Washington State Department of Ecology

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Treated Wood Waste

 Wood waste from construction, renovation and demolition work may be regulated dangerous waste due to pesticide treatment.

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.

Surface protection with pesticides is used to protect wood from sap staining, generally by dipping or spraying.

Pressure-treating provides much longer lasting protection to exposed wood.

Most preserved wood was used for the following purposes according to the 1988 Federal Register Vol. 53, No. 251 pg. 53286:

  1. Lumber and timber, mostly preserved with inorganic arsenic and chromium formulations
  2. Railroad crossties, switch ties and bridge ties, almost all preserved with creosote
  3. Poles, 60% preserved with pentachlorophenol, 23% preserved with creosote, and 17% preserved with inorganic preservatives.
  4. Fence posts, pilings, plywood, crossarms and other products, mostly preserved with inorganics.

No one can tell if wood has dangerous levels of pesticides by looking at it. Generally, wood waste from commercial (non-homeowner) sites must be designated or evaluated to see if it is dangerous waste before it is disposed. For more detailed information about testing and sampling refer to the pages on