Document ID: EPA-HQ-OPP-2006-0606-0015
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-01-10T05:00Z

SEQ CHAPTER \h \r 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

  SEQ CHAPTER \h \r 1 OFFICE OF

PREVENTION, PESTICIDES AND TOXIC SUBSTANCES

MEMORANDUM

SUBJECT:	Alternatives Assessment of Acid Copper Chromate (ACC) for
Residential Wood Treatment

FROM:	Andrew Lee, Economist	

Economic Analysis Branch

		Leonard Yourman, Biologist

		Richard Michell, Biologist	

Biological Analysis Branch

Biological and Economic Analysis Division (7503C)

THRU:		Richard Keigwin, Division Director 	

Biological and Economic Analysis Division (7503C)

		Arnet Jones, Chief 	

Biological Analysis Branch

Biological and Economic Analysis Division (7503C)

TO:		Mark Hartman, Chief

Reregistration Branch

Antimicrobial Division

Timothy Leighton, Senior Scientist

		Antimicrobial Division 

PRODUCT REVIEW PANEL: December 6, 2006

 

Summary:

BEAD conducted an alternatives analysis for acid copper chromate (ACC)
in support of the OPP regulatory decision on the registration of the ACC
products as the general use wood preservatives.  The analysis was
limited to the alternatives assessment for residential playground
equipment and deck uses.  The analysis focused on comparing the costs of
playground equipment and decks constructed of ACC-treated wood and wood
treated with currently registered chemicals, as well as non-chemical
alternatives such as plastic lumber and naturally durable untreated
wood.  The BEAD analysis determined that there are registered chemical
products available for residential uses that are feasible alternatives
to ACC although these alternatives result in playground equipment and
decks that are slightly more expensive than ACC-treated counterparts.   

Background:

  SEQ CHAPTER \h \r 1 Wood preservatives are applied to protect wood
from damage by bacteria, fungi, insects,

or marine borers.  The wood preservative industry provides treated wood
for industrial (railroad and electric utilities, pilings and bridge
construction timbers), commercial, and residential uses.  There are
three major wood preservatives for the industry users:   SEQ CHAPTER \h
\r 1 chromated copper arsenate (CCA), pentachlorophenol, and creosote. 
These three wood preservatives account for about 97% of all wood
preservatives for industrial purposes.  At the request of the
registrants, EPA revised CCA’s label to limit its use primarily to
industrial applications effective December 31, 2003 (69 FR 17366).  CCA
had most of the residential market until its cancellation in 2003. 
Currently, several chemical wood preservatives are available for the
residential market: ACQ, copper azole, copper naphthenate, copper
citrates, copper dimethyldithiocarbamate, copper-HDO, and polymeric
betaine.  

ACC was registered as a general use wood preservative in 1994 by Osmose,
but until recently, it was sold, for a brief period of time, as a
treatment of wood in cooling towers.  Since then, the Forest Products
Research Laboratory (FPRL) requested a general use label for an ACC wood
preservative product.  On May 30, 2006, based on the Agency risk
assessment, the EPA approved a registration for the ACC wood
preservative only for commercial and industrial uses.  The industrial
applications now registered to FPRL are not expected to result in
significant exposures to the general public.  

Based on the EPA risk assessment, there are several risks of concern. 
Workers in wood treatment facilities are expected to be potentially
exposed to Cr+6 as a result of the pressure treatment process and
handling treated wood.  Workers in manufacturing facilities that make
finished wood products can also be potentially exposed to Cr+6 by
contacting wood surfaces and by inhalation resulting from sawing
operations.  Similarly, contractors or consumers that build decks and
playsets could potentially be exposed via the dermal and inhalation
routes.  

Chemical Alternatives to ACC in Lumber and Timber Market:

The American Wood Preservatives Institute (AWPI, 1997) estimated that 75
billion board feet of pressure-treated wood were in use nationwide,
primarily in the residential settings such as playground equipment,
decks and fences.  Currently, chemical wood preservatives for use in the
lumber and timber market are: ACQ-C and D, copper azole -A and B, copper
naphthenate, copper citrates, copper dimethyldithiocarbamate, copper-HDO
also called Copper Xyligen (CX-A), and polymeric betaine.

