may be produced as part of the smoke and ash.

Arsenic and chromium treated wood

Chromated copper arsenate (CCA) is one of the most common chemical formulations found in treated wood. Specific uses and disposal of CCA treated wood have raised safety issues, primarily because of arsenic.

The U.S. Environmental Protection Agency and Ecology's Hazardous Waste and Toxics Reduction program regulate arsenic and chromium because they are toxic and can leach into water tables if disposed into a landfill.

Why do we care about arsenic, chromium, and copper?


Exposure to large amounts of arsenic can lead to serious illness or death. Ongoing exposure to smaller amounts over a long time can cause many different adverse health effects. Arsenic-treated wood is the major use of this chemical today. The EPA found that arsenic used in wood preserving formulations was typically contaminated with lead.


Exposure to chromium occurs from ingesting contaminates from food, drinking water, or workplace air. Potential health effects depend on dosage and routes of exposure.


Small amounts of copper are necessary for good health. However, very large amounts can cause dizziness, headaches, diarrhea, abdominal cramps, and liver and kidney damage. Copper is also toxic to salmon and other fish. Copper-treated lumber turns green as the preservatives dry and react to the sun’s ultraviolet rays.

Creosote treated wood

Coal tar creosote is the most widely used wood preservative in the United States. Creosote is the name used for a variety of products: wood creosote, coal tar creosote, coal tar, coal tar pitch, and coal tar pitch volatiles. These products are mixtures of many chemicals created by high-temperature treatment of beech and other woods, coal, or from the resin of the creosote bush.

Pentachlorophenol treated wood

Pentachlorophenol was at one time one of the most heavily used pesticides in the United States. The chemical was used as a biocide and wood preservative. Now, only certified applicators can purchase and use pentachlorophenol.

Pentachlorophenol is no longer found in wood preserving solutions, insecticides, and herbicides that you can buy for home and garden use. However, it is still used in certain industries as a wood preservative for power line poles, railroad ties, cross arms, and fence posts.

Exposure to pentachlorophenol happens mostly to workers at lumber mills and wood-treatment facilities where it is used as a wood preservative. Pentachlorophenol can harm the liver, kidneys, blood, lungs, nervous system, immune system, and gastrointestinal tract. It can also irritate the skin and eyes.