9 January 2006
Treated Wood A Long Term Environmental Threat
by Kate Melville
The arsenic used to treat wooden decks, utility poles and fences will leach into the environment for decades, posing a grave threat to groundwater reserves, say two studies in the journal Environmental Science & Technology.
The studies were based on wood treated with chromated copper arsenate (CCA). The researchers, from the University of Miami, the University of Florida and Florida International University, examined leaching from actual wooden decks as well as from simulated landfills. Their findings showed that deck wood leached high levels of arsenic into rainwater runoff and the soil, and continued leaching arsenic while sitting in simulated landfills.
Researcher Helena Solo-Gabriele said that arsenic contamination in a layer of sand underneath one of the decks had arsenic levels 15 to 30 times higher than background levels, while water that percolated through the sand also was contaminated by the toxic metal. "Only a small fraction leaches in any given year," Solo-Gabriele said. But because the wood can be in the ground for several years "the impacts can be significant, especially given the high concentrations of arsenic in the wood itself."
Previous studies on the arsenic leaching problem prompted the wood products industry to phase out CCA products for residential use in 2003, but CCA treated wood can still be used in utility poles and industrial timbers. The researchers suggested that authorities may want to carefully consider what should be the final resting place for CCA-treated wood that has been taken out of service. "What's important for people to realize is that arsenic is relatively mobile, so it's something we have to be relatively concerned about - how to manage this huge stock of CCA wood that remains to be disposed of," said co-researcher Tim Townsend.
One solution may be the use of lined landfills but Florida law does not require that construction-and-demolition landfills be equipped with linings. Additionally, the cost of lining landfills may put many landfills out of business and encourage illegal dumping.
Source: University of Florida