Questioning treated wood on playgrounds.

If members of your community have seen one of the sensationalized media reports on wood playground structures, they may have asked you about the safety of treated wood. Is there anything to fear? Are children at risk? The answer is no, but how do you best respond to such inquiries? And what about the use of treated wood in walkways, picnic tables, benches, and other park accessories?

The features of preserved wood make it a frequently specified building material for outdoor construction -- this wood is readily available, easily worked, fits comfortably into most park budgets, and lasts for a long time. Fears of the wood stem chiefly from fears of the chemicals that bring about its long life by protecting it against termites and rot. Various investigators have studied the likelihood of these chemicals leaching out of the wood and have examined the impacts of this movement; science overwhelmingly indicates that, when used as recommended, wood pressure-treated with CCA (chromated copper arsenate) is harmless to people, plants, and animals.

Studies Clear on Playground Equipment

The most thorough study dealing specifically with playground applications was done by the U.S. Consumer Products Safety Commission (CPSC's "Estimated Risk of Skin Cancer from Dislodgeable Arsenic on Pressure-Treated Wood Playground Equipment, 1990"). Eight sets of treated wood samples were tested. The most hazardous set -- unfinished timber neither intended nor acceptable for playground use -- had an estimated cancer risk of eight to nine per million for 40-pound children who play on wood equipment four days each week, six months per year, for a five-year period.

That sample set, not produced for playgrounds, was the most hazardous. For five of the sample sets, dislodgeable arsenic was below detectable limits.

In its Handbook for Public Playground Safety, the CPSC affirms that CCA-treated wood, produced in accordance with the playground equipment standard of the American Wood-Preservers' Association, is acceptable.

An evaluation of playground equipment by Consumer Reports magazine cited the CPSC study:

... tests conducted by the Consumer Products Safety Commission (CPSC) have shown the beams used in swing sets don't leach enough arsenic to pose a risk worth worrying about. If you'd rather not take any risk at all, you can always paint the wood, but we think that's a needless expense.

In 1985, the Environmental Protection Agency (EPA) finished an eight-year review of wood preservatives and preserved wood. The agency considered a wealth of evidence (including ingestion studies among dogs, maternal toxicity studies using rats, studies of treating plant workers and carpenters, a smoke study, and a report to the California State Department of Health Services titled "Evaluation of Risk to Children Using Arsenic-Treated Playground Equipment") and found no cause for restricting the use of CCA-treated wood in playgrounds.

Since then, in response to a media inquiry, EPA wrote:

Based on our evaluation, EPA has no risk concerns to public health, even children, from the use of pressure-treated wood. As part of our evaluation in the 1980s, EPA reviewed a study conducted to determine the safety of wood preservatives used on playground equipment. The study concluded that CCA use as a wood preservative does not pose an acute or chronic (non-carcinogenic) toxic hazard to children playing on treated wood.

Teri Hendy, CPSI, president of Site Masters and an instructor for the National Playground Safety Institute, reports that she has received some questions from manufactures of residential playground equipment. She concurs with other experts, saying, "CCA-treated wood is perfectly acceptable for playground structures."

OK for Picnic Tables

Preserves wood has long been used for park and residential picnic tables, with no known problems attributed to CCA preservative.

The EPA-approved "Consumer Information Sheet" on the use and handling of treated wood warns against using treated wood for counter tops and cutting boards, but offers no such precaution regarding picnic tables. The basis for the cutting-board warning is not related to chemicals -- it was included because knife blades will slice grooves into wood surfaces, where harmful bacteria can thrive and contaminate the food being cut. (Note: This application is troublesome for any material that can be marred; untreated wood is not recommended either, and some scientists have found that plastic products may be even more susceptible to bacterial problems.)

Picnic tables are typically used for serving food, not as surfaces for its preparation. Chopping and cutting are done on a plate or cloth rather than directly on a picnic table. As a result, contamination by bacteria is not a significant concern, and EPA placed no restrictions on the use of CCA-treated wood for picnic tables.

Common in Other Park Structures

CCA-treated wood is also used in many parks for walkways, benches, fences retaining walls, sand-dune crossovers, sheds, signposts, overlooks, osprey platforms, light poles, docks bulkheads, and other applications. CCA-treated wood can be seen in parks, botanical gardens, and wildlife sanctuaries across North American and around the world.

