AWPA Penta Re-Affirmation Data Package For AWPA Standards P8.1 and P35-08

98 Pages·2010·3.28 MB·English

by  Mike Freeman

AWPA
Penta Re-Affirmation Data Package
For AWPA Standards
P8.1 and P35-08

April 9, 2010

By

Mike H. Freeman
INDEPENDENT WOOD SCIENTIST

Project Sponsor:
KMG-Bernuth and KMG Chemicals
Houston, TX
Executive Summary
In 2009, the AWPA Sub-Committee P-3 formed a Task Force for the Re-
Affirmation of Pentachlorophenol (Penta or PCP) in the AWPA Book of
Standards. This Task Force was chaired by Mike Freeman and contained the
following TF membership:
Mike Freeman (Chair)
Dick Jackson John Falcone
Less Lonning Denny Morgan
Rick Blesky Darryl Smith
Jim Brient John Wilkinson

The charge of the TF was to Re-Affirm penta in the AWPA BoS utilizing AWPA
Appendix I as a Guideline. The following is a summary of the Task Force
findings:
Review Existing Standard
The Standard for penta in the AWPA BoS has historically been listed as
Standard P8 section 1. In 2007, Freeman and Jung re-formatted the wood
preservatives into the new Preservative Standard format and issued it for
publication to Colin McCown, as AWPA Executive Vice President, which included
a DRAFT watermark until final review and re-affirmation. This Standard has been
reviewed and is now ready for full publication as AWPA Standard P-35, after
removing the DRAFT watermark. AWPA Standard P8.1 is also adequate, but it is
the Task Forces understanding, this Standard will soon be retired and archived
under the AWPA System, much like the Use Category System replaced the
Commodity Standards. The Task Force suggests both standards be re-affirmed
until all P-8 Standardized wood preservatives are archived.

Efficacy Data and Reports
A complete efficacy review is attached to this Data Package and covers over six
decades of testing and evaluation of penta as a wood preservative. Additionally,
attached as under Appendix I to this Data Package, are the following documents:
Freeman, et al, 2005. This study is report on the 53-year exposure of penta
treated wood pole stubs in southern Mississippi (AWPA Hazard Zone 5). This
report and study indicates that wood treated to 0.30 PCF penta in # 2 Fuel oil has
an estimated service life in AWPA Hazard Zone 5 of 74 years. It should be noted
that this retention is far below the current AWPA recommendation for wood utility
poles in this hazard zone.
Nicholas and Freeman, 2000. Is a Summary of over 11 years of laboratory and
field testing by the authors, funded by EPRI, of penta in different carrier systems,
which was also comparing these systems to penta alternatives. This study
indicates that the carrier systems themselves are not particularly effective in ¾
inch stakes, but have some influence on the efficacy of the dissolved biocide in
those same carrier oils.
Blew, et al, 1957, indicates that from his work at the USDA-FPL, penta is an
effective biocide against Formosan Subterranean Termite attack and long term
exposure to both native termites and Hazard Zone 4 & 5 decay conditions.

Product Performance
There have been no widespread failures of penta treated wood products in
service, other than Cellon treated wood poles, failing to Soft Rot. Annually,
sparse penta pole failures are noted by utilities, but investigation into many of
these indicate either poor initial treatment, or a lack of a periodic inspection and
maintenance and remedial treatment program.

MSDS’s and US EPA Product Labels
Currently, only one basic manufacturer is registered by the US EPA to sell and
market penta into the USA. This company, KMG-Bernuth, a/k/a KMG Chemicals,
maintains multiple EPA Restricted Use Pesticide labels with the US EPA. Penta
has just recently undergone an extensive seven-year Re-registration program
with the US EPA and Industry and the RED has been issued. Penta will continue
to be registered by the US EPA for its intended purposes as a wood preservative.
Example US EPA labels and Product MSDS’s are attached under Appendix II.

