Lead hazard reemerges in post-Katrina New Orleans
Will the rebuilding of New Orleans take advantage of the opportunity to improve children’s health?
When Hurricane Katrina’s floodwaters receded, they left behind a chocolate malt-like coating of sediment and sludge on the yards, homes, and cars of New Orleans. Research published today on ES&T’s Research ASAP website (10.1021/es052219p) provides one of the first peer-reviewed analyses of contaminants in the sediment; it is based on samples taken just 2 weeks after Katrina’s August 29 strike. The findings reveal troubling levels of lead that, when considered alongside historic soil contamination, call for remediation, some scientists say.
Steve Presley and his colleagues at Texas Tech University collected sediment and soil samples from September 16 to 18 along a transect bisecting the city from the high ground of the French Quarter to the lowlands at Lake Pontchartrain. The researchers analyzed the samples for 26 metals and 90 compounds, such as pesticides. They also tested floodwaters for three kinds of disease-causing bacteria.
Concentrations of lead, arsenic, the pesticide aldrin, and seven other organic compounds in some of the samples exceeded the U.S. EPA’s thresholds for human health and soil cleanup, Presley says. The researchers also found concentrations of aeromonas bacteria as high as 26 million colony-forming units per milliliter (CFU/ml), more than twice the expected range of 100 to 10 million CFU/ml in polluted water. Some species of aeromonas are an emerging threat to human health and have been isolated from nearly one-quarter of infected wounds from tsunami survivors in Thailand, he says.
“The most concerning findings are the elevated lead concentrations in the soil, because children on playgrounds don’t wash their hands and [they] put everything in their mouths, which predisposes them to lead exposure,” Presley says. At 2 out of 12 sites, the researchers measured lead concentrations of 405.5 parts per million (ppm) and 642 ppm, exceeding EPA’s soil cleanup standard of 400 ppm. The crusty sediment and sludge layer, up to several inches thick, readily becomes airborne dust when disturbed, presenting a risk of exposure through inhalation, he says.
Presley and his colleagues are probably finding at least some lead contamination that existed before Katrina flooded New Orleans, says Howard Mielke, an environmental toxicologist at Xavier University. Before Katrina, Mielke analyzed nearly 5000 soil samples from across the city and revealed that 40% of New Orleans soils exceed the lead cleanup standard, with some lead concentrations above 1000 ppm. Lead sources include historic use of leaded gas, lead paint, and emissions from now-mothballed garbage incinerators, he says.
As a result, even before Hurricane Katrina, 20–30% of children in the inner city were suffering from lead poisoning, with blood lead levels greater than the Centers for Disease Control and Prevention’s health guideline of 10 micrograms per deciliter (µg/dL), Mielke says. Lead poisoning symptoms include a decline in intellectual ability and erratic behavior. Lead poisoning has also been linked to criminal activity in teenagers, he says.
EPA’s soil cleanup standard of “400 ppm lead is totally out of range with what a child can safely be exposed to,” Mielke adds. The European standards for soils, 40–80 ppm, and Canadian standards, 150 ppm, are far lower than the U.S. threshold, he says.
The absence of many citizens from New Orleans presents a golden opportunity to remediate the most polluted sites, Mielke says. He has estimated that it would cost $250,000 to cover 40% of the city with clean Mississippi River sediment 6 inches deep, enough to protect children from underlying lead pollution. This is a fraction of the $100 billion cost estimate for repairing the city, he notes. However, state and federal officials announced on December 9 that New Orleans is safe for residents to return and that a cleanup is not necessary.
What EPA is saying officially is that the Texas Tech findings are an important independent confirmation of the sampling done by the agency. “Being above 400 ppm lead in an urban environment is not particularly unusual,” says Bill Farland, EPA’s acting deputy assistant administrator for science.
