Katrina, Rita cleaned up polluted, lead-laden New Orleans soil
It appears that hurricanes Katrina and Rita, with all the devastation they have caused, made one beneficial contribution to the future of New Orleans: decades of Louisiana-type corruption and collusion between the oil industry and the state government have caused the city’s soil to be heavily polluted, laden with lead, arsenic, and other poisonous substances; the sediments washed into the city by the hurricanes have blanketed the polluted soil, resulting in a dramatic drop in the presence of lead and arsenic in the city’s soil — and in the blood stream of children in the city
Could the devastation caused by hurricanes Katrina and Rita have had a silver lining? The sediment washed into New Orleans by the floods accompanying the storms may have blanketed over heavily polluted, lead-laden soil in the city, leading to a decrease in lead levels in the bloodstreams of children across the city.
This is what Howard Mielke, who researches urban geochemistry at Tulane University in New Orleans, Louisiana, says. Celeste Biever writes that Mielke and his colleagues sampled soil in forty-six neighborhoods of New Orleans in 2000 and then again in 2006. Before the hurricanes, which both occurred in autumn 2005, soil lead levels in fifteen neighborhoods exceeded the U.S. Environmental Protection Agency’s (EPA) limit of 400 milligrams per kilogram, and that this dropped to just six neighborhoods in 2006. Lead levels declined in twenty-nine neighborhoods between 2000 and 2006 by an average of 45 percent.
As soil lead levels had remained fairly constant between 1990 and 2000, and as there were no efforts to remove lead from soil during this period that could have accounted for this reduction, the researchers conclude that this drop was due to the hurricanes, which likely brought unpolluted sediment in from Lake Pontchartrain and the coastal wetlands. “This material is generally much cleaner than what you see in the city,” says Mielke.
Child benefits
Biever writes that this drop in lead also seems to have caused a drop in lead in the bloodstream of children. When Mielke’s team examined data on thousands of children aged 6 years old and under living in these areas, they found that average bloodstream levels of lead decreased by around 30 percent between 2000 and 2006 — and that the largest declines were in the neighborhoods with a drop in soil lead greater than 50 per cent.
Lead can be transferred into the children’s bloodstream if they play outside and then lick their hands or put their fingers in their mouths, says Mielke. Higher levels of lead in the bloodstream have been linked to cognitive and behavioural problems, particularly in people who were exposed as young children.
Mielke says the natural effects of the hurricanes could be mimicked by soil-remediation efforts — and that his results indicate that this is a good way to reduce the amount of lead absorbed by children. “It demonstrates the possibility of improving the environment for children and protecting them against lead poisoning.”
Wash worry
“An important next step would be to look at materials contaminated with hurricane Katrina and Rita floodwaters to understand the extent and significance of any potential redistribution of lead-contaminated silt,” says Trey Brown, an environmental toxicologist at Texas Tech University in Lubbock. “The paper is a fascinating one and critically important for the health and well-being of children currently residing in New Orleans,” he adds.
Gina Solomon of the University of California, San Francisco, has measured arsenic levels before and after hurricane Katrina and found that they increased as a result of the hurricane. “It looks like the silt layer may have been lower in lead, but higher in arsenic,” she says. “Maybe you could call it a ‘wash’, but I’m not sure it’s reassuring.”
-Read more in Sammy Zahran et al., “New Orleans before and after Hurricanes Katrina/Rita: A Quasi-Experiment of the Association between Soil Lead and Children’s Blood Lead,” Environmental Science & Technology (21 April 2010) (DOI: 10.1021/es100572s)