Extension of Exposure Conditions
Penta has been widely tested for use in wooden crossties for decades. Formerly,
the work by Forintek Scientist Krzyzewski indicated both penta and copper
Naphthenate were suitable crosstie preservatives for either creosote or creosote-
petroleum solutions. In Fall 2009, the AWPA received specific proposals for
penta in specialized petroleum solvent mixtures for the treatment of crossties.
This new carrier system met the minimal requirements as established in the
AWPA Standard P9-Type A, but also has additional favorable properties to
extend wooden crosstie service life. This new system should be contained in the
upcoming AWPA BoS.
Re-Affirmation Support
Letters and comments from wood treaters and wood preserving plants have been
received in support of the re-affirmation of penta by the AWPA. Letters of support
for the re-affirmation of penta by consumers and users of penta treated wood
products have also been received. The TF chair has received no negative
comments from any party, Task Force member, treater, or utility, which do not
support the re-affirmation of penta in the AWPA Annual Bos. These are attached
under Appendix III.
Summary and Closing Remarks
Currently in the USA, roughly 16.5 millions pound of technical penta is used
annually to produce over 2 million wooden utility poles. Penta treated wooden
poles make up roughly 53-55 % of the treated wood pole market in N. America
according to surveys by Freeman (2009), Vlosky (2006), and Vlosky and Shupe
(2007). It is the unanimous recommendation by the current AWPA Penta Task
Force that penta be re-affirmed by the AWPA and continued to be listed in the
AWPA Annual Book of Standards.
PENTACHLOROPHENOL :
A Comprehensive Review of Its Efficacy and As A Wood Preservative

By

Mike. H. Freeman
Independent Wood Scientist
Memphis, TN

Corresponding Author: [email protected]

ABSTRACT
Pentachlorophenol used since the 1930’s was rated the least expensive of the three major
preservatives at least before rising cost of petroleum. Before 1987 penta was registered as
a herbicide, defoliant, molluskicide, mossicide, and disinfectant. Depending upon the
reporting country, the number of abandoned use patterns for penta ranges from all uses to
few uses. This paper reviews the properties of penta, its efficacy compared to that of older
preservatives such as creosote and chromated copper arsenates, and newer ones such as
copper naphthenate. It also reviews the factors that affect the efficacy of penta and more
especially its performance in oil-borne carriers. The performance of penta and the
properties of the treated wood are influenced by the properties of the solvent used.
Knowledge of the toxicology of penta has contributed to it being the most documented
substance in wood preservation. This paper also briefly reviews the EPA reregistration of
penta which showed that use in pressure treatment of wood did not pose an unacceptable
risk to man or the environment . Today penta remains the main wood preservative used
for utility poles in N. America with almost 55% of all poles being produced, utilizing penta in
P9-Type A oil as their preservative system.
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PCP INTRODUCTION
Pentachlorophenol, also known as penta or PCP, had its wood preserving properties
discovered in the 1930s and the production for wood preserving began on an experimental
basis then. Trade names include: Forpen®, Penta®, Pentacon®, Penwar®. Penta is a
standardized oil-borne preservative listed in the AWPA Book of Standards under P8-1.
Principal use in the United-States and Canada is now the pressure-treatment of railroad
ties, posts, cross arms, utility poles, and wharf pilings. Penta extends the functional life of
wood by at least eight times (Wilkinson 1995; Fishel 2005). It is dissolved in petroleum or
other organic solvents to allow adequate wood penetration.

Pure penta exists as colorless crystals with a sharp phenolic smell when hot but little odor
at room temperature. Impure penta is dark gray to brown and exists as dust, beads, or
flakes. The sodium salt dissolves easily in water, but penta itself does not. The two forms
have different physical properties, but are expected have similar toxic effects (ATSDR
2001). Treated wood typically contains about 130-140 (cid:0)g/m3 penta corresponding to
concentrations of 0,484 mmol/L in treated wood (Pohleven and Boh 2007). Advantages of
penta are that it can be dissolved in oils having a wide range of viscosity, vapor pressure
and color, and it is clean and easy to handle and use. It is highly effective against wood
destroying organisms. In terms of cost, it is rated the least expensive of the three major
preservatives (Hatcher 1980) at least before rising cost of petroleum. Due to continual
increase in petroleum costs and possible reduced availability of petroleum in the future
there has been need to find treating processes which will keep the industry competitive
and profitable in the face of competition from other materials (Hatcher 1980).

