Document ID: EPA-HQ-OPP-2006-0693-0064
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-01-26T05:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	OFFICE OF

	PREVENTION, PESTICIDES, AND

	TOXIC SUBSTANCES

January 25, 2007

MEMORANDUM

SUBJECT:  	Transmittal of Meeting Minutes of the FIFRA Scientific
Advisory Panel Meeting  Held November 15 - 16, 2006 on Studies
Evaluating the Impact of Surface Coatings on the Level of Dislodgeable
Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood

TO:		James J. Jones, Director

Office of Pesticide Programs

FROM:	Joseph E. Bailey, Designated Federal Official			

FIFRA Scientific Advisory Panel

Office of Science Coordination and Policy

THRU:	Steven Knott, Executive Secretary		

FIFRA Scientific Advisory Panel

Office of Science Coordination and Policy

Clifford J. Gabriel, Director	

Office of Science Coordination and Policy

Attached, please find the meeting minutes of the FIFRA Scientific
Advisory Panel open meeting held in Arlington, Virginia on November 15 -
16, 2006.  This report addresses a set of scientific issues being
considered by the Environmental Protection Agency pertaining to studies
evaluating the impact of surface coatings on the level of dislodgeable
arsenic, chromium and copper from chromated copper arsenate
(CCA)-treated wood.

Attachment

cc:

James B. Gulliford					Frank Sanders

Wendy Cleland-Hamnett				Betty Shackleford

Margaret Schneider					Richard Keigwin

Anne Lindsay					William Jordan

Margie Fehrenbach					Douglas Parsons

Janet Andersen					Enesta Jones

Debbie Edwards					Vanessa Vu (SAB)

Steven Bradbury					Nader Elkassabany

William Diamond					Frank Princiotta

Arnold Layne						Mark Mason

Tina Levine						Jacqueline Ferrante (CPSC)

Lois Rossi						Lisa Matthews

							OPP Docket

FIFRA Scientific Advisory Panel Members

Steven G. Heeringa, Ph.D. (FIFRA SAP Chair)

John R. Bucher, Ph.D., D.A.B.T.

Janice E. Chambers, Ph.D.

Stuart Handwerger, M.D.

Gary Isom, Ph.D.

Kenneth M. Portier, Ph.D.

Daniel Schlenk, Ph.D. 

FQPA Science Review Board Members

Paul R. Blankenhorn, Ph.D.

Mr. F. Louis Floyd

Natalie Freeman, Ph.D., M.P.H.

Dallas E. Johnson, Ph.D.

Peter D. M. Macdonald, D.Phil., P.Stat.

Peter McCullagh, Ph.D.

Nu-May Ruby Reed, Ph.D., D.A.B.T.

Mandla A. Tshabalala, Ph.D.



SAP Minutes No. 2007-02

A Set of Scientific Issues Being Considered by the Environmental
Protection Agency Regarding:

Studies Evaluating the Impact of Surface Coatings on the Level of
Dislodgeable Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood

November 15 - 16, 2006

FIFRA Scientific Advisory Panel Meeting

held at the

Environmental Protection Agency Conference Center

Arlington, Virginia

Notice

	These meeting minutes have been written as part of the activities of
the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA),
Scientific Advisory Panel (SAP).  The meeting minutes represent the
views and recommendations of the FIFRA SAP, not the United States
Environmental Protection Agency (Agency).  The content of the meeting
minutes does not represent information approved or disseminated by the
Agency.  The meeting minutes have not been reviewed for approval by the
Agency and, hence, the contents of these meeting minutes do not
necessarily represent the views and policies of the Agency, nor of other
agencies in the Executive Branch of the Federal government, nor does
mention of trade names or commercial products constitute a
recommendation for use.

	The FIFRA SAP is a Federal advisory committee operating in accordance
with the Federal Advisory Committee Act and established under the
provisions of FIFRA as amended by the Food Quality Protection Act (FQPA)
of 1996.  The FIFRA SAP provides advice, information, and
recommendations to the Agency Administrator on pesticides and
pesticide-related issues regarding the impact of regulatory actions on
health and the environment.  The Panel serves as the primary scientific
peer review mechanism of the Environmental Protection Agency, Office of
Pesticide Programs (OPP), and is structured to provide balanced expert
assessment of pesticide and pesticide-related matters facing the Agency.
 FQPA Science Review Board members serve the FIFRA SAP on an ad hoc
basis to assist in reviews conducted by the FIFRA SAP.  Further
information about FIFRA SAP reports and activities can be obtained from
its website at   HYPERLINK "http://www.epa.gov/scipoly/sap/" 
http://www.epa.gov/scipoly/sap/   or the OPP Docket at (703) 305-5805. 
Interested persons are invited to contact Joseph E. Bailey, SAP
Designated Federal Official, via e-mail at bailey.joseph@epa.gov.

	In preparing the meeting minutes, the Panel carefully considered all
information provided and presented by EPA and the Consumer Product
Safety Commission (CPSC) staff, as well as information presented by
public commenters.  This document addresses the information provided and
presented by EPA and the CPSC staff within the structure of the charge.

TABLE OF CONTENTS

PARTICIPANTS............................................................
...............................................................2

INTRODUCTION............................................................
.............................................................4

PUBLIC
COMMENTERS..............................................................
.............................................5

SUMMARY OF PANEL DISCUSSION AND
RECOMMENDATIONS...............................6

PANEL DELIBERATIONS AND RESPONSE TO
CHARGE................................................8

REFERENCES..............................................................
...............................................................26



SAP Minutes No. 2007-02

A Set of Scientific Issues Being Considered by the Environmental
Protection Agency Regarding:

Studies Evaluating the Impact of Surface Coatings on the Level of
Dislodgeable Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood

November 15 - 16, 2006

FIFRA Scientific Advisory Panel Meeting

held at the 

Environmental Protection Agency Conference Center

Arlington, Virginia

Steven G. Heeringa, Ph.D.					Joseph E. Bailey

FIFRA SAP Chair						Designated Federal Official

FIFRA Scientific Advisory Panel				FIFRA Scientific Advisory Panel

Date:	January 25, 2007					Date:  January 25, 2007

Federal Insecticide, Fungicide, and Rodenticide Act

Scientific Advisory Panel Meeting

November 15 - 16, 2006

Studies Evaluating the Impact of Surface Coatings on the Level of
Dislodgeable Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood

PARTICIPANTS

FIFRA SAP Chair

Steven G. Heeringa, Ph.D., Research Scientist & Director for Statistical
Design, University of Michigan, Institute for Social Research, Ann
Arbor, MI

Designated Federal Official

Joseph E. Bailey, FIFRA Scientific Advisory Panel, Office of Science
Coordination and Policy, EPA

FIFRA Scientific Advisory Panel Members

John R. Bucher, Ph.D., D.A.B.T., Deputy Director, Environmental
Toxicology Program, NIEHS, Research Triangle Park, NC

Stuart Handwerger, M.D., Professor of Pediatrics, University of
Cincinnati Children's Hospital Medical Center, Cincinnati, OH.

