Preservatives for Wood Lumber

Wood used in construction of decks, docks and buildings, utility poles, railroad ties, and bridge ties is typically treated with a chemical preservative to make it resistant against microbial degradation. Among those chemical preservatives, the most widely used were chromated copper arsenate (CCA), ammoniacal copper quat (ACQ), pen-tachlorophenol, and creosote. CCA was the most prevalent preservative due to its low cost, and because it provided a dry and paintable surface after its application and left the wood relatively leach-resistant [3]. 

Traditionally, solid sawn lumber products are dipped or pressure treated with solutions of preservative chemicals. 

CCA had been used to pressure treat lumber since the 1940s. Since the 1970s, the majority of the wood used in outdoor residential settings has been CCA-treated wood. 

However, as a result of growing concerns regarding leaching of arsenic salt around the home and in children s play areas, the Environmental Protection Agency (EPA) announced on February 12,2002 a voluntary decision by the industry to move away from the consumer use of CCA-treated lumber by December 31,2003, in favor of new alternative wood preservatives. According to the EPA, these alternatives of CCA are alkaline copper quarternary (ACQ), copper boron azole (CBA), cyprocon-azole, and propioconazole. Besides, as an alternative to pressure-treated wood, EPA has suggested to use WPC materials. 

Currently, EPA classifies CCA as a restricted use product, for use only by certified pesticide applicators. Effective from December 31,2003, pressure-treated wood containing CCA is no longer being produced for use in most residential uses, with certain exceptions. In fact, the EPA documents says On or after May 16, 2003, any sale, distribution, or use of existing CCA stock by the registrants is prohibited. (...) It is illegal to treat wood intended for consumer use with CCA.  

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