The Tasmanian Parks and Wildlife Service conducted a particularly relevant study. This study involved soil analyses under 15-year-old walkways, an evaluation of construction methods, and effects on soil invertebrates and plant germination rates. Its author concluded that, with minor qualifications, "CCA-treated timber used in track work [walkways] poses a very low risk to the environment and workers."

Another study, reported by the Occupational and Environmental Medicine Clinic in Orebro, Sweden, ended with this assessment of sandboxes built with CCA-treated wood walls:

The conclusion is, therefore, that there is no risk of arsenic poisoning as a result of playing in a sandpit. The risk of lung cancer can also be excluded because inhalation of arsenic is not involved. Neither can the risk of skin cancer be increased due to the fact that the arsenic contents in the play sand do not differ significantly from those in soil not contaminated with arsenic.

Compares Favorably With Alternatives

Safety is an essential prerequisite in selecting construction materials, but there are other considerations when comparing choices. Among these are availability, initial cost, installation requirements, upkeep, longevity, special properties, aesthetic appeal, and environmental impacts.

While no building product rates a perfect "10" in every category, the overall score for treated wood is quite high. Compared to alternatives, CCA-treated wood is readily available, long lasting, and economical. Materials can usually be installed with common tools and common skills, and wood's natural appearance is often preferred. The thermal properties of wood result in structures that are neither as hot as most non-wood alternatives when standing in sunshine, nor as cold during frigid weather.

For some projects, the maintenance of wood is an issue that should be addressed. In most applications, no upkeep is needed. However, where beauty or smooth surfaces are desired, treated wood should be coated periodically with a water repellent or other sealant to reduce moisture damage. Examples of such applications include boardwalks and docks where visitors might be expected to go barefoot.

As for environmental impacts, a strong case can be made for the benefits of CCA-treated wood. It is a renewable resource, using abundant species that are grown on managed timberlands. The treating process, which uses a preservative made in part from recycled ingredients, releases no air pollutants or wastewater. The finished product requires less energy to produce than do most alternatives. And, the preservative enables wood to last longer, thereby reducing demands on forests and other resources.

Conclusion

With no reported illnesses from playground exposure to CCA preservative, and so much scientific evidence confirming the safe use of preserved wood, why should there be any question?

Well, parents care a lot about their children's well-being, and many people have a fear of chemicals, especially chemicals with long names or bad reputations. Furthermore, some organizations think they may benefit by promoting unfounded anxieties. With regard to arsenic, few people realize that it is the 20th most common element in the Earth's crust, we have it in our bodies, and we consume it every time we eat shrimp, broccoli, and other foods.

Perhaps the most persuasive comment ap pears in the conclusion to an article in Priorities magazine ("Safe Long-lasting Pressure-Treated Wood", vol. 7 no. 3, 1995, by Dr. Craig E. Shuler, Dr. Patrick J. Pellicane, and Garrey Carruthers, Ph.D.), the quarterly publication of the American Council on Science and Health:

In the case of pressure-treated wood, consumers shouldn't be fooled by alarmist scare stories. They can be assured of what sound science has demonstrated: that when properly processed and appropriately used, CCA-treated wood is harmless to humans, plants and non-targeted animals. CCA-treated wood is a tested product offering minimal risks and substantial benefits. Its many real advantages are underscored by sound scientific research attesting to its safety; those advantages should not be overshadowed by ill-conceived, unfounded scare tactics.

RELATED ARTICLE: What Is Treated Wood?

Preserved wood (a.k.a. pressure-treated wood or treated wood) is wood that has been impregnated under pressure with a preservative chemical to extend its life by giving it resistance to termites and the fungi that cause rot. With such fortification, common species of wood, particularly various pines, can last for decades in outdoor environments. The treatment is performed at a wood-preservation facility and, for playground structures, nearly always involves chromated copper arsenate (CCA).

CCA is a combination of three natural elements diluted in a solution of water. The existence of arsenic--known for its lethal possibilities from its starring role in stories such as Arsenic and Old Lace--is enough to raise a red flag for many people before they consider the form, amount, or properties of the arsenate ingredient.

In a chemical reaction called fixation, CCA bonds to substances in wood. Fixed preservative is very leach resistant, which accounts for the longevity of the treated material. Some preservative does escape from the wood, but it is in a concentration and a form that have not produced adverse effects.

Pressure-treated wood has been produced since 1875, the CCA type since 1933. Over the past 60 years, preserved wood has been studied closely by scientists, regulators, and its own industry. Their findings regarding safety have been remarkably consistent.