Gary E. Isom, Ph.D., Professor of Toxicology, School of Pharmacy &
Pharmaceutical Sciences, Purdue University, West Lafayette, IN

Kenneth M. Portier, Ph.D., Program Director, Statistics, American Cancer
Society, Statistics and Evaluation Center, Atlanta, GA

FQPA Science Review Board Members

Paul R. Blankenhorn, Ph.D., Professor, Wood Technology, School of Forest
Resources, College of Agricultural Sciences, Pennsylvania State
University, University Park, PA 

Mr. F. Louis Floyd, FLF Consulting, Independence, OH  

Natalie Freeman, Ph.D., M.P.H., Associate Professor, Physiological
Sciences, College of Veterinary Medicine, University of Florida,
Gainesville, FL  

Dallas E. Johnson, Ph.D., Professor Emeritus, Department of Statistics,
Kansas State University, Manhattan, KS

Peter D.M. Macdonald, D.Phil., P. Stat., Professor of Mathematics and
Statistics, McMaster University, Hamilton, Ontario, Canada

Peter McCullagh, Ph.D., Professor, Department of Statistics, University
of Chicago, 

Chicago, IL

Nu-May Ruby Reed, Ph.D., D.A.B.T., Staff Toxicologist, Dept. of
Pesticide Regulation, California Environmental Protection Agency,
Sacramento, CA  

Mandla A. Tshabalala, Ph.D., Research Chemist, USDA Forest Service,
Forest Products Laboratory, Madison, WI

INTRODUCTION

	The FIFRA Scientific Advisory Panel (SAP) has completed its review of
Studies Evaluating the Impact of Surface Coatings on the Level of
Dislodgeable Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood.  Advance notice of the meeting was published in the
Federal Register on September 1, 2006. A notice announcing revision of
the meeting dates was published in the Federal Register on November 1,
2006. The review was conducted in an open Panel meeting November 15 –
16, 2006 held in Arlington, Virginia.  Dr. Steven G. Heeringa chaired
the meeting.  Joseph E. Bailey served as the Designated Federal
Official.

	  SEQ CHAPTER \h \r 1 The FIFRA SAP met to consider and review Studies
Evaluating the Impact of Surface Coatings on the Level of Dislodgeable
Arsenic, Chromium and Copper from Chromated Copper Arsenate
(CCA)-Treated Wood. The studies were conducted by EPA and the CPSC
staff.  The Agency was seeking input from the SAP on the design and
methodology employed in the studies, extrapolation of the results, and
areas for future research.  

	CCA is a preservative that is impregnated under pressure into wood to
protect it from decay and insect damage.  In October 2001, the EPA
requested guidance from the FIFRA SAP about risk mitigation measures,
such as the application of surface coatings, for CCA-treated wood (SAP
Report No. 2001-12).  The 2001 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 2001 Panel also recommended that “EPA inform the
public of the ability of certain coatings to substantially reduce
leachable and dislodgeable CCA chemicals…”  

	In response to these recommendations, EPA and CPSC staff (Interagency
Agreement # CPSC-I-03-1235) conducted studies evaluating the ability of
selected coatings to reduce the amount of dislodgeable chemicals on
CCA-treated wood surfaces under natural weather conditions for two years
(August 2003 – August, 2005).  The data presented are final data from
the studies; interim one-year data from the studies were reviewed
through a letter peer review process previously.  Data submitted for the
Panel's consideration included reports on the EPA and CPSC staff studies
and public comments submitted.	

	

	The agenda for this SAP meeting included an introduction of the issues
under consideration provided by Nader Elkassabany, Ph.D. (Antimicrobials
Division, OPP).  A summary of the coatings study conducted by EPA was
presented by Mr. Mark Mason (Air Pollution Prevention and Control
Division, National Risk Management Research Laboratory, Office of
Research and Development, EPA).  An overview of the CPSC staff study was
presented by Jacqueline Ferrante, Ph.D. (Directorate for Health
Sciences, CPSC).  Points of clarification about the EPA study were
provided by Leonard Stefanski, Ph.D., of the North Carolina State
University and Victor D'Amato, PE, of Arcadis.  Points of clarification
about the CPSC staff study were provided by David Cobb, M.S., Cheryl
Osterhout, Ph.D., Michael Greene, Ph.D., and Treye Thomas, Ph.D., all
CPSC staff members.



PUBLIC COMMENTERS

Oral statements on behalf of the Wood Preservative Science Council were
presented by:

Doug Splitstone, Splitstone & Associates 

Leila Barraj, Exponent, Inc. 

Kevin Archer, Chemical Specialties, Inc.

Written statements were provided by:

Jim Hale, Executive Director, Wood Preservative Science Council

Jeff Lloyd, Ph.D., Vice President of Research and Development, Nisus
Corporation

Joyce Tsuji (Exponent, Inc.) on behalf of the Wood Preservative Science
Council

SUMMARY OF PANEL DISCUSSION AND RECOMMENDATIONS

	The EPA and CPSC staff studies demonstrate convincingly that several
coatings applied to CCA-treated wood in accordance with the
manufacturer’s directives reduced the amount of dislodgeable arsenic
(DA) by a factor of 10 or more for a period of several months, after
which time the level of DA returned to near its original level. 
However, the studies were limited to only two geographic locations,
Maryland and North Carolina, which did not represent the climatic
extremes commonly utilized by the coatings and wood industries (Florida
for moisture and photodegradation and the Snow Belt for freeze-thaw
cyclic stress failures such as cracking).  The limited geographic
locations limit extrapolations to other sections of the country.  Two
sources of wood, southern yellow pine in both cases, were used. The
coatings tested were a small convenience sample of locally available
products and in no sense a random sample of products from all available
classes of coatings. None of the coatings were specifically formulated
to reduce levels of DA. In consequence, while the studies do show that
coatings can reduce DA, the results cannot be generalized to other
geographic regions, other sources of wood and all ages of decks in use.
The studies were designed to show what would happen if someone purchased
a product locally and applied it correctly. They do not show what could
be achieved by use of a coating specifically formulated to reduce DA.

	Because the coatings were applied according to manufacturers’
specifications, surface preparation is confounded with coating product,
so it is impossible to determine what role surface preparation played in
mitigation. Cleaning could be an effective alternative to coating, but
additional research is clearly warranted on this point.  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,
taking into consideration the maintenance needs compared with
alternative approaches.

	The graphical analyses are very clear and supported by the statistical
tests. Some issues were identified with the statistical analyses;
specifically, the EPA repeated-measures analysis requires an assumption
of compound symmetry and both analyses assume that intra-board variation
is less than inter-board variation and these assumptions need to be
addressed. Also, log transformation will make the analysis more
sensitive to small variations at low levels of DA and this could bias
the conclusions if the effect of coating on the level of DA is not
multiplicative. The Panel did not believe, however, that a more refined
analysis would lead to a substantial change in the conclusions.

	It is encouraging that the general conclusions of the EPA and CPSC
staff studies are in agreement despite some fundamental differences. In
particular, the choices of baseline value and normalization method were
different and the wipe protocols were very different. The wipe protocols
would benefit from further refinement based on the experience of both
studies. Particular issues to address include the use of saline versus
distilled water to wet the wipe, the effect of picking up splinters from
older wood, and the need to measure surface moisture at the time of the
wipe and adjust for it in the analysis. Soluble and particulate DAs
should be separately quantified. A scanning electron microscope
technique using dot-density imaging of each element separately would
give a better assessment of the wipe protocol.

	Without a measure of the associated risk, the Panel could not say with
certainty whether more studies would be worthwhile. The Panel did,
however, discuss possible improvements to the design and identified a
number of factors that may be important and could be incorporated in
future designs. These include the dimension and age of test specimens,
the orientation of the growth rings to the surface being tested, and
sapwood versus heartwood. The processes of mildew formation and
photodegradation are likely to be important and should be considered.
The Panel noted that future studies should include at least the two
geographic regions, Snow Belt and Southern (typically Florida), used by
the coatings and forest products industries in order to make the results
more applicable to the nation as a whole. The coatings industry could be
asked to formulate coatings specifically intended to reduce DA and these
could be tested. Studies such as these with a standardized wipe protocol
could be supplemented with simulation models of real-life exposure
scenarios.                                                              
                                                                        
                                                                        
                                                                        
                                                         

PANEL DELIBERATIONS AND RESPONSE TO CHARGE

	The specific issues addressed by the Panel are keyed to the background
documents, references, and the charge questions provided by EPA and the
CPSC staff.

