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CCA-treated wood poses long-term threat

(29.12.2005)


Background
About 80% of US outdoor lumber is treated with chromated copper arsenate (CCA) composed of copper and arsenic used to repel insects, kill molds and fungi and retard rot, and chromium used to stabilize the two other chemicals. While the chemicals can stay in the wood for 10 years or more, they can also slowly leach out of the wood and become dangerous to both children and adults. In the environment, arsenic cannot be destroyed; it can only change its form.


Recent Research Results
Researchers from the University of Miami, the University of Florida and Florida International University examined arsenic species leaching from chromated copper arsenate, or CCA-treated wood, from a real deck as well as from simulated landfills using HPLC-ICP-MS for speciation analysis.

Their troubling conclusion: The deck timber leached high levels of arsenic into rainwater runoff and the soil — and treated wood only continued leaching arsenic while sitting in simulated landfills. Both inorganic As(III) and As(V) were detected in the runoff from both decks, with inorganic As(V) predominating. No detectable levels of organoarsenic species were observed.

The two papers appeared as online versions of the journal Environmental Science & Technology in their Research ASAP section. The bulk of the funding for the research came from the Florida Center for Solid and Hazardous Waste Management, a statewide research center hosted by the UF College of Engineering.

“What’s important for people to realize is that arsenic is relatively mobile, so it’s something we have to be relatively concerned about – how to manage this huge stock of CCA wood that remains to be disposed of,” said Tim Townsend, a UF associate professor of environmental engineering.

Earlier studies on the arsenic leaching problem prompted the wood products industry to phase out CCA-products for residential use in 2003, but CCA-wood can still be used in utility poles and industrial timbers (see related EVISA News).

Helena Solo-Gabriele, a professor of environmental engineering at the University of Miami, Townsend and their colleagues studied rainwater runoff from a CCA-treated deck for a year. Their conclusion: Arsenic contamination was 200-300 times higher than runoff from an untreated deck. Even further, the runoff had contaminated the layer of sand underneath the deck to arsenic levels 15 to 30 times higher than background levels, while water that percolated through the sand also was contaminated by the toxic metal.

While only a small fraction of the arsenic leaches in any given year, the impacts can be significant, because of the high concentrations of arsenic in the wood and the fact that the wood can be in the ground for several years. The researchers concluded that by 2000, Florida had imported 28,000 metric tons of arsenic, 4,600 of which have already leached into the environment, according to estimations reported in one of their papers. The reported model  predicts that as much as 11,000 additional tons of arsenic will leach from decks and other structures in the next 40 years.

Such threatening numbers suggests that decision-makers may want to carefully consider what should be the final resting place for CCA-treated wood that has been taken out of service. Unfortunately, however, that won’t end the problem. A mathematical model based on the researchers’ experiments estimated that between 20 and 50 tons of arsenic may have leached into construction and demolition landfills in Florida before 2000, with an expected increase of between 350 and 830 tons of arsenic by 2040.

The high amounts of arsenic leaching from the wood together with their high mobility provide decision-makers with information that should help them decide whether or not CCA-treated wood should go into lined or unlined landfills. Up to now, Florida law does not require that construction-and-demolition landfills be equipped with linings. Although there isn’t yet much evidence of groundwater contamination in monitoring wells around those landfills, that could well become a problem in the future according to the results presented by the researchers.


Source: University of Florida News, December 23, 2005


Original research papers:

Bernine I. Khan, Helena M. Solo-Gabriele, Timothy G.Townsend, Yong Cai, Release of Arsenic to the Environment from CCA-Treated Wood. 1. Leaching and Speciation during Service, Environ. Sci. Technol., 40/3 (2005) 988-993. DOI: 10.1021/es0514702

Bernine I. Khan, Jenna Jambeck, Helena M. Solo-Gabriele, Timothy G. Townsend, Yong Cai, Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal, Environ. Sci. Technol., 40/3 (2005) 994-999. DOI: 10.1021/es051471u



Related studies:

 S. Lebow, R. Williams, P. Lebow, Effect of Simulated Rainfall and Weathering on Release of Preservative Elements from CCA Treated Wood, Environ. Sci. Technol., 37/18 (2003) 4077-4082. DOI: 10.1021/es0343048

