Web edition: March 23, 2004
Print edition: March 27, 2004; Vol.165 #13 (p. 207)
The article "Danger on Deck?" (SN: 1/31/04, p. 74: http://www.sciencenews.org/articles/20040131/bob9.asp), or at least part of it, could have been titled "Danger on Dock" or maybe "Danger under Dock." After reading about how chromated-copper arsenate (CCA) is leached from the wood, I began wondering how it affects aquatic organisms. Many fish, especially bluegills and other sunfish, make these docks their preferred habitat. If not eaten directly by humans, they are caught and used for bait, eaten by bigger fish, or consumed by other wildlife.
We have studied effects of CCA leaching in estuaries and salt marshes for over a decade and have clear evidence of harm, especially in poorly flushed areas and particularly with new wood. Wood in submerged parts of bulkheads is leaching constantly into the water. In estuarine systems, the metals accumulate in sediments and benthic organisms near the bulkheads. The benthic communities are reduced in numbers and diversity. Barnacles, algae, and oysters that settle on the wood accumulate high quantities of the metals and show deleterious effects. Metals accumulated in organisms can be passed up through the food chain. For aquatic organisms such as invertebrates and algae, it is copper, rather than arsenic that is the most toxic metal. Therefore the CCA substitutes that contain no arsenic but higher amounts of copper will not be an improvement but will pose even greater risks to the aquatic environment.
Judith S. Weis
As anyone knows who has worked on construction, or for that matter spent any time outside of Washington, D.C., the little blue consumer-awareness stickers stapled to each CCA-treated board are ignored and soon lost. We have observed routine private and commercial disposal of CCA wood into municipal incineration waste streams. The common scenario of a homeowner tearing up an old deck, burning it in a woodstove or brush pile, then using the ashes for the vegetable garden, far from being unlikely, is commonplace.
The article forgot to mention that there are environmentally friendly, high-performing, all-plastic composite alternatives to treated wood and wood-plastic composites.
Beaver Falls, Pa.