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Tuesday, December 5, 2023

Another Katrina Myth Bites the Dust

The first peer-reviewed analysis of New Orleans' hurricane floodwaters finds the stuff was no more polluted than what normally fills the city's storm drains after heavy rains -- there was just a lot more of it.

The first peer-reviewed analysis of New Orleans’ hurricane floodwaters finds the stuff was no more polluted than what normally fills the city’s storm drains after heavy rains — there was just a lot more of it.

The report is based on sampling done in several flooded neighborhoods around the city in early September _ about a week after water driven by Hurricane Katrina from Lake Pontchartrain breached several levees protecting the mostly-below-sea level city.

It shows that concerns of the floodwater being a “toxic soup” of chemicals and dangerous microbes were probably overstated, although the long-term effects of the muck left behind and of the pumped-out water on the ecology of Lake Pontchartrain remains unclear.

“We don’t see the very elevated levels of toxics that would make you think of this water as toxic waste,” said the study’s lead author, John Pardue, director of the Louisiana Water Resources Research Institute at Louisiana State University.

“But the evidence is still out on whether any of the sludge left behind on the streets and in homes and businesses after the water was pumped out is particularly toxic,” Pardue said. “I would certainly still caution anyone cleaning up and handling that material not to do it without good protective clothing and gear.”

Pardue’s team boated into the neighborhoods under police protection even as the federal Environmental Protection Agency was starting to do water quality sampling _ and getting public criticism for not releasing results quickly. So far, the EPA’s reports have not found any high concentrations of toxics, either, just high bacteria counts in the water that exceed standards for drinking water.

Partly because of that controversy, Pardue’s team decided to have their work reviewed by other scientists before publishing it online Tuesday through the journal Environmental Science & Technology, published by the American Chemical Society. “We wanted to measure some chemicals that were not on EPA’s list,” he said.

The biggest sources of pollution in the water aren’t underground storage tanks or waste storage sites, but rather the thousands upon thousands of submerged vehicles that leaked oil and gas.

Yet the LSU researchers did not detect extremely high levels of benzene, toluene and other cancer-causing chemicals from gasoline that were expected, given the oily sheen of the water.

“All of us around the world watched those people on television wading through oily water, but the benzene and many volatiles were gone,” said Louis Thibodeaux, a professor of chemical engineering at LSU and co-author of the study.

Thibodeaux noted that as oil spreads across water, it’s difficult to see how thick it really is and it is likely that most of the chemicals from the fuel evaporated quickly. But he cautioned that many of the chemicals that did not evaporate may be bound to particles in the muck left behind.

“You really can’t talk about cleaning up the city until they get all those vehicles hauled out,” Pardue said.

The researchers also found compounds common in household chemicals in the water, from aerosol paints, insecticides, caulking material, rubber adhesives and other substances, but not at levels thought to be of concern for human health.

Moreover, the researchers stress that the return of floodwater to Lake Pontchartrain doesn’t end the damage to the shallow, brackish estuary that eventually flows out into the Gulf of Mexico.

“We realize as people clean their homes out, they’re moving all this mud and material out to the curb, where it’s eventually going into the storm drain system. Every rain we get for the next six months or beyond will put more material into the lake,” Pardue said.

Although the concentrations of metals in the water were typical for storm runoff, “the volume of water that was pumped out was huge _ the equivalent of a couple years of storm runoff went out of the city in a matter of a few weeks. Metals going back into the lake are at much more toxic levels than we report for humans, and could prove damaging to marine life and fish in the lake and nearby waters over time,” the researcher said.

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(Contact Lee Bowman at BowmanL(at)

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