Chromated Copper Arsenate - Releases To The Environment

Releases To The Environment

Over time small amounts of the CCA constituents, mainly the arsenic, may leach out of the treated timber. This is particularly the case in acidic environments. The chemicals may leach from the wood into surrounding soil, resulting in concentrations higher than naturally occurring background levels. A study found that during a 12-month period 12–13 percent of the CCA leached from treated wood buried in compost. On the other hand there have been many other studies in less aggressive soil types that show leaching to be as low as 0.5 ppm (red pine poles in service,) or up to 14 ppm (treated pine in garden beds). Soil contamination due to the presence of CCA-treated wood after 45 years is minimal.

Should any chemicals leach from the wood they are likely to bind to soil particles, especially in soils with clay or soils that are more alkaline than neutral.

Although widespread restrictions (see below) followed the publication of studies which showed low-level leaching from in-situ timbers (such as children's playground equipment) into surrounding soil, a more serious risk is presented if CCA-treated timber is burnt in confined spaces such as a domestic fire or barbecue. Scrap CCA construction timber continues to be widely burnt through ignorance, in both commercial, and domestic fires.

Notwithstanding this, disposal by burning, e.g. in approved incinerators, is an acceptable option, and some energy may be captured in the process.

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