Treated Wood Safety

Industrial Treatments

For industrial purposes like preserving telephone poles and railroad ties, creosote tar is still the most common treatment. Another oily preservative called pentachlorophenol or PCP is also frequently used. Neither of these is approved for indoor use or in any application that might involve regular human or food contact. Even the fumes can be hazardous in an enclosed space. Creosote- or PCP-treated wood should not be used in any home-building projects, either indoors or outside.

The once widely used CCA treatment originally was approved even for playground structures. The water-soluble CCA solution was driven into the fibers of the wood under pressure and worked by poisoning any insect that ingested any of the treated wood fiber. Fears that children might be affected by transferring the chemical from hand to mouth spurred replacement of CCA with less-hazardous copper compounds. Many products treated with CCA are still in place.

Existing structures of CCA treated wood could be safely sealed with a yearly application of polyurethane or oil-based wood sealer. The exterior coating prevents CCA from leaching out during rainfall and forms a barrier to direct-skin contact. If replacing CCA-treated structures, be sure to learn local regulations regarding disposal of hazardous materials. Clean up all sawdust and wood scraps. The old lumber should never be burned since both smoke and ash are poisonous--a spoonful of ash from CCA lumber contains enough arsenic to be fatal if swallowed. Another formerly common use of CCA wood was as a raised border for vegetable gardens. As the wood gradually decomposes, the surrounding soil can be contaminated with arsenic. Though plants draw little of the chemical into their systems, old treated wood around raised beds should be replaced with safer products.

When building with approved treated wood, work in a well-ventilated area and wear a respirator. Contaminated dust can cause breathing problems. Wear gloves, because many preservatives are also strong skin irritants. Remove splinters immediately--the danger of poisoning from a splinter of treated wood is small, but the chemicals can add to the discomfort. Wear eye protection--any eye injury involving treated wood will be compounded by the irritants present.

Pressure treated wood considered safe for home use outdoors now uses either Ammoniacal Copper Quaternary (ACQ) or Copper Boron Azole (CBA). Other treatments that can be painted on include boron as the active ingredient. Borax is safe but not weatherproof. Some woods are naturally resistant to insects and rot. Cedar and white oak have long useful lifetimes if sealed and protected from water damage. Redwood is another long-lasting natural choice. Artificial composites of recycled materials can also take the place of wood lumber in many common applications.