Hi Ed, Thank you for this clarification and for the informative links. While I agree with you that copper is a necessary nutrient, my concern was that excessive amounts of copper could leach from the treated wood, such that concentrations would become toxic. After all, anything in excessive amounts, including oxygen and water, can become harmful. That said, I didn't do my research on this matter, so I thank you for providing us with these links.
I am still not sure if I would use treated lumber for a raised bed, just to be on the safe side, but I do think it would make for an interesting study. If I only had a research position and funding for this endeavor! Best regards, Guy On Sun, Mar 13, 2011 at 8:09 AM, Ed Thralls <ph...@earthlink.net> wrote: > Good morning, Guy. I just read your comment in the ACGA Community Garden > Digest to Joan that stated “treated wood is unsafe” > > It is statements such as that which perpetuate the myth about treated lumber. > Although I do not enourage the use of "reused" lumber where the treatment or > origin of the material is unknown, I do read as much information as I can so > I can make an educated decision. > > Here is some information I wish to share with you that may help you > understand the overall situation with treated lumber since 2003. > > ******** > Copper is essential for plant growth and activation of many enzymes. A copper > deficiency interferes with protein synthesis and causes a buildup of soluble > nitrogen compounds. > > Normal plants contain 8 to 20 ppm copper; deficient plants usually contain > less than 6 ppm. Each ton of dry hay contains about 0.002 pounds of copper. > Without copper all crops fail to grow. > > ***** > http://smallfarms.oregonstate.edu/sfn/w10PressurizedLumber provides the > scientific communities evidence on the use of such inorganic preservatives > include ammoniacal copper arsenate (ACA), chromated copper arsenate (CCA), > and acid copper chromate (ACC), while organic preservatives include > pentachlorophenol, creosote, and coal tars. > > On February 12, 2002, EPA announced a voluntary decision by pesticide > registrants to move consumer use of treated lumber products away from CCA > pressure-treated wood, in favor of new alternative wood preservatives. EPA no > longer allows CCA products to be used to treat wood intended for most > residential settings. By Dec. 31, 2003, the industry moved away from CCA in > favor of new, alternative wood preservatives. Alkaline cooper quaternary > (ACQ) is a relatively new wood treatment that is available. This product is > higher in copper than CCA but is free of arsenic. > > The lumber industry has voluntarily removed treated lumber using arsenic. If > you are buying new, treated lumber for use in raised bed gardens the material > is treated with non-arsenic preservatives. ACQ Preserve Treated Lumber- > treated with alkaline copper quaternary and is available at about retail > lumberyards. ACQ does not contain any arsenic. > > ***** > http://lancaster.unl.edu/hort/articles/2007/PressureLumber.shtml discusses > the different ACQ treatments that are available with the new treated lumber. > > ***** > http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July0101.html > “Some vegetable gardeners may be more comfortable taking additional steps to > minimize leaching into the surrounding soil. If so, install a plastic barrier > (like 6 mil polyethylene) between the crops and the treated wood. If you’re > constructing a new raised garden bed for vegetables, and the thought of using > CCA lumber bothers you, then consider ACQ treated lumber. ACQ does not > contain arsenic compounds, it costs more and its corrosive nature requires > the use of stainless steel fasteners. Another possibility is using a > naturally durable species such as cedar, white oak or redwood. Extractives > found only in the heartwood of these species provide a natural preservative, > but well-treated wood will typically outlast even these naturally durable > species. Heartwood availability and, more importantly, price may make it > difficult to justify using these species in applications where they would be > used in ground contact.” > > ***** > http://www.puyallup.wsu.edu/~linda%20chalker-scott/horticultural%20myths_files/Myths/CCA%20wood.pdf > is an publication by Dr. Linda Chalker-Scott that helps on understand the > CCA argument that you seem to believe is still the only answer when asked is > "treated lumber safe to use in raised bed gardens". > > Best wishes. > > > > _______________________________________________ The American Community Gardening Association listserve is only one of ACGA's services to community gardeners. To learn more about the ACGA and to find out how to join, please go to http://www.communitygarden.org To post an e-mail to the list: community_garden@list.communitygarden.org To subscribe, unsubscribe or change your subscription: http://list.communitygarden.org/mailman/listinfo/community_garden_list.communitygarden.org
