Environmental Protection Agency officials are taking samples daily at sites around New Orleans for biological pathogens and more than 100 chemical pollutants, including pesticides, metals and industrial chemicals.
Amid progress in restoring power and water service and the day after the release of government tests showing that the floodwaters still contain bacteria and chemicals, but that the air is safe to breathe, Mayor Ray Nagin announced that. The French Quarter is set to reopen the week after that.
"The city of New Orleans will start to breathe again," he said.
Elevated levels of E. coli and other coliform bacteria that can cause vomiting, diarrhea, stomach pain and fever have been found at up to 109 times the EPA's safe swimming limit.
Lead, which can cause nerve damage, was found in one sample at 56 times the EPA's limit for drinking water; two other samples had it at nearly twice and more than three times the limit.
A preliminary round of water and air tests done more than a week ago indicated that floodwaters in New Orleans contained bacteria at more than 10 times the acceptable levels, making direct contact by rescue workers and remaining residents dangerous.
"Human contact with the flood water should be avoided as much as possible," said EPA Administrator Stephen L. Johnson said last week.
Also found in the first round of testing were elevated lead levels, a risk if people, particularly children, were to drink the water.
Signaling a bacteria contamination, the floodwater changed color drastically in the first week after Katrina struck, Nagin told Harry Smith on The Early Show.
Five sites in the region containing some of the nation's worst toxic messes were flooded, and one of them, a landfill where residents took trash for decades, remains underwater and can't be reached.
Among all the flooded areas of Louisiana, Mississippi and Alabama, there are 31 such sites that are part of the federal government's "Superfund" program to clean up hazardous waste.