Comparison of Accelerated Methods for Evaluating Leaching from Preservative Treated Wood


  • Stan Lebow USDA, Forest Service, Forest Products Laboratory
  • Patricia Lebow USDA, Forest Service, Forest Products Laboratory
  • Kolby Hirth USDA, Forest Service, Forest Products Laboratory


Wood preservative, leaching, methods, boron, copper, rainfall, moisture content


Current standardized methods are not well-suited for estimating in-service preservative leaching from treated wood products. This study compared several alternative leaching methods to a commonly used standard method, and to leaching under natural exposure conditions. Small blocks or lumber specimens were pressure treated with a wood preservative containing borax and copper hydroxide. The specimens were leached using scenarios involving short periods of immersion, simulated rainfall, or to a longer period of outdoor exposure to natural precipitation. When compared with lumber specimens exposed to natural precipitation, leaching from immersed small blocks overestimated losses of both copper and of boron, whereas immersion of lumber specimens underestimated losses of copper. Stirring during immersion, which is required by some standard methods, did not affect leaching. Simulated rainfall most closely simulated leaching during outdoor exposure, but is relatively complex and may be difficult to standardize. Leaching appeared to be directly related to the time that specimens had sufficient moisture to allow diffusion to occur. Further research is needed to better characterize moisture contents of wood products outdoors and develop methods that simulate those moisture conditions.


Author Biographies

Stan Lebow, USDA, Forest Service, Forest Products Laboratory

Research Forest Products Technologist

Patricia Lebow, USDA, Forest Service, Forest Products Laboratory

Research Mathematical Statistician

Kolby Hirth, USDA, Forest Service, Forest Products Laboratory



AWPA (2015) E11. Standard Method for Accelerated Evaluation of Preservative Leaching. Book of Standards. American Wood Protection Association, Birmingham, AL. 638p.

Baines EF (2005) A review of the current status of the estimation of emissions from preserved wood and their use in the environmental risk assessment of wood preservatives under the Biocidal Products Directive. Int Res Group Wood Preservation Document No. IRG/WP 05-50224-7. Stockholm, Sweden. 13p.

Belford DS, Nicholson J (1969) Emulsion additives for CCA preservatives to control weathering. Proc. American Wood-Preservers’ Association. 65:38-46.

Brischke C, Rapp AO (2008) Influence of wood moisture content and wood temperature on fungal decay in the field. Observations in different micro-climates. Wood Sci. Technol. 42(8):663-677.

Brooks, KM (2011) Migration of Preservatives from Pressure-treated Wood. Chapter 7. In: Managing Treated Wood in Aquatic Environments, eds J. J. Morrell, K. M. Brooks and C.M. Davis. Forest Products Society, Madison, WI. p.163 – 207.

BSI (1997) BS EN 84:1997. Wood preservatives. Accelerated ageing of treated wood prior to biological testing. Leaching procedure. British Standards Institute, London.

Chung PA, Ruddick, JNR (2004) Leaching of copper from ACQ treated wood exposed above ground. Int Res Group Wood Preservation Document No. IRG/WP 04-50219. Stockholm, Sweden. 10p.

CNS (2000) Chinese National Standard CNS 6717.Qualitative Standards and Testing Methods of Wood Preservatives. Bureau of Standards, Metrology and Inspection, Ministry of Economic Affairs (MOEA), Taipei, Taiwan.

Cockroft R, Laidlaw RA (1978) Factors affecting leaching of preservatives in practice. Int Res Group Wood Preservation Document No. IRG/WP/3113. Stockholm, Sweden. 10p

Cooper PA (2003) Leaching of CCA- facts and contradictions. Proceedings, Annual Meeting of the American Wood-Preservers Association. April 27-30, 2003. American Wood-Preservers’ Association, Selma, AL. 99:73-99.

Cooper PA, MacVicar R (1995) Effect of water repellents on leaching from CCA treated wood. Int Res Group Wood Preservation Document No. Document No. IRG/WP 95-50044. Stockholm, Sweden. 6p.

Edlund ML, Sundman CE (1989) Moisture condition in treated wood exposed outdoors. A progress report. Int Res Group Wood Preservation Document No. IRG/WP 3533. Stockholm, Sweden. 16p.

Evans FG (1987) Leaching from CCA-impregnated wood to food, drinking water and silage. Int Res Group Wood Preservation Document No. IRG/WP/3433. Stockholm, Sweden. 17p.

García-Valcárcel AI, Bravo I, Jiménez C, Tadeo JL (2004) Influence of leaching medium and drying time between successive leaching periods on the emission of chromium, copper and boron from treated wood. Environ. Toxicol. Chem. 23: 2682-2688.

Hasan AR, Hu L, Solo-Gabriele HM, Fieber L, Cai y, Townsend TG (2010) Field-scale leaching of arsenic, chromium and copper from weathered treated wood, Environ. Pollution, 158(5):1479-1486.

