Wood-be alternatives: new wood preservatives offer choices and challenges for park and recreation professionals.

Protecting wood in park settings from rot and insects has been a challenge for park managers since public parks were created. Chromated copper arsenate, commonly known as CCA, replaced other known toxic substances that had been used for decades, such as creosote and pentachlorophenol, and was thought to be a stable method of treating wood with a preservative and insecticide.

However, recent findings have proved it not to be as stable and safe as once thought, and both government and industry have embarked on a wholesale changeover--including a voluntary phase-out of CCA in exchange for other methods of preserving wood. But when it comes to insecticides powerful enough to deter woodeating insects, the less toxic options are limited.

Although park and recreation agencies were not directly affected by this phase-out, the negative news reports and growing evidence about the possible hazards of human contact with arsenic leaching from CCA-treated wood surfaces led many agencies to examine their park structures, evaluate the potential for human exposure and begin replacement programs. Since children are the population most at risk, much attention has been focused on play structures and other wooden surfaces that may contain "dislodgeable" arsenic, or arsenic that leaches out of the surface of and which would be ingested by children from hand-to-mouth contact.

Other Treatments

With the phase out of CCA, a number of other insecticidal preservatives have vied for market share (estimated at more than $4 billion per year) to replace CCA. There is an alphabet soup of abbreviations for the various types of wood preservatives available, but all of them still depend on pressure treatment. This process forces the preservative completely into the wood fibers in a pressurized chamber so that the preservative impregnates the wood to the core.

Alternatives to CCA now on the commercial market include alkaline copper quat, or ACQ (also called by just the name "quat"); copper azole, called CA or CBA; and sodium silicate borate, or SBX. There are other types of treatments and other permutations of chemicals used, including those using ammonia-based carriers such as ACZA, but ACQ, CBA (or CA) and SBX seem to be the most available on the market at present. (See sidebar on page 58 for other alternatives.)

Due to limited supply of alternative-treated wood, and only anecdotal evidence of purchasing preferences, there is no clear trend yet in the choices that park and recreation agencies are making to replace CCA-treated wood used in parks and public areas.

Florida has been one of the states most attuned to the risks of CCA-treated wood in public settings, and in the 1990s, went further than federal guidelines suggested and committed the state park system to a full-scale replacement program. Florida's alternate choice was ACQ-treated wood, but it has not always been a smooth transition.

Ed Bowman, chief for the Florida State Park Service Bureau of Design and Construction, says ACQ-treated wood is more expensive, and has not always been readily available in Florida. He estimates the price differential with CCA-treated wood to be as much as 20 percent higher and notes, "It is normally a special order material."

Bowman says his department considers copper boron azole-treated wood to be an acceptable substitute, but that it is rarely available in lumber grades and more often only available in pilings. He also noted that Florida State Park biologists have recommended that they not use ACQ-treated wood within 60 feet of any water bodies because of concern about copper leaching into wetlands and water courses.

Fastener Problems

As the CCA wood treatment phase-out was taking place, the use of alternative wood preservative treatments such as ACQ took on much greater importance and economic significance. However, there is one persistent issue of significant concern, namely the fact that certain types of metal fasteners used with ACQ and other newer types of wood treatments will corrode at an accelerated rate.

A technical bulletin issued by Simpson Strong-Tie Company, a nationwide manufacturer of various types of coated wood fasteners, stated that "Changes in the preservative-treated wood industry have created additional concerns. Effective Dec. 31, 2003, the preservative-treated wood industry voluntarily transitioned from [CCA] used in residential applications to alternative treatments ... Simpson has shown that relative corrosion based on quantitative measurements, visual observation and calculations indicate the alternative wood preservatives tested are generally more corrosive than CCA."

Most park and recreation professionals installing wood in an outdoor environment or in contact with the ground learned long ago that unless they use nails and screws that are coated, or otherwise protected against corrosion, the fasteners will rust. Depending on the conditions of exposure to moisture, salt or other factors, the corrosion can be severe, and eventually cause untreated fasteners to fail.

The best fasteners for outdoor wooden structures have been those that are "hot-dipped" galvanized, or those treated with a molten coating of zinc. The thicker the coating of zinc, the better the protection. Hot-dipping fasteners in a molten bath provide better protection than electro-galvanizing, which is the less expensive process of coating nails and screws by electroplating. Hot-dipped galvanized products are now specified by the thickness of their coatings, and usually measured in designations such as G60, G90 and G185, which refers to the fraction of an ounce of zinc coating applied per square foot. There are alternatives to galvanized steel such as stainless steel, or the less widely available silicon bronze. Stainless steel nails and screws are brittle, but are long-lasting and extremely corrosion-resistant. However, the price of stainless fasteners can be as much as 10 times the cost of other fasteners.

