The U.S. Environmental Protection Agency and Department of Health and Human Services issued a joint statement yesterday warning people to "limit contact with floodwater because of potentially elevated levels of contamination associated with raw sewage and other hazardous substances."
"Early symptoms from exposure to contaminated floodwater may include upset stomach, intestinal problems, headache and other flu-like discomfort," the agencies warned.
Less clear is what impact the dirty water may have on Lake Pontchartrain. The 630-square-mile (1,600-square-kilometer) estuary is a breeding ground for birds and marine life.
The lake's surrounding basin is a 10,000-square-mile (26,000-square-kilometer) watershed that covers 20 percent of Louisiana and includes saltwater marshes near the Gulf Coast and freshwater cypress swamps near its center.
The basin leads the nation in oyster production and has a thriving blue crab population. Its Gulf coast is known for its rich shrimping grounds. A small group of manatees have recently settled in the lake, and nearby is a refuge for rare sandhill cranes.
When Hurricane Katrina tore through the region, it damaged nearby oil refineries.
Rodney Mallett, communications director of the Louisiana Department of Environmental Quality, said that about 10,000 barrels of oil leaked from Murphy Oil USA's refinery in Meraux into a nearby neighborhood.
The company ordinarily refines 125,000 barrels per day of oil. A retaining wall at the refinery has since been repaired, Mallett said.
State environmental officials have identified another oil spill of about 78,000 gallons at the Bass Enterprise storage depot near Venice. The depot sits near the Mississippi River, downstream from New Orleans, Mallett said.
In addition, the U.S. Coast Guard has identified more than 150 incidents of pollution, according to the EPA, and more than 114 sewage plants in New Orleans remain inoperable and submerged.
Senate Majority Leader Bill Frist, a physician, said he is worried about outbreaks of water-borne illnesses, such as cholera and dysentery, which are spread by standing, polluted water.
Some health officials have voiced concern about the transmission of Hepatitis A, a serious viral disease that affects the liver and displays symptoms three weeks after exposure.
Because of the grave public health threat posed by contaminated floodwater in New Orleans, the EPA granted the Army Corps of Engineers a waiver from treating floodwater before sending it back into Lake Ponchartrain.
"Katrina is forcing us to make tough decisions," said EPA spokesperson Eryn Witcher, noting the logistical challenge of treating water in such emergency conditions.
The EPA is assisting the Federal Emergency Management Agency in search and rescue efforts and has not begun to focus fully on the environmental cleanup, Witcher said. "Our first priority is to save lives," Witcher said.
New Orleans's mayor estimated that it would be three weeks before all the city floodwater, which in some places still stands at 15 feet (4.5 meters), is drained.
Even after it is pumped, the contaminated water still won't be out of sight of New Orleans, and some environmental experts are worried.
John Pardue directs the Louisiana Water Resources Research Institute at Louisiana State University. Pardue told the New Orleans Times-Picayune that testing at 26 locations found the floodwater to be oxygen depleted, a sign of bacterial contamination.
The samples will also be checked for chemicals, and Pardue said he hopes to release those results as soon as possible.
Jerald Schnoor, a professor of environmental engineering at the University of Iowa, notes that if the floodwater pumped back into Lake Ponchartrain is depleted of oxygen, fish that come into contact with it would suffocate and die.
The floodwater may also contain pesticides and petrochemical byproducts. Once it is pumped into the lake, however, it will become highly diluted.
Schnoor, who also edits the journal Environmental Science and Technology, says that only if the diluted water is found to be contaminated at levels above acceptable environmental standards would cleanup be required.
"Officials may not be too worried because of the washing out of the water from the lake to [the] Gulf [of Mexico]," Schnoor said. The muck left behind in the city is another matter and must also be tested for toxicity, he added.
Louisiana officials are inspecting chemical plants for leaks. Of 17 examined so far, no leaks have been detected, Mallett, the DEQ spokesperson, said.
Authorities checked nuclear plants and other potential sources of radioactive substances and so far no contamination has been detected.
Experts believe the majority of the contamination in New Orleans floodwater comes from ordinary household chemicals and oil-based products.
As Mike McDaniel, the Louisiana Secretary of Environmental Quality, told reporters, "Everywhere we look there's a spill. It all adds up."
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