Katrina's Floodwaters Far Less Toxic Than Feared

Studies show the hurricane did little to contaminate New Orleans' soil

Rick Ansorge

Rick Ansorge

Published on September 11, 2006

MONDAY, Sept. 11, 2006 (HealthDay News) -- While a devastated New Orleans still struggles to recover from Hurricane Katrina, the city apparently has avoided one of the storm's most-feared consequences -- "toxic soup" contamination of its soil.

That's the conclusion of dozens of scientific papers that show the hurricane-related flooding did not increase soil levels of heavy metals such as lead and arsenic; pesticides; or petrochemicals such as benzene, toluene, ethylbenzene and xylenes, collectively known as BTEX.

The papers were presented Monday at the start of the American Chemical Society's four-day annual meeting in San Francisco.

"Overall, there wasn't an acute health threat," said Dr. Maureen Lichtveld, chairwoman of environmental health sciences at the Tulane University School of Public Health and Tropical Medicine in New Orleans.

At least from an environmental health perspective, that means it's probably safe for most residents to return and rebuild their damaged homes, Lichtveld said.

Michael T. Abel, of Texas Tech University, and colleagues presented research showing that Katrina, which struck the Gulf Coast on Aug. 29, 2005, did not make a significant difference in soil and sediment levels of heavy metals.

"It is 'good news' that the city's scenario did not worsen and metal concentrations are in accordance with other cities of similar size and age," Abel said. "However, it should be noted that many of the soils/sediments had concentrations of lead and arsenic that exceeded human health soil screening levels set by the U.S. Environmental Protection Agency."

Of the 77 sites that Abel and his team tested, 14 (primarily in the southern district) had potentially hazardous levels of lead and 12 (primarily in the eastern district) had potentially hazardous levels of arsenic.

"Like many old cities, New Orleans has high surface soil levels of lead because of the lead paint that was used," Lichtveld said. "But that was there before Katrina."

Lead exposure can have adverse effects on the brain, blood, kidneys and endocrine system, particularly in children who play in contaminated soil and don't wash their hands. So, in areas where high lead levels have been detected, it may be necessary to either strip the topsoil or cover it with uncontaminated topsoil, Abel said.

Abel was surprised to find that post-Katrina contamination wasn't worse. "With the innumerable number of sources for toxic compounds being submerged by floodwaters, such as industrial facilities, gas stations, vehicles and so on, I expected to at least see a dispersion from high concentrations of contaminants to low concentrations across New Orleans," he said.

Although Abel is uncertain why the contamination wasn't more widespread, he suggested it may be because the brackish floodwater was highly alkaline. "This could explain the floodwaters' inability to mobilize and disperse metals," he said.

Jianmin Wang, an assistant professor in the School of Engineering at the University of Missouri-Rolla, and his colleagues presented research showing that soil and sediment levels of pesticides and BTEX in New Orleans were generally very low and not of great concern.

"This research focuses on the extractable or leachable pollutants, which is more meaningful when assessing the practical environmental health impact," Wang said in a statement.

Lichtveld isn't surprised that chemical contamination wasn't significant after Katrina. "You have to look at where the flooding originated," she said. "There was sampling of the fish, shrimp and oysters from Lake Pontchartrain that did not find levels that were an immediate health concern."

"Areas that were flooded were not primarily in areas where hazardous waste sites were located," she added.

Ruth A. Hathaway, organizer of the conference symposium "Recovery From and Prevention of Natural Disasters," said in a statement, "The data shows that there is no real need to ban fish consumption."

More information

For more on the impact of flooding caused by Hurricane Katrina, visit the American Chemical Society.

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