Addressing Pressured Treated Wood

Wood treated with chromated copper arsenate (CCA) has been identified by EPA as causing elevated arsenic concentrations and other toxins such as chromium exposure. Because of these concerns a voluntary decision by industry was to phase out CCA products by 2004. EPA will not allow CCA products for residential use and also has a special exemption from being considered a hazardous waste.

CCA-treated wood does leach arsenic into the environment. EPA has not at this time concluded that CCA-treated wood posses unreasonable risks or should be removed or replaced. Several studies have shown that arsenic in CCA does in fact leach out of CCA-treated wood, both, when the wood is new and when the wood ages. Also arsenic is easily transferable to the hands of anyone coming into contact with the wood according to several swipe tests. However, the jury is still out to the exact risk of this type of pressured treated wood since EPA is making several risk assessment of CCA-treated wood. One EPA study is evaluating children’s exposure at residential and recreational sites. The service life of CCA-treated wood products is 25-40 years.

Until the proposed phase-out of the chemical by the U.S. wood treatment industry by the end of 2003, Chromated copper arsenate (CCA) has been the predominant wood treatment preservative in the U.S. The amount of CCA-treated wood purchased in the US during the year 2000 is estimated at 14 million cubic meters. During the same year, it was estimated that roughly 2 million cubic meters were disposed. It is estimated 600 million cubic feet CCA-treated wood produced annually in the U.S.1 This includes play-structures, decks, picnic tables, landscaping timbers, fencing, walkways, poles and other applications. Most treated wood structures currently in-service within the U.S. are treated with CCA. So the impacts of this preserved wood during in-service use and disposal will be experienced in years to come. The amount of CCA chemical added to wood depends upon the intended use of the treated wood product. The wood preserving industry estimated that 32 percent of CCA-treated wood was used for decks. The CCA chemical typically imparts a green color to the wood.

It is forecasted that the quantity of CCA-treated wood disposed within the next 20 to 30 years (which corresponds to the typical service life of treated wood products) will be on the order of 14 million cubic meters per year, which is the approximate quantity that is currently purchased today. This quantity of arsenic is significant and can impact the environment to a considerable extent if the wood is not properly disposed.

There is debate as to the exact CCA-treated wood impact upon public health. CCA wood used in playground equipment has some activities calling it “Poisoned Playgrounds.” While those in the wood preservative industry contend that highest amount of arsenic found in dirt under CCA decks would still provide less than one-twelfth the average exposure of arsenic that a child receives merely in drinking water. The state appointed Florida Physicians Workgroup concluded last year that, “the available data have not demonstrated any clinical disease associated with arsenic exposure from playground equipment of the CCA-treated wood.[2]

EPA recommends that children who play outside around CCA structures should wash their hands prior to eating. Also people working with CCA- treated wood should reduce exposure by wearing dust mask, goggles, gloves and other protective clothing.

Since 1995 a research team from the University of Miami and University of Florida has evaluated the environmental impacts of CCA-treated wood within the State. This research has focused on two distinct areas: in-service leaching of the CCA chemical and disposal pathways for the discarded product.

In Florida, arsenic observed in soils was greater than background concentrations (28.5 mg/kg)3. Also below deck arsencis concentrations exceeded Florida's soil clean-up target levels, potentially threatening human health and the environment. The data further indicates that metals do migrate through soil released by runoff impacting groundwater.

The potential use of alternative wood preservatives must be promoted to subsitute CCA and minimize CCA waste. These alternatives are less harmful since they do not contain arsenic.

Improved disposal-end management play a key role in lessening the environmental impacts of CCA waste. Such new disposal methods can sort CCA wood from untreated wood and support full-scale technological methods to lessen arsenic exposure to the public and environment. Untreated wood can be recoverd as a fuel, mulch and other uses once reasonable assurances are provided that this wood is free of CCA.

More studies are required what happens to pressured treated wood in the US. Current disposal pathways for CCA-treated wood include construction and demolition (C&D) debris landfills. Many of these may be unlined. Also this pressure treated wood can be inadvertently mixed with mulch or wood fuel that is produced from recycled C&D wood. CCA-treated wood can represent up to 30% of the recycled wood by weight according to research conducted in Florida. Research has shown that the CCA chemical is capable of leaching from CCA-treated wood (both in the unburned form and as ash) in quantities that exceed regulatory thresholds established by the U.S. Environmental Protection Agency, thereby suggesting that discarded CCA-treated wood should in many cases be managed as a hazardous waste. When CCA-treated wood represents 5% or more of a recycled wood mixture, the ash from its combustion will typically be characterized as a toxicity characteristic (TC) hazardous waste. Both new and weathered CCA-treated wood has been found in a majority of cases to leach arsenic at concentrations greater than the TC regulatory limit. Leachable arsenic within the mulch may be attributed to the presence of CCA-treated wood.

There are three primary disposal pathways for CCA-treated wood: within construction and demolition (C&D) landfills, recycled as wood fuel, or recycled as mulch. In 1996, an evaluation of wood waste at three C&D facilities found that the wood waste piles were composed of 9 to 30% CCA-treated wood (Solo-Gabriele et al. 2000).

There are two types of waste leaching guidelines, the Synthetic Precipitation Leaching Procedure (SPLP) and the Toxicity Characteristics Leaching Procedure (TCLP). These tests involve the addition of a waste material to a leaching fluid and contacting the waste with the fluid for a period of 18 hours. The metal concentrations in the leachate are then measured at the end of the test. If the concentration of a given metal exceeds a set level, then the waste fails that particular test. In general, SPLP is used to evaluate whether a waste can be land applied or disposed in an unlined landfill. The TCLP test is used to evaluate whether the waste can be disposed in a lined landfill. Results have shown that CCA-treated wood consistently fails guidelines based on the SPLP test and will on occasion fail guidelines based on the TCLP results.

CCA-treated wood within wood fuel is of concern due to potential toxic air emissions, such as the incineration arsenic and chromium and the resulting metals found in the ash. Subsequent studies to characterize CCA-treated wood ash indicate that all ash samples made entirely from CCA-treated wood failed TCLP regulatory levels and would thus be considered a hazardous waste. It was also found that a mixture of 95% untreated wood with 5% CCA-treated wood would cause the ash to fail on some occasions. The proportion of CCA-treated wood within the wood fuel mix should be less than 5%.

There has been a recent increase in the use of C&D wood waste for the production of colored mulch. Since much of this may be contaminated with CCA, recycled C&D CCA-treated wood becomes land applied increasing the potential for contaminating the environment with arsenic, chromium, and copper.

CCA-treated wood best management practice must be developed to lessen CCA chemicals into the environment. Numerous alternative wood preservatives are being developed and used by the American Wood Preservers’ Association. However, there needs to be a CCA-treated wood management plan to minimize risks when CCA-treated wood is used, recycled, burned or disposed of. How we can best manage CCA-treated wood so it harm our health our environment?

*Much of the information in this paper was borrowed from Helena M. Solo-Gabriele¹, Timothy G. Townsend, John Schert, “Environmental Impacts of CCA-Treated Wood: A Summary from Seven Years of Study Focusing on the U.S. Florida Environment.”

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[1] Cole and Clausen, 1996; Micklewright, 1994

[2] Michael Fumento, “Protecting Kids Right off the Playground.” Scripps Howard News Service, August 28, 2003

[3] Helena M. Solo-Gabriele¹, Timothy G. Townsend², John Schert, “Environmental Impacts of CCA-Treated Wood: A Summary from Seven Years of Study Focusing on the U.S. Florida Environment.