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

Background

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?

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