Of these chemicals, ACQ is a dominant wood preservative.  Copper azole,
Copper-HDO, and polymeric betaine are also approved for use in the
lumber and timber market.  However, they are relatively new and only a
few facilities are using these preservatives (EPA proprietary report)
suggesting that they would not capture a large share of the residential
market in lumber and timber.  

Copper naphthenate is also approved for use in lumber and timber market
and has been in use in this market.  However, specific information was
not available on the extent of its use in this market.  It is likely
that copper naphthenate would capture a part of this market, but further
information is needed to determine the specific uses for which it is
more suitable.

Other alternatives such as copper citrates and copper
dimethyldithiocarbamate are approved by AWPA for certain lumber and
timber uses but they have limited commercial use (EPA proprietary
report).  These chemicals are unlikely to capture any of the lumber and
timber market for residential uses in the short run. Major preservative
manufacturers have also indicated that improvements in current products
and pipeline alternatives are expected to impact the marketplace. 

Table 1 shows costs of chemical wood preservatives.  As shown in the
table, ACC is much cheaper than ACQ.  However, this low chemical cost
does not translate into low prices for the final products (playground
equipment or decks) because chemical costs are a small part of the cost
of treated wood.   

Table 1. Costs of Chemical Alternatives per Gallon. 

CCA1	 $1.10 to $1.35 

	ACC2	 $       1.40 

ACQ	 $       4.00 	 	 	 	 	 	 

Source: Personal communication with Bill Price at Madison Wood.

	1 CCA use in the residential lumber and timber was cancelled in 2003.

2ACC is made by dissolving a 32% copper source with a 68% chromium
source.

Table 2 shows cost estimates for residential playground equipment
constructed of alternative materials.  For these cost estimates, a
playground consisting of a platform with vinyl cover, sliding board, two
swings and one additional piece of equipment (climbing rope, carriage
ride, trapeze rings, etc.) was used as a model.  In general, equipment
constructed of plastic lumber (recycled plastic) and naturally durable
untreated wood (redwood and cedar) are more expensive than those made of
chemical treated wood.  Since chemical costs of ACC and CCA are
comparable (see Table 1), we assumed that costs of playground equipment
constructed of ACC treated wood would also be comparable to those of CCA
treated wood.  Thus, in Table 2, the cost of playground equipment made
of ACC treated wood is the average of those of CCA treated pine.  As
noted above, comparison of ACQ- and ACC-treated equipment shows that the
former are not as expensive as the chemical costs of ACC and ACQ in
Table 1 would imply.  Playground equipment with ACQ treated wood costs
10% to 70% more than ACC treated playground equipment whereas ACQ
chemical costs 3 times more than ACC chemical as shown in 

Table 1.  The price variability in the cost of the different playground
equipment listed in Table 2 may be due to other costs such as
design/engineering costs, cost of the treated wood and other materials
used in the manufacturing processes.  The playground equipments listed
below in Table 2 are not made by the same manufacturers and they are not
identical. 

Table 2.  Cost Estimates for Residential Playground Equipment. 	 

Playground Manufacturer and System	Cost	 	Material

Play Mart Playgrounds Gator	 $             2,400 

Recycled Plastic

Play USA Outpost	 $             2,200 

Recycled Plastic

Rainbow Play Systems Carnival Clubhouse	 $             2,100 

Redwood

Play USA Outpost	 $             2,000 

Cedar

Rainbow Play Systems Backyard Circus	 $             1,700 

Redwood

PlayNation Play Systems Palace	 $             1,500 

ACQ Treated Pine

Play Kids Fun Swing Climber Model #3	 $             1,000 	 	ACQ
Treated Pine

Swing-N-Slide Shuttle Tower	 $                900

CCA Treated Pine

Detailed Play Systems Jungle Fort	 $                850

CCA Treated Pine

Playset	 $                9001

ACC Treated wood

Source: Lowe’s, Home Depot, K-Mart, Wal-Mart, Toys-R-US, playground
specialty outlets in the suburbs between Washington, DC and Baltimore,
MD, October 2001.

