Evaluating the leaching of biocides from preservative-treated wood products

Leaching of biocides is an important consideration in the long term durability and any potential for environmental impact of treated wood products. This chapter discusses factors affecting biocide leaching, as well as methods of evaluating rate and quantity of biocide released. The extent of leaching is a function of preservative formulation, treatment methods, wood properties, type of application and exposure conditions. Wood properties such as permeability, chemistry and heartwood content affect both the amount of biocide contained in the wood as well as its resistance to leaching. A range of exposure factors and site conditions can affect leaching, but the most important of these appears to be the extent of exposure to water. For wood that is immersed in water or placed in contact with the ground the characteristics of that water (pH and inorganic and organic constituents) also play a role. For wood that is used above-ground or above water, the frequency of precipitation and patterns of wetting and drying are key considerations. Current standardized methods are intended to greatly accelerate leaching but are not well-suited to estimating leaching in service. Continued research is needed to refine methods that utilize larger specimens and more closely simulate in-service moisture conditions. © 2014 American Chemical Society.