Bowman from the Florida State Park Service notes that his organization now specifies that all wood structure park projects have stainless or double hot-dipped galvanized fasteners despite the high cost because of the potential problem of accelerated corrosion. He says they have not seen any evidence of fastener failure, but notes that their experience with ACQ, CBA and other newer types of preservative-treated wood is only a year or 18 months. He agrees that you can not use regular steel nails or screws with these types of treated wood, and notes that superintendents and contract managers need to be alert to staff or contractors using cheaper, non-stainless or non-galvanized fasteners. "If you had non-galvanized or non-stainless fasteners in boardwalks, for example, the nail heads might still be there, and they would look OK, but the nails may have corroded completely in the middle," Bowman says. "It could be a life-safety issue in certain cases."

Replace or Leave in Place?

Since the time of the phase-out, park and recreation agencies have been faced with either dealing with CCA-treated wood that remains in place, or finding alternatives to using the wood. Most agencies reacted proactively to the increased concerns about exposure risk, and promptly began a program of replacing CCA-treated wood play structures, picnic tables, benches and other wooden structures that might allow the public to come in contact with CCA-treated wood. Playground manufacturers, in growing awareness of the potential dangers inherent in using CCA-treated wood, have made an industrywide switch to other alternatives, and no major manufacturers use CCA-treated wood any longer.

In replacing wooden play structures, most agencies made the commitment to fully replace the wood structure with a manufactured structure made of composite materials such as PVC or vinyl, (which may carry its own health risks), plastic and metal. However, the unplanned replacement of a major playground structure is a large expense and often unbudgeted. Nonetheless, most park and recreation agencies have begun the switch. George Friedenbach, park superintendent for the city of Santa Clara, Calif., and member of the Maintenance Superintendent's Association (MSA) says, "Most superintendents are aware of the issue by now. In California, most have gone to redwood when they need wood, but more often use metal or plastic as a replacement." He notes that their park and recreation system has gotten away from wooden picnic tables and has started using more durable materials such as concrete or PET plastic, which are resistant to general wear and tear.

Roland Anolin, senior building maintenance supervisor for Berkeley, Calif., says he uses oilborne wood sealer when he first became aware of the issues with CCA-treated wood in his parks, but he soon implemented a full-scale replacement program. Anolin says the major play structure vendors made substantial changes in the types of equipment offered for sale, replacing much of the wood with plastic and metal. "In fact," Anolin says, "our long-term costs actually went down due to reduced maintenance needs. With all wooden structures, we had very high inspection and maintenance costs, and we no longer have those costs with metal and plastic equipment."

Some smaller agencies have not yet come to grips with dealing with the potential hazards of CCA-treated wood for a variety of reasons. Cost, other priorities or even ignorance of the safety risks are some of the reasons they have not yet addressed the issue. In addition, replacing wood with plastic, metal or composites is not always a practical or feasible solution for many of the other possible sources of exposure to arsenic leaching from wood surfaces.

Sue Chiang, a researcher with the Safe Playgrounds Project of the Center for Environmental Health in Oakland, Calif., believes that a number of CCA-treated wooden play structures still remain untreated because there has been no public concern expressed about potential health hazards to children. "As I have been working on this project, I found several sites where large CCA-treated play structures still remain. I think in these cases, unless some public attention is paid to the issue, nothing gets done. It seems that it is the smaller parks and places where CCA play structures are still in existence that we need to concentrate on."

One temporary low-cost method of addressing the potential risk that has received provisional approval from the U.S. Environmental Protection Agency (EPA) is to seal the wood surfaces with an oil-based preservative stain. There is some evidence that such a practice can retard the leaching of arsenic and thus reduce its dislodgeability. EPA and the Consumer Product Safety Commission (CPSC) are just completing two, long-awaited evaluations of the effectiveness of a variety of coatings including paints, stains and encapsulating latex or epoxy sealants. Bill Jordan, senior policy advisor of the U.S. EPA Office of Pesticides, says recently that the data is expected soon on one study funded jointly by EPA and the CSPC. After a peer-review process, Jordan says the EPA will issue conclusions on the evaluations of the different types of sealants, probably in the spring of 2005.

Changing Landscape

As a result of nationwide public concern and significant media attention to the potential problems created by CCA-treated wood in public parks and recreation areas, park managers and superintendents need to be sure that they have at least begun to take the steps necessary to deal with public concerns about possible exposure to dislodgeable arsenic from CCA-treated wood, especially in areas where children might come in contact with these wood surfaces.

A good set of simple prescriptions of what to do with CCA-treated wood structures can be found on the Safe Playgrounds Project Web site at www.safe2play.org. Managers should also look for the spring 2005 release of the CPSC and EPA reports on the effectiveness of coatings and sealants to retard the dislodgeability of arsenic from CCA-treated wood. A link to these reports will be posted on the NRPA Web site, www.nrpa.org, as soon as they are made public.

Park managers and maintenance superintendents need to know that the nature of wood preservatives has fundamentally changed. With the new alternatives come many choices, and not all choices are suitable for all applications. Some pressure-treated woods are highly corrosive to non-galvanized fasteners, and managers and superintendents should know exactly what kind of fasteners to use on what types of woods. Galvanized and stainless steel fasteners should not be mixed; they are dissimilar metals and corrosion can be accelerated if they come in contact with each other. Managers should be aware of what species of wood has been treated, the type of preservative used, and the rate of retention of the preservative, usually expressed in pounds of preservative per cubic foot (pcf). Preservative treatment concentrations range from. 10 pcf for dry conditions to .40 pcf or above for ground contact applications.