PHYSICAL AND CHEMICAL PROPERTIES
The physical/chemical properties of penta are well characterized (Table 1). It is freely
soluble in organic solvents, slightly soluble in cold petroleum ether, carbon tetrachloride
and paraffins and is inflammable. Technical penta used in wood preservation contains
toxic impurities. Those of regulatory concern penta’s microcontaminants (FAO 1996).

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Table 1. Physicochemical properties of penta (WHO 1987)

Property Value value
Physical state Light tan to white needle-like crystals. Crystalline, aromatic
compound
Water solubility (at 20°C) 14 mg/litre (pH 5), 2 g/litre (pH 7), 8 g/litre (pH 8)
Log octanol–water partition 3.56 (pH 6.5)
coefficient 3.32 (pH 7.2)
Melting point 191ºC (anhydrous), 174ºC (monohydrous).
Vapour pressure 2 × 10-6 kPa at 20°C
Boiling point 309-310°C (decomposition)
Density 1.987 g/cm3
pKa 4.7 at 25°C

HISTORY
The wood preserving properties of penta were discovered in the 1930s. Water-repellent
solutions containing penta in solvents of the mineral spirits type, were first used in
commercial dip treatments of wood by the millwork industry in1931. Commercial pressure
treatment of poles with penta in heavy petroleum oils began in 1941, and considerable
quantities of various products soon were pressure treated. Penta became a restricted-use
pesticide in 1987 and is only available to certified applicators. It now has no registered
residential uses (Fishel 2005; EPA 2008). Before the 1987 Federal register notice that
canceled and restricted certain uses, penta was registered as a herbicide, defoliant,
mossicide, and as a disinfectant. It was then one of the most widely used biocides (EPA
2007). In 1947 nearly 3,200 metric tons of penta was reported to have been used in the
U.S. by the wood preserving industry. As of 2002, about 11 million pounds of penta was
produced. It may not be used in residential, industrial, or commercial interiors except for
laminated beams or building components in ground contact and where two coats of sealer
are applied. It may not be used in farm buildings where there may be contact with animals
or in beehives.

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Because penta was used for a wide range of domestic, agricultural, and industrial
purposes for more than 60 years, the compound is ubiquitously distributed in the
environment (Pohleven and Boh 2007). Its occurrence in aquatic and terrestrial food
chains has been established (Fishel 2005). Penta continues to be used but depending
upon the reporting country, the number of banned uses ranges from all uses to few uses.
Most reporting countries banned residential indoor uses. Austria, India, Indonesia, New
Zealand, Sweden and Switzerland have reported a total ban (FAO 1996).

In 1997 the manufacturers of penta voluntarily removed groundline/remedial treatment
applications from the U.S. EPA registered labels for the product. All non-pressure and non-
thermal treatment uses (i.e., spray uses) were deleted from the registrants' labels since
2004. This action left only pressure and thermal treatments with penta. Non-pressure/non-
thermal treatments generally lead to higher applicator exposures.

MODE OF ACTION
Penta is toxic to all forms of life because it is an inhibitor of oxidative phosphorylation.
Often used in combination with an insecticide, penta/NaPCP at low concentrations causes
significant uncoupling of oxidation and phosphorylation cycles in tissues. At high
concentrations it inhibits mitochondrial and myosin adenosine triphosphatase, inhibits
glycolytic phosphorylation, inactivates respiratory enzymes and causes gross damage to
mitochondria (Ozanne 1995). This results in accelerated aerobic metabolism and
increasing heat production. It also causes loss of membrane electrical resistance (FAO
1996).