Charge Question 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.   

Panel Response

	The response to this question will be divided into three parts. The
first addresses the EPA study, the second the CPSC staff study, and the
third refers to both studies.

Part 1 - EPA Study

	The design used in the EPA study to evaluate the effectiveness of
coatings in reducing dislodgeable chromium, copper and arsenic (DCCA)
was reasonable.  The study design is composed of a treatment structure
and a design or randomization structure.  The treatment structure is a
three-way factorial with factors identified by coating type, wood
source, and end grain orientation.  The design structure is a split-plot
design with repeated measures on the subplot units.  Minidecks
correspond to the whole plots to which coatings are randomly assigned. 
Each coating is replicated on three different minidecks.   Four of the
boards on each minideck correspond to the four combinations of wood
source and end grain orientation.  Repeated measurements were taken over
time after 1, 3, 7, 11, 15, 20, and 24 months.  Two baseline
measurements were obtained for each board prior to coating and the two
measurements were averaged to create a single covariate for each board. 
The variables analyzed were the logs (to the base 10) of the observed
levels of arsenic, chromium, and copper.

	The models used to analyze the data are appropriate provided that the
repeated measures satisfy compound symmetry.  Compound symmetry implies
that the variances are the same at all time points and that the
correlations between pairs of measures at all time points are equal. In
this case, the effect of the covariate is assumed to be the same for all
combinations of coating, wood source, grain orientation, and time.  It
would be helpful if the final study reports addressed the
appropriateness of this assumption.  It is doubtful that assuming a
different covariance structure will change the main conclusions from
this study, but the reports should address this issue.

	The graphical displays of observed results are useful and informative,
especially Figures 3.14 – 3.26.  These displays suggest that coatings
will reduce amounts of DCCA for several months and then the amounts of
DCCA tend to increase over time.  The statistical tests performed show
that the observed results are statistically significant. Table 3.5 in
the report does not agree with the results in Appendix O and this
discrepancy needs to be resolved. Table 3.6 should be removed from the
final report as the study was not designed to consider such comparisons.

	The limitations of the study have been correctly identified in that
only two sources of deck wood were used and the experiment was performed
in only one location.

Part 2 - CPSC Staff Study

	Nine minidecks were constructed.  Each minideck contained nine planks. 
While the planks on the minidecks were sampled at three different
frequencies, all planks were sampled at 12 months and 24 months.   The
statistical analyses presented in the report correspond to the 12 month
and 24 month data only, and the Panel's response is focused on the 12
month and 24 month data.  Planks used in the study came from new
CCA-treated wood boards, and two planks came from each board. In
constructing the minidecks, no two planks from the same board were used
on the same minideck.  

	Coatings were randomly assigned to the minidecks.  One and only one
coating was applied to all boards in each minideck, except for coating
11.  Coating 11 was assigned to four planks in its minideck.  The
variable analyzed is the log of the ratio of the DA at months 12 and 24
divided by the baseline values of the DA.  

	Exploratory analyses were interesting and useful.  Two Rp values were
obtained from each of the planks measured according to the prescribed
sampling schedule on each minideck (except for coating 11).   Plots of
the geometric means of the measured  Rp values were plotted against
time.  The plots indicate that coatings tend to reduce levels of DA
initially and then the levels of DA increase toward baseline values over
two years.  It was noted that the geometric mean of the Rp values is
equivalent to the exponentiated average of the logs of the Rp values.  

	It is noted that whereas the EPA recognized the split-plot repeated
measures structure of their experimental design, the CPSC staff study
does not.  One or two panelists believed that this limits
generalizations from the CPSC staff study while other panelists did not
see this as a serious issue.  This affects the appropriateness of the
statistical model described in Table A and whether statistically sound
generalizations can be made from this study.

Part 3 – Issues common to both studies

Scientific merits of the design(s):

	The scientific merits of the designs rest on the answers to the
question of whether the designs address the appropriate study objective.
Or another way of putting it is “what specific objective is each study
design good for?” The study objectives have big implications on the
ability of the study results to be generalized. Five potential
objectives were identified either from the two reports or the
presentations and discussions before the Panel.  The Panel recognizes
that the studies are designed to assess the potential for individual
surface contact with arsenic, chromium and copper and are not designed
to address the consequent risk.

Objective 1.  To support efforts to inform the public regarding the use
and maintenance of existing CCA-treated wood products, such as decks and
playground equipment. This objective assumes study objectives will apply
to all CCA decks in the U.S. regardless of their current condition.  The
EPA study and the CPSC staff study are limited in spatial extent and age
of decks and may fall short of providing sufficient information to
address this objective.  There was little support among the Panel
members that the studies addressed Objective 1.

Objective 2.  To identify specific surface coatings (or even coating
types) that could reduce arsenic availability from CCA-treated wood.
Inference space is all potential CCA-treated wood coatings.  This
objective implies that the study results relate to expectations of what
we might see from the whole range of possible surface coatings and or
coating types. The EPA and CPSC staff studies identified the different
coating types and had multiple representatives from each type. At issue
is the number of representatives of each coating type, which was too
small to support estimating the range and distribution of effectiveness
from all members of each coating type. In addition, the coatings were
chosen from a limited regional set with subjective criteria. They were
not a random selection from the whole population of products in a
particular coating type class. This makes it difficult to extrapolate
results to the broader population of coating products and, hence,
difficult to see that these studies are adequate for this objective. 
There was discussion and some disagreement as to whether the studies
actually addressed Objective 2.

Objective 3.  To evaluate the ability of typical deck coating products
to reduce DCCA chemicals on pressure-treated wood. This objective is
stated in some of the material that the Agency presented to the Panel.
The implied inference space for this objective is limited to the issue
of whether DCCA on the wood tested is capable of being reduced by some
coatings.  The studies are then seen as proof of concept experiments. 
These studies are clearly adequate to address this objective and do
indeed demonstrate clearly that certain coatings can reduce levels of
DCCA.  Further, they provide information helpful in identifying which
factors will affect the effectiveness of certain types of coating in
DCCA reduction, and they establish the fact that coatings work
initially, but the effectiveness of all of the coatings tested
diminished over time. The available information is limited due to the
limited number of factors addressed in the studies compared to the many
factors that are known to have an effect or are suspected as having an
effect on DCCA levels.  The following list of factors was compiled by a
Panel member.

Wipe method: number of passes (1, 2) controlled.

Wipe method: wipe length (EPA, CPSC) defined.

Wipe method: speed of passes (continuous) not controlled.

Wipe method: preparation of wipe before sampling  (EPA acid wash/EPA 
unwashed wipe 2X DI water/CPSC 1X Saline) controlled.

Wipe method: sample preparation (EPA/CPSC) controlled.

Wipe method: sample extraction (EPA 3 step/CPSC 1 step) controlled.

Wipe method: analysis of wipe sample (EPA/CPSC) controlled.

Wipe method: amount of shape forming (1/4 sheet/ ½ sheet).

Wipe method: degree of cleaning effect – uncontrolled.

Wood: source deck (two for EPA, one for CPSC).

Wood: bark side up or down (both used in EPA study, up only in CPSC
staff 	study).

Wood: blocking to incorporate multiple sample areas on a board.

Wood: top face vs. bottom face (only top face used).

Wood: grain orientation (not used).

Wood: grain spacing (not used).

Wood: grain type (edge/flat, not used).

Wood: wood season (spring/summer, not used but both present).

Wood: wood type (heart/sap, not used but both present).