 S. Lebow, D. Foster, J. Evans, Long-Term Soil Accumulation of Chromium, Copper and Arsenic Adjacent to Preservative-Treated Wood, Bull. Environ. Contam. Toxicol., 72 (2004) 225-232. DOI: 10.1007/s00128-003-9055-y

T. Townsend, T. Tolaymat, H. Solo-Gabriele, B. Dubey, K. Stook, L. Wadanambi, Leaching of CCA-treated wood: implications for waste disposal, J. Hazard. Mater., 114/1-3 (2004) 75-91. doi:10.1016/j.jhazmat.2004.06.025



J.R. Jambeck, T. Townsend, H. Solo-Gabriele, Leaching of chromated copper arsenate (CCA)-treated wood in a simulated and its potential impacts to landfill leachate, J. Hazard. Mater., 135/1-3 (2006) 21-31. doi:10.1016/j.jhazmat.2005.11.043

Peter S. Nico, Michael V. Ruby, Yvette W. Lowney, Stewart E. Holm, Chemical Speciation and Bioaccessibility of Arsenic and Chromium in Chromated Copper Arsenate-Treated Wood and Soils, Environ. Sci. Technol., 40/1 (2006) 402-408. doi: 10.1021/es050950q

Simona Dobran, Gérald J. Zagury, Arsenic speciation and mobilization in CCA-contaminated soils: Influence of organic matter content, Sci. Total Environ., 364/1-3 (2006) 239-250. doi:10.1016/j.scitotenv.2005.06.006

 Michael C. Kavanaugh, Neven Kresic, and Alexandra P. (Sandy) Wright, Comment on "Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal", Environ. Sci. Technol., 40/15 (2006) 4809-4810. doi.org/10.1021/es060601b
 
 Bernine I. Khan and Helena M. Solo-Gabriele, Jenna Jambeck, Timothy G. Townsend, Yong Cai, Response to Comments on "Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal", Environ. Sci. Technol., 40/15 (2006) 4811-4812. doi: 10.1021/es068006x

Tomoyuki Shibata, Helena M. Solo-Gabriele, Brajesh Dubey, Timothy G. Townsend, and Gary A. Jacobi, Jr., Arsenic Leaching from Mulch Made from Recycled Construction and Demolition Wood and Impacts of Iron-Oxide Colorants, Environ. Sci. Technol., 40/16 (2006) 15102 - 5107; DOI: 10.1021/es060623y

Tomoyuki Shibata, Helena M. Solo-Gabriele, Lora E. Fleming, Yong Cai,
Timothy G. Townsend, A mass balance approach for evaluating leachable arsenic and chromium from an in-service CCA-treated wood structure, Sci. Total Environ., 372/2-3 (2007) 624-635. doi:10.1016/j.scitotenv.2006.10.037

Brad Bessinger Brooke Redding, Yvette Lowney, Comment on "Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal", Environ. Sci. Technol., 41/1 (2007) 345-346. DOI: 10.1021/es061792l

Bernine I. Khan, Helena M. Solo-Gabriele, Jenna Jambeck, Timothy G. Townsend, Yong Cai, Response to Comment on "Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal", Environ. Sci. Technol., 41/1 (2007) 347-348. DOI: 10.1021/es0622913

S. Nami Kartal, Won-Joung Hwang, Yuji Imamura, Evaluation of effect of leaching medium on the release of copper, chromium, and arsenic from treated wood, Building and Environment, 42/3 (2007) 1188-1193. doi:10.1016/j.buildenv.2005.12.009




Related Information

Treated Timber, Ticking Time-Bomb
Florida Center for Environmental Solutions, February 8-12, 2004: Conference: Environmental Impact of Preservative Treated Wood



 Related News (and references cited therein):

EVISA News, March 19, 2005: Phasing out of chromated copper arsenate as a wood preservative
EVISA News, May 17, 2005: Arsenic in Pressure-Treated Lumber - Enhancing Childrens Cancer Risks
NewsWise, August 22, 2007: Arsenic Imports for Lumber Plunge; Center Sets Sights on Disposal



last time modified: August 23, 2007









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