Measuring Natural Disasters' Punch

In the wake of last year's gulf coast hurricanes, scientists from numerous governmental agencies and universities rushed to New Orleans to assess how the storms had affected the quality of the city's soils. Their efforts would have been uninformative, were it not for Howard Mielke.

Mielke has spent the past three decades mapping the metal content of inner-city soils, motivated in part by his daughter's being diagnosed with lead poisoning in the early 1980s. He later moved to Xavier University in New Orleans, where he painstakingly mapped lead, mercury, and arsenic levels in the city's soils.

Mielke's metal-mapping efforts were heralded as "invaluable" by environmental chemists and geochemists who took part in "Recovery from and Prevention of Natural Disasters," a special multiday symposium at last month's American Chemical Society national meeting in San Francisco. "Without baseline data like Howard's, our job would have been much harder," said Geoffrey S. Plumlee of the U.S. Geological Survey (USGS) in Denver, speaking to C&EN in San Francisco.

Plumlee, who participated in USGS's efforts to assess the metal content and source of sediments deposited in New Orleans by Hurricanes Katrina and Rita, helped organize one of several symposium sessions devoted to assessing the storms' impact on Gulf Coast soil, water, and air quality. He and other scientists emphasized the importance of baseline, or "heritage," environmental data in assessing the impact of natural disasters.

"The story of the New Orleans sediments doesn't start with Hurricane Katrina," said Mielke, who lost his job in Xavier's pharmacy department after the storm and has since joined Tulane University and Xavier's joint Center for Bioevironmental Research. Mielke's efforts to systematically sample surface soils by census tract between 1988 and 2000, conducted with the help of students and staff members Eric T. Powell and Christopher Gonzales, revealed high levels of lead in the city center. He attributed the contamination to historical use of leaded gasoline and the current use of lead weights to balance car tires, combined with heavy traffic in the city center. Flaking lead-based paints are also likely a key source of lead in these soils, Mielke added. He also described his team's successful pilot program to reduce residents' lead levels in blood by covering lead-rich surface soils with a few inches of uncontaminated soil.

After the storms, Mielke's maps were an important reference for those characterizing the sediments the floodwaters left behind, including USGS's Plumlee. With these maps, his team was able to conclude that "the soils in downtown New Orleans were reworked as a result of the storms." The floodwaters that inundated the city did not introduce significant new metal contamination, Plumlee noted. Rather, "what we detected were heavy metals that were already present in city soils," he explained. USGS has made its data available at pubs.usgs.gov/of/2006/1023.

USGS's data are similar to those recently published by George P. Cobb's group at Texas Tech University's Institute of Environmental & Human Health (Environ. Sci. Technol. 2006, 40, 468). The team found potentially hazardous levels of arsenic and lead in city soils, graduate student Michael T. Abel reported. "But it should be noted that similar values found in this sampling effort were present in studies conducted before the hurricanes," he added. Jianming Wang of the University of Missouri, Rolla, reported similar findings from a survey of New Orleans and surrounding areas after the storm.

Scientists were concerned the hurricanes might have an impact on Gulf Coast water, air, and aquatic life, too. Christopher M. Piehler of the Louisiana Department of Environmental Quality described his team's efforts to sample fish and seafood tissue for volatile organic compounds, pesticides, polychlorinated biphenyls, metals, and bacteria in the months following the hurricanes. "There's no reason to avoid Louisiana seafood," he told the audience. Steven M. Presley of Texas Tech University reported that his survey of New Orleans mosquitoes after the storm revealed little danger of vector-borne diseases. And John H. Pardue of Louisiana State University, Baton Rouge, discussed his lab's efforts to measure asbestos and other particulates, as well as mold spores in the city's air, as residents work to clean out or demolish their homes.

Pardue and others emphasized that their environmental data indicate that initial reports of New Orleans floodwaters being a "toxic soup" were exaggerated (Environ. Sci. Technol. 2005, 39, 8591; C&EN, Oct. 17, 2005, page 11). Many had feared the floodwaters might be a dangerous brew of sewage, gasoline, and various household and industrial pollutants, including heavy metals and pesticides. Results presented at the symposium showed that "the situation in New Orleans was not as bad as people had thought or feared," Cobb told C&EN.

"But there remain sites that may pose human health risks," Cobb added, including those lead-rich inner-city soils pinpointed by Mielke prior to the storm. "Nevertheless, just because this contamination predates the storm doesn't mean we shouldn't be doing anything about it," added Plumlee.

Despite the key role it played in assessing the hurricanes' impact in New Orleans, baseline environmental data like those Mielke provided remain tough to come by, participants warned. Mielke told C&EN he has long scrambled to get his efforts funded. Cobb expressed fear that the National Oceanographic & Atmospheric Administration's continuing efforts to track toxic metal and organic contaminants in the nation's seafood, water, and sediments are on the brink of being eliminated. According to JoAnn M. Holloway of USGS, who described her efforts to characterize microbial communities in post-Katrina sediments in New Orleans, "We continue to fight to get baseline environmental data—even in areas prone to natural disasters."