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Questions & Answers on CCA-Treated Wood Sealant Studies (Interim Results)
Background
The U.S. Environmental Protection Agency (EPA) and the U.S. Consumer Product Safety Commission (CPSC) are releasing preliminary results from a collaborative two-year study to inform the public on the effectiveness of commercially available sealants in reducing or eliminating the potential of arsenic exposure from contact with the surfaces of CCA-treated wood. The study, which uses older CCA-treated wood, began in August 2003 and will continue until August 2005. The final report is expected to be available by the end of this year. CPSC is also conducting a similar study using new CCA-treated wood.
CCA is a wood preservative that has been registered to protect wood from dry rot, fungi, molds, termites and other pests that can threaten the integrity of wood products. In 2002, EPA reached an agreement with the manufacturers of wood preservative products containing CCA to cancel the registration of CCA for use in virtually all residential applications. As of December 31, 2003, it is illegal to treat dimensional lumber used in residential applications with CCA.
- What are the sealant studies and why are EPA and CPSC doing this research?
- How are the studies being conducted?
- What are the preliminary results from the sealant studies?
- What can consumers do if they are concerned with exposure from contact with CCA-treated wood structures?
- What are the key points for parents and consumers concerned about exposure from structures made of CCA-treated wood?
- What are the limitations of these studies?
- What is the status of EPA's activities on CCA?
- Where can I find more information?
1. What are the sealant studies and why are EPA and CPSC doing this research?
EPA and CPSC staff began this collaborative research program on both new (new wood when the study was initiated) and existing CCA-treated decks in August 2003 to study the effectiveness of sealants in reducing or eliminating exposures to arsenic which could occur from contact by the public, especially children. Most exposure occurs with decks and play sets that have been constructed with CCA-treated wood. EPA is evaluating the performance of 12 coatings on outdoor minidecks made from older CCA treated wood; CPSC is evaluating eight coatings on outdoor minidecks made from new CCA-treated wood. Even though CCA can no longer be used in residential settings, many existing decks and other structures are made of wood that was treated with CCA. These studies are designed to help provide information regarding which types of sealants do the best job of preventing potential exposure to arsenic from contacting treated wood surfaces. It should be noted, however, that most sealants are marketed by their manufacturers to protect wood from deterioration due to exposure to the elements (e.g., rain, sun, UV radiation), or simple "wear and tear," and not to seal in chemical compounds such as arsenic.
2. How are the studies being conducted?
EPA and CPSC staff developed a research protocol that was externally peer-reviewed. The EPA study is evaluating the performance of 12 commercially available products, a combination of film-forming (e.g., paints) and non film-forming products (e.g., stains), on outdoor "mini-decks," over a two-year period. The work is being done in Research Triangle Park, NC, and uses wood from older, in-service decks. The CPSC study is very similar except that the study site is in Gaithersburg, MD., and eight commercially available stains and sealants (seven of which are the same as those tested by EPA) are being evaluated on new (as of August 2003) CCA-treated wood.
3. What are the preliminary results from the sealant studies?
The preliminary studies show that all of the sealants tested reduced dislodgeable arsenic from CCA-treated wood for up to 12 months of natural weathering. These results are based on information collected during the first 12 month period of the study. Within the limitations of the study, the interim results indicate that the sealants tested provide a reduction in the amount of dislodgeable arsenic at the surface of the CCA-treated wood.
The products tested included:
- "Film formers" such as paints that form a film on the wood surface,
- Penetrating stains and sealants which absorb into the wood, and,
- Those designed to encapsulate CCA (e.g., plastic-type products).
EPA Study
While the top two performers were film-forming coatings (e.g., paints), the other more typical deck treatment products-specifically sealants and stains--performed similarly in reducing the amount of dislodgeable arsenic at the surface of the wood. However, there are concerns about the use of paints on exposed outdoor surfaces subject to abrasion. Generally, film formers are not preferred because they can chip or flake, and when removed through sanding or power washing, can increase the consumer's potential exposure to arsenic. Another film-former, an elastic vinyl product designed to encapsulate CCA wood, performed very well initially, but some chipping occurred, and recoat preparation might require product removal before re-treatment.
