November 15-17, 2006 Charge / Question to the Panel
Background Paper and Charge to the Panel
FIFRA SAP review of: Studies Evaluating the Effectiveness of Coatings in Reducing Dislodgeable Arsenic, Chromium, and Copper from CCA Treated Wood
CCA is a wood preservative that is impregnated under pressure into wood to protect it from decay and insect damage. CCA is registered under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) by EPA’s Office of Pesticide Programs (OPP). In October 2001, EPA-OPP prepared a preliminary deterministic exposure assessment for selective internal and external peer review comments as an interim report intended to address child residential “playground” exposures. In addition, EPA requested guidance from the FIFRA Scientific Advisory Panel (SAP) for risk mitigation measures such as sealants and coating processes. The SAP Panel made “recommendations regarding the need for additional studies in this area...” because the “weight-of-evidence from available studies indicates that certain coatings can substantially reduce dislodgeable and leachable CCA chemicals.” The Panel also recommended that “EPA inform the public of the ability of certain coatings to substantially reduce leachable and dislodgeable CCA chemicals…”
In March 2003, the registrants of CCA wood preservatives signed an agreement with EPA for voluntary cancellation of CCA-treated wood for residential uses (such as playsets and decks) effective beginning January 1, 2004. However, existing decks and playsets made of CCA-treated wood will still be in use. Therefore, the potential remains for dermal contact with arsenic, chromium, and copper residues on treated surfaces, and this may be a concern for infants and small children, due to their close contact with surfaces and hand-to-mouth activities.
In collaboration with the staff of the Consumer Product Safety Commission (CPSC), EPA’s Office of Research and Development (ORD) developed a draft research protocol in the spring of 2003 to evaluate efficacy of coatings to reduce dislodgeable CCA residues on the surfaces of CCA-treated wood. EPA’s draft protocol was submitted for external letter peer review and posted for public and stakeholder comment. Based upon comments received from stakeholders and the peer reviewers, ORD revised the protocol and commenced the two-year mini-deck coatings study in the summer of 2003. The staff of the CSPC initiated a similar study in Gaithersburg, Maryland at the same time. EPA drafted an interim report in the spring of 2005 that presented results through the first year of the study and CPSC staff reported results through 15 months of sampling.
The draft interim reports were submitted for external peer review and posted for public comment after revisions in response to peer review comments. The draft final reports, which are the subjects of this review, present the results and findings from the two-year studies. The draft final EPA report utilizes a data analysis that addresses issues raised in a Request for Corrections that was received from the Wood Preservatives Science Council following the posting of the interim report. The draft final reports have undergone internal agency review as well as review from selected experts throughout the government.
The EPA and CPSC staff studies have several key elements in common and minor differences in approach and scope. Both studies evaluate dislodgeable CCA residues on the surfaces of CCA-treated wood by periodically sampling over a two-year period of outdoor weathering using a wipe technique developed by the staff of the CPSC. The studies utilize miniature decks constructed of CCA-treated lumber to which deck coating products, available to consumers, were applied per manufacturer’s instructions. The products included oil and water-based stains, sealants, and paints as well as products that were advertised to encapsulate CCA-treated wood. The EPA study evaluated the performance of twelve products applied to decking recovered from two in-service decks whereas the CPSC staff study evaluated performance of eight products on minidecks constructed from recently purchased CCA decking material.
In spite of the differences in overall experimental design, the two studies convey a remarkably similar picture of the ability of the products tested to impact the amount of dislodgeable CCA residue as the coatings weather. Common to all products tested (as well as uncoated CCA-treated controls) was a general upward trend over time in dislodgeable residues. The studies revealed wide differences in performance; the paints reduced dislodgeable CCA residues to levels statistically below those of the CCA controls over the two year study period whereas a water-based sealant did not reduce residues significantly below the controls at any time during the study. Other oil and water-based sealants and stains performed between these extremes and dislodgeable residues were found to be statistically below those of the uncoated controls through 11 to 15 months of weathering.
As with any study that endeavors to address a complex question, there are limitations that impact the extent to which the results may be generalized. The principal limitations of these studies are that a limited number of products were tested on three sources of wood in one climatic region, in the absence of the normal stresses that a full-scale, in-use deck may experience. EPA and CPSC staff seek the guidance of the FIFRA SAP in evaluation of the reliability of the findings of the studies and guidance in use of the data for informing conclusions regarding the ability of coatings to reduce dislodgeable CCA residues from decks and play structures.
Charge to the Panel
The Agency requests the Scientific Advisory Panel to provide review of both the EPA and CPSC staff studies and to provide advice in the following areas:
1. The Scientific Advisory Panel (SAP) members are asked to identify the scientific merits and limitations of the design of the studies and the analyses of the results. The SAP members are also asked to comment on the quality of the data, including its objectivity and utility.
2. Please comment on whether the reports have captured the critical findings of the studies objectively and appropriately consistent with the data. Please identify any other conclusions that can be drawn from the data.
3. Please comment on whether the statistical methods employed by EPA and CPSC staff represent a scientifically justifiable and robust approach to evaluation of the data. Have the statistical analyses, including the analyses of variance, been presented in an appropriate, useful, clear and transparent manner?
4. Certain specific issues, such as the impact of abrasion and coating reapplication, were not examined in these studies. Please comment on how these data gaps have been sufficiently accounted for in the discussion of the results of these studies.
5. The studies were performed under limited study conditions (one climatic region, i.e., the mid-Atlantic U.S., the structures were not subjected to normal use or wear, etc.) with a limited set of products. Please comment on whether it is appropriate to extrapolate these results to other conditions.
6. Please comment on whether the methodology is suitable for use by others (e.g., the coating industry, wood treaters, or consumer groups) for evaluating and developing new products. Are there elements of the protocol that you recommend be modified or explored (e.g., the moisture content of the wipe material, wipe contact time on the wood surface, etc.)?
7. Please comment on whether these studies are of sufficient quality and breadth to be used to assist in developing conclusions about the ability of certain coatings to substantially reduce dislodgeable CCA chemicals. Have the agencies identified the most important information and findings? Are there other findings/conclusions that could be made from these studies?