Early tests on the floodwater that covered most of this city do not suggest it will leave a permanent toxic residue or render residential areas uninhabitable for more than a short time, officials of both state and federal environmental agencies said yesterday.
The pollution consists primarily of fecal matter and slightly elevated concentrations of metals such as lead and chromium that were in the city's soil before Hurricane Katrina. There are also trace amounts of many petroleum-based chemicals and some pesticides.
Despite descriptions of the floodwater as a "toxic soup" and a "witch's brew" of contaminants, the preliminary tests reveal it contains little that is different from what has been seen after past floods in other cities and here.
The exception is a residential area in the suburb of Meraux southeast of the city, where 672,000 gallons of oil leaked from a refinery storage tank. Areas around six smaller oil spills may also require special cleanup, the officials said.
"The early results do not indicate specific toxic pollutants at any levels of concern," said Chris M. Piehler, a senior environmental scientist at the Louisiana Department of Environmental Quality. Asked if residue from floodwaters posed hazards that would keep residents from moving back, he answered: "No. The limiting factor is going to be what structures are going to be salvageable and which ones are not."
Piehler's observations were similar to those of Jerry Fenner, the leader of the environmental health team sent by the Centers for Disease Control and Prevention.
"So far, all the test results show there shouldn't be any long-term problems of health and habitability," he said, adding that the chemical and oil spills "are a special issue and will require abatement."
The generally optimistic view of the experts here contrasted somewhat with the impression given yesterday by Stephen L. Johnson, administrator of the federal Environmental Protection Agency, at a telephone news conference from Washington. Johnson stressed the uncertainty over toxic hazards that remain in flooded parts of the city.
"What we are focused on is assessing what the problems are. It really is impossible to speculate on what it's going to take and how long it's going to take" to clean up environmental problems, he said.
The EPA is taking daily samples of floodwater both in the city and in the outfalls to Lake Pontchartrain. It is also sampling air and wet and dry mud at dozens of locations. Tests from Sept. 3, 4 and 6 showed levels of hexavalent chromium, lead and arsenic exceeding agency standards for drinking water.
"These compounds would pose a risk to children only if a child were to drink a liter of flood water a day. Long-term exposure [a year or longer] to arsenic would be required before health effects would be a concern," said a statement on the EPA Web site.
The city's drinking water comes from the Mississippi River and not from Lake Pontchartrain, where the floodwater is being pumped.
The most obvious pollutant in the floodwater is fecal bacteria. The city's sewage-treatment plant is not operating, and the standing water is mingling with the sewage in the underground system. Tests from Sept. 3 to 5 found that some sites had bacteria levels above the EPA's measurement scale. From Sept. 7 to Sept. 10, however, the amount of bacteria was falling.
Fecal bacteria have a limited life span in the open water and will not cause lasting contamination. On land, the bacteria dies once the residue dries out.
"The stuff will desiccate and you can clean it up. You fertilize your lawn? It's the same thing," Fenner said.
While the environmental findings so far have not been surprising, many potentially hazardous areas remain to be assessed. They include five Superfund sites in New Orleans. EPA inspectors have visited four, but one remains underwater. "One of the things we need to do is make sure that these sites have not been compromised," Johnson said.
The agency and local officials are also evaluating numerable small spills and hazards, including more than 5,000 "orphan containers" found floating in the water. These include everything from gas cylinders to a drum containing medical waste, he said.
A U.S. Coast Guard spokeswoman said there have been seven oil spills of more than 100,000 gallons since the storm. The biggest is at the Meraux Refinery, operated by Murphy Oil Corp. in St. Bernard Parish, southeast of the city.
During a sampling trip there two days ago, the EPA's Paul Doherty said the company estimated that about 9,600 of the 16,000 barrels of oil that leaked were recoverable and most of the rest had evaporated.
In a housing development nearby, workers in yellow safety suits scooped up samples of fine-grained mud that smelled partly of sulfurous decay and partly of petroleum.
The houses were severely damaged. At several, the flood floated cars that came to rest with their rear ends on the roof and the front ends on the lawn. Even without the spill, the neighborhood seemed unlikely to be habitable anytime soon.