Wood: board preparation (as per coating directions, pre-rinsed/as is).

Wood: amount of As, Cr, Cu in wood core (measured, used as covariate?).

Wood: age (assumed even aged within source deck).

Wood: degree of wear (visual inspection).

Coating: product type (paint, stain, sealant, encapsulant - more than
150).

Coating: product base (oil, water).

Coating: number of coats (1, 2).

Coating: pre-application preparation (none, clean/rinse, pressure wash).

Coating: application method (brush, roll, spray).

Coating: manufacturer’s expectation of lifetime (may not have effect).

Coating: permeability (not used).

Design: handling of controls (positive and negative, matched or group).

Design: degree of treatment replication (3 per coating/4 boards per
deck).

Design: method of randomization.

Design: strategy of determination of baseline (blocked/matched
spatially).

Design: when baseline samples taken.

Design: how to do repeated measurements.

Most of the Panel agreed that the studies addressed Objective 3.

Objective 4.  To develop, evaluate and demonstrate protocols for
measuring DCCA and to begin to understand the protocol’s utility and
realism. This objective was stated in the documentation provided to the
Panel on the wipe studies performed to support the wipe and sample
preparation protocols, but could be construed as the objective for the
full DCCA studies. This objective suggests that the studies are simply
experiments designed to work out the issues surrounding a new data
collection protocol in a situation where an established protocol is not
available.  At issue is the question of whether reasonable measurements
can be achieved and the protocol repeated consistently. The EPA and CPSC
staff studies provide information sufficient to support this objective. 
Most of the Panel agreed that the studies addressed Objective 4.

Objective 5.  To identify future research needs. This objective
underlies most scientific research and relates to the goal of gathering
new facts in order to support developing conceptual models of a process
or system and identifying the next set of hypotheses to examine.  If
this were the only valid objective for the studies under discussion, the
inference space of the studies would not be an issue.  The Panel's view
is that the studies only provide information that will be useful to
designing the next studies.  The EPA and CPSC staff studies support this
basic objective by providing useful information on factors affecting
DCCA level reduction and failure trends for coating types.  Most of the
Panel agreed that the studies addressed Objective 5. 

Scientific merits of the analyses:

	The scientific merits of the analysis rest on the answers to two
questions. First, does the analysis methodology (e.g., the statistical
models and tests) properly identify and incorporate the actual study
characteristics? Second, are the assumptions that underlie the analyses
supported by the data?

	There was extensive discussion about whether and why a log
transformation was necessary in the analysis models. It was pointed out
that the log transformation was needed to address both the additivity
assumption inherent in the use of linear analysis models and in
supporting the assumption underlying the use of formal statistical
tests.  There was discussion as to whether data were available to
estimate intra-board (within board) variability and inter-board
(board-to-board) variability in baseline levels of DCCA. The study
designs imply that intra-board variability would be much less than
inter-board variability, but a check on this assumption was not provided
in the reports. This issue is related to the assumption that all boards
used from a given deck have had relatively uniform wear. 

	A linear analysis of the log-transformed data is motivated by the
assumption that the effect of each coating is to reduce the level of DA
by a multiplicative factor. This effectiveness factor varies from
coating to coating, and may diminish over time, but is assumed to be
independent of the initial level of DA. Thus, the linear analysis on the
log scale gives as much weight to a small absolute reduction from an
initially low level as it does to a large reduction from an initially
high level. These reductions are not equivalent in terms of their
protective effect.

Limitations of the design:

	At least one Panel member thought that the studies used insufficient
numbers of different products of each coating type to be able to
estimate the variability of responses for each coating type, thus
limiting the researchers' ability to make inferences to a global
population.

	Other Panel members felt that the specific wood factor characteristics
used as design factors in the studies were not necessarily those that
would have been expected to affect the ability of coatings to reduce
DCCA.  Further, the differences in the designs and conduct of the two
studies and the lack of detailed data provided in the CPSC staff study
make it difficult to compare the results.  

	Differences in wipe protocols or justifications for the differences
were not explained in the documents. For example, EPA used deionized
water and CPSC staff used saline. Why the difference, and would the
difference influence what was collected on the wipe sample? An Agency
presenter explained that they were concerned about salts on the wood as
a result of using saline, but then said that they didn’t think that
was an issue. No salt assessment was conducted.

	The EPA wipe protocol is reported to be based on the CPSC staff
protocol. The CPSC staff wipe protocol is not described in detail, but a
reference is cited. Unfortunately, the journal is defunct and the
reference difficult to obtain. Polyester wipe material has the potential
for snagging on the wood. The EPA study report (page 42) refers to
‘hold ups’ from rough wood; was any of the wipe material lost in
‘hold ups’?  If so, what is the likelihood that some CCA was also
lost?  Was this observed?  Since the wipes are not pre-weighed, the
usual method of assessing wipe loss, via mass loss or no mass change,
could not be assessed. One might expect that as the wood ages, more
‘hold ups’ would occur and that the production of splinters or loss
of wipe medium during wiping would increase.  The report mentions that
wood bits larger than a grain of rice were removed from the wipe samples
before analysis. What is the likelihood that CCA on smaller lumps might
influence the results? One might expect more lumps to come off as the
wood ages; in other words, the increase seen over time may simply
reflect the wood lumps smaller than a grain of rice that were adhering
to the wipe sample.

	The use of one-year old and seven-year old wood in the EPA study is
representative of what might be found in newer structures, but not
necessarily the full range of CCA-treated wood that is in residential
use. It therefore provides only a preliminary assessment of what the
effects might be of treating relatively new wood.  It does not address
the effectiveness of coatings for older woods.

	Descriptive assessment of the boards note that some of the wood
suffered from major to severe mildew build-up. One issue is whether the
wipes on heavily mildewed wood would actually be contacting wood
surface?  There are a number of articles suggesting arsenic methylation
from mildew causes some of the arsenic to volatilize and, therefore,
leaves less to wipe off the surface (Cullen et al., 1984).  

	Appendix D describes the application protocol for coatings 1 and 8 as
"wood is allowed to dry for 2-3 days after the power wash"; coatings 2,
3, 4, 5, 11 “allow to dry;” and coating 12  “allow to dry for 24
hours.” For those coatings in which it states, “allow to dry,” how
long was the drying time? If based on professional judgment, what is the
rationale/protocol? 

	The wipe media in the two studies use different amounts of fluid to
pre-wet the wipes. Are the differences found in the cross comparison
study due to differences in fluid used in the wipe method?

Limitations of the analysis:

	The EPA analysis model utilized a log-transformed concentration
response using the log-transformed concentration baseline value as a
covariate. The CPSC staff analysis model utilized the ratio of log
transformed concentration to log transformed baseline as the response.
Statisticians on the Panel suggested that the CPSC staff model can be
viewed as a restricted form of the EPA model and, as a result, they felt
that the CPSC staff analysis was limited by the model used. Panel
members who were not statisticians were more comfortable with the CPSC
staff analysis. There was concern about the low correlation between the
EPA and CPSC staff wipe results. Perhaps the comparison was done over
too narrow a range of arsenic concentrations.

	The authors of the EPA and CPSC staff reports, as well as the Panel,
acknowledged the limitations of the studies.  Public commentators
challenged the universality of the studies without acknowledging their
value.  While the studies may not meet standards of universality in
their application, they should not be entirely invalidated, but rather
the conclusions limited. The range of wood ages is not ideal, nor is the
range of climates tested. But if the pattern of effectiveness of the
different coatings is consistent across these ages and climates, the
results should be reliable, at least qualitatively, for areas that
experience similar ranges of temperature and humidity. Also, decks that
are in use are likely to suffer some degree of abrasion from foot
traffic, whereas the experimental decks were not subjected to foot
traffic. While this limits the interpretation and scope of the results,
it has no bearing on the objectivity of the studies.

