The EPA on Monday, Aug. 2, 2010, released peer reviewed results from the second phase of its independent toxicity testing on mixtures of eight oil dispersants with Louisiana Sweet Crude Oil. The agency concluded that all but one of the eight similar dispersant technologies tested were at least no more dangerous than oil.

The agency's results indicate that the eight dispersants tested have similar toxicities to one another when mixed with Louisiana Sweet Crude Oil. These results confirmed that the dispersant used in response to the oil spill in the gulf, Corexit 9500A, when mixed with oil, was generally no more or less toxic than mixtures with other available alternatives. The results also indicated that dispersant-oil mixtures were generally no more toxic to the aquatic test species than oil alone.

The standard acute toxicity tests were conducted on juvenile shrimp and small fish from the gulf. The tests were conducted on mixtures of Louisiana Sweet Crude Oil and eight different dispersant products found on the National Contingency Plan Product Schedule – Dispersit SPC 1000, Nokomis 3-F4, Nokomis 3-AA, ZI-400, SAFRON Gold, Sea Brat #4, Corexit 9500 A and JD 2000. The same eight dispersants were used during the agency's first round of independent toxicity testing.

All eight dispersants were found to be less toxic than the dispersant-oil mixture to both test species. Louisiana Sweet Crude Oil was more toxic to mysid shrimp than the eight dispersants when tested alone. Oil alone had similar toxicity to mysid shrimp as the dispersant-oil mixtures, with exception of the mixture of Nokomis 3-AA and oil, which was found to be more toxic than oil.

"EPA has committed to following the science at every stage of this response - that's why we required BP to launch a rigorous dispersant monitoring program, why we directed BP to analyze potential alternatives and why EPA undertook this independent analysis of dispersant products," said EPA Administrator Lisa P. Jackson. "We have said all along that the use of dispersant presents environmental tradeoffs, which is why we took steps to ensure other response efforts were prioritized above dispersant use and to dramatically cut dispersant use. Dispersant use virtually ended when the cap was placed on the well and its use dropped 72 percent from peak volumes following the joint EPA-U.S. Coast Guard directive to BP in late May."

There has been virtually no dispersant use since the well was capped on July 15 – only 200 gallons total applied on July 19. The agency has required rigorous, ongoing monitoring as a condition of authorizing BP's use of dispersant in the gulf. It is expected that one more round of testing might free BP to apply dispersants on a wide scale and break up the crude that escaped.

Before directing BP to ramp down dispersant use, the EPA directed BP to analyze potential alternative dispersants for toxicity and effectiveness. BP reported to the agency that they were unable to find a dispersant that is less toxic than Corexit 9500, the product then in use. Following that, the EPA began its own scientific testing of eight dispersant products.

View the toxicity test results at www.epa.gov/bpspill/dispersants.

SOURCE: EPA Press Release