Questions Remain Over Safety Of Katrina Floodwaters

Were the floodwaters that inundated New Orleans immediately following Hurricane Katrina as toxic as experts had feared? While the findings of a recent study find that the impact was not the chemical catastrophe some experts had expected, an environmental group cautions that the findings been widely misinterpreted as giving New Orleans a relatively clean bill of health.

A study by researchers at Louisiana State University (LSU), the first peer-reviewed scientific assessment of the water quality of the Katrina floodwaters, found that the floodwaters were similar in content to the city's normal stormwater. According to the researchers, the study's findings (released on Oct. 11) are "good news for those who've been exposed directly to the floodwaters."

However, the LSU researchers caution that the same floodwaters that were pumped back into Lake Pontchartrain contain high levels of some toxic metals, especially copper and zinc, and could pose a long-term danger to the area's aquatic life, which are more sensitive to the metals than humans. Their findings appeared in the Oct. 11 online issue of the American Chemical Society's ( journal Environmental Science & Technology.

"What we had in New Orleans was basically a year's worth of stormwater flowing through the city in only a few days," says study leader John Pardue, PhD, an environmental engineer and director of the Louisiana Water Resources Research Institute at LSU in Baton Rouge ( "We still don't think the floodwaters were safe, but it could have been a lot worse."

Some experts had predicted that the floodwaters from Katrina could potentially destroy chemical plants and refineries in the area, releasing a deadly brew containing toxic levels of benzene, hydrochloric acid and chlorine. Instead, high levels of bacteria and viruses were the biggest human threat, not exposure to chemicals, Pardue and his associates said.

The researchers obtained 38 floodwater samples from widespread sections of New Orleans, primarily in the area of the city known as the "East Bank," where the main human contact with the floodwaters occurred. The samples, which included both surface waters and bottom samples, were taken within five to nine days after flooding occurred. Additional samples were also obtained from the 17th Street drainage canal, after pumping of the floodwater began, to evaluate the flood's impact on Lake Pontchartrain, the receiving body for the pumped floodwaters.

The researchers found high levels of bacteria, most likely from fecal contamination resulting from sewage. Levels were within the range of typical stormwater runoff in the city, the scientists said. They also detected high levels of lead, arsenic and chromium and noted that levels of these toxic metals were also similar to those typically found in the area's stormwater. In general, these particular findings were similar to those obtained by EPA in their initial assessment of the floodwaters, the researchers said.

Gasoline also was a significant component of the floodwaters, as measured by elevated levels of three of its components: benzene, toluene and ethylbenzene. These compounds were somewhat elevated in comparison to typical stormwater runoff, the researchers said. The chemicals most likely came from cars and storage tanks submerged in the floodwaters, they add.

Compounds found in common household chemicals were also detected in the floodwaters, Pardue said. The waters contained chemical compounds from aerosol paints, insecticides, caulking compounds, rubber adhesives and other common substances, they say, but at levels that typically do not create concern for human health.

If the floodwaters had occurred in another location near more industrial sites in the city and if the wind damage or water surge had been more severe, then the resultant floodwaters could have been a more serious toxic threat, Pardue said. "Instead, the city filled slowly, like a bathtub, and the water velocities and forces on the buildings, including chemical storage facilities, were relatively benign," he said. The large volume of floodwater also diluted the potency of many of the chemicals, he added.

While serious toxicity to human life was largely avoided, the floodwater may pose a chemical risk to aquatic life in the area, Pardue said. He believes that low oxygen levels in the water that is being pumped back into Lake Pontchartrain could result in fish kills. He also says that heavy metals being discharged into the lake, particularly copper and zinc, can be toxic to fish and other marine life and may bioaccumulate and contaminate seafood collected from the region. More studies are needed to assess the long-term impact of the flood on aquatic life, Pardue said.

In commenting on the study, officials with the Natural Resources Defense Council (NRDC -- cautioned that the LSU study's own data, as well as more comprehensive EPA and other independent data, show there are in fact significant toxic risks in New Orleans and surrounding areas.

"The scientific information is far from reassuring, said NRDC health expert Erik D. Olson. "All of the data collected so far still show dangerous toxic pollution levels in the air and in dried mud. Now there is also pervasive mold that threatens public health."

Dr. Gina Solomon, an NRDC physician, added that "residents returning to flooded areas should know that there are still very real health risks and that they need to be careful to wear appropriate masks, gloves and protective clothing if they are going to spend much time or start cleaning up in these areas. Children, the elderly, and people with heart or lung disease should stay completely out of these areas for now."

On Oct. 7, the Louisiana Environmental Action Network (LEAN) released a report concluding that flooding associated with Hurricane Katrina deposited a layer of sediment in many areas of south east Louisiana. On Sept. 16, Subra Co. was assisted by Altamont Environmental with sediment and surface water sampling in five residential areas in New Orleans, Chalmette and Meraux that were impacted by flood waters from Hurricane Katrina. The sampling was conducted to assess potential organic and inorganic contamination of those residential areas.

LEAN stated that sediment samples collected from three neighborhoods contained arsenic, benzo(a)pyrene and petroleum hydrocarbons at levels exceeding EPA and Louisiana Department of Environmental Quality standards.

After evaluating the data Subra Co. president Wilma Subra commented that, "the community members should not have been allowed to return to the areas where they could come in contact with the contaminated sediments. Community members have been allowed to return to the sampled residential areas to check on and clean up their homes. The community members were not provided with information about the contamination nor provided with protective equipment to minimize their exposure to the toxic chemicals in the sediment. The cumulative impacts of the large number of toxic chemicals in the sediment pose a risk to community members and response personnel working in the area with out protective equipment. There is a need for EPA to establish cleanup levels and require that the cleanup levels be met before community members are allowed to return to the currently contaminated areas."

The full report is available at

This article originally appeared in the 10/01/2005 issue of Environmental Protection.

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