Penetrating stains or sealants are an effective alternative to film formers (paints) since they reduce potential exposure to arsenic almost as well, and they do not have a tendency to flake and peel, like paints. Based on the data for the remaining products, they all showed an ability to reduce exposure to arsenic, but further data is needed to identify more defined clear trends with respect to product type or characteristics. Interim study results indicate that the top five non-film-forming products were:
- Clear, water-based, acrylic tint base stain (no tint added);
- Oil-based deck toner base deck stain (no tint added).
- Semi-transparent, oil-based, sealant with UV blocker
- Clear, oil-based penetrating sealant with alkyd and acrylic; and
- Clear, oil-based, acrylic stain
Other penetrating sealant products, either oil- or water-based, did reduce arsenic exposures and should continue to be considered.
We believe the one year results provide helpful guidance for consumers. However, since this is a two year study, there will be additional results to consider at the end of that time period. It is important that we evaluate the performance of coatings for the entire two-year study period to determine which coatings produce the greatest reduction in dislodgeable arsenic over the longest time period. We will update the findings when the study is completed.
4. What can consumers do if they are concerned with exposure from contact with CCA-treated wood structures?
If consumers are concerned with potential exposures that may result from contact with CCA-treated wood, they may treat the structure with a sealant. Available data suggest that application of penetrating coatings to decks or other residential CCA-treated structures at least once a year can reduce exposure to arsenic. Oil or water-based stains that can penetrate wood surfaces are preferable to products such as paint. This is because paints and other film-formers can chip or flake, requiring scraping or sanding for removal which can increase a consumer's exposure to arsenic. Consumers should consider the required preparation steps (e.g., sanding, power washing, etc.) before selecting a product to minimize potential exposure to arsenic, both for initial application and re-coating.
5. What are the key points for parents and consumers concerned about exposure from structures made of CCA-treated wood?
- If you are concerned about potential exposure to arsenic, sealants, when applied at least once a year, have been shown to reduce dislodgeable arsenic from the wood.
- Oil or water-based, penetrating sealants or stains are preferred.
- As always, parents and other caretakers should follow these precautions for children who play on or near decks. Always wash hands thoroughly after contact with treated wood, especially prior to eating and drinking, and ensure that food does not come into direct contact with any treated wood.
- At this time, we do not believe there is any reason to remove or replace CCA treated structures, including decks and playground equipment.
- Consumers should follow manufacturer recommendations when handling the wood, including the same precautions that workers should take: wear gloves when handling wood, wear goggles and dust masks when sawing and sanding, always wash hands before eating, and never burn CCA treated wood.
- The majority of exposure that is estimated to occur to children is from hand-to-mouth activities (i.e., children touching the surface of CCA-treated wood and then putting his/her hand in his/her mouth). This activity is most prevalent in children aged 1 to 6 years of age.
6. What are the limitations of these studies?
These studies examined the effects of natural outdoor weathering on coating effectiveness in two geographic locations. There was no physical abrasion component that would simulate "wear and tear" or use. Therefore, more severe weather conditions (i.e., increased heat, UV radiation, humidity, etc.) and intensive use of a CCA-treated structure may reduce coating effectiveness.
7. What is the status of EPA's activities on CCA?
The CCA probabilistic children's risk assessment, which examines the potential risks from exposure to arsenic and chromium from CCA-treated wood decks and playgrounds, is scheduled to be revised and finalized in June 2006.
EPA is also evaluating CCA through its re-registration process. A preliminary risk assessment for the CCA RED (re-registration eligibility decision) has already been released for public comment (see the CCA fact sheet Web page). This document describes the potential risks from the use of CCA to workers handling the product when treating the wood, to workers exposed to treated wood, and to the environment from potential exposures resulting from leaching of treated wood. The comments received will be evaluated and the risk assessment will be revised, as appropriate. The Agency will release the revised risk assessment and solicit public input on risk mitigation measures before making its final reregistration decision.
8. Where can I find more information?
More information for consumers and the sealant studies are available
from the CCA fact sheet Web page
and CPSC's Web site
. Additional sealant information can be found on the USDA
Forest Service web site.