Some wood treatments have caused environmental concerns, and it is still undetermined what their overall impact to sensitive plant life and wildlife is, especially in water contact areas and wetlands. Managers should become more educated and aware of the choices, and the costs associated with those choices. A good reference site for a general discussion on the corrosiveness of certain types of wood treatments available, as well as an overview of recommended fastener types, can be found at the Simpson Strong-Tie Web site, www.strongtie.com.

Another good resource is NRPA's National Playground Safety Institute (NPSI), an educational training program that also certifies participants to be playground safety inspectors. NPSI includes the CPSC fact sheet on CCA in its manual, and NPSI Chairman of the Board Tom Kalousek says, "There is always much concern and discussion during our two-day training program on playground safety regarding toxins like CCA in the playground environment." NPSI is also concerned about fastener corrosion and the long-term effects of alternative wood preservatives now beginning to replace CCA. As a result, NPSI regularly updates its courses to reflect these changes.

As for the future, there is clearly keen interest in finding suitable non-toxic replacements for the universally used CCA-treated wood. Nicky DeVeny, a market research analyst for the National Association of Homebuilders Research Center in Upper Marlboro, Md., contacted NRPA to inquire about the preferences of park and recreation buyers who were replacing CCA-treated exterior lumber with alternatives. "We feel that people in parks and recreation are more concerned with the potential effects of chemical by-products, and would have some good insights," DeVeny says. She is doing market research that will help at least one company, which she declined to identify due to the "intense competition in the industry," and is likely to soon release a new wood treatment process that this company believes to be environmentally safe and gives off no toxic by-products. DeVeny says the treated wood "is straighter, splinters less, warps less and even retains paint longer. We recommended that they bring it to market."

RELATED ARTICLE: Arsenic alternatives.

Replacing CCA-treated wood is not always as simple or as cost-effective
as you may believe. And there are some alternatives that are inferior
or may be even more dangerous than CCA-treated wood structures. Below
is a list of some of the alternatives.

Types        Brand Names                History

Composite    Trex[R]                    Wood products comprised of
wood         RUBINATE[R]                a resin matrix in combination
                                        with a wood fiber reinforcment.
                                        Composite wood pertains to, but
                                        is not limited to, particle-
                                        board, plywood, medium-density
                                        fiberboard, composite veneer
                                        and oriented strandboard. Has
                                        multiple uses, from decking to
                                        playgrounds and picnic tables.

Petroleum-   Polyvinyl chloride         Plastic-based, these materials
based wood   (PVC), Polyurethane        are used pervasively in our
materials    (PU), Polystyrene (PS),    society.
             Acrylonitrile-
             butadiene-styrene
             (ABS), Polycarbonate
             (PC), Polyethylene-
             terephthalate (PET),
             Polyolefins
             (PE,PP,etc.)

Types        Pros                           Cons

Composite    The plastic shields the        Formaldehyde is used as
wood         wood from moisture and         part of the glue or adhe-
             insect damage. The wood        sive in composite wood
             in the product protects the    products. Formaldehyde
             plastic from UV damage,        emissions have been
             and provides additional        known to have cancer
             stability and traction.        effects and to exacerbate
                                            asthma. May not be fully
                                            water-resistant.

Petroleum-   Inexpensive, malleable,        Many of the plastic sub-
based wood   easy to replace.               stances are considered
materials                                   toxic to the environment
                                            when burned.

Types        Type of Treated Wood *         Trade Names

Composite    Sodium Borate (SBX), also      Advance Guard
wood         called Disodium Octaborate     SillBor
             Tetra hydrate (DOT)            Tim-bor
                                            Pac-Bor
                                            TimberSaver PT
                                            Smart Guard
                                            Hi-Bor
                                            Cal-Bor
                                            DuraBor
                                            DuraSill
                                            Composibor

Petroleum-   Alkaline Copper Quat (ACQ-     Preserve
based wood   ACQ-D, ACQ-D Carbonate)        Nature Wood
materials                                   Preserve Plus

             Copper Azole (CA-B, CBA-A)     Natural Select
                                            Wolmanized
                                              Natural Select

             Sodium Silicate Borate (SBX    Envirosafe Select

             Ammoniacal Copper Zinc         Chemonite
             Arsenate (ACZA)

             Chemical Manufacturer
Types        /Treater

Composite    Osmose
wood         Arch
             U.S. Borax
             U.S. Borax/ Pacific Wood Pres.
             CSI
             Osmose
             Osmose
             Osmose / California Cascade
             CSI
             CSI
             U.S. Borax

Petroleum-   CSI
based wood   Osmose
materials    CSI

             Arch

             Arch

             Wood Treatment Products
             with NaSi02)

             J.H. Baxter

* Table courtesy of the Simpson Strong-Tie Co.