In the wake of Hurricane Katrina, when Lake Pontchartrain breached its levees and filled the low-lying city of New Orleans like a bathtub, public health officials feared floodwaters would expose residents and first responders to a brew of toxic chemicals and pathogenic organisms. A newly published analysis, however, indicates that those floodwaters were no more toxic than the city’s normal storm runoff (Environ. Sci. Technol., published online Oct. 11, dx.doi.org/10.1021/es0518631).
“What we had in New Orleans was basically a year’s worth of storm water flowing through the city in only a few days,” says John H. Pardue, director of the Louisiana Water Resources Research Institute at Louisiana State University, Baton Rouge. “We still don’t think the floodwaters were safe, but it could have been a lot worse. It was not the chemical catastrophe some had expected,” he adds.
In early September, Pardue and coworkers collected floodwater samples from the city’s West End and Lakeview neighborhoods—an area where rescue efforts led to widespread exposure to floodwaters—and from the Tulane-Gravier neighborhood.
Pardue’s team detected slightly-elevated levels of lead and gasoline, but these were similar to those found in normal storm runoff and did not pose a major threat to human health. They found that the greatest potential risk to human health came from very elevated levels of fecal bacteria, probably from the city’s overwhelmed sewer system.
Pardue notes that the water pumped back into Lake Pontchartrain may pose a threat to aquatic life because of its low oxygen concentration and the presence of heavy metals such as zinc and copper.