Contaminated Soil in New Orleans: New Research Finds Arsenic is from Katrina Flood

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"The arsenic was probably there all along." That's what our team of scientists kept hearing from EPA and Louisiana Department of Environmental Quality (LDEQ) staff in the months and years following Hurricane Katrina. As a public health advocate, I didn't see that it mattered: After all, tests by EPA and others in 2005-2006 repeatedly showed significant levels of arsenic in sediment and soil in New Orleans. These levels exceeded State and Federal clean-up standards, and posed a risk of cancer and chronic illness to returning residents, especially children who play in the dirt and put their hands in their mouths. It turns out it did matter, since clean-up funds were earmarked for contamination that was from the storm, not preexisting contamination, regardless of the public health significance.

So the government didn't clean the arsenic up, and the residents returned.

The problem gnawed at me. I worried about the health risks, and I wondered where all that arsenic came from. I searched the scientific literature and State data, finding no useful information on historic levels of arsenic in New Orleans. Until one day in late-2006 when I talked with Dr. Howard Mielke, a soils expert at Xavier University, who told me about his soil archive. Dr. Mielke and his team of graduate students had spent two years from 1998-2000, collecting soil samples from throughout New Orleans for studies of lead contamination (lead was a KNOWN preexisting problem in New Orleans). Their samples were carefully geo-coded, sealed in polyethylene, and stored at 20-24 degrees Centigrade for the past six years, undisturbed and unaffected by the flooding of New Orleans. What a gold mine! The results of our research were published this month in the journal Environmental Research.

Our team of researchers identified 70 residential locations in the City of New Orleans where post-Katrina samples showed levels of arsenic above Louisiana soil screening levels, and where location-matched samples were available from the soil archive. When the laboratory results came back, the findings were stunningly clear: the arsenic was new!

Every single one of the samples had higher levels after the flooding compared with pre-flood. The average level of arsenic in the soil samples post-flood was over 23 milligrams per cubic meter (mg/m3); pre-flood, the average was below 4 mg/m3. The Louisiana soil screening level is 12 mg/m3, and EPA suggests a cancer concern at even lower levels, so this dramatic increase was highly significant - both statistically and from a health perspective.

When the arsenic results came in, we decided to go back to all these residential locations one more time, to see whether the arsenic was lingering during the recovery period. During that trip, we also sampled at 15 schoolyards and 15 playgrounds that had reopened to children. We were reassured to see that the arsenic contamination in the residential neighborhoods had dropped significantly - Probably some had washed down storm drains, some had been cleaned by street sweeping, and some had been ground deeper into the soil. But in some areas, such as the Lower 9th Ward, 75% of the samples were still higher than they were pre-Katrina.

The more worrisome story was at the schools and playgrounds. One-third of the samples taken in schoolyards, and 13 percent of samples at playgrounds still exceeded the Louisiana soil screening level that could (and should) trigger clean-up. Yet as far as I know, these sites have still not been cleaned up.

We still don't know where the arsenic came from. There are numerous theories, but the most likely source was arsenic-treated wood used in the past to build decks, fences, playground equipment, and even houses. The wood can leach arsenic into the soil below the wooden structures, and when the wood is soaked in water it can also release arsenic. A group of researchers found arsenic contamination in 23 percent of the wood waste from destroyed structures after Katrina. This arsenic was mobilized by the flood waters and deposited as a layer of grayish sediment all over people's land and homes after the flooding.

Some community groups have undertaken volunteer efforts to clean up their own neighborhoods, such as the Deep South Center for Environmental Justice's Safe Way Back Home campaign. But the money to clean up these remaining contaminated sites has been tied up at the state level for years. Now the professional staff in city government with the expertise to oversee proper spending of the clean-up funds will no longer be employed after this month. 

The Federal EPA had walked away years ago. Fortunately, this week, the new EPA Administrator , Lisa Jackson, and other senior EPA officials are in New Orleans to talk about the problem of contaminated soil, and to listen to the community's concerns.

I hope that this new research convinces the Agencies to re-engage. It's definitely not too late to learn from the mistakes of the past, and to move forward and rebuild a safer New Orleans.

This post originally appeared on NRDC's Switchboard blog.