Hedley M, Durbin G, Wichmann-Hansen L, Knowles L (2004) Comparative moisture uptake of Douglas fir and radiata pine structural lumber when exposed to rain wetting as an indicator of relative decay resistance. Int Res Group Wood Preservation Document No. IRG/WP 04-20285. Stockholm, Sweden. 8p.

JSA (2004) JIS K 1571: Wood preservatives -- Performance requirements and their test methods for determining effectiveness. Japan Standards Association, Tokyo.

Lebow PK, Lebow ST, Halverson SA (2013) Boron Diffusion in Surface-Treated Framing Lumber. Forest Prod. J. 63(7-8): 275-282.

Lebow ST, Lebow PK, Foster, DO (2008) Estimating preservative release from treated wood exposed to precipitation. Wood and Fiber Sci. 40(4): 562-571.

Lebow ST, Foster, DO and PK Lebow (2004) Rate of CCA leaching from commercially treated decking. Forest Prod. J. 54(2): 81-88.

Lebow ST, Williams RS, Lebow PK (2003) Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood. Environ. Sci. Technol. 37:4077-4082

Lindegaard B, Morsing N (2003) Natural durability of European wood species for exterior use above ground. Int Res Group Wood Preservation Document No. IRG/WP 03-10499. Stockholm, Sweden. 12p.

Militz H, Broertjes M, Bloom CJ (1998). Moisture content development in lap-joints of different wood species in outside exposure trials. Int Res Group Wood Preservation Document No. IRG/WP 98-20143. Stockholm, Sweden. 14p.

Mitsuhashi J, Love CS, Freitag C, Morrell JJ (2007). Migration of boron from Douglas-fir lumber subjected to simulated rainfall. Forest Prod. J. 57(12): 52–57.

Morrell, JJ, Chen H, Simonsen J, (2004) Migration of metals from Douglas-fir lumber treated with ACZA using Best Management Practices: Preliminary tests. Proceedings, American Wood Preserver’s Association Annual Meeting, Vancouver, B.C. 100:158-161.

Morsing, N, Lindegaard B (2004) Leaching of active components from preservative-treated timber: Stages 2 & 3: Laboratory testing and comparison with semi-field testing. Int Res Group Wood Preservation Document No. IRG/WP 04-20303. Stockholm, Sweden. 15p.

OECD (2009) OECD Guidance on the Estimation of Emissions from Wood Preservative-Treated Wood to the Environment: for Wood held in Storage after Treatment and for Wooden Commodities that are not covered and are not in Contact with Ground. Series on Testing and Assessment No. 107. OECD Environment, Health and Safety Publications. OECD Environment Directorate, Paris, France.

Rapp AO, Peek RD, Sailer M (2000) Modeling of the moisture induced risk of decay for treated and untreated wood above ground. Holzforschung 54:111-118

Ruddick JNR (2008) Chapter 17. Biocide depletion: chemical, physical, and photodegradation. IN: Development of Commercial Wood Preservatives: Efficacy, Environmental and Health Issues, Schultz, et al., Editors. ACS Symposium Series 982, Amercian Chemical Society, Washington DC. 285-311.

Rydell A, Bergstrom M, Elowson T (2005) Mass loss and moisture dynamics of Scots pine (Pinus sylvestris L.) exposed outdoors above ground in Sweden. Holzforschung, 59:183-189.

Saladis J, Rapp A (2004) Moisture content and other tested values in Double layer tests of different size in Lithuania and Germany. Int Res Group Wood Preservation Document No. IRG/WP 04-20299. Stockholm, Sweden. 12p.

Siau, JF (1995) Wood: Influence of moisture on physical properties. Department of Wood Science and Forest Products, Virginia Polytechnic Institute and State University, Blacksburg. 227 pp.

Tao W, Sh, S, Kroll CN (2013) Influences of wood preservation, lumber size, and weather on field leaching of red pine lumber. J. Haz. Mat. 260 (15): 296-304

Taylor JL, Cooper PA (2005) Effect of climatic variables on chromated copper arsenate (CCA) leaching during above-ground exposure. Holzforschung 59: 467-472.

van Eetvelde G, Homan JW, Militz H, Stevens M (1995) Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Pt. 1. Laboratory Investigation. Int Res Group Wood Preservation Document No. IRG/WP 95-50046. Stockholm, Sweden. 16p.

Waldron L, Cooper PA (2010) Modeling of simultaneous three-dimensional leaching and chemical reaction of CCA components in unfixed wood exposed to water. Wood Sci. Technol. 44:129–147.

Xiao Y, Simonsen, J, Morrell JJ (2002) Effects of water flow rate and temperature on leaching from creosote-treated wood. Res. Note FPL–RN–0286. U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, Wisconsin. 6p.






Technical Notes