Quality of the data (objectivity and utility):

	One Panel member commented on the change in Data Quality Indicator
(DQI) goals for precision and accuracy for concentrations <10µg/l,
indicated in Section 4.1 (see page 115) of the EPA report. Discussion
with EPA staff indicated that this change affected only the lowest level
of spiked samples (1 µg/l) and very few actual measurements. In
general, the vast majority of observations were 10 times greater than
this lowest level and hence this DQI goal change had little impact on
overall data quality.  This should be clarified in the report.

	In general, the Panel felt that the experiments strongly demonstrated
that coatings in general can and do reduce DCCA levels.  However, the
Panel expressed concern about extrapolation of experimental results to
untested conditions. The Panel recognized that these studies are the
first to test coating of CCA-treated wood directly and that the results
clearly indicate the efficacy and limitations of these coatings in
reducing DCCA.

Charge Question 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. 

Panel Response

Do the reports objectively and consistently capture the critical
findings of studies?

	There are several ways in which to approach the response to this
question. One is in overall perspective, a second is in terms of whether
the statements in the Executive Summaries of the two documents
objectively and consistently capture the critical findings of the
studies, and the third is in terms of whether the statements in the
conclusions capture the critical findings of the studies.

	The general conclusion that there is a short term reduction in DCCA
does capture the general findings for both studies, within the confines
of the methods and products used, the type and ages of woods tested, and
the region of the country in which the studies were conducted.  The EPA
report objectively captures the primary finding that there is a
significant decrease between background and samples taken one month
afterwards, although the differences are not always statistically
significant (see page 119). The CPSC staff report also objectively
captures the primary finding of a short term reduction in arsenic after
application within the confines of new wood sources weathered in the
Mid-Atlantic area.  Both studies provide many caveats as to whether the
findings can be extended to other woods, other coatings, and other
environmental conditions.

	In so far as evaluating the effects of coating on dislodgeable arsenic
from the surface of treated wood, the basis for the conclusions of both
studies was clearly presented, including recognizing the limited scope
of the study design and the nature of wide variability of the collected
data.  These and other study limitations are further discussed in the
Panel's response to Question 1. 

	However, from the standpoint that these tests will support EPA and CPSC
staff efforts to “inform the public regarding the use and maintenance
of existing CCA-treated wood products”, data collected from these two
studies by themselves would appear to have limited application for other
scenarios nationwide, for example, type of wood, geographic factors,
coating formulation, etc.  This is not to say that extrapolation of
these data cannot be made useful as a component of exposure modeling. 

	Some of the statements in the conclusions sections of the reports
stretch the data, considering that it is a limited database.  The EPA
study evaluated two sources of used deck boards, with a limited number
of coatings in one region of the United States, without abrasion similar
to normal use in service, while the CPSC staff study evaluated new
treated boards with a limited number of coatings in one location,
without abrasion similar to normal use.  Taking results from either of
the studies and predicting what will happen in other geographical
locations under different climatic conditions and under normal
in-service abrasion conditions as a function of age in-service is beyond
the scientific merits of the database from both studies.  

	Some of the statements in the conclusions section tend to be subjective
considering that the report contains a database designed to accomplish
specific objectives.  For example, the conclusion section in the EPA
report states that products recommended for application with more than
one coat performed significantly better than single coat products, but
the study design did not examine this question directly. It would be
appropriate to move inference statements such as  this, that were not
part of the experimental design, to a new section related to future
research. Further, the fact that the effects of wood surface
pretreatments prior to coating were not considered severely limits the
conclusions and predictions that can be drawn from the analyses of the
data.

	The authors have reached too far in many of their subsidiary
conclusions, such as the relative performance between coating types. 
While the statistics may be valid, in practice, the conclusions are at
best misleading.  A competent formulator of coatings, for example, can
readily alter any of the coatings in the various classes to achieve very
different results from those reported.  The coatings chosen were based
on local availability, not on their claimed ability to perform as an
agent to block DCCA.  If the experimental base is inadequate, one cannot
competently comment on the relative performance of the various classes
of coatings.

	The authors of both reports are encouraged instead to create a new
section of their report wherein they can legitimately comment that the
data are suggestive of further differentiation of performance, but do
not by any means prove it.  They should not attempt to even speculate as
to the relative performance of given classes of coatings, but rather
only suggest that further work designed to test for this is clearly
justified.

	The EPA report and its supporting documentation is fairly thorough and
adequately captures the findings and the limitations of the study
(ARCADIS document).  The writers appear to be aware of the challenges in
the study design, and the impact of the study design on the data that
was obtained. The CPSC staff report does not provide the same level of
detail regarding methodology and sample results. This makes it difficult
to evaluate critically whether the report objectively and consistently
captures critical findings.

	There is a lack of consistency between the conclusions and the
Executive Summary in the EPA report. For example, in the conclusions
there is a discussion of effects of abrasion versus cleaning, which is
not fully substantiated by the study results as presented. 

	A number of areas in the EPA report contain statements lacking
statistical analysis to support them, or the statistical analysis does
not support the statement. One example (see page 58) about
cross-contamination states, “there appears to be more DA from the
cross-contaminated controls versus the blank minideck controls.” No
statistical analysis follows and Table A-7 in Appendix A does not
provide much insight into the issue. 

	No distinction is made in DCCA between water-soluble and insoluble
particulate forms.  This is unfortunate, because such information would
have spoken to both the extent of hazard actually encountered, and to
the best manner in which it could be addressed.

What other conclusions might be drawn from the data?

	The Panel believed that in order to draw other conclusions from the
data, further data analysis would need to be done. For example, it would
be interesting to see if more analysis can be made on the effects of
weather and DA.  This interest stemmed from the segment of plateau
during December-April in some scenarios, more evident in the EPA study
than the CPSC staff study.  The analysis with weather data also may lead
further into the interaction of multiple weather variants (radiation,
precipitation and temperature) which in turn may inform what is needed
for modeling the behavior of coatings on DA for other weather types and
geographic locations in the U.S.

	With a little effort it might be possible to compare the results of the
two studies.  To the extent possible, whether it is about weather or
other factors in the study design, the similarities and differences with
respect to the outcome on DA can be a valuable first step in looking to
see if these and other existing data can be used to address different
exposure scenarios.

	These are the first studies attempting to quantify reductions in DCCA
using selected coatings on CCA-treated wood.  Given the large volume of
CCA-treated wood currently in use, and that there are over 100 different
coatings available for use in retarding moisture adsorption in wood, the
results of these two studies are a respectable start for this research
focus.  However, the current database needs to be significantly expanded
before the methodologies will be accepted by the coating industry, wood
treaters, or consumer groups.  All standard tests used by the wood
industry (ASTM, AWPA, etc.) require many studies before they are
accepted.

 

	The data suggest that the effect of washing/preparation may be as
significant as some coatings. However, it would be desirable to think
about procedures that will not cause downstream problems such as those
that could occur when paints and other coatings fail and potentially
create bigger problems.

	The Panel was concerned that artifacts may be produced by the wipe
method. This might be resolved by using a scanning electron microscope
to create maps of individual elements.  Instead of scanning for all
elements at a given spot, the EDAX analysis (energy-dispersive analysis
of X-rays) can be set to a single element (energy level) and a
dot-density image created that represents the distribution of the
element in question over the image surface.  At low magnifications, this
technique can be used to unequivocally answer the question of whether
the wiping technique actually removes the element in question, or merely
moves it around on the surface of the panel being tested.

