U.S. EPA today released the results of its new tests on federally approved Gulf of Mexico oil dispersants, reporting that the product now used in copious amounts by BP PLC is not a significant endocrine disruptor and is no more acutely toxic than alternative products.
But the data did not appear likely to dispel concerns about the long-term consequences of massive dispersant use that have persisted among marine scientists and toxicologists since the start of the Gulf disaster. A senior EPA official described the results as an affirmation of the agency's strings-attached approach to BP dispersant use, while warning that a complete picture of the chemicals' broad effects requires more testing.
"Let me be clear: This is the first round of data," Paul Anastas, EPA assistant administrator for research and development, told reporters.
Anastas added that "we have additional testing to do" before asking BP to switch from its Corexit 9500 dispersant to another product, partially walking back a previous EPA order that the oil giant identify a less toxic option for use in the Gulf (Greenwire, May 20).
After BP fought that edict, asserting that other dispersants could degrade into a type of hormone-disrupting chemical, EPA began a new effort to compare Corexit with seven other products approved under the government's National Contingency Plan (NCP).
The earliest rounds of tests were performed on two marine species found in the Gulf, the inland silverside and the mysid. EPA used in vitro cells for a separate evaluation of dispersants' potential endocrine-disrupting characteristics.
Corexit ranked as the second-least acutely toxic dispersant in short-term tests on the inland silverside, with another product, JD-2000, emerging as the least toxic option. When the products' effects on the Gulf mysid were considered, Corexit ranked the third-most toxic and JD-2000 also came out orders of magnitude ahead of the field.
In the cellular testing, Corexit was not shown to induce human hormone-disrupting activity. One specific measure of cell health ranked it the second-most toxic dispersant, and another ranked it the fourth-most toxic.
"All the dispersants are roughly equal in toxicity and generally less toxic than oil," Anastas said. Later in his briefing with reporters, Anastas sought to contextualize the complex test information: "In the overall range of exposures, these are very similar as a group."
The newly released tests examine the dispersants alone; EPA's next evaluations are set to compare the acute toxicity of each product when mixed in varying concentrations with Louisiana crude oil, according to Anastas. More endocrine tests are also in progress.
Anastas defended the agency's success in policing the application of Corexit, about 1.4 million gallons of which have been used in the Gulf since the oil leak began. "The decision that EPA and the Coast Guard made to authorize the use of dispersants was a difficult choice, but one suited to this disaster," he said.
Anastas cited statistics showing that BP has complied with a May 26 EPA-Coast Guard order to reduce dispersant use from its previous peak but did not address a separate part of that directive requiring the oil company to avoid surface sprays unless required "in rare cases." Since May 26, BP has applied more than 272,000 gallons of surface dispersant (Greenwire, June 24).
In addition, Anastas did not take issue with a recent Environmental Defense Fund analysis that found there is no maximum limit on toxicity that would prevent a dispersant from being added to the NCP, which governs response to emergency events such as oil spills.
"The scale and magnitude of this event has raised important questions on how these previous regulations may need to be re-examined and revisited," he said.