The US Environmental Protection Agency on Monday released peer reviewed results of tests that indicate the use of oil dispersants in the Gulf of Mexico is no more toxic than oil alone.
There has been great concern since cleanup efforts began for the BP oil spill that the chemicals used in dispersants like Corexit 9500A could exacerbate ecological damage.
EPA’s results indicate that the eight dispersants tested have similar toxicities to one another when mixed with Louisiana Sweet Crude Oil. These results confirm that the dispersant used in response to the oil spill in the gulf, Corexit 9500A, when mixed with oil, is generally no more or less toxic than mixtures with the other available alternatives. The results also indicate that dispersant-oil mixtures are generally no more toxic to the aquatic test species than oil alone, EPA said.
However, it should be noted that the tests do not evaluate whether the volume of dispersants added to the ocean was an equal trade-off for damage that would have occured without dispersants--or whether using dispersants to spread the oil throughout the water column is even a good idea to begin with. These questions should be answered in future studies--and arguably should have been addressed years ago, following spills like the Exxon Valdez.
“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% from peak volumes
following the joint EPA-U.S. Coast Guard directive to BP in late May,” said EPA Administrator Lisa P. Jackson.
The toxicity tests released by the EPA were conducted on juvenile shrimp and
small fish that are found in the gulf and are commonly used in 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.
Before directing BP to ramp down dispersant use, EPA directed BP to analyze potential alternative dispersants for toxicity and effectiveness. BP reported to EPA that they were unable to find a dispersant that is less toxic than Corexit 9500, the product then in use. Following that, EPA began its own scientific testing of eight dispersant products.
EPA released the first round of data--on the dispersant products alone--on June 30. Today’s results represent the second and final stage of the acute toxicity tests.
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