	While not specifically tested or proved, the data in the report suggest
that the preparation steps might prove to be of significant value in
mitigation, separate from any coating steps.  They are significant
because non-coating solutions could be developed which are simpler and
less expensive and would not suffer the drawbacks of re-coating after
relatively short times.  This issue is discussed in the response to
later questions.

Charge Question 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?

Panel Response

	The Panel's responses to Questions 1 and 2, which include extensive
discussions of the statistical analysis and whether the results can be
extrapolated to broader conditions, have largely addressed Charge
Question 3.

	The graphical analyses, supported by mixed model analysis of variance,
indicate that some cleaning and coating processes can reduce DA by a
factor of 10 or more for a few months.

	Because the decks were not subject to normal use, which is likely to
abrade and degrade the coatings faster than weathering alone, the
indicated duration of DA reduction can only be taken as an upper bound
for the coatings and preparation processes studied. On the other hand,
the selection of coatings and surface preparation methods was limited
and it is possible that longer durations could be achieved.

	Perhaps this is already enough information for deciding whether or not
to pursue the idea of coating existing decks and play structures to
reduce exposure to arsenic. However, this Panel is only looking at
mitigation of exposure. Without an understanding of the associated risk,
one cannot determine whether or not the observed reduction in DA is
enough to mitigate the risk to children.

	Both the EPA and the CPSC staff studies are limited by the restriction
to yellow southern pine, non-random choice of location, and limited
number of sources of the wood. The CPSC staff study, in particular, is
limited by the confounding of coating type with mini-deck. This
restricts extrapolation of the results. The general agreement between
the two studies gives some assurance that the results will be
reproducible in a better-designed study.

	The statisticians on the Panel agreed that an improved statistical
analysis would not change the conclusions or make the result more
general; however, it would be worth including a random effect for board
and plank within board in the EPA study. Including a sapwood/heartwood
factor may also be worthwhile. It would be worth repeating the analysis
in original rather than logarithmic units to see if that changes any of
the conclusions.

	The documentation for both studies is not easy to read, but is thorough
and, for the most part, clearly states the limitations of the studies. A
discussion of the compound symmetry assumption is needed (see Panel's
response to Question 1). A more forthright discussion of sources of
variability in the analysis models would be useful for future study
design, particularly in the calculation of sample sizes required to
achieve the desired power in the statistical tests.

Charge Question 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.

Panel Response

	The objective of these studies was to evaluate the impact of surface
coatings on the level of DCCA from CCA-treated wood. Other specific
issues such as the impact of abrasion and coating reapplication were not
examined and, therefore, are not adequately accounted for in these
studies. This question addresses essentially an extrapolation of the
study results to factors not tested in the current experiments.  The
statistical models used to analyze the study data can only be used to do
a very limited amount of extrapolation.  The larger issue is what other
information can be used to perform this extrapolation?  Does the
extrapolation have to be quantitative or qualitative? There was
discussion among the Panel about how the data from these studies, along
with qualitative information from the over 50 years of research on
coating of CCA wood products, should allow a qualitative assessment on
the impact of abrasion and coating reapplication.

	The original question was whether surface coatings could reduce levels
of DA. It now appears that the preparation of the wood may be as
important as the coatings themselves in reducing DA. The studies have
confounded the coating with the preparation and are not able to answer
this question. If the preparation removes the surface arsenic, then the
process may be hazardous to the applicator and may increase the toxicity
of the soil under the structure. This would require a study of its own.

	It is important to note that in the EPA study the effect of abrasion
due to repeated wiping of the sampling areas seems to indicate that this
type of abrasion may have had the effect of temporarily cleaning up the
sampling areas, although there was no significant influence on the DCCA
levels by the number of previous wipes (NOPW factor), which was
described as a surrogate for the effect of abrasion at each sampling
event.

	The authors of the EPA study state that they did not examine the impact
of abrasion on the measurable DCCA.  Abrasion has been identified as an
important variable in coating performance.  The EPA study recommends
additional testing to examine the effects of abrasion including
simulating foot-traffic on the deck surfaces.  However, this particular
issue is very complex because the extent of UV degradation of the
treated wood surface and coated wood surface, surface preparation prior
to application of the coating, moisture content of the wood surface,
history of past and current surface and coating treatments, and wood
characteristics are some of the many confounding variables related to
the effects of abrasion.  

	The study design also did not control the time period for each wipe
stroke because the time for the polyester wipe material to traverse the
test section of the different boards was influenced by the board
roughness.  The authors are aware that these issues may have influenced
the differences in DA observed between the two sources of deck material.
 The experimental design and sampling method did not differentiate
between dislodged treated wood particles and soluble DCCA.  The study
design did not address the impact of particle collection on coating
performance.

	The authors of the EPA study state in the Executive Summary that the
results of the study suggest that the coatings need to be periodically
reapplied to maintain DA mitigation compared to an uncoated treated
board.  They also state that it appears a one-year recoat schedule would
be appropriate for the conditions tested in the study.  Different
geographic locations, different coatings, and a significant abrasion
component to the experimental design may change the time frame from the
one-year recoat recommendation.  The CPSC staff report recommends that
applying oil- or water-based penetrating stains to CCA-treated wood
structures every one to two years may reduce arsenic availability.  They
also state that their experimental design did not include abrasion to
simulate in-service use.  The frequency of reapplication is product
dependent and is influenced by weather conditions, geographic location,
the condition of the wood, and use patterns of the structure.

	Coatings were applied based on manufacturers' recommendations.  These
recommendations varied with regard to surface preparation steps prior to
application of the coatings and number of coats applied.  The study
design did not examine the question directly as to the effectiveness of
multiple coats versus single coats or reapplication of coatings.

	Additional studies would be needed to specifically evaluate the impact
of coating reapplication on the dislodgement of CCA components.  The
reapplication of coatings to a treated wood surface is a complex issue
that is influenced by a considerable number of parameters.  In addition,
coating formulations are constantly being reformulated in an effort to
improve their effectiveness, in particular, moisture excluding
effectiveness.  Neither of these studies attempted to examine the
moisture excluding effectiveness of the coatings.  Moisture is related
to abrasion.  Surface checking in wood surfaces exposed to changes in
the moisture content of the wood surface is a result of adsorption and
desorption of the moisture from the wood surface.  Abrasion, surface
checking, and UV degradation will directly influence the formation of
dislodged treated wood particles.  Adsorption and desorption of moisture
from the surface of the wood, along with abrasion, surface checking, and
UV degradation, will influence the amount of  soluble DCCA.

	In the coatings industry, substrate preparation is crucial to the
subsequent performance of all coatings systems.  Such preparation is not
just helpful, advisable, or useful; it is absolutely essential.  The
significance of this is:  

	(1) Substrate preparation is the major determinant of the lifetime of
subsequently-applied coatings.  Lifetimes can vary by factors of 2-5,
simply due to differing degrees of preparation.  This plays a major role
in the time interval for performance before recoating is needed.

	(2) Experience suggests that it is likely that a well-designed future
study would show that a proper preparation step is at least as
significant as the use of coatings in achieving mitigation of DCCA, and
might even obviate the need for coatings to achieve the desired
reduction in DCCA.  

	(3) Some of the substrate preparations involved the use of oxidative
cleaners.  This is ill-advised for CCA-treated woods, since it will both
oxidize and solubilize the treatment chemicals, which will increase
their bioavailability.  It will also alter their toxicity:  for example
the chrome can be oxidized by such cleaners to Cr6+, which is
carcinogenic.

	(4) While manufacturers’ recommendations for substrate preparation
were followed in the present studies, the consequence is that this
became yet another uncontrolled variable, since manufacturers don’t
have common recommendations.  It should also be remembered that such
label information is a negotiated settlement among the various
constituents in a given company, including legal, and does not
necessarily represent the best scientific advice of their R&D
departments.

