Richard S. Judson, Matthew T. Martin, David M. Reif, Keith A. Houck, Thomas B. Knudsen, Daniel M. Rotroff, Menghang Xia, Srilatha Sakamuru, Ruili Huang, Paul Shinn, Christopher P. Austin, Robert J. Kavlock and David J. Dix.
National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, and NIH Chemical Genomics Center, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892
The Deepwater Horizon oil spill has led to the use of >1 M gallons of oil spill dispersants, which are mixtures of surfactants and solvents. Because of this large scale use there is a critical need to understand the potential for toxicity of the currently used dispersant and potential alternatives, especially given the limited toxicity testing information that is available. In particular, some dispersants contain nonylphenol ethoxylates (NPEs), which can degrade to nonylphenol (NP), a known endocrine disruptor. Given the urgent need to generate toxicity data, we carried out a series of in vitro high-throughput assays on eight commercial dispersants. These assays focused on the estrogen and androgen receptors (ER and AR), but also included a larger battery of assays probing other biological pathways. Cytotoxicity in mammalian cells was also quantified. No activity was seen in any AR assay. Two dispersants showed a weak ER signal in one assay (EC50 of 16 ppm for Nokomis 3-F4 and 25 ppm for ZI-400). NPs and NPEs also had a weak signal in this same ER assay. Note that Corexit 9500, the currently used product, does not contain NPEs and did not show any ER activity. Cytotoxicity values for six of the dispersants were statistically indistinguishable, with median LC50 values 100 ppm. Two dispersants, JD 2000 and SAF-RON GOLD, were significantly less cytotoxic than the others with LC50 values approaching or exceeding 1000 ppm.
Corexit 9500, the predominant dispersant used by BP in attempting to break up the 140 million gallons of oil spilled by the runaway Macondo well, appears to have all of the toxicity and poisonous capacity of your average bottle of Dawn dishwashing liquid.
The company that makes the stuff, NALCO, has been thrown into the blender of conspiracy theories surrounding this disaster. Other ingredients in the conspiracy mix are Halliburton, George Soros, Brazilian Petrobras, the North Korean submarine Navy and giant, asphalt-eating monsters living on the floor of the Gulf.
Have faith, conspiracists. I'm sure you'll concoct some other evil plot to reduce world population and bring forth the New World Order of the Bilderberger Rothschild clan. Or, maybe that Corexit is racist!
Gimme some feedback in the comments.