1The average of playground equipment made of CCA treated pine.

Tables 3 shows cost estimates for decks constructed of alternative
materials.  These costs represent the material costs for a 15' x 20'
deck with a railing on three sides (50 feet) located six feet off of the
ground (10 steps) (http://decks.com/).  As shown in the table, decks
constructed of plastic lumber and naturally durable untreated wood are
considerably more expensive than those made of chemical treated wood. 
Again, despite a large difference in the chemical costs of ACC and ACQ,
ACC- and ACQ-treated decks do not differ much in cost.  ACQ treated
decks cost only 3% more than ACC treated decks.  As mentioned above, the
cost of a CCA-treated deck was used as a proxy for the cost of
ACC-treated decks.  Cost differences between ACC and ACQ treated decks
(3%) are smaller than that between ACC and ACQ playground equipment (10%
to 70%).  This may be due to the additional non-wood material required
in the manufacturing of the playground equipments and cost of design and
engineering.

 

Table 3.  Costs of Decks1 Constructed of Alternative Materials.

Deck material	Cost of deck1 	% difference compared to ACC treated pine

ACC treated pine 	 $        1,9452 

	ACQ treated pine 	 $        2,000	3%

Cedar	 $        2,330 	20%

Redwood	 $        2,695 	39%

Composite plastic	 $        3,090 	59%

Recycled plastic	 $        3,500 	80%

1Cost of material for a 15' x 20' deck with a railing and 10 steps
(http://decks.com/ and the Home Depot).

2 Since chemical costs of ACC and CCA are comparable (Table 1) the cost
of a

  CCA treated deck is used as a proxy for that of an ACC treated deck.

3An estimate from the Home Depot.

Efficacy of Wood Preservatives for Residential Uses:

The American Wood Preservers’ Association (AWPA) is a non-profit,
technical association founded in 1904 to provide a common forum for
exchange of technical information between industry, research and users
of treated wood.  AWPA is the principal standards-writing body for wood
preservation in the United States.  Individuals with various areas of
interest including consumers, users, government, academia, specifiers
and producers meet on regular basis to develop and maintain these
standards for preservatives, treatment, testing methods, quality
control, and inspection of treated wood products.

Table 4 lists efficacy of wood preservatives for residential uses.  As
shown in the table, ACC is as efficacious as the currently registered
wood preservatives according to the AWPA standards.  Polymeric Betaine
is still being investigated at the task group level.  The data regarding
this preservative system has not yet been formally proposed to AWPA
technical committees at this time.  Therefore, there is no listing of
this system.

Table 4.  Uses of Chemical Alternatives to ACC Products.

AWPA Std.1

	

Uses	

Alternatives 2,3

C2 4	

Lumber and timber for above ground, soil and fresh water use	

ACC, ACQ, ACZA, CBA,CC, CDDC, Creosote & creosote solution,
Pentachlorophenol, Copper Naphthenate, and C8Q

C5	

Fence posts	

ACC, ACQ, ACZA, CC, CBA, Creosote & creosote solution,
Pentachlorophenol, and Copper Naphthenate

C15	

Wood for commercial-residential construction: To include studs, roof
decking, decking exposed to weather, flooring, sawn post and columns
supporting decks, posts, square fence, fencing slats, pickets, landscape
ties.	

ACC, ACQ, ACZA, CBA, CC, CDDC, Creosote & creosote solution,
Pentachlorophenol, and C8Q

C16 5	

Wood used on farms, including fence posts, lumber, millwork and grape
stakes.	