	(5) It is possible that there are simple chemical pretreatments, e.g.
precipitants, that could adequately reduce future DCCA, so as to obviate
the need for coatings.  Such treatments could be simpler to use,
cheaper, and would eliminate the need to deal with the inevitability of
future failures of the coatings system, which will require further
preparation and recoating.  Such treatments could be applied as part of
the substrate preparation step.

	The issue of re-application of coatings after the initial coating has
failed is not covered in the study.  While that is understandable, given
the scope of the study, some comment is needed in the report that the
use of coatings must be considered in the context of both their initial
properties, plus the steps (and frequency) needed to properly maintain
the coatings and their desired effects. 

	The issue of abrasion is relevant to the bare, uncoated pressure
treated wood, as well as any coating that may be subsequently applied to
the pressure-treated wood.

	The impact of abrasion and coating reapplication issues were not
examined in either study, but have been identified in both studies as
being important issues. These studies have highlighted the need to
conduct additional studies specifically designed to evaluate the
dislodgement of CCA components resulting from foot-traffic abrasion on
in-service decks.  In addition, because of the complexity of the
interactions of a number of variables with both of these issues, it is
difficult to account for these data gaps sufficiently in the discussion
of the results and subsequent recommendations.  More detailed studies
are needed to address these issues.

Charge Question 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.

Panel Response

	Performance characteristics of any wood coating should be determined by
its desired end use. In this instance, performance characteristics of
coating products for reducing levels of DCCA on wood structures outdoors
is desired. Thus, if claims are to be made that a particular coating
product reduces the levels of DCCA from CCA-treated wood, then it must
be subjected to more extensive evaluation under a wider range of
climatic conditions. In the current studies, a limited set of coating
products were evaluated in only two contiguous climatic regions, the
lower Mid-Atlantic and upper Southeast regions (Maryland and North
Carolina). It is desirable that these studies be conducted in all the
different climatic regions in the continental United States, namely: (i)
the Northwestern, (ii) the High Plains,(iii) the Midwest/Ohio Valley,
(iv) the upper New England/Mid-Atlantic, (v) the lower Southeast, (vi)
the Southern and (vii) the Southwestern climatic regions.

	The primary mode of failure of coatings over wood is that of cracking
(initiation) followed by flaking and peeling (propagation). Traffic
abrasion accelerates the removal of the flaking/peeling coating, but
does not materially influence the initiation. The coatings and forest
products industry routinely use two locations:  northern Snow Belt and
southern (typically Florida) region.  The former maximizes cyclic
stresses that accelerate cracking, while the latter maximizes
photochemical degradation and biological fouling.  The reports state
that coatings may be useful for mitigation for one to two years;
however, the time interval of usefulness could be reduced by a factor of
two to five if the same studies were conducted in the Snow Belt. Thus,
extrapolating the results from these two studies to other climatic
regions may be premature.

	It is also important to note that in these studies the wood coatings
were evaluated for a performance characteristic for which they were not
originally designed. Therefore, in addition to climatic conditions, the
effect of the wood substrate on their performance characteristics for
this “new” end-use warrants further investigation. For example in
addition to southern yellow pine, other wood species such as
hemlock-fir, Douglas-fir, spruce-pine fir, red pine, ponderosa pine and
radiata pine should be considered for evaluation in future studies.

	Evaluation of the effect of normal use, and wear and tear on the
performance characteristics of coatings in mitigating DCCA levels is
complex and difficult and cannot be completed within the limited
timeframes as was the case with the current studies. It will require a
separate study design and protocol. Elements of such a study design and
protocol may include new and aged decks built from different wood
species. In addition, the use patterns of decks selected for the study
would have to be meticulously monitored both before and during the
conduct of the study for a period of no less than two years or until
failure.

	The simple conclusion, that some coatings make a difference, is clear
enough. Before the EPA or CPSC staff conduct a more definitive study,
the coatings industry should be invited to develop products with
specific characteristics intended to reduce DCCA levels on CCA-treated
wood. The new study should be designed to test whether these new
products meet specifications.

	We are still far from being able to make a recommendation to the
consumer. The choice might be to recoat every two years for the life of
the deck, or replace the deck and dispose of the CCA-treated wood. We
aren’t even sure if the expected reduction in DCCA levels from coating
alone is enough to affect potential health risks to children. These
studies did not address potential health risk to children and the Panel
was not asked to determine if the reduction in DCCA levels reduced such
risk.

Charge Question 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.)?

Panel Response

	These are the first studies attempting to quantify reductions in DCCA
using selected coatings on CCA-treated wood.  Given the large volume of
CCA-treated wood currently in use and the fact that there are over 100
different coatings available for use in retarding moisture adsorption
and absorption in wood, the results of these two studies are a
respectable start for this research focus. However, the current database
needs to be significantly expanded before the methodologies will be
accepted by the coating industry, wood treaters, or consumer groups. All
standard tests used by the wood industry (ASTM, AWPA, etc.) required
many studies before being accepted.   

	The Panel discussed the utility of the experimental protocol and/or
modifications of this protocol and suggested that at an appropriate
point, a challenge be issued to the coatings and wood treatment
industries to develop products designed to reduce DCCA to levels that
may be determined to be appropriate.

	The wipe testing device and protocol represent an excellent starting
point for sampling a surface for removables.  As such, it should be of
interest to others, including the coatings industry, wood treaters, and
consumer groups.  However, the test will need further development before
it reaches the level of approved standard testing procedure.  Examples
of issues that should be considered in future enhancement of the wipe
methodology include the following:

Concern was expressed about the low correlation in the EPA-CPSC staff
wipe calibration studies. The scatter plots are not given.  Were the
correlations computed on a log or linear scale?  Was the range of
concentrations wide enough?  Did it cover the whole practical range of
concentrations?

Procedures for the wipe test are different in the two studies.  The
procedures for analyzing and obtaining baseline uncoated results for
comparison to the results for the coated specimens need to be evaluated
and, if needed, modified for future studies.  

Since moisture is critical to the soluble portion of the DCCA, the
surface moisture content of the wood substrate at the time of sampling
needs to be part of the data collection and analyses.  

The wiping protocol results in splinters being picked up from older
pressure-treated wood and represents a problem in data analysis by
biasing the results from older wood sources.  The protocol should be
adjusted to include the removal of all splinters before conducting
analyses, or alternately, one could analyze splinters separately from
non-splinter wipings to determine the magnitude of this potential
problem.

Soluble and particulate DCCA need to be separately quantified.

The sampling method and sampling apparatus developed by CPSC staff needs
to be standardized:

size of the sampling area 

the number of sampling strokes 

the travel time per stroke of the sampling disk

type of sampling cloth, size, and its moisture content 

extraction methodology of the CCA chemicals from the sampling cloth 

	The goal of the wipe methodology is to determine material present on
the surface of pressure treated woods, and to estimate from that what a
child might pick up.  The polyester material and method used in this
study is well correlated (r = 0.86) with hand collection when measured
with a rinse-wipe-rinse technique (Thomas et al., 2004).  However, the
dry wipe method captured approximately 3-4 times as much as did a hand
when both are rubbed a comparable number of times over the surface. 
Additionally, a wet wipe collects about twice as much as a dry wipe.  In
spite of these differences, the correlations between cloth and human
hand wiping remain essentially constant and high.

