Water Pollution

The timber industry treats timber and wood products with chemical preservatives to protect the wood from degradation due to various organisms including fungi, and insects such as borers and termites. This treatment extends the range of applications and the service life of the wood. By design, the chemicals used to protect wood must be toxic to the target organisms, but they may also affect nontarget organisms and the environment [1].

The following groups of preservatives are commonly used for wood preservation: (a) copper chrome arsenate (CCA); (b) copper-based alternatives to CCA [ammoniacal copper quaternary (ACQ) and copper azole]; (c) boron; (d) creosote; and (e) pyrethroid-and metalbased light organic solvent preservatives (LOSPs). Section 31.2.1 presents a complete list of toxic chemicals used in wood preservation in the United States.

Copper chrome arsenate (also known as CCA or chromated copper arsenate) consists of three metals: copper, chromium, and arsenic. All three metals pose a risk to the environment. Both hexavalent chromium and arsenic can cause cancer in humans. The

CCA concentrate is diluted with water to create a working solution that is used in the pressure treatment of timber.

CCA-treated timber is commonly a greenish color, but this is also often the case with the other copper-based preservatives. CCA-treated timber is registered for use by the industrial countries under their laws. The registered uses include internal building uses and external uses such as decks, walkways, fences, playground equipment and retaining walls, and some marine water applications such as wharfs and jetty piles.

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