ACC, ACQ, ACZA,CBA, CDDC, CC, Creosote and creosote solutions,
Pentachlorophenol, Copper naphthenate, and C8Q

C17	

Playground equipment	

ACQ, ACZA, CBA, CDDC, and C8Q

C22	

Lumber and plywood for permanent wood foundations (residential and light
commercial)	

ACQ and ACZA

UC1,UC2,UC3-46

	

For use in sawn products (boards, lumber and timbers, above ground
only.7	

CX-A

	Source: American Wood-Preserver’s Association Standards 2001.

American Wood-Preservers’ Association Standards 2001.

The alternatives include:

	ACC =	Acid Copper Chromate: Combination of Copper Oxide and Chromic
Acid

	ACQ =	Ammoniacal Copper Quaternary: Combination of Copper Oxide
(042401) and either ADBAC (069105) or DDAC (069149)

	ACZA = Ammoniacal Copper Zinc Arsenate

	CBA =	 Copper Boron Azole/ aka., Copper Azole: Combination of metallic
Copper (022501), Boric Acid (011001), and an Azole compound such as
Tebuconazole (128997) or Propiconazole (122101)

	CC =	Ammoniacal Copper Citrate: Combination of Copper Hydroxide (PC
Code 023401) and Citric Acid (PC Code 021801)

	CDDC = Copper bis Dimethyl Dithiocarbamate: Produced from SDDC (034804)
and Copper Hydroxide (023401) at time of treatment

	C8Q =	Copper-8-Quinolinolate (Oxine Copper)

The alternatives may not be specified for use on all kinds of  wood. 
See the AWPA standards for more details.

Lumber and timber for salt water use only in this standard may still be
treated with CCA - See guidance doc.  CCA may not be used to treat
lumber and timber for above ground, soil and fresh water use, effective
January 1, 2004.

Some wood used on farms may still be treated with CCA, specifically
poles, piles and posts used as structural members and plywood.  CCA may
not be used to treat other wood used on farms such as fence posts,
lumber, millwork and grape stakes, effective January 1, 2004.

Provides a general description of the purpose and use of the Use
Category System set by AWPA.  

Commodity specification used by AWPA.  It covers general requirements,
minimum preservative penetration and retention requirements and
specification information.  

Non-Chemical Alternatives to ACC-Treated Wood:

In the lumber and timber market, alternatives to treated wood exist. 
These include vinyl or fiberglass, plastic wood composites, and recycled
plastic.  The main advantages of these alternative materials are that
they do not contain chemicals associated with pressure-treated lumber
and they can be recycled.  However, most of these alternatives are
expensive, costing 2 to 3 times more than treated wood (EPA proprietary
report).      

Alternative Materials

In 2000, the alternative materials market was estimated to be valued at
$250-$300 million (EPA proprietary report).  Its growth is expected to
be between 10-15% annually.  According to the Plastic Lumber Trade
Association (PLTA), the largest use for plastic lumber is for commercial
and residential decking (30-40%), followed by parks and recreation
(20-30%) and industrial/original equipment manufacturer
(OEM)/agriculture (20-25%).  Other uses include marine waterfronts,
railroad ties, material handling, and fencing.  The fastest growing
applications of alternative lumber are rails and decks. Composite lumber
has different structural characteristics and may not be a good
alternative for load-bearing uses of lumber or heavy timbers, such as
bridge timbers, crossarms, etc.

There are three types of alternative materials that are available for
use (EPA proprietary report):

1) Vinyl or fiberglass plastic lumber (no wood fibers) are engineered
plastic materials that can have a similar strength and weight to treated
wood.  The estimated sales of plastic lumber are $80-$100 million.

2) Plastic wood composites are a 50/50 mixture of polyolefins and wood
fiber.  Plastic wood composites are easier to cut and drill than pure
plastic lumber, have lower thermal expansion, better paintability, and
better traction.  Plastic wood composites have the largest sales among
alternative lumber types.

3) Recycled polyethylene plastic lumber (no wood fibers) is typically
reinforced with fiberglass and steel for added strength.