	In one of the CPSC staff experiments, the amount collected in a series
of 4 consecutive wipes was measured.  The quantity collected declined
from about 500 µg (wet) and 200 µg (dry) on the first pass to about
150 µg (wet) and 0 µg (dry) on the 4th pass.  In the CPSC staff field
study, the differences for some experiments were as great as 10 times
depending on the surface.  The saline-wetted polyester surrogate has
effectively a lower detection limit than that of the dry polyester
surrogate (Levenson et al., 2004). In other words, for the same
hand-wipe amount, the saline wetted polyester surrogate will pick up
more arsenic than the dry polyester surrogate, resulting in a greater
detection ability for the saline-wetted polyester surrogate (Levinson et
al., 2004).  From a risk point of view, this wipe method appears to be
conservative because it captures more than might be expected from a hand
wipe, and is, therefore, desirable, if one can have confidence that it
reflects what will adhere to a child’s hands, food, or objects that
may be mouthed. One could then simply calculate transfer coefficients.

Data reduction and analysis:

	Reduction of experimental measurements of DCCA levels for statistical
analysis should be standardized.  For example, in the CPSC staff study
the experimental outcome was reduced to the amount of DCCA measured at a
specific time point relative to the baseline amount, whereas the EPA
study compared the amount of DCCA measured at a specific time point from
coated specimens to the amount of DCCA measured at a specific time point
from control uncoated specimens. Although both approaches led to the
same conclusions, this element of the protocol does warrant
standardization.

Normalization of data:

	While direct normalization (CPSC staff approach) and ANOVA with
covariates (EPA approach) produces the same statistical results,
experience in the coatings industry has shown that direct normalization
does a much better job of filtering out experimental noise and
differentiating among coatings types in exposure experiments.

Charge Question 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?

Panel Response

	The EPA and CPSC staff studies investigated the impact of a set of
coating products on southern yellow pine specimens that are either new
(never been in service) or aged (one and seven year old decks).  In
general, the studies were well presented in the reports for review.  
Both studies demonstrated a fairly consistent pattern of initial DA
reduction when coatings were applied according to the manufacturer’s
recommendations that varied for each product (e.g., pre-coating
treatment, number of coats).  The Panel recognized that while one might
argue as to whether all of them were appropriate as agents to reduce the
DA, they could reflect what people might actually do.

	Although both studies are of sufficient quality for the observations on
certain aspects of DA reduction, limitations of the breadth of these
studies do not allow for developing strong and unassailable conclusions
about the pattern for the types of coatings to reduce DCCA from treated
wood surfaces.  Under the experimental conditions, the longevity of the
effects of DA reduction varied within each selected coating and between
coating products.  It is also uncertain as to how these data can be used
in estimating human exposures since some key factors representing the
real-life situations were not a part of the testing design (e.g.,
abrasion, woods other than southern yellow pine, climatic effects of
different geographic locations).  There may also be regional differences
in the formulation of coating products designed to accommodate climatic
conditions and types of woods that are available.

	These studies also did not allow a clear conclusion as to whether
coatings are the best for DA reduction, or most economical or most
desirable approach.  Nor can the studies prove which types of coatings
are best or most desirable.  Just as the study is suggestive that
coatings likely differ in their effectiveness, the evidence from these
two studies suggests that the pretreatment steps can be highly
significant and useful in mitigating DCCA.  The Panel also contemplated
the needed context to defining whether coatings substantially reduce
DCCA.  It was understood that the Agency is proactive in carrying out
these two studies in preparation for when and if mitigation may be
deemed necessary.  A better context for understanding the significance
of DCCA reduction as seen in these two studies can be obtained after the
Agency completes its risk assessment and determines the target exposure
level for public health protection.  

	The two groups of investigators are to be commended for setting the
benchmark for new study protocols and future data collection and
evaluation on DCCA reduction.  These studies provided the first solid
scientific foundation for a more thorough and rigorous investigation of
the effect of coatings on release of CCA chemicals from CCA-treated wood
used in outdoor structures such as decks and children’s play
structures.  These include informing an understanding of the complexity
of testing coating products for an end-use purpose for which they were
not originally designed, and highlighted and delineated those factors
that need to be incorporated into standardized testing protocols
designed to evaluate the efficacy of coating products for reducing DCCA
levels in CCA-treated wood surfaces.  

	From the standpoint of collecting data to inform the mitigation of
children’s exposure to arsenic from CCA-treated wood, future data
collection should be guided by how it can be applied to modeling the
real life exposure scenarios.  For example, one of the impressive
findings in these studies is the inherent variability in the type of
data such as changes in DA by coating.  Properly characterized, they can
be effectively used in probabilistic exposure models.  Another area in
which data may be used is to determine how to provide linkage such that
the current wipe sampling method can be adapted to reflect the real-life
exposure scenarios for hand-to-mouth activities of young children. 
Understandably, all of these considerations are predicated by knowing
the target level of acceptable exposure.  Knowing the target level would
help inform the extent to which the reduction of DA is deemed
sufficient, and would also inform the level of detection limit in the
chemical analysis.

Panel Suggestions for Future Research Efforts

	The Panel made a number of suggestions for future directions for data
collection.  One area is to more thoroughly utilize the information that
is currently available, especially since  these two reports did not
particularly mention how extensively the Agency looked into the existing
knowledge base related to the movement of CCA in woods and coating.  The
Agency is encouraged to make use of current information to enhance its
understanding for the ultimate goal of finding viable ways to reduce
DCCA.  The Agency is also encouraged to collaborate with bodies of other
expert panels who are familiar with coatings and photodegradation
responses, another important component in the performance outcome of
coatings. The complexity of the issue of reducing DCCA through coating
would argue strongly for the development of an overall conceptual model
that provides a context for current and future studies.  What does the
literature have to say about various processes involved in affecting
DCCA? What are the physical processes with which we are dealing? What do
we know about weathering of wood; of CCA treated wood; of erosion of
wood from the deck surface; of abrasion processes; of the composition of
coatings; of the relationship of substrate and coating composition; of
the moisture exclusion aspects of the coating; and of delamination of
the coating as a function of climate?

Additional Considerations for Future Experimental Design Needs:

Consider developing and evaluating results from different climatic
conditions and geographic regions that may place more or less stress on
the coatings

Consider age-in-service and effects of abrasion. 

Coating formulations are important to understanding the relative
performance of different classes.

Coating products should be tested on substrate/s for which it will be
used. 

Substrate issues should be standardized:  e.g, dimensions and age of
test specimens; the surfaces of test specimens, including orientation of
the growth rings to the surface to be tested; density; and sapwood
versus heartwood.  

It will be difficult to have more than one treatment on the same
mini-deck if they require different preparations, unless the planks were
individually treated and coated prior to assembling the mini-decks.

Consider using scanning electron microscopy techniques for remote
assessment and low level spatial analysis using dot density imaging of
each element separately to better assess the wiping technique. This
could help determine the adequacy of removal of the items under study
vs. merely moving them around.

Soluble and particulate DCCA need to be separately quantified.



REFERENCES

Cullen WR, McBridge BC, Pickett AW and Reglinki J. 1984.  The wood
preservative chromated copper arsenate is a substrate for
trimethylarsine biosynthesis. Appl  Envir Microb. 47 (2): 443-444.

Levenson MS, Thomas TA, Porter WK, Cobb DG, Davis D, Midgett JD,
Saltzman LE, Bittner PM. 2004.  A Field Study of Dislodgeable Arsenic
from CCA-Treated Wood Using Human-Hand and Surrogate Wipes.  J Child
Health. 2(3-4): 197-213.

Thomas TA, Levenson MS, Cobb DG, Midgett JD, Porter WK, Saltzman LE,
Bittner PM.  2004.  The Development of a Standard Hand Method and
Correlated Surrogate Method for Sampling CCA (Pressure)-Treated Wood
Surfaces for Chemical Residue.  J. Child Health. 2(3-4): 181-196.

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