Arsenic in Hurricane Katrina wood debris
Treated lumber from houses and other structures destroyed by the hurricane poses a hazardous waste disposal problem.
Hurricane Katrina left behind an estimated 55 million cubic meters (m3) of tangled debris in Louisiana and Mississippi—enough to cover 150 football fields piled 15 meters high. To add to the disposal problem, much of the lumber in those piles contains arsenic, a known carcinogen.
The arsenic comes from chromated copper arsenate (CCA) treatments that were applied to wood to protect it against termites and decay, two big problems in the steamy southeastern U.S. that made the pesticide very popular until recently. To sort the good wood from the bad, a team of researchers led by Helena Solo-Gabriele of the University of Miami used handheld X-ray fluorescence devices to make on-the-ground measurements of arsenic in the New Orleans debris. The results were published today on ES&T’s Research ASAP website (DOI: 10.1021/es0622812).
The team sampled more than 200 pieces of lumber at seven sites in New Orleans, including the hard-hit Ninth Ward neighborhood, where piles of housing still remain untouched. From their measurements in New Orleans, they estimate that in total, Katrina debris in Mississippi and Louisiana contained about 1740 metric tons of arsenic from treated wood.
Arsenic-treated wood was banned in U.S. playground equipment in 2001, and CCA manufacturers and users agreed to work with the U.S. EPA in 2002 to take the pesticide out of residential use. This led to the creation of arsenic-free replacement chemicals, which contain copper, for most applications.
“If you go into Lowe’s or Home Depot today, you can’t buy CCA-treated wood anymore,” says John Schert, director of the Hinkley Center for Solid and Hazardous Waste Management at the University of Florida. “Meanwhile, we have huge volumes of wood out there that will be in use for a long time, and we don’t know what to do with it,” Schert says.
In two studies published previously in ES&T (DOI: 10.1021/es0493603 and es051471u), Solo-Gabriele and colleagues showed that arsenic in treated lumber leaches slowly into soil. But discarded CCA-treated wood is excluded by EPA as a hazardous waste material under the Resource Conservation and Recovery Act, Solo-Gabriele notes, despite the fact that it fails EPA’s leaching tests designed to protect groundwater. “I would think it’s time to reconsider that exclusion,” she says. The researchers recommend that CCA-treated debris from natural disasters not be placed into unlined landfills, where it could contaminate groundwater.
“There needs to be a discussion about whether these materials need to be treated differently in future disaster management plans,” says Tim Townsend of the University of Florida, a coauthor of the new research. Separating treated lumber from the waste stream after a natural disaster would be very difficult, Townsend says, but decisions about which landfill facilities are suitable to accept construction and debris waste could be made ahead of time. The team’s handheld scanning device also could prove useful in sorting treated lumber at recycling facilities to avoid improper reuse, for example, as shredded mulch that could leach arsenic into backyard soil.
The new research also provides much-needed information that can be used to understand the fate of CCA on a low-lying wet coastal plain, where the likelihood of future groundwater impacts remains unknown, Schert adds.
Almost 500,000 m3 of debris remain in New Orleans, according to estimates from the U.S. Army Corps of Engineers, which is in charge of Katrina debris removal. The Corps has attempted to separate some materials such as electronics from the waste stream, but mixed construction debris is harder to sort. In addition, much of the debris cannot be legally removed because homeowners cannot be located to give permission for demolition.
In the meantime, tons of debris from Hurricane Katrina already have ended up in unlined landfills, such as the new Chef Menteur landfill in east New Orleans. The landfill lies in a wetland, and the debris deposits have sparked an outcry from neighbours concerned about groundwater contamination and ecosystem impacts.
