In general, water samples taken soon after the flood caused by Hurricane Katrina found that the water resembled normal rain runoff in its chemical makeup, said the study's lead author, John Pardue.
"We don't feel anything we've seen will point to any kind of a problem on the chemical side" for human exposure, said Pardue, director of the Louisiana Water Resources Research Institute at Louisiana State University.
Still, people returning to their homes should protect themselves from germs that may be left behind in the sludge, he said.
The study, funded by the institute, found high levels of fecal bacteria in the water, just as previously published testing by the federal Environmental Protection Agency did. Normal rainwater in the area has high levels too because of leaky sewers, but Katrina flooding was different because of its sheer volume, Pardue said.
The study didn't sample water from industrial areas, and researchers cautioned that their results can't be used to assess non-residential areas. Their findings were published online Tuesday by the journal Environmental Science & Technology.
Virtually all the floodwater that once covered New Orleans has been pumped into Lake Pontchartrain, and Pardue said he and his colleagues are now analyzing the sediment it left behind.
As for the impact of the pumped water on the lake, Pardue said it didn't introduce any new chemicals but provided a large dose in a short time. He noted that all rainwater that falls in New Orleans is eventually pumped into the lake.
"What this really represented was a year or two's worth of rain being pumped out in a very short time," he said.
What's more, Pardue said that chemicals left behind in the sediment will eventually find their way to the lake as the sediment is cleaned up and rain washes it into the canals that feed Pontchartrain.
Copper, zinc, cadmium and lead found in the floodwater could build up in the lake sediment and pose long-term hazards for wildlife. The study can't evaluate that, Pardue said, but the results suggest officials should keep an eye out for trouble.
Pardue noted that the state Department of Environmental Quality is studying the problem and said he's satisfied with their efforts.