The disadvantages of alternative lumber include its weight, which can be
up to four times heavier than wood, and its lack of strength.  Higher
density of plastic lumber can also require pre-drilling prior to nailing
and screwing that can add to labor costs.  In addition, due to the low
stiffness-to-weight ratio, plastic lumber can cause creep (a measure of
deformation), which requires additional reinforcements and increases its
cost for many uses.  There is no consensus on the life expectancy of
alternative lumber.  Producers claim that it should last several times
longer than treated wood, while other industry sources state that life
expectancy is still undetermined due to its relatively recent market
entry.  

Since 1997, ASTM (American Society of Testing and Materials) has
established several quality standards and minimum performance
requirements for plastic lumber in residential decking.  The new ASTM
standards for plastic lumber should benefit plastic lumber manufacturers
since it would allow architects, specifiers, designers, engineers, and
others in the construction industry to understand better the benefits of
plastic lumber and its applications.  

Naturally Durable Wood

An alternative to ACC-treated wood is naturally durable untreated wood,
such as western red cedar, yellow cypress, eastern white cedar, or
redwood.  Switching to these alternatives, however, could have a
significant impact on forests and the forestry industry.  Availability
and long term durability of these woods could also be an issue as would
be their cost (EPA proprietary report).  These species are resistant to
decay in their natural state, due to high levels of organic chemicals
called extractives.  Extractives are chemicals that are deposited in the
heartwood of certain tree species as they convert sapwood to heartwood. 
Only the heartwood has these protective deposits. The sapwood of all
North American softwoods is susceptible to decay and must be chemically
preserved when decay resistance is required.  Sapwood is the newer part
of the tree, closer to the bark.  It needs no decay protection in the
live tree because wound responses keep out any invading organisms.  The
heartwood is the inner, older part of the tree and is no longer alive
(Canadian Wood Council, 2005). 

Limitations of the Analyisis:

Expert opinion was the only source of information for some of the data
used in the analysis.  

Conclusion:

For residential playground equipment and deck uses, BEAD determined that
there are several chemical wood preservatives that are economically and
technically feasible.  Although ACC is much cheaper than the available
chemicals, this lower chemical cost does not translate into
substantially lower prices for playground equipment or decks because
chemical costs represent only a small part of the cost of treated wood. 
For example, ACQ-treated decks are only 3% more expensive than
ACC-treated decks.  However, to the extent that ACC is cheaper than the
currently available chemicals there could be some benefits to society. 

	

There are also several non-chemical alternatives to treated wood
including plastic lumber and naturally durable untreated wood. 
Playground equipment and decks constructed of plastic lumber may be
expensive and lack strength.  For the naturally durable wood,
availability, long term durability, and cost could be issues.  The main
advantage of these alternatives is that they do not contain chemicals
associated with pressure-treated lumber.  Also, alternative lumber can
be recycled.

References:

Abt Associates, Inc.  “Draft Impact Assessment for Chromated Copper
Arsenate (CCA).”  2004.

American Wood Preservatives Institute (AWPI). 1997.

AWPA  Wood Preservatives Association, Standards 2006.

AWPA.  “Wood Preserving Plants in the United States.”  Prepared for
the American Wood-Preservers’ Association by James T. Micklewright,
Consulting Forest Products. 1997.

Canadian Wood Council, 2005.

Lebow, S. Alternatives to chromated copper arsenate (CCA) for
residential construction.  Proceedings of the Environmental Impacts of
Preservative Treated Wood Conference. February, 2004.

Table 1 Source: Personal communication with Bill Price at Madison Wood.

Table 2 Source: K-mart, Wal-mart, Toys-R-US, playground specialty
outlets in the suburbs of Washington, DC and Baltimore, MD, October
2001.

Table 3 Source:   HYPERLINK "http://decks.com/"  http://decks.com/ .

Table 4 Source: American Wood-Preservatives Association Standards 2001.

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