PRODUCTION AND USE
Penta is produced by the stepwise chlorination of phenol in the presence anhydrous
aluminum or ferric chloride catalyst at 191°C. Outside of the United States, it is also
produced by the alkaline hydrolysis of hexachlorobenzene. Because the production
process is incomplete, commercial grade penta is 84-90% pure. Several contaminants
including other polychlorinated phenols, polychlorinated dibenzo-p-dioxins and
polychlorinated dibenzofurans are produced too.
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Production volumes steadily decreased from 45 million pounds in 1983 to 9.1 million
pounds in 1996 (IARC 1999). Up to 2004, Vulcan Chemicals, a division of Vulcan Materials
Co. was the only domestic manufacturer of penta. Production volumes declined due to
restriction in uses. From 1983–1986 it declined as follows: 42 million pounds in 1984; 38
million pounds in 1985; and 32 million pounds in 1986 and about 24 million pounds were
manufactured in 1987. In 2004, Vulcan Materials sold the assets of its Vulcan Chemicals,
to Basic Chemical Co. LLC, a subsidiary of Occidental Chemical Corporation but decided
against entering the penta business (vulcanmaterials.com). In 2005, KMG Chemicals, Inc.
a global provider of specialty chemicals acquired assets used in the manufacture and sale
of penta from Occidental Chemical Corporation. The equipment was used to back-up
KMG's then existing penta plant, thereby assuring security of supply for penta. KMG had
acquired the original penta distribution business in 1984 and built a penta manufacturing
plant in Matamoros, Mexico in 1986. KMG is currently the only producer of penta in North
America. Penta revenues were projected to increase by over $3 million per year. Demand
for penta and creosote was near record levels during fiscal 2007, driven by continued
strong demand for utility poles and rail ties. KMG’s penta revenues increased 2% to $28.4
million as compared to fiscal 2006. The Railway Tie Association forecasted demand for rail
ties to be relatively flat in 2008 and KMG anticipated the same for utility pole demand. The
company's penta products include penta blocks, solutions of penta concentrate, and
byproduct hydrochloric acid manufactured at its Matamoros, Mexico and Tuscaloosa,
Alabama facilities( Alabama is only a formulating plant only). In the U.S., the company
sells penta primarily in Alabama, Arkansas, Georgia, Louisiana, Mississippi and Missouri.
The penta segment constituted 17% of the company's net sales in fiscal 2008 and the
creosote segment constituted 36% of the company's net sales in fiscal 2008.

STANDARDS AND SOLVENTS FOR PENTA
The standard AWPA P8 defines the properties of penta wood preservative. Penta solutions
for wood preservation shall contain not less than 95% chlorinated phenols, as determined
by titration of the hydroxyl group and calculated as pentachlorophenol. The performance of
penta and the properties of the treated wood are influenced by the properties of the solvent
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used (Ibach 1999). AWPA P9 standard defines solvents and formulations for organic
preservative systems.

i. AWPA P9- Hydrocarbon solvent Type A- The heavy petroleum solvent included
in P9-A is preferable when the wood is used in ground contact and for bridge
applications. The solvents are petroleum oils and hydrocarbon solvents (No. 2
diesel, and blends of diesel oils with auxiliary solvents that are intended to stay in
the wood due to the high boiling characteristics. The heavy oils remain in the wood
for a long time but do not usually provide a clean or paintable surface. They are
designed to provide permanent penta solvency in wood and physical properties that
will minimize the depletion rate of penta from wood.

ii. AWPA P9- Hydrocarbon solvent Type B- Consists of a highly volatile carrier
system such as LPG, isopropyl ether, or butane with sufficient penta solvency. The
carrier must be removed in the cylinder or the preservative will migrate to the
surface and be lost after treatment. Hence the vapor pressure of the carrier must
be extremely high at ambient temperature. Butane leaves a clean surface. A
commercial process using penta/LPG was introduced in 1961, but its field
performance was found inferior thus it is no longer used. Type D is similar to B.

iii. AWPA P9- Hydrocarbon solvent Type C- A system of light naphtha (mineral oils
or VMP naphtha) with a high-boiling and non-water soluble high viscousity auxillary
solvent with ability to dissolve nearly its own weight of penta. It is used when
treating glulam before gluing. These co-solvents must have ability to prevent
migration and blooming as the light carrier solvent evaporates and migrates to the
surface. The light naphtha may be either recovered in the cylinder by a solvent
recovery process or left to evaporate from the wood.

iv. AWPA P9- Hydrocarbon solvent Type E-This is an oil dispersion in water. It is
only approved for aboveground use in lumber, bridge ties, mine ties, and plywood
(Ibach 1999).

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