None of the eight oil dispersants tested by the U.S. Environmental Protection Agency (EPA), including Corexit 9500, which is being used to break up the U.S. Gulf of Mexico oil spill, displayed "biologically significant endocrine disrupting activity" in a first round of toxicity tests by the EPA.
However, Dr. Paul Anastas, assistant administrator for research and development at EPA, emphasized that more testing was needed, and that the agency will not be making a decision at this time on whether BP should switch from Corexit to a different dispersant.
EPA had directed BP on May 23 to ramp down use of the Corexit dispersant; prior to that direction, EPA asked BP to first 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. EPA then began its own scientific research into eight dispersant products, including Dispersit SPC 1000, Nokomis 3-F4, Nokomis 3-AA, ZI-400, SAF-RON Gold, Sea Brat #4, Corexit 9500 A and JD 2000, on the National Contingency Plan Product Schedule.
Testing conducted so far indicates that, while all eight dispersants alone, not mixed with oil, show roughly the same effects, JD-2000 and Corexit 9500 proved to be the least toxic to small fish, and JD-2000 and SAF-RON GOLD were the least toxic to the mysid shrimp. Test results have not shown the dispersant to be settling in oyster beds on the ocean floor.
The next phase of EPA's testing will assess the acute toxicity of multiple concentrations of Louisiana Sweet Crude Oil alone and combinations of Louisiana Sweet Crude Oil with each of the eight dispersants for two test species.
In the meantime, the EPA will continue monitor BP's use of dispersant in the Gulf. Anastas noted that EPA scientists are working 24/7 to study the effects of dispersants on the Gulf environment.
"The decision of the EPA and the Coast Guard to use dispersants was a difficult choice but necessary to break up the oil from a spill of this size," said Dr. Paul Anastas, assistant administrator for research and development for the EPA.
Anastas noted BP has been responsive to its requests to limit dispersant use. On May 23, EPA requested that BP reduce dispersant usage by 75 percent from peak usage. Over the next month, BP reduced dispersant use 68 percent from peak usage level.
Anastas could not give a timetable on how long the Corexit dispersant would take to biodegrade in the Gulf. The process could take longer on the water's surface, where sunshine warms the water, and slower in the colder water depths.
EPA noted that dispersants are generally less toxic than oil and can prevent some oil from impacting sensitive areas along the Gulf Coast.
"We want to ensure that every tool is available to mitigate the impact of the BP spill and protect our fragile wetlands. But we continue to direct BP to use dispersants responsibly and in as limited an amount as possible," said EPA Administration Lisa P. Jackson.
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