Current as of April 2008
Coatings are designed to maintain the aesthetic appearance of wood. The use of such products is not necessary to extend the life of chromated copper arsenate (CCA)-treated wood.
To enhance the appearance of CCA-treated wood structures, consumers may want to consider using oil-based penetrating finishes with a transparent or semi-transparent color. These types of products will provide the most consistent aesthetic improvement. It is important to follow the manufacturer's directions regarding application.
Paints or other continuous coatings used on exposed wood surfaces will require substantial long-term maintenance. For that reason, wood experts do not recommend the use of film-forming coatings.
CCA-treated wood products have been used safely and effectively for more than 70 years. On that basis the WPSC does not believe that coatings of any kind are necessary.
There have been several studies conducted on coatings to determine whether coatings could reduce dislodgeable residues from CCA-treated wood structures. In 2007, the FIFRA Scientific Advisory Panel (SAP) to EPA Office of Pesticide Programs reported on its consideration of studies on coatings conducted by EPA and by CPSC. The FIFRA SAP did agree that a few of the tested coatings showed some reduction in dislodgeable residues, but only under very limited circumstances of the specific study conditions; they also noted it was unclear how much reduction resulted from the precleaning steps and how much from the actual coating. Results could not be generalized to other circumstances. The SAP said:
“It should also be noted that the use of coatings for exposure mitigation carries with it the complexity of dealing with coating failure and the need for removal and re-application. Thus, the value and advisability of the use of coatings for exposure mitigation should be carefully evaluated”
The SAP did not address whether there was any inherent need to reduce potential exposures and suggested significant additional research is needed before it would be possible to provide recommendations to consumers, should such exposure reductions be considered as appropriate. EPA does not recommend the use of coatings for safe handling of CCA-treated wood.
The WPSC believes that there may be some aesthetic reasons to consider use of coatings on wood products but no reason or scientific basis to use coatings for safe-handling of CCA-treated wood.
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